A New Epoxy-Based Layered Silicate Nanocomposite Using a Hyperbranched Polymer: Study of the Curing Reaction and Nanostructure Development

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Pilar Cortés

2014-03-01

Full Text Available Polymer layered silicate (PLS nanocomposites have been prepared with diglycidyl ether of bisphenol-A (DGEBA epoxy resin as the matrix and organically modified montmorillonite (MMT as the clay nanofiller. Resin-clay mixtures with different clay contents (zero, two, five and 10 wt% were cured, both isothermally and non-isothermally, using a poly(ethyleneimine hyperbranched polymer (HBP, the cure kinetics being monitored by differential scanning calorimetry (DSC. The nanostructure of the cured nanocomposites was characterized by small angle X-ray scattering (SAXS and transmission electron microscopy (TEM, and their mechanical properties were determined by dynamic mechanical analysis (DMA and impact testing. The results are compared with an earlier study of the structure and properties of the same DGEBA-MMT system cured with a polyoxypropylene diamine, Jeffamine. There are very few examples of the use of HBP as a curing agent in epoxy PLS nanocomposites; here, it is found to enhance significantly the degree of exfoliation of these nanocomposites compared with those cured with Jeffamine, with a corresponding enhancement in the impact energy for nanocomposites with the low clay content of 2 wt%. These changes are attributed to the different cure kinetics with the HBP, in which the intra-gallery homopolymerization reaction is accelerated, such that it occurs before the bulk cross-linking reaction.

Effects of Surface Treatments of Montmorillonite Nanoclay on Cure Behavior of Diglycidyl Ether of Bisphenol A Epoxy Resin

International Nuclear Information System (INIS)

Tcherbi-Narteh, A.; Hosur, M.V.; Triggs, E.; Jelaani, S.

2013-01-01

Diglycidyl ether of Bisphenol A (DGEBA) based SC-15 epoxy resin was modified with three different commercially available montmorillonite (MMT) nanoclay: Nanomer I.28E and Cloisite 10A and 30B. Cure behavior of nanocomposites was studied using a variety of techniques. Primary focus of this study was to investigate influence of different surface modifications of MMT nanoclay on rheological properties and cure behavior of SC-15 epoxy resin. By adding MMT to SC-15 epoxy resin, chemistry of the epoxy is altered leading to changes in rheological properties and ultimately enthalpy and activation energy of reactions. Addition of Nanomer I.28E delayed gelation, while Cloisite 10A and 30B accelerated gelation, regardless of the curing temperature. Activation energy of reaction was lower with the addition of Nanomer I.28E and Cloisite 10A and higher for Cloisite 30B compared to neat SC-15 epoxy composite.

Elastic properties, reaction kinetics, and structural relaxation of an epoxy resin polymer during cure

Science.gov (United States)

Heili, Manon; Bielawski, Andrew; Kieffer, John

The cure kinetics of a DGEBA/DETA epoxy is investigated using concurrent Raman and Brillouin light scattering. Raman scattering allows us to monitor the in-situ reaction and quantitatively assess the degree of cure. Brillouin scattering yields the elastic properties of the system, providing a measure of network connectivity. We show that the adiabatic modulus evolves non-uniquely as a function of cure degree, depending on the cure temperature and the molar ratio of the epoxy. Two mechanisms contribute to the increase in the elastic modulus of the material during curing. First, there is the formation of covalent bonds in the network during the curing process. Second, following bond formation, the epoxy undergoes structural relaxation toward an optimally packed network configuration, enhancing non-bonded interactions. We investigate to what extent the non-bonded interaction contribution to structural rigidity in cross-linked polymers is reversible, and to what extent it corresponds to the difference between adiabatic and isothermal moduli obtained from static tensile, i.e. the so-called relaxational modulus. To this end, we simultaneously measure the adiabatic and isothermal elastic moduli as a function of applied strain and deformation rate.

CURING OF POLYMERIC COMPOSITES USING MICROWAVE RESIN TRANSFER MOULDING (RTM

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R. YUSOFF

2007-08-01

Full Text Available The main objective of this work is to compare the difference between microwave heating and conventional thermal heating in fabricating carbon/epoxy composites. Two types of epoxy resin systems were used as matrices, LY5052-HY5052 and DGEBA-HY917-DY073. All composite samples were fabricated using resin transfer moulding (RTM technique. The curing of the LY5052-HY5052-carbon and the DGEBA-HY917-DY073-carbon composite systems, were carried out at 100 °C and 120 °C, respectively. Microwave heating showed better temperature control than conventional heating, however, the heating rate of the microwave cured samples were slower than the conventionally cured samples. This was attributed to the lower power (250 W used when heating with microwaves compared to 2000 W used in conventional heating. Study of thermal characteristics as curing progressed showed that the polymerisation reaction occurred at a faster rate during microwave curing than in conventional curing for both the DGEBA and the LY/HY5052 carbon composite systems. The actual cure cycle was reduced from 60 minutes to 40 minutes when using microwaves for curing DGEBA-carbon composites. As for LY/HY5052-carbon composites, the actual cure cycle was reduced from 3 hours to 40 minutes. Both conventional and microwave heating yielded similar glass transition temperatures (120 °C for DGEBA systems and 130 °C for LY/HY5052 systems. Microwave cured composites had higher void contents than conventionally cured composites (2.2-2.8% and 1.8-2.4% for DGEBA and LY/HY5052 microwave cured composites, respectively, compared to 0.2-0.4% for both DGEBA and LY/HY5052 thermally cured composites. C-scan traces showed that all composites, regardless of methods of curing, had minimal defects.

Effects of Different Montmorillonite Nanoclay Loading on Cure Behavior and Properties of Diglycidyl Ether of Bisphenol A Epoxy

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Alfred Tcherbi-Narteh

2016-01-01

Full Text Available The primary focus of this study was to understand the effects of different amounts of montmorillonite nanoclay (MMT loading on viscosity, cure behavior, reaction mechanism, and properties of diglycidyl ether of bisphenol A (DGEBA epoxy composites. Influence of 1–3 wt.% MMT on rheological and subsequent cure behavior of SC-15 epoxy resin was studied using nonisothermal and isothermal rheometry and differential scanning calorimetry (DSC. Rheological properties were influenced by different amounts of MMT at lower shear rates prior to and during curing. Cure reaction mechanism was unaffected by different MMT concentration; however heat and activation energy of reactions increased with increasing MMT loading. Samples with 2 wt.% MMT showed highest reaction rate constant, indicative of catalytic behavior. X-ray diffraction (XRD and transmission electron microscope (TEM revealed mainly intercalated microstructure throughout the MMT infused epoxy composite samples irrespective of the percent loading.

The non-isothermal DSC kinetics of polyethylene tereftalate–epoxy compatible blends

International Nuclear Information System (INIS)

Zvetkov, V.L.; Djoumaliisky, S.; Simeonova-Ivanova, E.

2013-01-01

Highlights: ► The non-isothermal DSC kinetics of the reaction of DGEBA with DDS, in particular in the presence of phase separating PET, has been studied. ► The specific features in the kinetics of PET formulations in comparison to the pure system have been discussed. ► The fast pre-curing of the epoxy phase allows supposing sub-micro phase separation of PET and efficient toughening of the epoxy matrix. - Abstract: Polyethylene tereftalate has been dissolved in an epoxy resin based on diglycidyl ether of bisphenol-A, DGEBA, and the epoxy component has been cross-linked with the aid of two diamine hardeners. Two series of samples have been tested at the epoxy-amine stoichiometry applying the differential scanning calorimetry, DSC, in scanning mode. One of the series of samples was pre-cured at low temperatures with the aid of an aliphatic diamine hardener near the gel point and post-cured with diaminodiphenyl sulfone, DDS. The other series of samples contained the higher temperature hardener only. Consequently, the experimental data obtained in this study on both systems relate to the non-isothermal curing of DGEBA with DDS. The kinetics has been estimated applying preferably isoconversional (model free) methods. It has been established that the fast pre-curing allows performing a sub-micro phase separation and efficient toughening of the epoxy matrix

The non-isothermal DSC kinetics of polyethylene tereftalate–epoxy compatible blends

Energy Technology Data Exchange (ETDEWEB)

Zvetkov, V.L., E-mail: zvetval@yahoo.com [Institute of Mechanics, Bulgarian Academy of Sciences, bl. I, Sofia 1113 (Bulgaria); Djoumaliisky, S.; Simeonova-Ivanova, E. [Institute of Mechanics, Bulgarian Academy of Sciences, bl. I, Sofia 1113 (Bulgaria)

2013-02-10

Highlights: ► The non-isothermal DSC kinetics of the reaction of DGEBA with DDS, in particular in the presence of phase separating PET, has been studied. ► The specific features in the kinetics of PET formulations in comparison to the pure system have been discussed. ► The fast pre-curing of the epoxy phase allows supposing sub-micro phase separation of PET and efficient toughening of the epoxy matrix. - Abstract: Polyethylene tereftalate has been dissolved in an epoxy resin based on diglycidyl ether of bisphenol-A, DGEBA, and the epoxy component has been cross-linked with the aid of two diamine hardeners. Two series of samples have been tested at the epoxy-amine stoichiometry applying the differential scanning calorimetry, DSC, in scanning mode. One of the series of samples was pre-cured at low temperatures with the aid of an aliphatic diamine hardener near the gel point and post-cured with diaminodiphenyl sulfone, DDS. The other series of samples contained the higher temperature hardener only. Consequently, the experimental data obtained in this study on both systems relate to the non-isothermal curing of DGEBA with DDS. The kinetics has been estimated applying preferably isoconversional (model free) methods. It has been established that the fast pre-curing allows performing a sub-micro phase separation and efficient toughening of the epoxy matrix.

Characterization of cure kinetics and physical properties of a high performance, glass fiber-reinforced epoxy prepreg and a novel fluorine-modified, amine-cured commercial epoxy

Science.gov (United States)

Bilyeu, Bryan

Kinetic equation parameters for the curing reaction of a commercial glass fiber reinforced high performance epoxy prepreg composed of the tetrafunctional epoxy tetraglycidyl 4,4-diaminodiphenyl methane (TGDDM), the tetrafunctional amine curing agent 4,4'-diaminodiphenylsulfone (DDS) and an ionic initiator/accelerator, are determined by various thermal analysis techniques and the results compared. The reaction is monitored by heat generated determined by differential scanning calorimetry (DSC) and by high speed DSC when the reaction rate is high. The changes in physical properties indicating increasing conversion are followed by shifts in glass transition temperature determined by DSC, temperature-modulated DSC (TMDSC), step scan DSC and high speed DSC, thermomechanical (TMA) and dynamic mechanical (DMA) analysis and thermally stimulated depolarization (TSD). Changes in viscosity, also indicative of degree of conversion, are monitored by DMA. Thermal stability as a function of degree of cure is monitored by thermogravimetric analysis (TGA). The parameters of the general kinetic equations, including activation energy and rate constant, are explained and used to compare results of various techniques. The utilities of the kinetic descriptions are demonstrated in the construction of a useful time-temperature-transformation (TTT) diagram and a continuous heating transformation (CHT) diagram for rapid determination of processing parameters in the processing of prepregs. Shrinkage due to both resin consolidation and fiber rearrangement is measured as the linear expansion of the piston on a quartz dilatometry cell using TMA. The shrinkage of prepregs was determined to depend on the curing temperature, pressure applied and the fiber orientation. Chemical modification of an epoxy was done by mixing a fluorinated aromatic amine (aniline) with a standard aliphatic amine as a curing agent for a commercial Diglycidylether of Bisphenol-A (DGEBA) epoxy. The resulting cured network

Structure, thermal and fracture mechanical properties of benzoxazine-modified amine-cured DGEBA epoxy resins

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2011-03-01

Full Text Available First, traditional diamine hardeners of epoxy resins (EP were checked as potential accelerators for the benzoxazine (BOX homopolymerization. It was established that the acceleration effect depends on both the type and amount of the diamine compounds. In the follow-up work amine-curable diglycidyl ether bisphenol A (DGEBA type EP was modified with BOX keeping the EP/BOX ratio constant (75/25 wt.%. The amine hardeners, added in the EP in stoichiometric amounts, were of aliphatic and aromatic nature, viz. diethylenetriamine (DETA, 4,4'-diaminodiphenyl methane (DDM, and their 1/1 mixture. The thermal, viscoelastic, flexural and fracture mechanical properties of the EP/BOX hybrids were determined and compared to those of the reference EPs. Based on dynamic-mechanical thermal analysis and atomic force microscopy the formation of co-network between EP and BOX was concluded. Homopolymerized BOX was built in the network in nanoscaled inclusions and it was associated with internal antiplasticization. Incorporation of BOX improved the charring, enhanced the flexural modulus and strength, and reduced the glass transition of the parent EP. The fracture toughness and energy were not improved by hybridization with BOX.

Effect of the hardener to epoxy monomer ratio on the water absorption behavior of the DGEBA/TETA epoxy system

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Ayrton Alef Castanheira Pereira

2016-02-01

Full Text Available Abstract The water absorption behavior of the DGEBA/TETA epoxy system was evaluated as a function of the epoxy monomer to amine hardener ratio. Weight gain versus immersion time curves were obtained and the experimental points were fitted using Fickian and Non-Fickian diffusion models. The results obtained showed that for all epoxy monomer to hardener ratios analyzed water diffusion followed non-Fickian behavior. It was possible to correlate the water absorption behavior to the macromolecular structure developed when the epoxy/ hardener ratio was varied. All epoxy/hardener ratios present a two-phase macromolecular structure, composed of regions with high crosslink density and regions with lower crosslinking. Epoxy rich systems have a more open macromolecular structure with a lower fraction of the dense phase than the amine rich systems, which present a more compact two-phase structure.

Intrinsic Flame-Retardant and Thermally Stable Epoxy Endowed by a Highly Efficient, Multifunctional Curing Agent

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Chunlei Dong

2016-12-01

Full Text Available It is difficult to realize flame retardancy of epoxy without suffering much detriment in thermal stability. To solve the problem, a super-efficient phosphorus-nitrogen-containing reactive-type flame retardant, 10-(hydroxy(4-hydroxyphenylmethyl-5,10-dihydrophenophosphazinine-10-oxide (HB-DPPA is synthesized and characterized. When it is used as a co-curing agent of 4,4′-methylenedianiline (DDM for curing diglycidyl ether of bisphenol A (DGEBA, the cured epoxy achieves UL-94 V-0 rating with the limiting oxygen index of 29.3%. In this case, the phosphorus content in the system is exceptionally low (0.18 wt %. To the best of our knowledge, it currently has the highest efficiency among similar epoxy systems. Such excellent flame retardancy originates from the exclusive chemical structure of the phenophosphazine moiety, in which the phosphorus element is stabilized by the two adjacent aromatic rings. The action in the condensed phase is enhanced and followed by pressurization of the pyrolytic gases that induces the blowing-out effect during combustion. The cone calorimeter result reveals the formation of a unique intumescent char structure with five discernible layers. Owing to the super-efficient flame retardancy and the rigid molecular structure of HB-DPPA, the flame-retardant epoxy acquires high thermal stability and its initial decomposition temperature only decreases by 4.6 °C as compared with the unmodified one.

Modification of (DGEBA epoxy resin with maleated depolymerised natural rubber

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2008-04-01

Full Text Available In this work, diglycidyl ether of bisphenol A (DEGBA type epoxy resin has been modified with maleated depolymerised natural rubber (MDPR. MDPR was prepared by grafting maleic anhydride onto depolymerised natural rubber. MDPR has been characterized by Fourier transform infrared (FT-IR spectroscopy and nuclear magnetic resonance spectroscopy. MDPR was blended with epoxy resin at three different ratios (97/3, 98/2 and 99/1, by keeping the epoxy resin component as the major phase and maleated depolymerised natural rubber component as the minor phase. The reaction between the two blend components took place between the acid/anhydride group in the MDPR and the epoxide group of the epoxy resin. The proposed reaction schemes were supported by the FT-IR spectrum of the uncured Epoxy/MDPR blends. The neat epoxy resin and Epoxy/MDPR blends were cured by methylene dianiline (DDM at 100°C for three hours. Thermal, morphological and mechanical properties of the neat epoxy and the blends were investigated. Free volume studies of the cured, neat epoxy and Epoxy/MDPR blends were correlated with the morphological and mechanical properties of the same systems using Positron Annihilation Lifetime Studies.

Study of the reaction between polyethylene glycol and epoxy resins using N,N-dimethylbenzylamine as catalyst

International Nuclear Information System (INIS)

Zacharuk, Mario; Coelho, Luiz A.F.; Pezzin, Sergio H.; Becker, Daniela

2009-01-01

In this work the use of N,N-dimethylbenzylamine as a catalyst of the reaction of polyethylene glycol (PEG) and epoxy resin (DGEBA) was studied. The reaction products were evaluated by infra-red spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR) and viscosity measurements. Samples cured with a polyamine-based hardener were also submitted to tensile tests and differential scanning calorimetry (DSC). The results of the viscosity analyses, FTIR and RMN ( 1 H) had confirmed the occurrence of the reaction between DGEBA epoxy groups and PEG hydroxyl groups in the presence of N, N-dimethylbenzylamine as catalyst, at 100 deg C. DSC analyses and tensile tests of cured systems showed that the reaction of DGEBA with PEG leads to a reduction of the Tg, generating a more flexible material. (author)

Fabrication of High Gas Barrier Epoxy Nanocomposites: An Approach Based on Layered Silicate Functionalized by a Compatible and Reactive Modifier of Epoxy-Diamine Adduct

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Ran Wei

2018-05-01

Full Text Available To solve the drawbacks of poor dispersion and weak interface in gas barrier nanocomposites, a novel epoxy-diamine adduct (DDA was synthesized by reacting epoxy monomer DGEBA with curing agent D400 to functionalize montmorillonite (MMT, which could provide complete compatibility and reactivity with a DGEBA/D400 epoxy matrix. Thereafter, sodium type montmorillonite (Na-MMT and organic-MMTs functionalized by DDA and polyether amines were incorporated with epoxy to manufacture nanocomposites. The effects of MMT functionalization on the morphology and gas barrier property of nanocomposites were evaluated. The results showed that DDA was successfully synthesized, terminating with epoxy and amine groups. By simulating the small-angle neutron scattering data with a sandwich structure model, the optimal dispersion/exfoliation of MMT was observed in a DDA-MMT/DGEBA nanocomposite with a mean radius of 751 Å, a layer thickness of 30.8 Å, and only two layers in each tactoid. Moreover, the DDA-MMT/DGEBA nanocomposite exhibited the best N2 barrier properties, which were about five times those of neat epoxy. Based on a modified Nielsen model, it was clarified that this excellent gas barrier property was due to the homogeneously dispersed lamellas with almost exfoliated structures. The improved morphology and barrier property confirmed the superiority of the adduct, which provides a general method for developing gas barrier nanocomposites.

Syntheses and characterization of novel P/Si polysilsesquioxanes/epoxy nanocomposites

International Nuclear Information System (INIS)

Chiu Yiechan; Liu Fangyi; Ma, C.-C.M.; Chou, I.-C.; Riang Linawati; Chiang, C.-L.; Yang, J.-C.

2008-01-01

Phosphorus-containing polysilsesquioxane (PSSQ) was introduced into diglycidyl ether of bisphenol A epoxy (DGEBA) to generate a novel P/Si PSSQ nanocomposite. A series of nanocomposites was fabricated by changing the content of the 2-(diphenylphosphino)ethyltriethoxysilane (DPPETES) monomer or P/Si PSSQ cured with DGEBA epoxy and modified epoxy. The structure, thermal properties and flame-retardancy of the P/Si PSSQ nanocomposites were characterized by FT-IR, solid-state 29 Si NMR, thermogravimetric analysis (TGA) and limited oxygen index (LOI) instruments. The nano-sizes of the particles in P/Si PSSQ were approximately 30-50 nm, and the polarity of nanocomposites might generate the nanophase-separated structure from transmission electron microscopy (TEM). The urethane-like side group of the modified epoxy and the fabrication of oligomers in the curing reaction affected the T d5 values of nanocomposites. TGA and LOI results indicated that the char yield (29 wt%) increased and the nanocomposites were not very flammable (LOI = 30). The hybrid materials also exhibited high thermal stability, good flame-retardance and a lack of phase separation

Carboxyl-terminated butadiene-acrylonitrile-toughened epoxy/carboxyl-modified carbon nanotube nanocomposites: Thermal and mechanical properties

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H. F. Xie

2012-09-01

Full Text Available Carboxyl-modified multi-walled carbon nanotubes (MWCNT–COOHs as nanofillers were incorporated into diglycidyl ether of bisphenol A (DGEBA toughened with carboxyl-terminated butadiene-acrylonitrile (CTBN. The carboxyl functional carbon nanotubes were characterized by Fourier-transform infrared spectroscopy and thermogravimetric analysis. Furthermore, cure kinetics, glass transition temperature (Tg, mechanical properties, thermal stability and morphology of DGEBA/CTBN/MWCNT–COOHs nanocomposites were investigated by differential scanning calorimetry (DSC, dynamic mechanical analysis (DMA, universal test machine, thermogravimetric analysis and scanning electron microscopy (SEM. DSC kinetic studies showed that the addition of MWCNT–COOHs accelerated the curing reaction of the rubber-toughened epoxy resin. DMA results revealed that Tg of rubber-toughened epoxy nanocomposites lowered with MWCNT–COOH contents. The tensile strength, elongation at break, flexural strength and flexural modulus of DGEBA/CTBN/MWCNT-COOHs nanocomposites were increased at lower MWCNT-COOH concentration. A homogenous dispersion of nanocomposites at lower MWCNT–COOH concentration was observed by SEM.

Effect of Alkyl Phenol from Cashew Nutshell Liquid on Mechanical and Dry Sliding Wear Behavior of Epoxy Resin

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Rajesh Panda

2015-05-01

Full Text Available A phenalkamine made from the reaction of alkyl phenol from cashew nutshell liquid (CSNL and polyamine was added at three different weight percentages (30%, 40%, and 50% as a diglycidyl ether of bisphenol A (DGEBA epoxy hardener. This curing agent was compared to a traditional polyamine epoxy hardener. It was observed that an increase in phenalkamine concentration resulted in considerable improvement to impact strength and elongation, which ultimately translated to better wear resistance of the cured epoxy compound. Lancaster–Ratner correlations between mechanical and wear resistance properties were found to be linear. Optical microscope observations were used to understand the wear mechanisms of the cured epoxy materials.

Comparative study of the use of non-ionizing and ionizing radiation in the cure of epoxy resin: microwave versus electron electron

Energy Technology Data Exchange (ETDEWEB)

Kersting, Daniel, E-mail: daniel.kersting@usp.br [Centro Tecnologico da Marinha em Sao Paulo (CTMSP/USP), Sao Paulo, SP (Brazil); Wiebeck, Helio, E-mail: hwiebeck@usp.br [Universidade de Sao Paulo (USP), Sao Paulo, SP (Brazil). Escola Politecnica. Dept. de Engenharia Metalurgica; Marinucci, Gerson; Silva, Leonardo G.A. e, E-mail: marinuci@ipen.br, E-mail: gasilva@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

2013-07-01

Several processes for curing epoxy resins were developed over the years. Two methods are discussed in this paper, in order to present the main advantages and disadvantages of using microwave radiation (non-ionizing radiation) and electron beam radiation (ionizing radiation). The microwave radiation is a non-ionizing radiation, with great power of penetration and transfer of heat in microwave absorbing materials, or materials with microwave absorbing fillers. The frequency usually used in research and development is 2.45 GHz, the same available in commercial equipment. The microwave effect provides increase on the collision velocity between the reactant which, combined with energy absorbed by the reaction system, accelerates the curing reaction. None modifications in the epoxy system are required to use microwave heating for the curing process.On the other hand, the electron beam is a form of ionizing radiation in which the high energy electrons have the ability to interact with the irradiated material and produce ions, free radicals, and molecules in excited state, which can be used to initiate and propagate a polymerization. Specific initiators are necessary for an effective cure of the resin. In this study, a DGEBA epoxy resin with initiators based on anhydride and amine was used under the same conditions indicated by the manufacturer. The curing of the catalyzed system was performed in a domestic microwave oven adapted for laboratory use. The degradation and glass transition temperatures were evaluated by thermal analysis techniques. For comparative purposes, it was used data available in the literature for electron beam irradiation. (author)

Comparative study of the use of non-ionizing and ionizing radiation in the cure of epoxy resin: microwave versus electron electron

International Nuclear Information System (INIS)

Kersting, Daniel; Wiebeck, Helio

2013-01-01

Several processes for curing epoxy resins were developed over the years. Two methods are discussed in this paper, in order to present the main advantages and disadvantages of using microwave radiation (non-ionizing radiation) and electron beam radiation (ionizing radiation). The microwave radiation is a non-ionizing radiation, with great power of penetration and transfer of heat in microwave absorbing materials, or materials with microwave absorbing fillers. The frequency usually used in research and development is 2.45 GHz, the same available in commercial equipment. The microwave effect provides increase on the collision velocity between the reactant which, combined with energy absorbed by the reaction system, accelerates the curing reaction. None modifications in the epoxy system are required to use microwave heating for the curing process.On the other hand, the electron beam is a form of ionizing radiation in which the high energy electrons have the ability to interact with the irradiated material and produce ions, free radicals, and molecules in excited state, which can be used to initiate and propagate a polymerization. Specific initiators are necessary for an effective cure of the resin. In this study, a DGEBA epoxy resin with initiators based on anhydride and amine was used under the same conditions indicated by the manufacturer. The curing of the catalyzed system was performed in a domestic microwave oven adapted for laboratory use. The degradation and glass transition temperatures were evaluated by thermal analysis techniques. For comparative purposes, it was used data available in the literature for electron beam irradiation. (author)

Effect of cure cycle on curing process and hardness for epoxy resin

Directory of Open Access Journals (Sweden)

2009-09-01

Full Text Available A 3-dimensional finite element model is developed to simulate and analyze the temperature and degree of cure field of epoxy casting part during cure process. The present model based on general finite element software ABAQUS is verified by literature example and experimental data. The numerical results show good agreement with literature example and measured data, and are even more accurate than the simulation of literature. After modeling successfully, the influence of temperature cure cycle ramps have on the temperature and degree of cure gradient is investigated. Moreover, the effect of non-uniform temperature and degree of cure field within epoxy casting part on hardness is demonstrated. The present model provides an accurate and novel method that allows further insight into the process of cure for epoxy resin.

Improvement of thermal properties and flame retardancy of epoxy-amine thermosets by introducing bisphenol containing azomethine moiety

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2007-05-01

Full Text Available A novel bisphenol 1, 4'-bis{4-[(4-hydroxy phenyliminomethylidene] phenoxy} benzene (BHPB, which contains azomethine moiety and flexible aromatic ether linkage, was synthesized and introduced into the curing system composed of diglycidyl ether of bisphenol A (DGEBA and diamine. The curing behavior of DGEBA/diamine changed dramatically due to the introduction of BHPB. The resultant epoxy thermosets containing BHPB had high Tgs (127-160 °C, high Td, 5% (>=330°C and high integral procedure decomposition temperature (IPDT values (662-1230°C and good flame retardancy for their high Limited Oxygen Index (LOI values (above 29.5.

Comportamento de cura de adesivo epoxídico contendo grupo mercaptana avaliado por espectroscopia no infravermelho (MIR/NIR e calorimetria exploratória diferencial (DSC Cure behavior of epoxy adhesive containig mercaptan group evaluated by infrared spectroscopy (MIR/NIR and differential scanning calorimetry (DSC

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Hilzette P. C. Andrade

2008-01-01

Full Text Available No presente trabalho, a flexibilidade de um adesivo epoxídico contendo diglicidiléter de bisfenol A (DGEBA e dietilenotriamina (DETA como agente de cura foi modificada pela adição de um segundo componente contendo grupos mercaptana (CAPCURE. A adição de amianto ao adesivo contendo CAPCURE também foi avaliada. As reações entre os grupos epoxídicos e os grupos amina, assim como entre os grupos epoxídicos e os grupos mercaptana, foram estudadas nas regiões espectrais do infravermelho médio (MIR e próximo (NIR. Observou-se que o amianto não interfere nas reações de cura e que a espectroscopia FT-NIR evidencia melhor as alterações espectrométricas ocorridas durante as reações em relação à análise FT-MIR. O tempo das reações de cura foi monitorado por calorimetria exploratória diferencial (DSC, observando-se que a introdução do CAPCURE acelerou a cura da resina. A energia de ativação (Ea das reações de cura foi obtida pelos métodos de Barrett e Borchardt-Daniels. Os adesivos contendo CAPCURE mostraram Ea em torno de 30 kJ.mol-1, enquanto o adesivo DGEBA/DETA apresentou Ea de 46 kJ.mol-1, ambas calculadas pelo método de Barrett.In the present work, the flexibility of an epoxy adhesive containing diglycidylether of bisphenol-A (DGEBA and diethylenetriamine (DETA as curing agent was changed by the addition of a second component containing mercaptan groups (CAPCURE. The addition of asbestos as a filler in the adhesive containing CAPCURE was also evaluated. Epoxy-amine and epoxy-mercaptan reactions were studied in NIR and MIR spectral regions. The filler addition did not cause influence on the cure reactions and spectrometric changes of cure reactions could be better observed by FT-NIR than FT-MIR analysis. The cure reaction time was monitored by DSC experiments and it was observed that the introduction of CAPCURE accelerated the cure reaction. The activation energies (Ea of curing reactions were obtained using Barrett

Vegetable oil-derived epoxy monomers and polymer blends: A comparative study with review

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T. P. Schuman

2013-03-01

Full Text Available Glycidyl esters of epoxidized fatty acids derived from soybean oil (EGS and linseed oil (EGL have been synthesized to have higher oxirane content, more reactivity and lower viscosity than epoxidized soybean oil (ESO or epoxidized linseed oil (ELO. The EGS and ESO, for comparison, were used neat and in blends with diglycidyl ether of bisphenol A (DGEBA. Thermosetting resins were fabricated with the epoxy monomers and either BF3 catalyst or anhydride. The curing behaviors, glass transition temperatures, crosslink densities and mechanical properties were tested. The results indicated that polymer glass transition temperatures were mostly a function of oxirane content with additional influence of glycidyl versus internal oxirane reactivity, pendant chain content, and chemical structure and presence of saturated components. EGS provided better compatibility with DGEBA, improved intermolecular crosslinking and glass transition temperature, and yielded mechanically stronger polymerized materials than materials obtained using ESO. Other benefits of the EGS resin blend systems were significantly reduced viscosities compared to either DGEBA or ESO-blended DGEBA counterparts. Therefore, EGS that is derived from renewable sources has improved potential for fabrication of structural and structurally complex epoxy composites, e.g., by vacuum-assisted resin transfer molding.

Optimization of process variables on flexural properties of epoxy/organo-montmorillonite nanocomposite by response surface methodology

Directory of Open Access Journals (Sweden)

2008-01-01

Full Text Available This study attempted to investigate the preparation and optimization of the flexural properties for epoxy/organomontmorillonite (OMMT nanocomposites. In-situ polymerization method was used to prepare epoxy/OMMT nanocomposites. The diglycidyl ether bisphenol A (DGEBA and curing agent were mixed first, followed by the addition of OMMT. In this study, computer aided statistical methods of experimental design (Response Surface Methodology, RSM was used to investigate the process variables on the flexural properties of epoxy/4wt% OMMT nanocomposites. Speed of mechanical stirrer, post-curing time and post-curing temperature were chosen as process variables in the experimental design. Results showed that the speed of mechanical stirrer, post-curing time and post-curing temperature were able to influence the flexural modulus and flexural yield stress of epoxy/4 wt% OMMT nanocomposites. The results of optimization showed that the design of experiment (DOE has six combination of operating variables which have been obtained in order to attain the greatest overall desirability.

Cure monitoring of epoxy resin by using fiber bragg grating sensor

Energy Technology Data Exchange (ETDEWEB)

Lee, Jin Hyuk [KEPCO, Naju (Korea, Republic of); Kim, Dae Hyun [Dept. of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, Seoul (Korea, Republic of)

2016-06-15

In several industrial fields, epoxy resin is widely used as an adhesive for co-curing and manufacturing various structures. Controlling the manufacturing process is required for ensuring robust bonding performance and the stability of the structures. A fiber optic sensor is suitable for the cure monitoring of epoxy resin owing to the thready shape of the sensor. In this paper, a fiber Bragg grating (FBG) sensor was applied for the cure monitoring of epoxy resin. Based on the experimental results, it was demonstrated that the FBG sensor can monitor the status of epoxy resin curing by measuring the strain caused by volume shrinkage and considering the compensation of temperature. In addition, two types of epoxy resin were used for the cure-monitoring; moreover, when compared to each other, it was found that the two types of epoxy had different cure-processes in terms of the change of strain during the curing. Therefore, the study proved that the FBG sensor is very profitable for the cure-monitoring of epoxy resin.

Kinetic study by FTIR and DSC on the cationic curing of a DGEBA/{gamma}-valerolactone mixture with ytterbium triflate as an initiator

Energy Technology Data Exchange (ETDEWEB)

Arasa, M. [Departament de Quimica Analitica i Quimica Organica, Universitat Rovira i Virgili. C/Marcel.li Domingo s/n, 43007 Tarragona (Spain); Ramis, X. [Laboratori de Termodinamica, ETSEIB. Universitat Politecnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain)], E-mail: ramis@mmt.upc.edu; Salla, J.M. [Laboratori de Termodinamica, ETSEIB. Universitat Politecnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain); Mantecon, A.; Serra, A. [Departament de Quimica Analitica i Quimica Organica, Universitat Rovira i Virgili. C/Marcel.li Domingo s/n, 43007 Tarragona (Spain)

2008-12-05

A mixture of diglycidylether of bisphenol A (DGEBA) and {gamma}-valerolactone ({gamma}-VL) was cured in the presence of ytterbium triflate as an initiator to obtain poly(esther-ether) thermosets. The kinetics of the various elemental reactions, which take place during the curing process, was studied by means of isothermal curing in the FTIR spectrometer. The kinetic parameters were calculated by means of the isoconversional procedure and the best-fit kinetic model was determined with the so-called compensation effect (isokinetic relationship). The isothermal kinetic analysis was compared with that obtained by dynamic curing in DSC.

Kinetic study by FTIR and DSC on the cationic curing of a DGEBA/γ-valerolactone mixture with ytterbium triflate as an initiator

International Nuclear Information System (INIS)

Arasa, M.; Ramis, X.; Salla, J.M.; Mantecon, A.; Serra, A.

2008-01-01

A mixture of diglycidylether of bisphenol A (DGEBA) and γ-valerolactone (γ-VL) was cured in the presence of ytterbium triflate as an initiator to obtain poly(esther-ether) thermosets. The kinetics of the various elemental reactions, which take place during the curing process, was studied by means of isothermal curing in the FTIR spectrometer. The kinetic parameters were calculated by means of the isoconversional procedure and the best-fit kinetic model was determined with the so-called compensation effect (isokinetic relationship). The isothermal kinetic analysis was compared with that obtained by dynamic curing in DSC

Curing behavior and thermal properties of trifunctional epoxy resin cured by 4, 4’-diaminodiphenyl sulfone

Directory of Open Access Journals (Sweden)

2009-08-01

Full Text Available A novel trifunctional epoxy resin 4-(3, 3-dihydro-7-hydroxy-2, 4, 4-trimethyl-2H-1-benzopyran-2-yl-1, 3-benzenediol glycidyl (shorted as TMBPBTH-EPOXY was synthesized in our lab to improve thermal performance. Its curing behavior and performance were studied by using 4, 4′-diaminodiphenyl sulfone (DDS as hardener with the mass ratio of 100:41 of TMBPBTH-EPOXY and DDS. The curing activation energy was investigated by differential scanning calorimetry (DSC to be 64.0 kJ/mol estimated by Kissinger’s method and 68.7 kJ/mol estimated by Flynn-Wall-Ozawa method respectively. Thermogravimetric analyzer (TGA was used to investigate the thermal decomposition of cured compounds. It was found that when curing temperature was lower than 180°C, the thermal decomposition temperature increased with the rise of curing temperature and curing time. On the other hand, when the curing temperature was higher than 180°C, the thermal decomposition temperature went down instead with the increase of curing time that might be the over-crosslinking of TMBPBTH-EPOXY and DDS hardener. The glass transition temperature (Tg of cured TMBPBTH-EPOXY/DDS compound determined by dynamic mechanical thermal analysis (DMTA is 290.1°C.

Effect of gamma irradiation on mechanical and thermal properties of DGEBA/cycloaliphatic amine networks with potential for medical applications; Efeito da irradiacao gama nas propriedades mecanicas e termicas de redes DGEBA/amina cicloalifatica com potencial para aplicacoes medicas

Energy Technology Data Exchange (ETDEWEB)

Neves, Juliana C.; Silva, Glaura G., E-mail: glaura@qui.ufmg.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil); Mendes, Marcio W. Duarte; Bressiani, Ana H.; Bressiani, Jose C. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Garcia, Filiberto Gonzalez [Universidade Federal de Itajuba (UNIFEI), MG (Brazil)

2013-07-01

Two epoxy polymers based on diglycidyl ether of bisphenol A (DGEBA), cured with piperidine (Pip) and 4,4'-diamino-3,3'-dimethyldicyclohexylmethane (3DCM), were characterized before and after treatment with γ irradiation. The changes in the mechanical and thermal properties were studied by elastic modulus, glass transition temperature and degradation temperature measurements. A dose of 50 kGy of irradiation caused subtle variations in properties such as rigidity and stability, which are relevant from the fundamental point of view. The variations do not imply on negative impact when considering the stage of sterilization during the use of these systems as a biomaterial in the medical area. (author)

Curing agent for polyepoxides and epoxy resins and composites cured therewith. [preventing carbon fiber release

Science.gov (United States)

Serafini, T. T.; Delvigs, P.; Vannucci, R. D. (Inventor)

1981-01-01

A curing for a polyepoxide is described which contains a divalent aryl radical such as phenylene a tetravalent aryl radical such as a tetravalent benzene radical. An epoxide is cured by admixture with the curing agent. The cured epoxy product retains the usual properties of cured epoxides and, in addition, has a higher char residue after burning, on the order of 45% by weight. The higher char residue is of value in preventing release to the atmosphere of carbon fibers from carbon fiber-epoxy resin composites in the event of burning of the composite.

E-Beam-Cured Layered-Silicate and Spherical Silica Epoxy Nanocomposites (Preprint)

National Research Council Canada - National Science Library

Chen, Chenggang; Anderson, David P

2007-01-01

.... The nanofillers can be two dimensional (layered-silicate) and zero dimensional (spherical silica). Both the spherical silica epoxy nanocomposite and the layered-silicate epoxy nanocomposite can be cured to a high degree of curing...

Non-isothermal cure and exfoliation of tri-functional epoxy-clay nanocomposites

Directory of Open Access Journals (Sweden)

F. Shiravand

2015-08-01

Full Text Available The non-isothermal cure kinetics of polymer silicate layered nanocomposites based on a tri-functional epoxy resin has been investigated by differential scanning calorimetry. From an analysis of the kinetics as a function of the clay content, it can be concluded that the non-isothermal cure reaction can be considered to consist of four different processes: the reaction of epoxy groups with the diamine curing agent; an intra-gallery homopolymerisation reaction which occurs concurrently with the epoxy-amine reaction; and two extra-gallery homopolymerisation reactions, catalysed by the onium ion of the organically modified clay and by the tertiary amines resulting from the epoxy-amine reaction. The final nanostructure displays a similar quality of exfoliation as that observed for the isothermal cure of the same nanocomposite system. This implies that the intra-gallery reaction, which is responsible for the exfoliation, is not significantly inhibited by the extra-gallery epoxy-amine cross-linking reaction.

Evaluation of Out-of-Autoclave (OOA epoxy system

Directory of Open Access Journals (Sweden)

Fernanda Guilherme

Full Text Available Abstract Epoxy resins (EP usually cure in autoclave to minimize resin voids and to achieve the desired resin/fiber ratio. Cure parameters such as temperature, vacuum and pressure levels are controlled and monitored. Aiming time and cost optimization, new out-of-autoclave (OOA cure processes have been developed lately. This study evaluated the cure cycle and the effect of non-programmed interruptions in an OOA process. Fourier Transform Infrared spectroscopy (FT-IR results show similarities between the resin used and diglycidyl ether of bisphenol A (DGEBA and also that the curing system is composed of cyan and sulfur hardeners, codified in industry, as Components of #2511 Resin System. The cure cycle and its interruptions were simulated by dynamic-mechanical analysis (DMA. The samples obtained were evaluated by FT-IR and differential scanning calorimetry (DSC, whose results show that the degree of cure varying between 0.8 to 0.85 was achieved at 120 °C.

Development of radioactive standards in epoxy matrix for the control of quality of activimeters; Desenvolvimento de padroes radioativos em matriz epoxi para controle da qualidade de ativimetros

Energy Technology Data Exchange (ETDEWEB)

Fragoso, Maria da Conceicao de Farias; Monteiro, Luciane Carollyne de Oliveira Reis; Oliveira, Marcia Liane de, E-mail: mcfragoso@cnen.gov.br [Centro Regional de Ciencias Nucleares do Nordeste (CRCN-NE), Recife, PE (Brazil)

2016-07-01

In the present study, a new approach for development of the standards for positron emitting radionuclides in epoxy matrix is presented. Different formulations were prepared using epoxy resin (bisphenol A diglycidyl ether - DGEBA) and curing agents, to immobilize the radioactive material. The efficiency curve and standard sample methods were applied for activity determination of a long-lived positron emitter ({sup 22}Na). Satisfactory results were obtained in the 3{sup rd} combination. Thus, these radioactive standards can be used to evaluate the metrological behavior of the systems used for the measurement of the radiopharmaceuticals (activimeters) in the production centers and in nuclear medicine services. (author)

Preparations and applications in UV curing coatings of epoxy acrylates containing carboxyl

International Nuclear Information System (INIS)

Wu Yu Min

1999-01-01

This paper introduces preparations of epoxy acrylates containing carboxyl through the reactions of epoxy acrylates with butanedioic anhydride, pentanedioic anhydride, cis-butenedioic anhydride, phthalic anhydride, tetrabromophthalic anhydride and -tetrahydrophthalic anhydride. These epoxy acrylates containing carboxyl have been applied to UV-curing coatings and their effects on properties of UV-curing coatings have been studied

Compatibility of anhydride cured epoxies with hexanitroazobenzene (HNAB) and hexanitrostilbene (HNS)

International Nuclear Information System (INIS)

Massis, T.M.; Wischmann, K.B.

1985-01-01

The explosives HNAB (hexanitroazobenzene) and HNS (hexanitrostilbene) have compatibility problems with amine-cured epoxy systems. A program was instituted to find compatible polymeric substitutes for use with these explosives. These polymeric materials must have rigid structures after curing for both adhesive and encapsulant applications. A promising class of epoxy materials using anhydride curing agents with various catalysts to trigger the cure reaction were developed. These polymeric systems have very good compatibility with HNS. Of those tested with HNAB, the anhydride epoxy system that used uranyl nitrate as the catalyst was found to be marginally compatible while the others were incompatible. These results indicated further studies are needed. The CRT (chemical reactivity test) was used to evaluate the compatibility of these materials. 6 references, 2 figures, 5 tables

Epoxy-silicate nanocomposites: Cure monitoring and characterization

International Nuclear Information System (INIS)

Hussain, Farzana; Chen, Jihua; Hojjati, Mehdi

2007-01-01

Epoxy-clay nanocomposites were prepared with organically modified layered clay with varying clay contents (1-8 wt.%). Neat resin and nanocomposite were characterized using different techniques. At first, the effect of nanoclay concentration on the cure behaviour was investigated using an on-line dielectric cure monitoring technique. Differential scanning calorimetry (DSC) was used to verify the dielectric measurement results. Furthermore, mechanical and thermal properties were studied using tensile test and Dynamic Mechanical Analysis (DMA), respectively. Experimental results showed that properties of the epoxy were changed evidently because of the nanoclay loading. The tensile modulus of the nanocomposites increased by 47%, however, no improvement in tensile strength and glass transition temperature (T g ) was observed. Fracture surface of the tensile samples were analyzed by Scanning Electron Microscope (SEM). The nanocomposites structures were characterized with Wide Angle X-Ray Diffraction (WAXD) and Transmission Electron Microscopy (TEM), which revealed the intercalated morphology of clay layers in the epoxy resin systems

Morphological Study on Room-Temperature-Cured PMMA-Grafted Natural Rubber-Toughened Epoxy/Layered Silicate Nanocomposite

OpenAIRE

Yuhana, N. Y.; Ahmad, S.; Kamal, M. R.; Jana, S. C.; Bahri, A. R. Shamsul

2012-01-01

A morphological study was conducted on ternary systems containing epoxy, PMMA-grafted natural rubber, and organic chemically modified montmorillonite (Cloisite 30B). Optical microscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and wide-angle X-ray diffraction (WAXD) analysis were used. The following four materials were prepared at room temperature: cured unmodified epoxy, cured toughened epoxy, cured unmodified epoxy/Cloisite 3...

Positron annihilation lifetime spectroscopy study on the structural relaxation of phenylmethylsiloxane-modified epoxy hybrids at different aging temperatures

Energy Technology Data Exchange (ETDEWEB)

Hsu, Chia-Wen [Department of Chemical Engineering, National Tsing Hua University, Hsinchu, Taiwan (China); Material and Chemical Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan (China); Ma, Chen-Chi M., E-mail: ccma@che.nthu.edu.tw [Department of Chemical Engineering, National Tsing Hua University, Hsinchu, Taiwan (China); Tan, Chung-Sung [Department of Chemical Engineering, National Tsing Hua University, Hsinchu, Taiwan (China); Li, Hsun-Tien [Material and Chemical Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan (China)

2015-07-15

The cured network conformations and structural relaxation behaviours of the diglycidyl ether of bisphenol A (DGEBA)-methylhexahydrophthalic anhydride (MHHPA) modified with phenylmethylsiloxane-modified epoxy (PMSE) at different aging temperatures were studied using dynamic mechanical analysis (DMA) and positron annihilation lifetime spectroscopy (PALS). The DMA results revealed that the cured PMSE network can insert into the cured DGEBA network to form interpenetrating polymer networks (IPNs). The structural relaxation behaviours of DGEBA–PMSE-0.4 produced using DGEBA, PMSE, and MHHPA at a ratio of 0.6:0.4:1 by equivalent weight were studied using PALS at 150 °C and 55 °C. The aging-induced free volume relaxation parameters of DGEBA–PMSE-0.4 at 150 °C and 55 °C were investigated using the double additive exponential model and the Kohlrausch–Williams–Watts exponential model. For double additive exponential model, only one relaxation time (ζ) of 584.5 h was found at 150 °C; By contrast, there were two separate relaxation times of 37.4 h (ζ{sub 1}) and 753.6 h (ζ{sub 2}) at 55 °C. The ζ{sub 1} of the IPNs hybrid can be attributed to the network relaxation of PMSE, and the ζ{sub 2} can be attributed to the network relaxation of DGEBA at 55 °C. The results suggested the double additive exponential model can effectively predict DGEBA–PMSE hybrid relaxation behaviours. - Highlights: • The cured network conformations of DGEBA–PMSE hybrids were studied using DMA. • The structural relaxation behaviours of DGEBA–PMSE hybrids were studied using PALS. • The cured DGEBA–PMSE hybrids were interpenetrating polymer networks (IPNs). • PALS studies provided a quantitative demonstration of relaxation behaviours. • Double additive exponential model effectively predicted the relaxation times of hybrids.

Positron annihilation lifetime spectroscopy study on the structural relaxation of phenylmethylsiloxane-modified epoxy hybrids at different aging temperatures

International Nuclear Information System (INIS)

Hsu, Chia-Wen; Ma, Chen-Chi M.; Tan, Chung-Sung; Li, Hsun-Tien

2015-01-01

The cured network conformations and structural relaxation behaviours of the diglycidyl ether of bisphenol A (DGEBA)-methylhexahydrophthalic anhydride (MHHPA) modified with phenylmethylsiloxane-modified epoxy (PMSE) at different aging temperatures were studied using dynamic mechanical analysis (DMA) and positron annihilation lifetime spectroscopy (PALS). The DMA results revealed that the cured PMSE network can insert into the cured DGEBA network to form interpenetrating polymer networks (IPNs). The structural relaxation behaviours of DGEBA–PMSE-0.4 produced using DGEBA, PMSE, and MHHPA at a ratio of 0.6:0.4:1 by equivalent weight were studied using PALS at 150 °C and 55 °C. The aging-induced free volume relaxation parameters of DGEBA–PMSE-0.4 at 150 °C and 55 °C were investigated using the double additive exponential model and the Kohlrausch–Williams–Watts exponential model. For double additive exponential model, only one relaxation time (ζ) of 584.5 h was found at 150 °C; By contrast, there were two separate relaxation times of 37.4 h (ζ 1 ) and 753.6 h (ζ 2 ) at 55 °C. The ζ 1 of the IPNs hybrid can be attributed to the network relaxation of PMSE, and the ζ 2 can be attributed to the network relaxation of DGEBA at 55 °C. The results suggested the double additive exponential model can effectively predict DGEBA–PMSE hybrid relaxation behaviours. - Highlights: • The cured network conformations of DGEBA–PMSE hybrids were studied using DMA. • The structural relaxation behaviours of DGEBA–PMSE hybrids were studied using PALS. • The cured DGEBA–PMSE hybrids were interpenetrating polymer networks (IPNs). • PALS studies provided a quantitative demonstration of relaxation behaviours. • Double additive exponential model effectively predicted the relaxation times of hybrids

Preparation of epoxy/zirconia hybrid materials via in situ polymerization using zirconium alkoxide coordinated with acid anhydride

International Nuclear Information System (INIS)

Ochi, Mitsukazu; Nii, Daisuke; Harada, Miyuki

2011-01-01

Highlights: → Novel epoxy/zirconia hybrid materials were synthesized via in situ polymerization using zirconium alkoxide coordinated with acid anhydride. → The half-ester compound of acid anhydride desorbed from zirconium played as curing agent of epoxy resin. → The zirconia was uniformly dispersed in the epoxy matrix on the nanometer or sub-nanometer scale by synchronizing the epoxy curing and sol-gel reactions. → The refractive indices of the hybrid materials significantly improved with an increase in the zirconia content. - Abstract: Novel epoxy/zirconia hybrid materials were synthesized using a bisphenol A epoxy resin (diglycidyl ether of bisphenol A; DGEBA), zirconium(IV)-n-propoxide (ZTNP), and hexahydrophthalic anhydride (HHPA) via in situ polymerization. HHPA played two roles in this system: it acted as a modifier to control the hydrolysis and condensation reactions of zirconium alkoxide and also as a curing agent - the half-ester compound of HHPA desorbed from zirconium reacted with the epoxy resin to form the epoxy network. As a result, both the sol-gel reaction and epoxy curing occurred simultaneously in a homogeneous solution, and organic-inorganic hybrid materials were readily obtained. Further, the zirconia produced by the in situ polymerization was uniformly dispersed in the epoxy matrix on the nanometer or sub-nanometer scale; thus, hybrid materials that exhibited excellent optical transparency were obtained. Furthermore, the heat resistance of the hybrid materials could be improved by hybridization with zirconia. And, the refractive indices of the hybrid materials significantly improved with an increase in the zirconia content.

Contact allergy to epoxy (meth)acrylates.

Science.gov (United States)

Aalto-Korte, Kristiina; Jungewelter, Soile; Henriks-Eckerman, Maj-Len; Kuuliala, Outi; Jolanki, Riitta

2009-07-01

Contact allergy to epoxy (meth)acrylates, 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy) phenyl]propane (bis-GMA), 2,2-bis[4-(2-hydroxy-3-acryloxypropoxy)phenyl]-propane (bis-GA), 2,2-bis[4-(methacryl-oxyethoxy)phenyl] propane (bis-EMA), 2,2-bis[4-(methacryloxy)phenyl]-propane (bis-MA), and glycidyl methacrylate (GMA) is often manifested together with contact allergy to diglycidyl ether of bisphenol A (DGEBA) epoxy resin. To analyse patterns of concomitant allergic reactions to the five epoxy (meth)acrylates in relation to exposure. We reviewed the 1994-2008 patch test files at the Finnish Institute of Occupational Health (FIOH) for reactions to the five epoxy (meth)acrylates, and examined the patients' medical records for exposure. Twenty-four patients had an allergic reaction to at least one of the studied epoxy (meth)acrylates, but specific exposure was found only in five patients: two bis-GMA allergies from dental products, two bis-GA allergies from UV-curable printing inks, and one bis-GA allergy from an anaerobic glue. Only 25% of the patients were negative to DGEBA epoxy resin. The great majority of allergic patch test reactions to bis-GMA, bis-GA, GMA and bis-EMA were not associated with specific exposure, and cross-allergy to DGEBA epoxy resin remained a probable explanation. However, independent reactions to bis-GA indicated specific exposure. Anaerobic sealants may induce sensitization not only to aliphatic (meth)acrylates but also to aromatic bis-GA.

Realtime 3D stress measurement in curing epoxy packaging

DEFF Research Database (Denmark)

Richter, Jacob; Hyldgård, A.; Birkelund, Karen

2007-01-01

This paper presents a novel method to characterize stress in microsystem packaging. A circular p-type piezoresistor is implemented on a (001) silicon chip. We use the circular stress sensor to determine the packaging induced stress in a polystyrene tube filled with epoxy. The epoxy curing process...

Development of radioactive standards in epoxy matrix for the control of quality of activimeters

International Nuclear Information System (INIS)

Fragoso, Maria da Conceicao de Farias; Monteiro, Luciane Carollyne de Oliveira Reis; Oliveira, Marcia Liane de

2016-01-01

In the present study, a new approach for development of the standards for positron emitting radionuclides in epoxy matrix is presented. Different formulations were prepared using epoxy resin (bisphenol A diglycidyl ether - DGEBA) and curing agents, to immobilize the radioactive material. The efficiency curve and standard sample methods were applied for activity determination of a long-lived positron emitter ("2"2Na). Satisfactory results were obtained in the 3"r"d combination. Thus, these radioactive standards can be used to evaluate the metrological behavior of the systems used for the measurement of the radiopharmaceuticals (activimeters) in the production centers and in nuclear medicine services. (author)

Synthesis, Characterization and Curing Studies of Thermosetting Epoxy Resin with Amines

International Nuclear Information System (INIS)

Lakshmi, B.; Mahendra, K. N.; Shivananda, K. N.

2010-01-01

A new hybrid thermosetting maleimido epoxy compound 4-(N-maleimidophenyl) glycidylether (N-MPGE) is prepared by reacting N-(4-hydroxyphenyl) maleimide (HPM) with Epichlorohydrin by using benzyltrimethylammonium chloride as a catalyst. The resulting compound possesses both the oxirane ring and maleimide group. The curing reaction of these maleimidophenyl glycidylether epoxy compound (N-MPGE) with amines as curing agents such as ethylendiamine (EDA), diethylentriamine (DETA) and triethylenetetramine (TETA), aminoethylpiperazine (AEP) and isophoronediamine, IPDA), are studied. Incorporation of maleimide groups in the epichlorohydrin provides cyclic imide structure and high cross-linking density to the cured resins. The cured samples exhibited good thermal stability, excellent chemical (acid/alkali/solvent) and water absorption resistance. Morphological studies by the SEM technique further confirmed the phase homogeneity net work of the cured systems

Synthesis, Characterization and Curing Studies of Thermosetting Epoxy Resin with Amines

Energy Technology Data Exchange (ETDEWEB)

Lakshmi, B.; Mahendra, K. N. [Bangalore University, Bangalore (India); Shivananda, K. N. [Technion - Israel Institute of Technology, Haifa (Israel)

2010-08-15

A new hybrid thermosetting maleimido epoxy compound 4-(N-maleimidophenyl) glycidylether (N-MPGE) is prepared by reacting N-(4-hydroxyphenyl) maleimide (HPM) with Epichlorohydrin by using benzyltrimethylammonium chloride as a catalyst. The resulting compound possesses both the oxirane ring and maleimide group. The curing reaction of these maleimidophenyl glycidylether epoxy compound (N-MPGE) with amines as curing agents such as ethylendiamine (EDA), diethylentriamine (DETA) and triethylenetetramine (TETA), aminoethylpiperazine (AEP) and isophoronediamine, IPDA), are studied. Incorporation of maleimide groups in the epichlorohydrin provides cyclic imide structure and high cross-linking density to the cured resins. The cured samples exhibited good thermal stability, excellent chemical (acid/alkali/solvent) and water absorption resistance. Morphological studies by the SEM technique further confirmed the phase homogeneity net work of the cured systems.

Preparation of low viscosity epoxy acrylic acid photopolymer prepolymer in light curing system

Science.gov (United States)

Li, P.; Huang, J. Y.; Liu, G. Z.

2018-01-01

With the integration and development of materials engineering, applied mechanics, automatic control and bionics, light cured composite has become one of the most favourite research topics in the field of materials and engineering at home and abroad. In the UV curing system, the prepolymer and the reactive diluent form the backbone of the cured material together. And they account for more than 90% of the total mass. The basic properties of the cured product are mainly determined by the prepolymer. A low viscosity epoxy acrylate photosensitive prepolymer with a viscosity of 6800 mPa • s (25 °C ) was obtained by esterification of 5 hours with bisphenol A epoxy resin with high epoxy value and low viscosity.

Effect of aluminium particles on mechanical and morphological properties of epoxy nanocomposites

Directory of Open Access Journals (Sweden)

Bello Sefiu A.

2017-01-01

Full Text Available Bumper is a front or rear part of automobiles. It is designed and shaped to be impact absorbing and protecting automobiles from damage in low impact collisions. Initially, they were made from heavy steels, increasing the weight of automobiles and fuel consumption. Also, high impacts of steel bumpers on pedestrians during accidental collision cause fatalities and or disabilities. An effort to enhance fuel efficiency, safety, freedom of design and shape detailing, heavy alloys for automobile applications are now being replaced with polymeric composites. Aluminium micro particles and nanoparticles were prepared from aluminium cans through sand casting, lathe machine spinning, and ball milling techniques. Both types of aluminium particles were incorporated into a mixture of diglycidyl ether of bisphenol A (DGEBA, epoxy resin cured with amine base hardener (ABH. Phases of the epoxy polymer and composites were identified using Xray Diffraction (XRD. Spatial arrangement of the phases within the matrix and their elemental composition were examined using Scanning Electron Microscope with attached energy dispersive X-ray spectroscopy (SEM/EDX. Tensile, impact and micro hardness tests were conducted on the prepared epoxy/aluminium composites. Results of the XRD showed the presence of aluminium compounds/phases due to chemical reactions between aluminium particles and DGEBA/ABH system. SEM confirmed a homogeneous distribution of the phases within the epoxy matrix, and that there is a strong adhesion between the epoxy matrix and aluminium particles. Correlation between the mechanical properties of the prepared nanocomposite and the procured bumper materials exhibited a fair suitability of the prepared nanocomposites for automobile applications.

Kinetic analysis by DSC of the cationic curing of mixtures of DGEBA and 6,6-dimethyl (4,8-dioxaspiro[2.5]octane-5,7-dione)

Energy Technology Data Exchange (ETDEWEB)

Gonzalez, Lidia [Departament de Quimica Analitica i Quimica Organica, Universitat Rovira i Virgili, C/Marcelli Domingo s/n, 43007 Tarragona (Spain); Ramis, Xavier [Laboratori de Termodinamica, ETSEIB, Universitat Politecnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain); Salla, Josep Maria [Laboratori de Termodinamica, ETSEIB, Universitat Politecnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain)], E-mail: salla@mmt.upc.edu; Mantecon, Ana; Serra, Angels [Departament de Quimica Analitica i Quimica Organica, Universitat Rovira i Virgili, C/Marcelli Domingo s/n, 43007 Tarragona (Spain)

2007-11-25

The kinetics of the thermal cationic cure reaction of mixtures in different proportions of diglycidylether of bisphenol A (DGEBA) with 6,6-dimethyl (4,8-dioxaspiro[2.5]octane-5,7-dione) (MCP) initiated by ytterbium or lanthanum triflates or using a conventional initiator, BF{sub 3}.MEA was investigated. The non-isothermal differential scanning calorimetry (DSC) experiments at a controlled heating rate was used for obtaining the kinetic parameters of the reactive systems. BF{sub 3}.MEA and lanthanide triflates initiated curing systems follow a complete different kinetic model. Among lanthanide triflates, ytterbium is the most active initiator.

Kinetic analysis by DSC of the cationic curing of mixtures of DGEBA and 6,6-dimethyl (4,8-dioxaspiro[2.5]octane-5,7-dione)

International Nuclear Information System (INIS)

Gonzalez, Lidia; Ramis, Xavier; Salla, Josep Maria; Mantecon, Ana; Serra, Angels

2007-01-01

The kinetics of the thermal cationic cure reaction of mixtures in different proportions of diglycidylether of bisphenol A (DGEBA) with 6,6-dimethyl (4,8-dioxaspiro[2.5]octane-5,7-dione) (MCP) initiated by ytterbium or lanthanum triflates or using a conventional initiator, BF 3 .MEA was investigated. The non-isothermal differential scanning calorimetry (DSC) experiments at a controlled heating rate was used for obtaining the kinetic parameters of the reactive systems. BF 3 .MEA and lanthanide triflates initiated curing systems follow a complete different kinetic model. Among lanthanide triflates, ytterbium is the most active initiator

Cure Kinetics of Epoxy Nanocomposites Affected by MWCNTs Functionalization: A Review

Science.gov (United States)

Saeb, Mohammad Reza; Bakhshandeh, Ehsan; Khonakdar, Hossein Ali; Mäder, Edith; Scheffler, Christina; Heinrich, Gert

2013-01-01

The current paper provides an overview to emphasize the role of functionalization of multiwalled carbon nanotubes (MWCNTs) in manipulating cure kinetics of epoxy nanocomposites, which itself determines ultimate properties of the resulting compound. In this regard, the most commonly used functionalization schemes, that is, carboxylation and amidation, are thoroughly surveyed to highlight the role of functionalized nanotubes in controlling the rate of autocatalytic and vitrification kinetics. The current literature elucidates that the mechanism of curing in epoxy/MWCNTs nanocomposites remains almost unaffected by the functionalization of carbon nanotubes. On the other hand, early stage facilitation of autocatalytic reactions in the presence of MWCNTs bearing amine groups has been addressed by several researchers. When carboxylated nanotubes were used to modify MWCNTs, the rate of such reactions diminished as a consequence of heterogeneous dispersion within the epoxy matrix. At later stages of curing, however, the prolonged vitrification was seen to be dominant. Thus, the type of functional groups covalently located on the surface of MWCNTs directly affects the degree of polymer-nanotube interaction followed by enhancement of curing reaction. Our survey demonstrated that most widespread efforts ever made to represent multifarious surface-treated MWCNTs have not been directed towards preparation of epoxy nanocomposites, but they could result in property synergism. PMID:24348181

Morphological Study on Room-Temperature-Cured PMMA-Grafted Natural Rubber-Toughened Epoxy/Layered Silicate Nanocomposite

Directory of Open Access Journals (Sweden)

N. Y. Yuhana

2012-01-01

Full Text Available A morphological study was conducted on ternary systems containing epoxy, PMMA-grafted natural rubber, and organic chemically modified montmorillonite (Cloisite 30B. Optical microscopy, transmission electron microscopy (TEM, scanning electron microscopy (SEM, energy dispersive X-ray (EDX, and wide-angle X-ray diffraction (WAXD analysis were used. The following four materials were prepared at room temperature: cured unmodified epoxy, cured toughened epoxy, cured unmodified epoxy/Cloisite 30B nanocomposites, and cured toughened epoxy/Cloisite 30B nanocomposites. Mixing process was performed by mechanical stirring. Poly(etheramine was used as the curing agent. The detailed TEM images revealed co-continuous and dispersed spherical rubber in the epoxy-rubber blend, suggesting a new proposed mechanism of phase separation. High-magnification TEM analysis showed good interactions between rubber and Cloisite 30B in the ternary system. Also, it was found that rubber particles could enhance the separation of silicates layers. Both XRD and TEM analyses confirmed that the intercalation of Cloisite 30B was achieved. No distinct exfoliated silicates were observed by TEM. Aggregates of layered silicates (tactoids were observed by SEM and EDX, in addition to TEM at low magnification. EDX analysis confirmed the presence of organic and inorganic elements in the binary and ternary epoxy systems containing Cloisite 30B.

Syringaresinol: A Renewable and Safer Alternative to Bisphenol A for Epoxy-Amine Resins.

Science.gov (United States)

Janvier, Marine; Hollande, Louis; Jaufurally, Abdus Samad; Pernes, Miguel; Ménard, Raphaël; Grimaldi, Marina; Beaugrand, Johnny; Balaguer, Patrick; Ducrot, Paul-Henri; Allais, Florent

2017-02-22

A renewable bisepoxide, SYR-EPO, was prepared from syringaresinol, a naturally occurring bisphenol deriving from sinapic acid, by using a chemo-enzymatic synthetic pathway. Estrogenic activity tests revealed no endocrine disruption for syringaresinol. Its glycidylation afforded SYR-EPO with excellent yield and purity. This biobased, safe epoxy precursor was then cured with conventional and renewable diamines for the preparation of epoxy-amine resins. The resulting thermosets were thermally and mechanically characterized. Thermal analyses of these new resins showed excellent thermal stabilities (T d5 % =279-309 °C) and T g ranging from 73 to 126 °C, almost reaching the properties of those obtained with the diglycidylether of bisphenol A (DGEBA), extensively used in the polymer industry (T d5 % =319 °C and T g =150 °C for DGEBA/isophorone diamine resins). Degradation studies in NaOH and HCl aqueous solutions also highlighted the robustness of the syringaresinol-based resins, similar to bisphenol A (BPA). All these results undoubtedly confirmed the potential of syringaresinol as a greener and safer substitute for BPA. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Strain Rate Dependence of Compressive Yield and Relaxation in DGEBA Epoxies

Science.gov (United States)

Arechederra, Gabriel K.; Reprogle, Riley C.; Clarkson, Caitlyn M.; McCoy, John D.; Kropka, Jamie M.; Long, Kevin N.; Chambers, Robert S.

2015-03-01

The mechanical response in uniaxial compression of two diglycidyl ether of bisphenol-A epoxies were studied. These were 828DEA (Epon 828 cured with diethanolamine (DEA)) and 828T403 (Epon 828 cured with Jeffamine T-403). Two types of uniaxial compression tests were performed: A) constant strain rate compression and B) constant strain rate compression followed by a constant strain relaxation. The peak (yield) stress was analyzed as a function of strain rate from Eyring theory for activation volume. Runs at different temperatures permitted the construction of a mastercurve, and the resulting shift factors resulted in an activation energy. Strain and hold tests were performed for a low strain rate where a peak stress was lacking and for a higher strain rate where the peak stress was apparent. Relaxation from strains at different places along the stress-strain curve was tracked and compared. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Thermoset Blends of an Epoxy Resin and Polydicyclopentadiene

Energy Technology Data Exchange (ETDEWEB)

Rohde, Brian J.; Le, Kim Mai; Krishnamoorti, Ramanan; Robertson, Megan L.

2016-12-13

The mechanical properties of two chemically distinct and complementary thermoset polymers were manipulated through development of thermoset blends. The thermoset blend system was composed of an anhydride-cured diglycidyl ether of bisphenol A (DGEBA)-based epoxy resin, contributing high tensile strength and modulus, and polydicyclopentadiene (PDCPD), which has a higher toughness and impact strength as compared to other thermoset polymers. Ultra-small-angle and small-angle X-ray scattering analysis explored the morphology of concurrently cured thermoset blends, revealing a macroscopically phase separated system with a surface fractal structure across blended systems of varying composition. The epoxy resin rich and PDCPD rich phases exhibited distinct glass transitions (Tg’s): the Tg observed at higher temperature was associated with the epoxy resin rich phase and was largely unaffected by the presence of PDCPD, whereas the PDCPD rich phase Tg systematically decreased with increasing epoxy resin content due to inhibition of dicyclopentadiene ring-opening metathesis polymerization. The mechanical properties of these phase-separated blends were in reasonable agreement with predictions by the rule of mixtures for the blend tensile strength, modulus, and fracture toughness. Scanning electron microscopy analysis of the tensile and fracture specimen fracture surfaces showed an increase in energy dissipation mechanisms, such as crazing, shear banding, and surface roughness, as the fraction of the more ductile component, PDPCD, increased. These results present a facile method to tune the mechanical properties of a toughened thermoset network, in which the high modulus and tensile strength of the epoxy resin can be largely retained at high epoxy resin content in the blend, while increasing the fracture toughness.

Microwave and thermal curing of an epoxy resin for microelectronic applications

Energy Technology Data Exchange (ETDEWEB)

Johnston, K. [Institute of Chemical Sciences, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom); Pavuluri, S.K.; Leonard, M.T.; Desmulliez, M.P.Y. [MIcroSystems Engineering Centre (MISEC), Institute of Signals, Sensors and Systems, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom); Arrighi, V., E-mail: v.arrighi@hw.ac.uk [Institute of Chemical Sciences, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom)

2015-09-20

Graphical abstract: - Highlights: • Thermal and microwave curing of a commercial epoxy resin EO1080 are compared. • Microwave curing increases cure rate and does not adversely affect properties. • The curing of EO1080 is generally autocatalytic but deviates at high conversion. • Microwave radiation has a more complex effect on curing kinetics. - Abstract: Microwave curing of thermosetting polymers has a number of advantages to natural or thermal oven curing and is considered a cost-effective alternative. Here we present a detailed study of a commercially available epoxy resin, EO1080. Samples that are thermally cured are compared to curing using a recently developed modular microwave processing system. For commercial purposes it is crucial to demonstrate that microwave curing does not adversely affect the thermal and chemical properties of the material. Therefore, the kinetics of cure and various post cure properties of the resin are investigated. Attenuated Total Reflectance Fourier-Transform Infrared (ATR-FTIR) analysis shows no significant difference between the conventionally and microwave cured samples. Differential scanning calorimetry (DSC) is used to monitor the kinetics of the curing reaction, as well as determine the thermal and ageing properties of the material. As expected, the rate of curing is higher when using microwave energy and we attempt to quantify differences compared to conventional thermal curing. No change in glass transition temperature (T{sub g}) is observed. For the first time, enthalpy relaxation measurements performed on conventional and microwave cured samples are reported and these indicate similar ageing properties at any given temperature under T{sub g}.

Microwave and thermal curing of an epoxy resin for microelectronic applications

International Nuclear Information System (INIS)

Johnston, K.; Pavuluri, S.K.; Leonard, M.T.; Desmulliez, M.P.Y.; Arrighi, V.

2015-01-01

Graphical abstract: - Highlights: • Thermal and microwave curing of a commercial epoxy resin EO1080 are compared. • Microwave curing increases cure rate and does not adversely affect properties. • The curing of EO1080 is generally autocatalytic but deviates at high conversion. • Microwave radiation has a more complex effect on curing kinetics. - Abstract: Microwave curing of thermosetting polymers has a number of advantages to natural or thermal oven curing and is considered a cost-effective alternative. Here we present a detailed study of a commercially available epoxy resin, EO1080. Samples that are thermally cured are compared to curing using a recently developed modular microwave processing system. For commercial purposes it is crucial to demonstrate that microwave curing does not adversely affect the thermal and chemical properties of the material. Therefore, the kinetics of cure and various post cure properties of the resin are investigated. Attenuated Total Reflectance Fourier-Transform Infrared (ATR-FTIR) analysis shows no significant difference between the conventionally and microwave cured samples. Differential scanning calorimetry (DSC) is used to monitor the kinetics of the curing reaction, as well as determine the thermal and ageing properties of the material. As expected, the rate of curing is higher when using microwave energy and we attempt to quantify differences compared to conventional thermal curing. No change in glass transition temperature (T g ) is observed. For the first time, enthalpy relaxation measurements performed on conventional and microwave cured samples are reported and these indicate similar ageing properties at any given temperature under T g

Effects of graphene oxides on the cure behaviors of a tetrafunctional epoxy resin

Directory of Open Access Journals (Sweden)

2011-09-01

Full Text Available The influence of graphene oxides (GOs on the cure behavior and thermal stability of a tetrafunctional tetraglycidyl-4,4’-diaminodiphenylmethane cured with 4,4’-diaminodiphenylsulfone was investigated by using dynamic differential scanning calorimetry (DSC and thermogravimetric analysis (TGA. The dynamic DSC results showed that the initial reaction temperature and exothermal peak temperature decreased with the increase of GO contents. Furthermore, the addition of GO increased the enthalpy of epoxy cure reaction. Results from activation energy method showed that activation energies of GO/epoxy nanocomposites greatly decreased with the GO content in the latter stage, indicating that GOs significantly hindered the occurrence of vitrification. The oxygen functionalities, such as hydroxyl and carboxyl groups, on the surface of GOs acted as catalysts and facilitated the curing reaction and the catalytic effect increased with the GO contents. TGA results revealed that the addition of GOs decreased the thermal stability of epoxy.

Effect of addition of Ag nano powder on mechanical properties of epoxy/polyaminoamide adduct coatings filled with conducting polymer

Energy Technology Data Exchange (ETDEWEB)

Samad, Ubair Abdus [Department of Chemical Engineering, College of Engineering, King Saud University, P. O. Box 800, Riyadh 11421 (Saudi Arabia); Center of excellence for research in engineering materials (CEREM), Advance Manufacturing Institute, King Saud University, P. O. Box 800, Riyadh 11421 (Saudi Arabia); Khan, Rawaiz [Department of Chemical Engineering, College of Engineering, King Saud University, P. O. Box 800, Riyadh 11421 (Saudi Arabia); Alam, Mohammad Asif [Center of excellence for research in engineering materials (CEREM), Advance Manufacturing Institute, King Saud University, P. O. Box 800, Riyadh 11421 (Saudi Arabia); Al-Othman, Othman Y. [Department of Chemical Engineering, College of Engineering, King Saud University, P. O. Box 800, Riyadh 11421 (Saudi Arabia); Deanship of Graduate Studies, The Saudi Electric University, P. O. Box 93499, Riyadh 11673 (Saudi Arabia); Al-Zahrani, Saeed M. [Center of excellence for research in engineering materials (CEREM), Advance Manufacturing Institute, King Saud University, P. O. Box 800, Riyadh 11421 (Saudi Arabia); SABIC Polymer Research Center (SPRC) and department of chemical engineering, college of engineering, King Saud University, P. O. Box 800, Riyadh 11421 (Saudi Arabia)

2015-05-22

In this study the effect of Ag Nano powder on mechanical properties of epoxy coatings filled with optimized ratio of conducting polymers (Polyaniline and Polyppyrole) was evaluated. Bisphenol A diglycidyl ether epoxy resin (DGEBA) along with polyaminoamide adduct (ARADUR 3282-1 BD) is used as curing agent under optimized stoichiometry values. Curing is performed at room temperature with different percentages of Nano filler. Glass and steel panels were used as coating substrate. Bird applicator was used to coat the samples in order to obtain thin film with wet film thickness (WFT) of about 70-90 µm. The samples were kept in dust free environment for about 7 days at room temperature for complete curing. The coated steel panels were used to evaluate the mechanical properties of coating such as hardness, scratch and impact tests whereas coated glass panels were used for measuring pendulum hardness of the coatings. To check the dispersion and morphology of Nano filler in epoxy matrix scanning electron microscopy (SEM) was used in addition Nano indentation was also performed to observe the effect of Nano filler on modulus of elasticity and hardness at Nano scale.

Effect of addition of Ag nano powder on mechanical properties of epoxy/polyaminoamide adduct coatings filled with conducting polymer

International Nuclear Information System (INIS)

Samad, Ubair Abdus; Khan, Rawaiz; Alam, Mohammad Asif; Al-Othman, Othman Y.; Al-Zahrani, Saeed M.

2015-01-01

In this study the effect of Ag Nano powder on mechanical properties of epoxy coatings filled with optimized ratio of conducting polymers (Polyaniline and Polyppyrole) was evaluated. Bisphenol A diglycidyl ether epoxy resin (DGEBA) along with polyaminoamide adduct (ARADUR 3282-1 BD) is used as curing agent under optimized stoichiometry values. Curing is performed at room temperature with different percentages of Nano filler. Glass and steel panels were used as coating substrate. Bird applicator was used to coat the samples in order to obtain thin film with wet film thickness (WFT) of about 70-90 µm. The samples were kept in dust free environment for about 7 days at room temperature for complete curing. The coated steel panels were used to evaluate the mechanical properties of coating such as hardness, scratch and impact tests whereas coated glass panels were used for measuring pendulum hardness of the coatings. To check the dispersion and morphology of Nano filler in epoxy matrix scanning electron microscopy (SEM) was used in addition Nano indentation was also performed to observe the effect of Nano filler on modulus of elasticity and hardness at Nano scale

Effect of addition of Ag nano powder on mechanical properties of epoxy/polyaminoamide adduct coatings filled with conducting polymer

Science.gov (United States)

Samad, Ubair Abdus; Khan, Rawaiz; Alam, Mohammad Asif; Al-Othman, Othman Y.; Al-Zahrani, Saeed M.

2015-05-01

In this study the effect of Ag Nano powder on mechanical properties of epoxy coatings filled with optimized ratio of conducting polymers (Polyaniline and Polyppyrole) was evaluated. Bisphenol A diglycidyl ether epoxy resin (DGEBA) along with polyaminoamide adduct (ARADUR 3282-1 BD) is used as curing agent under optimized stoichiometry values. Curing is performed at room temperature with different percentages of Nano filler. Glass and steel panels were used as coating substrate. Bird applicator was used to coat the samples in order to obtain thin film with wet film thickness (WFT) of about 70-90 µm. The samples were kept in dust free environment for about 7 days at room temperature for complete curing. The coated steel panels were used to evaluate the mechanical properties of coating such as hardness, scratch and impact tests whereas coated glass panels were used for measuring pendulum hardness of the coatings. To check the dispersion and morphology of Nano filler in epoxy matrix scanning electron microscopy (SEM) was used in addition Nano indentation was also performed to observe the effect of Nano filler on modulus of elasticity and hardness at Nano scale.

Epoxy Nanocomposites - Curing Rheokinetics, Wetting and Adhesion to Fibers

International Nuclear Information System (INIS)

Ilyin, S. O.; Kotomin, S. V.; Kulichikhin, V. G.

2010-01-01

Epoxy nanocomposites considered as challenging polymeric matrix for advanced reinforced plastics. Nanofillers change rheokinetics of epoxy resin curing, affect wetting and adhesion to aramid and carbon fibers. In all cases extreme dependence of adhesive strength vs filler content in the binder was observed. New experimental techniques were developed to study wettability and fiber-matrix adhesion interaction, using yarn penetration path length, aramid fiber knot pull-up test and electrical admittance of the fracture surface of CFRP.

Estudo da reação entre polietileno glicol e resina epoxídica na presença de N,N-dimetilbenzilamina Study of the reaction between polyethylene glycol and epoxy resins Using N,N-dimethylbenzylamine as catalyst

Directory of Open Access Journals (Sweden)

Mario Zacharuk

2011-01-01

Full Text Available Neste trabalho foi estudada a reação entre polietileno glicol (PEG e uma resina epoxídica à base de diglicidil éter de bisfenol A (DGEBA, na presença de N,N-dimetilbenzilamina (DMBA, sendo os produtos desta reação avaliados por espectroscopia no infravermelho (FTIR, espectroscopia de ressonância magnética nuclear de próton (RMN-1H e medidas de viscosidade cone-prato. Amostras curadas com um endurecedor à base de poliamina foram também submetidas a ensaios de tração e calorimetria exploratória diferencial (DSC. Os resultados das análises de viscosidade, FTIR e RMN (1H confirmaram a ocorrência da reação entre grupos epóxi do DGEBA e grupos hidroxila do PEG na presença de DMBA, a 100 ºC. As análises de DSC e os ensaios de tração dos sistemas curados mostram que a reação de DGEBA com PEG gera um material com temperatura de transição vítrea (Tg significativamente menor, em conjunto com o aumento da deformação na ruptura e decréscimo do modulo de elasticidade, quando comparados ao sistema epoxídico de referência (DGEBA.In this work the reaction of polyethylene glycol (PEG and epoxy resin (BADGE in the presence of N,N-dimethylbenzylamine (DMBA was studied. The reaction products were evaluated by infrared spectroscopy (FTIR, nuclear magnetic resonance spectroscopy (NMR and viscosity measurements. Samples cured with a polyamine-based hardener were also submitted to tensile tests and differential scanning calorimetry (DSC. The results of the viscosity analyses, FTIR and RMN (¹H confirmed the reaction between DGEBA epoxy groups and PEG hydroxyl groups in the presence of DMBA, at 100 ºC. DSC analyses and tensile tests of cured systems showed that the reaction of DGEBA with PEG leads to a reduction of Tg, generating a more flexible material.

The influence of montmorillonite content on the kinetics of curing of epoxy nanocomposites

Directory of Open Access Journals (Sweden)

Jovičić Mirjana C.

2012-01-01

Full Text Available In this work, the attention was paid at the investigation of montmorillonite dispersion in epoxy/amine systems due to improved final properties of the nanocomposites. The influence of different montmorillonite content on the kinetics of curing of epoxy/Jeffamine D-230 systems was followed by differential scanning calorimetry (DSC. The curing of epoxy nanocomposites was performed using dynamic regime at three different heating rates: 5, 10 and 20°C/min. Three isoconversional methods were applied: two integral (Ozawa-Flynn-Wall and Kissinger-Akahira-Sunose methods and one differential (Friedman method. The presence of montmorillonite (MMT causes the beginning of curing at lower temperatures. The shape of the DSC curves has been changed by the addition of MMT, supporting the hypothesis of a change in the reaction mechanism. For hybrids with 3 and 5 wt.% of MMT, the Eα dependence is very similar to those found for the reference system (epoxy/Jeffamine D-230 for the curing degree less than 60%. The hybrid with 10 wt.% of MMT has lower energy activation in regard to the referent system without montmorillonite. Greater differences are observed in the second part of the reaction, where it is known that the curing process is more controlled by diffusion (α>0.60. The Ea value increases at the end of the reaction (α→1, which was observed for all systems, and is more pronounced in the presence of montmorillonite. [Projekat Ministarstva nauke Republike Srbije, br. III45022

Evolution of microstructure of epoxy coating during UV degradation progress studied by slow positron annihilation spectroscopy and electrochemical impedance spectroscopy

International Nuclear Information System (INIS)

Liu, Fuwei; Yin, Mingxi; Xiong, Bangyun; Zheng, Feng; Mao, Wenfeng; Chen, Zhe; He, Chunqing; Zhao, Xipo; Fang, Pengfei

2014-01-01

Graphical abstract: - Highlights: • Decrements in S value and water uptake coefficient confirm the post-cure process. • Molecular chain scission leads to the formation of microporous structure. • The formation of an aged layer with high density is verified by EIS. - Abstract: Evolution of chemical functional groups, microstructure and water barrier properties of a polyamide-cured epoxy (diglycidyl ether of bisphenol-A epoxy resin, DGEBA) coating during ultraviolet A (UV-A) photo-oxidative aging is systematically investigated. At the early stage of aging, decrements of S parameter and water uptake coefficient indicate the formation of a more compact structure induced by the post-curing process. After 208 hours (h) of UV irradiation, a novel time constant at relatively high frequency (3.5 × 10 2 Hz) appears in the electrochemical impedance spectroscopy (EIS) spectra suggesting that a microporous layer generates near the surface of DGEBA film. With the increase in irradiation time, overlap of two time constants at frequencies around 18 Hz and 3.7 × 10 3 Hz is observed after 1.33 h of immersion, indicating that the micropores grow towards the bulk and form more characteristic layers with microporous structures. After irradiation for 399 h, a low S parameter region near the sample surface is observed, which implies that a surface layer with low free volume may have formed. With longer exposure, EIS results also reveal that the water barrier property of the coating can be improved, which confirms the formation of the denser surface layer near the surface as a result of radical recombination during UV-A treatment

Effect of Zirconia Nanoparticles in Epoxy-Silica Hybrid Adhesives to Join Aluminum Substrates

Directory of Open Access Journals (Sweden)

José de Jesús Figueroa-Lara

2017-09-01

Full Text Available This research presents the interaction of the epoxy polymer diglicydil ether of bisphenol-A (DGEBA with silica (SiO2 nanoparticles plus zirconia (ZrO2 nanoparticles obtained via the sol-gel method in the synthesis of an epoxy-silica-zirconia hybrid adhesive cured with polyamide. ZrO2 nanoparticles were added to the epoxy-silica hybrid adhesive produced in situ to modify the apparent shear strength of two adhesively bonded aluminum specimens. The results showed that the addition of different amounts of ZrO2 nanoparticles increased the shear strength of the adhesively bonded aluminum joint, previously treated by sandblasting, immersion in hot water and silanized with a solution of hydrolyzed 3-glycidoxipropyltrimethoxysilane (GPTMS. The morphology and microstructure of the nanoparticles and aluminum surfaces were examined by scanning electron microscopy (SEM, and elemental analysis was performed with the Energy-dispersive X-ray spectroscopy (EDS detector; the chemical groups were investigated during the aluminum surface modification using Fourier transform infrared spectroscopy (FTIR.

Atomistic modeling of thermomechanical properties of SWNT/Epoxy nanocomposites

Science.gov (United States)

Fasanella, Nicholas; Sundararaghavan, Veera

2015-09-01

Molecular dynamics simulations are performed to compute thermomechanical properties of cured epoxy resins reinforced with pristine and covalently functionalized carbon nanotubes. A DGEBA-DDS epoxy network was built using the ‘dendrimer’ growth approach where 75% of available epoxy sites were cross-linked. The epoxy model is verified through comparisons to experiments, and simulations are performed on nanotube reinforced cross-linked epoxy matrix using the CVFF force field in LAMMPS. Full stiffness matrices and linear coefficient of thermal expansion vectors are obtained for the nanocomposite. Large increases in stiffness and large decreases in thermal expansion were seen along the direction of the nanotube for both nanocomposite systems when compared to neat epoxy. The direction transverse to nanotube saw a 40% increase in stiffness due to covalent functionalization over neat epoxy at 1 K whereas the pristine nanotube system only saw a 7% increase due to van der Waals effects. The functionalized SWNT/epoxy nanocomposite showed an additional 42% decrease in thermal expansion along the nanotube direction when compared to the pristine SWNT/epoxy nanocomposite. The stiffness matrices are rotated over every possible orientation to simulate the effects of an isotropic system of randomly oriented nanotubes in the epoxy. The randomly oriented covalently functionalized SWNT/Epoxy nanocomposites showed substantial improvements over the plain epoxy in terms of higher stiffness (200% increase) and lower thermal expansion (32% reduction). Through MD simulations, we develop means to build simulation cells, perform annealing to reach correct densities, compute thermomechanical properties and compare with experiments.

Atomistic modeling of thermomechanical properties of SWNT/Epoxy nanocomposites

International Nuclear Information System (INIS)

Fasanella, Nicholas; Sundararaghavan, Veera

2015-01-01

Molecular dynamics simulations are performed to compute thermomechanical properties of cured epoxy resins reinforced with pristine and covalently functionalized carbon nanotubes. A DGEBA-DDS epoxy network was built using the ‘dendrimer’ growth approach where 75% of available epoxy sites were cross-linked. The epoxy model is verified through comparisons to experiments, and simulations are performed on nanotube reinforced cross-linked epoxy matrix using the CVFF force field in LAMMPS. Full stiffness matrices and linear coefficient of thermal expansion vectors are obtained for the nanocomposite. Large increases in stiffness and large decreases in thermal expansion were seen along the direction of the nanotube for both nanocomposite systems when compared to neat epoxy. The direction transverse to nanotube saw a 40% increase in stiffness due to covalent functionalization over neat epoxy at 1 K whereas the pristine nanotube system only saw a 7% increase due to van der Waals effects. The functionalized SWNT/epoxy nanocomposite showed an additional 42% decrease in thermal expansion along the nanotube direction when compared to the pristine SWNT/epoxy nanocomposite. The stiffness matrices are rotated over every possible orientation to simulate the effects of an isotropic system of randomly oriented nanotubes in the epoxy. The randomly oriented covalently functionalized SWNT/Epoxy nanocomposites showed substantial improvements over the plain epoxy in terms of higher stiffness (200% increase) and lower thermal expansion (32% reduction). Through MD simulations, we develop means to build simulation cells, perform annealing to reach correct densities, compute thermomechanical properties and compare with experiments. (paper)

Preparation of Microcellular Epoxy Foams through a Limited-Foaming Process: A Contradiction with the Time-Temperature-Transformation Cure Diagram.

Science.gov (United States)

Wang, Lijun; Zhang, Chun; Gong, Wei; Ji, Yubi; Qin, Shuhao; He, Li

2018-01-01

3D cross-linking networks are generated through chemical reactions between thermosetting epoxy resin and hardener during curing. The curing degree of epoxy material can be increased by increasing curing temperature and/or time. The epoxy material must then be fully cured through a postcuring process to optimize its material characteristics. Here, a limited-foaming method is introduced for the preparation of microcellular epoxy foams (Lim-foams) with improved cell morphology, high thermal expansion coefficient, and good compressive properties. Lim-foams exhibit a lower glass transition temperature (T g ) and curing degree than epoxy foams fabricated through free-foaming process (Fre-foams). Surprisingly, however, the T g of Lim-foams is unaffected by postcuring temperature and time. This phenomenon, which is related to high gas pressure in the bubbles, contradicts that indicated by the time-temperature-transformation cure diagram. High bubble pressure promotes the movement of molecular chains under heating at low temperature and simultaneously suppresses the etherification cross-linking reaction during post-curing. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A One-Component, Fast-Cure, and Economical Epoxy Resin System Suitable for Liquid Molding of Automotive Composite Parts

Directory of Open Access Journals (Sweden)

Yiru Wang

2018-04-01

Full Text Available Imidazole cured epoxy resin systems were evaluated for one-component, fast-curing resins for liquid molding of automotive composite parts according to industry requirements. It was demonstrated that an epoxy resin-1-(cyanoethyl-2-ethyl-4-methylimidazol(EP-1C2E4MIM system would cure in a few minutes at 120 °C, while exhibiting acceptable pot life, viscosity profiles, and low water absorption. Moreover, this system yielded high Tg parts with mechanical properties similar to the amine-epoxy systems, which are the mainstream two-component epoxy resin systems for automobiles.

Comparison of tensile strength of different carbon fabric reinforced epoxy composites

Directory of Open Access Journals (Sweden)

Jane Maria Faulstich de Paiva

2006-03-01

Full Text Available Carbon fabric/epoxy composites are materials used in aeronautical industry to manufacture several components as flaps, aileron, landing-gear doors and others. To evaluate these materials become important to know their mechanical properties, for example, the tensile strength. Tensile tests are usually performed in aeronautical industry to determinate tensile property data for material specifications, quality assurance and structural analysis. For this work, it was manufactured four different laminate families (F155/PW, F155/HS, F584/PW and F584/HS using pre-impregnated materials (prepregs based on F155TM and F584TM epoxy resins reinforced with carbon fiber fabric styles Plain Weave (PW and Eight Harness Satin (8HS. The matrix F155TM code is an epoxy resin type DGEBA (diglycidil ether of bisphenol A that contains a curing agent and the F584TM code is a modified epoxy resin type. The laminates were obtained by handing lay-up process following an appropriate curing cycle in autoclave. The samples were evaluated by tensile tests according to the ASTM D3039. The F584/PW laminates presented the highest values of tensile strength. However, the highest modulus results were determined for the 8HS composite laminates. The correlation of these results emphasizes the importance of the adequate combination of the polymeric matrix and the reinforcement arrangement in the structural composite manufacture. The microscopic analyses of the tested specimens show valid failure modes for composites used in aeronautical industry.

The electron beam cure of epoxy paste adhesives

International Nuclear Information System (INIS)

Farmer, J.D.; Janke, C.J.; Lopata, V.J.

1998-01-01

Recently developed epoxy paste adhesives were electron beam cured and experimentally explored to determine their suitability for use in an aerospace-quality aircraft component. There were two major goals for this program. The first was to determine whether the electron beam-curable past adhesives were capable of meeting the requirements of the US Air Force T-38 supersonic jet trainer composite windshield frame. The T-38 windshield frame's arch is currently manufactured by bonding thin stainless steel plies using an aerospace-grade thermally-cured epoxy film adhesive. The second goal was to develop the lowest cost hand layup and debulk process that could be used to produce laminated steel plies with acceptable properties. The laminate properties examined to determine adhesive suitability include laminate mechanical and physical properties at room, adhesive tack, out-time capability, and the debulk requirements needed to achieve these properties. Eighteen past adhesives and four scrim cloths were experimentally examined using this criteria. One paste adhesive was found to have suitable characteristics in each of these categories and was later chosen for the manufacture of the T-38 windshield frame. This experimental study shows that by using low-cost debulk and layup processes, the electron beam-cured past adhesive mechanical and physical properties meet the specifications of the T-38 composite windshield frame

Steel Protective Coating Based on Plasticized Epoxy Acrylate Formulation Cured by Electron Beam Irradiation

International Nuclear Information System (INIS)

Ibrahim, M.S.; Said, H.M.; Mohamed, I.M.; Mohamed, H.A.; Kandile, N.G.

2011-01-01

Electron beam (EB) was used to cure coatings based on epoxy acrylate oligomer (EA) and different plasticizers such as epoxidized soybean oil, glycerol and castor oil. The effect of irradiation doses (10, 25, 50 kGy) on the curing epoxy acrylate formulations containing plasticizers was studied. In the addition, the effect of the different plasticizers on the end use performance properties of epoxy acrylate coatings such as hardness, bending, adhesion, acid and alkali resistance tests were investigated. It was observed that the incorporation of castor oil in epoxy acrylate, diluted by 1,6 hexandiol diacrylate monomer (HD) with a ratio (EA 70%, HD 20%, castor oil 10%) under the dose 10 kGy improved the physical, chemical and mechanical properties of cured films than the other plasticizers. On the other hand, sunflower free fatty acids were epoxidized in-situ under well established conditions and then was subjected to react with aniline in sealed ampoules under inert atmosphere at 140 degree C. The produced adduct was added at different concentrations to epoxy acrylate coatings under certain EB irradiation dose and then evaluated as corrosion inhibitors for carbon steel surfaces in terms of weight loss measurements and corrosion resistance tests. It was observed that the formula containing 0.4 gm of aniline adduct / 100 gm epoxy acrylate resin gave the best corrosion protection for carbon steel

The thermal properties of a carbon nanotube-enriched epoxy: Thermal conductivity, curing, and degradation kinetics

KAUST Repository

Ventura, Isaac Aguilar

2013-05-31

Multiwalled carbon nanotube-enriched epoxy polymers were prepared by solvent evaporation based on a commercially available epoxy system and functionalized multiwalled carbon nanotubes (COOH-MWCNTs). Three weight ratio configurations (0.05, 0.5, and 1.0 wt %) of COOH-MWCNTs were considered and compared with neat epoxy and ethanol-treated epoxy to investigate the effects of nano enrichment and processing. Here, the thermal properties of the epoxy polymers, including curing kinetics, thermal conductivity, and degradation kinetics were studied. Introducing the MWCNTs increased the curing activation energy as revealed by differential scanning calorimetry. The final thermal conductivity of the 0.5 and 1.0 wt % MWCNT-enriched epoxy samples measured by laser flash technique increased by up to 15% compared with the neat material. The activation energy of the degradation process, investigated by thermogravimetric analysis, was found to increase with increasing CNT content, suggesting that the addition of MWCNTs improved the thermal stability of the epoxy polymers. © 2013 Wiley Periodicals, Inc.

Development of silane grafted ZnO core shell nanoparticles loaded diglycidyl epoxy nanocomposites film for antimicrobial applications.

Science.gov (United States)

Suresh, S; Saravanan, P; Jayamoorthy, K; Ananda Kumar, S; Karthikeyan, S

2016-07-01

In this article a series of epoxy nanocomposites film were developed using amine functionalized (ZnO-APTES) core shell nanoparticles as the dispersed phase and a commercially available epoxy resin as the matrix phase. The functional group of the samples was characterized using FT-IR spectra. The most prominent peaks of epoxy resin were found in bare epoxy and in all the functionalized ZnO dispersed epoxy nanocomposites (ZnO-APTES-DGEBA). The XRD analysis of all the samples exhibits considerable shift in 2θ, intensity and d-spacing values but the best and optimum concentration is found to be 3% ZnO-APTES core shell nanoparticles loaded epoxy nanocomposites supported by FT-IR results. From TGA measurements, 100wt% residue is obtained in bare ZnO nanoparticles whereas in ZnO core shell nanoparticles grafted DGEBA residue percentages are 37, 41, 45, 46 and 52% for 0, 1, 3, 5 and 7% ZnO-APTES-DGEBA respectively, which is confirmed with ICP-OES analysis. From antimicrobial activity test, it was notable that antimicrobial activity of 7% ZnO-APTES core shell nanoparticles loaded epoxy nanocomposite film has best inhibition zone effect against all pathogens under study. Copyright © 2016 Elsevier B.V. All rights reserved.

Simultaneous acoustic and dielectric real time curing monitoring of epoxy systems

Science.gov (United States)

Gkikas, G.; Saganas, Ch.; Grammatikos, S. A.; Aggelis, D. G.; Paipetis, A. S.

2012-04-01

The attainment of structural integrity of the reinforcing matrix in composite materials is of primary importance for the final properties of the composite structure. The detailed monitoring of the curing process on the other hand is paramount (i) in defining the optimal conditions for the impregnation of the reinforcement by the matrix (ii) in limiting the effects of the exotherm produced by the polymerization reaction which create unwanted thermal stresses and (iii) in securing optimal behavior in matrix controlled properties, such as off axis or shear properties and in general the durability of the composite. Dielectric curing monitoring is a well known technique for distinguishing between the different stages of the polymerization of a typical epoxy system. The technique successfully predicts the gelation and the vitrification of the epoxy and has been extended for the monitoring of prepregs. Recent work has shown that distinct changes in the properties of the propagated sound in the epoxy which undergoes polymerization is as well directly related to the gelation and vitrification of the resin, as well as to the attainment of the final properties of the resin system. In this work, a typical epoxy is simultaneously monitored using acoustic and dielectric methods. The system is isothermally cured in an oven to avoid effects from the polymerization exotherm. Typical broadband sensors are employed for the acoustic monitoring, while flat interdigital sensors are employed for the dielectric scans. All stages of the polymerization process were successfully monitored and the validity of both methods was cross checked and verified.

Structural investigation of e-beam cured epoxy resins through solid state NMR

International Nuclear Information System (INIS)

Alessi, Sabina; Spinella, Alberto; Caponetti, Eugenio; Dispenza, Clelia; Spadaro, Giuseppe

2012-01-01

In this paper the network structure of e-beam cured DGEBF based epoxy resins is investigated. Two epoxy systems, having different reactivity and cured in different process conditions, were analyzed through solid state NMR spectroscopy. The analysis shows that the more reactive system has higher cross-linking density and higher uniformity of network distribution. Similar information were obtained, in a previous work, on the same systems through dynamic mechanical thermal analysis. It is worth noting that unlike DMTA tests, which interfere with the molecular structure of the analyzed material, due to the heating during the analysis itself, more reliable information, without any artefact, are obtained by solid state NMR, carried out at constant room temperature. - Highlights: ► The structure of two e-beam cured epoxy systems is investigated through solid state NMR. ► The aim is to have direct information about the structure without inducing modifications. ► The different molecular structures are able to emphasize the response of solid state NMR. ► T 1 H, T 1ρ H and T CH measurements indicate different cross-linking degrees. ► The NMR results are in agreement with DMTA analysis performed in a previous paper.

Cure Kinetics of Benzoxazine/Cycloaliphatic Epoxy Resin by Differential Scanning Calorimetry

Science.gov (United States)

Gouni, Sreeja Reddy

Understanding the curing kinetics of a thermoset resin has a significant importance in developing and optimizing curing cycles in various industrial manufacturing processes. This can assist in improving the quality of final product and minimizing the manufacturing-associated costs. One approach towards developing such an understanding is to formulate kinetic models that can be used to optimize curing time and temperature to reach a full cure state or to determine time to apply pressure in an autoclave process. Various phenomenological reaction models have been used in the literature to successfully predict the kinetic behavior of a thermoset system. The current research work was designed to investigate the cure kinetics of Bisphenol-A based Benzoxazine (BZ-a) and Cycloaliphatic epoxy resin (CER) system under isothermal and nonisothermal conditions by Differential Scanning Calorimetry (DSC). The cure characteristics of BZ-a/CER copolymer systems with 75/25 wt% and 50/50 wt% have been studied and compared to that of pure benzoxazine under nonisothermal conditions. The DSC thermograms exhibited by these BZ-a/CER copolymer systems showed a single exothermic peak, indicating that the reactions between benzoxazine-benzoxazine monomers and benzoxazine-cycloaliphatic epoxy resin were interactive and occurred simultaneously. The Kissinger method and isoconversional methods including Ozawa-Flynn-Wall and Freidman were employed to obtain the activation energy values and determine the nature of the reaction. The cure behavior and the kinetic parameters were determined by adopting a single step autocatalytic model based on Kamal and Sourour phenomenological reaction model. The model was found to suitably describe the cure kinetics of copolymer system prior to the diffusion-control reaction. Analyzing and understanding the thermoset resin system under isothermal conditions is also important since it is the most common practice in the industry. The BZ-a/CER copolymer system with

Use of 2,5-dimethyl-2,5-hexane diamine as a curing agent for epoxy resins. [Patent application

Science.gov (United States)

Rinde, J.A.; Newey, H.A.

Primary diamines are prepared for use as a curing agent for epoxy resins. These curing agents can be used to form epoxy resin mixtures useful in filament winding and preimpregnated fiber molding and in formulating film adhesives, powder coatings and molding powders. The epoxy mixtures form for such uses a room temperature non-reacting, intermediate stable state which has a latent cross-linking capability.

Clay/Polyaniline Hybrid through Diazonium Chemistry: Conductive Nanofiller with Unusual Effects on Interfacial Properties of Epoxy Nanocomposites.

Science.gov (United States)

Jlassi, Khouloud; Chandran, Sarath; Poothanari, Mohammed A; Benna-Zayani, Mémia; Thomas, Sabu; Chehimi, Mohamed M

2016-04-12

The concept of conductive network structure in thermoset matrix without sacrificing the inherent mechanical properties of thermoset polymer (e.g., epoxy) is investigated here using "hairy" bentonite fillers. The latter were prepared through the in situ polymerization of aniline in the presence of 4-diphenylamine diazonium (DPA)-modified bentonite (B-DPA) resulting in a highly exfoliated bentonite-DPA/polyaniline (B-DPA/PANI). The nanocomposite filler was mixed with diglycidyl ether of bisphenol A (DGEBA), and the curing agent (4,4'-diaminodiphenylsulfone) (DDS) at high temperature in order to obtain nanocomposites through the conventional melt mixing technique. The role of B-DPA in the modification of the interface between epoxy and B-DPA/polyaniline (B-DPA/PANI) is investigated and compared with the filler B/PANI prepared without any diazonium modification of the bentonite. Synergistic improvement in dielectric properties and mechanical properties points to the fact that the DPA aryl groups from the diazonium precursor significantly modify the interface by acting as an efficient stress transfer medium. In DPA-containing nanocomposites, unique fibril formation was observed on the fracture surface. Moreover, dramatic improvement (210-220%) in fracture toughness of epoxy composite was obtained with B-DPA/PANI filler as compared to the weak improvement of 20-30% noted in the case of the B/PANI filler. This work shows that the DPA diazonium salt has an important effect on the improvement of the interfacial properties and adhesion of DGEBA and clay/PANI nanofillers.

Morphology and contact angle studies of poly(styrene-co-acrylonitrile modified epoxy resin blends and their glass fibre reinforced composites

Directory of Open Access Journals (Sweden)

2007-06-01

Full Text Available In this study, the surface characteristics of blends and composites of epoxy resin were investigated. Poly(styrene-co-acylonitrile (SAN was used to modify diglycedyl ether of bisphenol-A (DGEBA type epoxy resin cured with diamino diphenyl sulfone (DDS and the modified epoxy resin was used as the matrix for fibre reinforced composites (FRP’s. E-glass fibre was used as the fibre reinforcement. The scanning electron micrographs of the fractured surfaces of the blends and composites were analyzed. Morphological analysis revealed different morphologies such as dispersed, cocontinuous and phase-inverted structures for the blends. Contact angle studies were carried out using water and methylene iodide at room temperature. The solid surface energy was calculated using harmonic mean equations. Blending of epoxy resin increases its contact angle. The surface free energy, work of adhesion, interfacial free energy, spreading coefficient and Girifalco-Good’s interaction parameter were changed significantly in the case of blends and composites. The incorporation of thermoplastic and glass fibre reduces the wetting and hydrophilicity of epoxy resin.

Studies on the structural changes during curing of epoxy and its blend with CTBN

Science.gov (United States)

Srivastava, Kavita; Rathore, Ashwani Kumar; Srivastava, Deepak

2018-01-01

Cashew nut shell liquid (CNSL), an agricultural renewable resource material, produces natural phenolic distillates such as cardanol. Cardanol condenses with formaldehyde at the ortho- and para-position of the phenolic ring under acidic or alkaline condition to yield a series of polymers of novolac- or resol-type phenolic resins. These phenolic resins may further be modified by epoxidation with epichlorohydrin to duplicate the performance of such phenolic-type novolacs (CFN). The structural changes during curing of blend samples of epoxy and carboxyl terminated poly (butadiene-co-acrylonitrile) (CTBN) were studies by Fourier-transform infrared (FTIR) spectrophotometer. The epoxy samples were synthesized by biomass material, cardanol. Blend sample was prepared by physical mixing of CTBN ranging between 0 and 20 weight percent CTBN liquid rubber into cardanol-based epoxidized novolac (CEN) resin. The FTIR spectrum of uncured blend sample clearly indicated that there appeared a band in the region of 3200-3500 cm- 1 which might be due to the presence of phenolic hydroxyl group and sbnd OH group of the opened epoxide. Pure epoxy resin showed peaks near 856 cm- 1 which might be due to oxirane functionality of the epoxidized novolac resin. Both epoxy and its blend sample was cured with polyamine. The cure temperature of CEN resin was found to be decreased by the incorporation of CTBN. The decomposition behavior was also studied by thermogravimetric analyzer (TGA). Two-step decomposition behavior was observed in both epoxy and its blend samples.

Curing kinetics, mechanism and chemorheological behavior of methanol etherified amino/novolac epoxy systems

Directory of Open Access Journals (Sweden)

S. F. Zhao

2014-02-01

Full Text Available The curing kinetics and mechanism of epoxy novolac resin (DEN and modified epoxy novolac resin (MDEN with methanol etherified amino resin were studied by means of differential scanning calorimetry (DSC, Fourier transforminfrared (FT-IR spectroscopy and chemorheological analysis. Their kinetics parameters and models of the curing were examined utilizing isoconversional methods, Flynn-Wall-Ozawa and Friedman methods. For the DEN mixture, its average activation energy (Ea was 71.05 kJ/mol and the autocatalytic model was established to describe the curing reaction. The MDEN mixture exhibited three dominant curing processes, termed as reaction 1, reaction 2 and reaction 3; and their Ea were 70.05, 106.55 and 101.91 kJ/mol, respectively. Besides, Ea of reaction 1 was similar to that of DEN mixture, while Ea of reactions 2 and 3 corresponded to that of the etherification reaction between hydroxyl and epoxide group. Moreover, these three dominant reactions were nth order in nature. Furthermore, their curing mechanisms were proposed from the results of DSC and FTIR. The chemorheological behavior was also investigated to obtain better plastics products via optimizing the processing schedules.

Novas tendências dos polímeros epoxídicos: propriedades biológicas in vitro de formulações para aplicações médicas New trend for epoxy polymers: in vitro biological properties of formulations for medical applications

Directory of Open Access Journals (Sweden)

Filiberto González Garcia

2009-01-01

Full Text Available Este trabalho descreve as propriedades biológicas in vitro de três formulações epoxídicas usando o monômero do tipo éter diglicidílico do bisphenol-A (DGEBA com três co-monômeros do tipo poliamina alifática de maneira independente; trietilenotetramina (TETA, 1-(2-aminoetilpiperazina (AEP e isoforonodiamina (IPD. As interações biológicas entre os polímeros obtidos e o sangue foram estudadas in vitro utilizando quatro métodos biológicos diferentes. Estudos de adsorção protéica, adesão plaquetária, formação de trombos e citotoxicidade são apresentados e discutidos. Os ensaios de adsorção protéica mostraram que a superfície dos polímeros adsorve mais albumina humana do que fibrinogênio humano. Os resultados de adesão plaquetária e formação de trombos indicaram que os sistemas DGEBA-IPD e DGEBA-AEP exibem boa hemocompatibilidade. Os três polímeros epoxídicos não revelaram toxicidade com células de ovário de hamster chinês. Os resultados obtidos indicam que os polímeros epoxídicos baseados no IPD obedecem aos critérios de hemocompatibilidade e citotoxicidade exigidos de um biomaterial. Os polímeros epoxídicos baseados nas aminas AEP e TETA exibem apenas um comportamento não citotóxico.In this paper the in vitro biological properties are presented for three epoxy networks based on diglycidyl ether of bisphenol-A epoxy prepolymer cured with aliphatic amines, namely triethylenetetramine (TETA, 1-(2-aminoethyl piperazine (AEP and isophoronediamine (IPD. The biological interactions between the fully-cured epoxy materials and blood were studied by in vitro methods. Research on the protein adsorption, platelet adhesion and thrombus formation is presented using a UV/VIS spectrometer and SEM analysis. Studies of protein adsorption onto polymeric surfaces showed that the three epoxy materials adsorbed more albumin than fibrinogen. Studies about platelet adhesion and thrombus formation of two epoxy polymers

Evaluation of the use of inorganic pigments and fillers in cure of epoxy resins by microwave irradiation

International Nuclear Information System (INIS)

Kersting, Daniel; Wiebeck, Helio

2013-01-01

The use of microwave in chemical processes began soon after the WW II. The mechanism of curing via microwave heating is independent of the thermal conductivity of the irradiated material and offers a good solution to operate with materials that do not have a good thermal conductivity, such as polymers. Despite these advantages, the use of multimode microwave ovens, the main source used today, indicates some challenges to overcome. Associated with the use of epoxy resins in various applications, the use of pigments and inorganic fillers has added more variables to be studied. Much of the inorganic fillers used commercially are good absorbers of microwave providing changes in the amount of radiation absorbed, and thus the amount of heat transferred to the epoxy resin curing process. After selecting the key fillers and pigments traditionally used in the production of parts with epoxy resins they were subjected to the same microwave irradiation for evaluation of their behavior alone. In order to observe the effect of mixtures 1, 2, and 5% by weight of filler were added to epoxy resin, and it was verified these effects in the curing process. The preliminary results are promising, because for the same cure cycle for different types of fillers added separately, gains in curing time were obtained, making the process of cure via microwave quick and efficient without substantial losses in thermal properties of the final products obtained. (author)

UV curing silicon-containing epoxy resin and its glass cloth reinforced composites

International Nuclear Information System (INIS)

Yang Guang; Tang Zhuo; Huang Pengcheng

2007-01-01

A UV-curable cationic silicon-containing epoxy resin formulation was developed. The gel conversion of the cured resin after 10-min UV irradiation reached 80% in the presence of 5% diaryliodonium salt photoinitiator and 5.5% polyol chain transfer agent by cationic ring-opening polymerization. The glass cloth-reinforced composites were fabricated with the silicon-containing epoxy resin using the wet lay-up technique and UV irradiation. The mechanical properties of the composites were evaluated. Compared with glass cloth reinforced bisphenol A epoxy resin matrix composites, the silicon-containing epoxy resin matrix composites possessed higher tensile strength and interlayer shear strength which was 158.5MPa and 9.9MPa respectively while other mechanical properties such as flexural property and tensile modulus were similar. (authors)

Curing behaviour of epoxy resin/graphite composites containing ionic liquid

International Nuclear Information System (INIS)

Guo Baochun; Wan Jingjing; Lei Yanda; Jia Demin

2009-01-01

By adopting the isoconversional method, subtle changes in the curing activation energy (E α ) among epoxy resin/graphite composites by the inclusion of expanded graphite (EG), ionic liquid of 1-butyl-3-methyl-imidazolium hexafluorophosphate ([BMIm]PF 6 ) or their combination are shown in the whole conversion range. At lower concentrations (1 phr) of EG, compared with the E α of the neat epoxy resin, the composite with EG has a lower E α before the gelation, and a higher E α after the gelation. At higher concentrations of EG, however, in the whole conversion range, the composite with EG shows a higher E α compared with the neat epoxy resin. As the curing proceeded, a peculiar increase in E α is found in systems containing [BMIm]PF 6 . Due to the formation of hydrogen bonding between [BMIm]PF 6 and the hardener (Jeffamine), the reactivity of Jeffamine is considerably decreased, leading to a much higher E α in [BMIm]PF 6 -containing systems, especially at higher conversion. In systems containing a combination of [BMIm]PF 6 and EG, due to the interactions between EG and [BMIm]PF 6 , the shielding effect provided by the well-dispersed EG sheets constrains the formation of the hydrogen bonding between [BMIm]PF 6 and Jeffamine, leading to lowered E α compared with that for the system containing [BMIm]PF 6 only.

Influence of nano-AlN particles on thermal conductivity, thermal stability and cure behavior of cycloaliphatic epoxy/trimethacrylate system

Directory of Open Access Journals (Sweden)

2011-02-01

Full Text Available We have prepared a series of nano-sized aluminium nitride (nano-AlN/cycloaliphatic epoxy/trimethacrylate (TMPTMA systems and investigated their morphology, thermal conductivity, thermal stability and curing behavior. Experimental results show that the thermal conductivity of composites increases with the nano-AlN filler content, the maximum value is up to 0.47 W/(m.K. Incorporation of a small amount of the nano-AlN filler into the epoxy/TMPTMA system improves the thermal stability. For instance, the thermal degradation temperature at 5% weight loss of nano-AlN/epoxy/TMPTMA system with only 1 wt% nano-AlN was improved by ~8ºC over the neat epoxy/TMPTMA system. The effect of nano-AlN particles on the cure behavior of epoxy/TMPTMA systems was studied by dynamic differential scanning calorimetry. The results showed that the addition of silane treated nano-AlN particles does not change the curing reaction mechanism and silane treated nano-AlN particles could bring positive effect on the processing of composite since it needs shorter pre-cure time and lower pre-temperature, meanwhile the increase of glass transition temperature of the nanocomposite improves the heat resistance.

Surface engineering of nanoparticles with macromolecules for epoxy curing: Development of super-reactive nitrogen-rich nanosilica through surface chemistry manipulation

Science.gov (United States)

Jouyandeh, Maryam; Jazani, Omid Moini; Navarchian, Amir H.; Shabanian, Meisam; Vahabi, Henri; Saeb, Mohammad Reza

2018-07-01

Curing behavior of epoxy-based nanocomposites depends on dispersion state of nanofillers and their physical and chemical interactions with the curing moieties. In this work, a systematic approach was introduced for chemical functionalization of nanoparticles with macromolecules in order to enrich crosslinking potential of epoxy/amine systems, particularly at late stages of cure where the curing is diffusion-controlled. Super-reactive hyperbranched polyethylenimine (PEI)-attached nanosilica was materialized in this work to facilitate epoxy-amine curing. Starting from coupling [3-(2,3-epoxypropoxy) propyl] trimethoxysilane (EPPTMS) with hyperbranched PEI, a super-reactive macromolecule was obtained and subsequently grafted onto the nanosilica surface. Eventually, a thermally-stable highly-curable nanocomposite was attained by replacement of amine and imine groups of the PEI with imide and amide groups through the reaction with pyromellitic acid dianhydride. Fourier-transform infrared spectrophotometry, X-ray diffractometry, X-ray photoelectron spectroscopy and transmission electron microscopy approved successful grafting of polymer chains onto the nanosilica surface. Thermogravimetric analyses approved a relatively high grafting ratio of ca. 21%. Curing potential of the developed super-reactive nanoparticle was uncovered through nonisothermal differential scanning calorimetry signifying an enthalpy rise of ca. 120 J/g by addition of 2 wt.% to epoxy at 5 °C/min heating rate. Even at low concentration of 0.5 wt.%, the glass transition temperature of epoxy increased from 128 to 156 °C, demonstrating prolonged crosslinking.

Investigation of the cure behaviour of an epoxy polyester powder coating

International Nuclear Information System (INIS)

Ishrat, S.; Nadeem, M.

1993-01-01

The epoxy polyester based thermo sets make attractive matrix materials for many industrial and commercial applications because of their excellent performance properties. These properties for example, dimensional stability, adhesion, chemical resistance, and thermal stability arise primarily from the formation of crosslinks during cure. While many factors, such as the reactivity and stoichiometry of the reactants can influence the course of the crosslinking reaction, the cure temperature and cure time ultimately govern the end use performance of the thermosetting systems of powder coatings. The interrelationship between the network formation process and performance properties makes cure process studies critically important in product development. A products end use performance properties can be correlated with the processing conditions by monitoring specific polymeric properties such as gel points, glass transition temperature (TgS,) and the kinetics of the crosslinking reaction. By plotting the change in these properties against cure time and or cure temperature, a 'profile' or degree of cure (DOC) curve can be formed. These profiles illustrate the progress of the crosslinking reaction and can be used to optimize thermo set handling, processing and cure process. (author)

Development of ricehusk ash reinforced bismaleimide toughened epoxy nanocomposites

Science.gov (United States)

Kanimozhi, K.; Sethuraman, K.; Selvaraj, V.; Alagar, M.

2014-01-01

Recent past decades have witnessed remarkable advances in composites with potential applications in biomedical devices, aerospace, textiles, civil engineering, energy, electronic engineering, and household products. Thermoset polymer composites have further enhanced and broadened the area of applications of composites. In the present work epoxy-BMI toughened-silica hybrid (RHA/DGEBA-BMI) was prepared using bismaleimide as toughener, bisphenol-A as matrix and a silica precursor derived from rice husk ash as reinforcement with glycidoxypropyltrimethoxysilane as coupling agent. Differential scanning calorimetry, electron microscopy, thermogravimetric analysis, and goniometry were used to characterize RHA/DGEBA-BMI composites developed in the present work. Tensile, impact and flexural strength, tensile and flexural modulus, hardness, dielectric properties were also studied and discussed. The hybrid nanocomposites possess the higher values of the glass transition temperature (Tg) and mechanical properties than those of neat epoxy matrix. PMID:25279372

The role of the epoxy resin: Curing agent ratio in composite interfacial strength by single fibre microbond test

DEFF Research Database (Denmark)

Minty, Ross; Thomason, James L.; Petersen, Helga Nørgaard

2015-01-01

This paper focuses on an investigation into the role of the epoxy resin: curing agent ratio in composite interfacial shear strength of glass fibre composites. The procedure involved changing the percentage of curing agent (Triethylenetetramine [TETA]) used in the mixture with several different...... percentages used, ranging from 4% up to 30%, including the stoichiometric ratio. It was found by using the microbond test, that there may exist a relationship between the epoxy resin to curing agent ratio and the level of adhesion between the reinforcing fibre and the polymer matrix of the composite....

Isothermal and non-isothermal cure of a tri-functional epoxy resin (TGAP): a stochastic TMDSC study

OpenAIRE

Hutchinson, John M.; Shiravand, Fatemeh; Calventus Solé, Yolanda; Fraga Rivas, Iria

2012-01-01

The isothermal cure of a highly reactive tri-functional epoxy resin, tri-glycidyl para-amino phenol (TGAP), with diamino diphenyl sulphone (DDS), at two different cure temperatures Tc has been studied by both conventional differential scanning calorimetry (DSC) and by a stochastic temperature modulated DSC technique, TOPEM. From a series of isothermal cure experiments for increasing cure times, the glass transition temperature Tg as a function of isothermal cure time is determined by co...

Response behavior of an epoxy resin/amine curing agent/carbon black composite film to various solvents

Energy Technology Data Exchange (ETDEWEB)

Luo Yanling [School of Chemistry and Materials Science, Shaanxi Normal University, Xi' an 710062 (China)]. E-mail: luoyl0401@yahoo.com.cn; Li Zhanqing [School of Chemistry and Materials Science, Shaanxi Normal University, Xi' an 710062 (China); Lan Wenxiang [School of Chemistry and Materials Science, Shaanxi Normal University, Xi' an 710062 (China)

2007-04-25

A novel polymer based sensitive film was prepared from thermosetting epoxy resins (EP) filled with carbon blacks. The curing reaction of amine curing agents with epoxy resins and the response of the curing resultants to solvent vapors were dealt with. The influence of the types and content of carbon blacks and curing agents, and curing temperatures and time on curing reactions and response selectivity of the conductive films were investigated. The structural characterization was conducted on a Fourier transform infrared spectrophotometer (FTIR). The results indicated that the conductive films showed high response selectivity to polar solvent vapors, especially to chloroform vapor, while no response was observed in non-polar solvent vapors. The responsivity of the film increased with the decreased carbon black contents. The film filled with acetylene carbon black gave an optimal response, with responsivity of about 700 times. The response performances were improved with the amount of curing agents increased, and an optimal response appeared at the amount of the curing agent of 8%. The film's responsivity was remarkably enhanced, the reversibility property, however, rapidly declined in the order of diethyleneltriamine < triethylenetetramine < ethylenediamine. The curing reaction tended to complete with the curing temperature elevated and the curing time prolonged. But the response performance dropped because of over cross-linking as the temperature was too high or the time was too long.

Response behavior of an epoxy resin/amine curing agent/carbon black composite film to various solvents

International Nuclear Information System (INIS)

Luo Yanling; Li Zhanqing; Lan Wenxiang

2007-01-01

A novel polymer based sensitive film was prepared from thermosetting epoxy resins (EP) filled with carbon blacks. The curing reaction of amine curing agents with epoxy resins and the response of the curing resultants to solvent vapors were dealt with. The influence of the types and content of carbon blacks and curing agents, and curing temperatures and time on curing reactions and response selectivity of the conductive films were investigated. The structural characterization was conducted on a Fourier transform infrared spectrophotometer (FTIR). The results indicated that the conductive films showed high response selectivity to polar solvent vapors, especially to chloroform vapor, while no response was observed in non-polar solvent vapors. The responsivity of the film increased with the decreased carbon black contents. The film filled with acetylene carbon black gave an optimal response, with responsivity of about 700 times. The response performances were improved with the amount of curing agents increased, and an optimal response appeared at the amount of the curing agent of 8%. The film's responsivity was remarkably enhanced, the reversibility property, however, rapidly declined in the order of diethyleneltriamine < triethylenetetramine < ethylenediamine. The curing reaction tended to complete with the curing temperature elevated and the curing time prolonged. But the response performance dropped because of over cross-linking as the temperature was too high or the time was too long

Microstructure aspects of radiation-cured networks: Cationically polymerized aromatic epoxy resins

Science.gov (United States)

Kowandy, Christelle; Ranoux, Guillaume; Walo, Marta; Vissouvanadin, Bertrand; Teyssedre, Gilbert; Laurent, Christian; Berquand, Alexandre; Molinari, Michaël; Coqueret, Xavier

2018-02-01

The thermo-mechanical properties and nanostructural features of epoxy aromatic resins cationically cured by UV-visible or electron beam radiation have been studied by FT-NIR spectroscopy, dynamic mechanical analysis (DMA), dielectric spectroscopy (DS), and atomic force microscopy (AFM). The influence of formulation (nature and content of onium salt) and of curing parameters (doses, thermal treatment) on the thermophysical have been investigated. The presence of several relaxation domains observed by DMA and DS analysis confirms the presence of heterogeneities in the cured materials. Network formation is described by the percolation of glassy nanoclusters which are evidenced by AFM analyses. AFM probing by quantitative nanomechanical measurements confirms the gradual build-up of the local Young's modulus in good agreement with the macroscopic value.

Thermomechanical Behavior of High Performance Epoxy/Organoclay Nanocomposites

Directory of Open Access Journals (Sweden)

Artur Soares Cavalcanti Leal

2014-01-01

Full Text Available Nanocomposites of epoxy resin containing bentonite clay were fabricated to evaluate the thermomechanical behavior during heating. The epoxy resin system studied was prepared using bifunctional diglycidyl ether of bisphenol A (DGEBA, crosslinking agent diaminodiphenylsulfone (DDS, and diethylenetriamine (DETA. The purified bentonite organoclay (APOC was used in all experiments. The formation of nanocomposite was confirmed by X-ray diffraction analysis. Specimens of the fabricated nanocomposites were characterized by dynamic mechanical analysis (DMA. According to the DMA results a significant increase in glass transition temperature and storage modulus was evidenced when 1 phr of clay is added to epoxy resin.

Preparation of hyperbranched poly (amidoamine)-grafted graphene nanolayers as a composite and curing agent for epoxy resin

Science.gov (United States)

Gholipour-Mahmoudalilou, Meysam; Roghani-Mamaqani, Hossein; Azimi, Reza; Abdollahi, Amin

2018-01-01

Thermal properties of epoxy resin were improved by preparation of a curing agent of poly (amidoamine) (PAMAM) dendrimer-grafted graphene oxide (GO). Hyperbranched PAMAM-modified GO (GD) was prepared by a divergent dendrimer synthesis methodology. Modification of GO with (3-Aminopropyl)triethoxysilane (APTES), Michael addition of methacrylic acid, and amidation reaction with ethylenediamine results in the curing agent of GD. Then, epoxy resin was cured in the presence of different amounts of GD and the final products were compared with ethylenediamine-cured epoxy resin (E) in their thermal degradation temperature and char contents. Functionalization of GO with APTES and hyperbranched dendrimer formation at the surface of GO were evaluated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and thermogravimetric analysis (TGA) results. TGA results showed that the weight loss associated with chemical moieties in GONH2, GOMA, and GD is estimated to be 10.1, 12.2, and 14.1%, respectively. Covalent attachment of dendrimer at the surface of GO increases its thermal stability. TGA also showed that decomposition temperature and char content are higher for composites compared with E. Scanning and transmission electron microscopies show that flat and smooth graphene nanolayers are wrinkled in GO and re-stacking and flattening of nanolayers is observed in GD.

How carbon nanotubes affect the cure kinetics and glass transition temperature of their epoxy composites? – A review

Directory of Open Access Journals (Sweden)

2009-09-01

Full Text Available Motivated by the widespread and contradictory results regarding the glass transition temperature of carbon nanotube (CNT/epoxy composites, we reviewed and analyzed the literature results dealing with the effect of unmodified multiwall carbon nanotubes (MWNT on the cure behaviour of an epoxy resin (as a possible source of this discrepancy. The aim of this work was to clarify the effective role of unmodified multiwall carbon nanotubes on the cure kinetics and glass transition temperature (Tg of their epoxy composites. It was found that various authors reported an acceleration effect of CNT. The cure reaction was promoted in its early stage which may be due to the catalyst particles present in the CNT raw material. While SWNT may lead to a decrease of Tg due to their bundling tendency, results reported for MWNT suggested an increased or unchanged Tg of the composites. The present status of the literature does not allow to isolate the effect of MWNT on the Tg due to the lack of a study providing essential information such as CNT purity, glass transition temperature along with the corresponding cure degree.

Isothermal and non-isothermal cure of a tri-functional epoxy resin (TGAP): A stochastic TMDSC study

International Nuclear Information System (INIS)

Hutchinson, John M.; Shiravand, Fatemeh; Calventus, Yolanda; Fraga, Iria

2012-01-01

Highlights: ► First evaluation of T g of tri-functional epoxy resin TGAP by DSC. ► Clearly shows advantages of TOPEM for isothermal and non-isothermal cure analysis. ► Evidence of highly non-linear enthalpy relaxation in partially cured TGAP system. - Abstract: The isothermal cure of a highly reactive tri-functional epoxy resin, tri-glycidyl para-amino phenol (TGAP), with diamino diphenyl sulphone (DDS), at two different cure temperatures T c has been studied by both conventional differential scanning calorimetry (DSC) and by a stochastic temperature modulated DSC technique, TOPEM. From a series of isothermal cure experiments for increasing cure times, the glass transition temperature T g as a function of isothermal cure time is determined by conventional DSC from a second (non-isothermal) scan, and the vitrification time t v is obtained as the time at which T g = T c . In parallel, TOPEM experiments at the same T c lead directly to the determination of t v from the sigmoidal change in the quasi-static heat capacity. It is not possible to identify the glass transition temperature of the fully cured system, T g∞ , in a third scan by conventional DSC. In contrast, with TOPEM a second (non-isothermal) scan at 2 K/min after the isothermal cure gives rise to three separate transitions: devitrification of the partially cured and vitrified material; almost immediate vitrification as the T g of the system again rises; finally another devitrification, at a temperature approximating closely to T g∞ . Thus with TOPEM it is possible to obtain a calorimetric measure of the glass transition temperature of this fully cured system.

Block Copolymer Modified Epoxy Amine System for Reactive Rotational Molding: Structures, Properties and Processability

Science.gov (United States)

Lecocq, Eva; Nony, Fabien; Tcharkhtchi, Abbas; Gérard, Jean-François

2011-05-01

Poly(styrene-butadiene-methylmethacrylate) (SBM) and poly(methylmethacrylate-butyle-acrylate-methylmethacrylate) (MAM) triblock copolymers have been dissolved in liquid DGEBA epoxy resin which is subsequently polymerized by meta-xylene diamine (MXDA) or Jeffamine EDR-148. A chemorheology study of these formulations by plate-plate rheology and by thermal analysis has allowed to conclude that the addition of these copolymer blocks improve the reactive rotational moulding processability without affecting the processing time. Indeed, it prevents the pooling of the formulation at the bottom of the mould and a too rapid build up of resin viscosity of these thermosetting systems. The morphology of the cured blends examined by scanning electron microscopy (SEM) shows an increase of fracture surface area and thereby a potential increase of the toughness with the modification of epoxy system. Dynamic mechanical spectroscopy (DMA) and opalescence of final material show that the block PMMA, initially miscible, is likely to induce phase separation from the epoxy-amine matrix. Thereby, the poor compatibilisation between the toughener and the matrix has a detrimental effect on the tensile mechanical properties. The compatibilisation has to be increased to improve in synergy the processability and the final properties of these block copolymer modified formulations. First attempts could be by adapting the length and ratio of each block.

Synthesis of polyoxometalate-loaded epoxy composites

Science.gov (United States)

Anderson, Benjamin J

2014-10-07

The synthesis of a polyoxometalate-loaded epoxy uses a one-step cure by applying an external stimulus to release the acid from the polyoxometalate and thereby catalyze the cure reaction of the epoxy resin. Such polyoxometalate-loaded epoxy composites afford the cured epoxy unique properties imparted by the intrinsic properties of the polyoxometalate. For example, polyoxometalate-loaded epoxy composites can be used as corrosion resistant epoxy coatings, for encapsulation of electronics with improved dielectric properties, and for structural applications with improved mechanical properties.

The thermal properties of a carbon nanotube-enriched epoxy: Thermal conductivity, curing, and degradation kinetics

KAUST Repository

Ventura, Isaac Aguilar; Rahaman, Ariful; Lubineau, Gilles

2013-01-01

conductivity, and degradation kinetics were studied. Introducing the MWCNTs increased the curing activation energy as revealed by differential scanning calorimetry. The final thermal conductivity of the 0.5 and 1.0 wt % MWCNT-enriched epoxy samples measured

Evolution of the macroscopic properties of two epoxy resins during ageing under irradiation

International Nuclear Information System (INIS)

Vignoud, L.

2001-11-01

In this study, the thermomechanical properties of two epoxy resins (DGEBA/TETA and DGEBA/DDM systems) are analysed as a function of the irradiation dose. The maximum conversion and reticulation is obtained by post-curing treatment. Irradiation by electrons results in a decrease of the glass transition temperature and of the elastic modulus in the rubbery region. These results can be interpreted invoking a destruction of the crosslinks and chains breaks within the resin. The Arrhenius diagrams obtained for the various doses shows that the cooperative mobility associated with the α relaxation becomes faster after the irradiation. On the contrary, more local mobility corresponding to the γ relaxation is also modified, but in a lesser extent. The stress-strain curves are also discussed. In uniaxial compression test, the plastic flow stress σ p decreases when the irradiation dose increases and this effect can largely be accounted for by a variation of T g . Post-irradiative effects are studied in inert atmosphere. Reticulation increases when the material is heated to a higher temperature than its T g . This effect suggest the presence of radical formed during irradiation. For DGEBA/TETA system, glass transition temperature T g shifts towards lowest temperatures. This shift increases the molecular mobility and enhances the physical ageing process at the ambient temperature. The results are well described by the quasi point defects theory. Direct effect of irradiation and physical ageing evolve with the scale parameter t 0 . This parameter characterizes the gap (in time and/or temperature) between the principal relaxation and simplest ones. By connecting t 0 to the amount of irradiation, it is possible to predict the modifications of the behaviour and to predict these evolutions for various amounts. (author)

Epoxy composites based on inexpensive tire waste filler

Science.gov (United States)

Ahmetli, Gulnare; Gungor, Ahmet; Kocaman, Suheyla

2014-05-01

Tire waste (TW) was recycled as raw material for the preparation of DGEBA-type epoxy composite materials. The effects of filler amount and epoxy type on the mechanical properties of the composites were investigated. Tensile strength and Young's modulus of the composites with NPEL were generally higher than composites with NPEF. The appropriate mass level for TW in both type composites was found to be 20 wt%. The equilibrium water sorption of NPEL/TW and NPEF/TW composites for 14-day immersion was determined as 0.10 % and 0.21 %, respectively. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used for characterization of the composites.

Epoxy composites based on inexpensive tire waste filler

International Nuclear Information System (INIS)

Ahmetli, Gulnare; Gungor, Ahmet; Kocaman, Suheyla

2014-01-01

Tire waste (TW) was recycled as raw material for the preparation of DGEBA-type epoxy composite materials. The effects of filler amount and epoxy type on the mechanical properties of the composites were investigated. Tensile strength and Young’s modulus of the composites with NPEL were generally higher than composites with NPEF. The appropriate mass level for TW in both type composites was found to be 20 wt%. The equilibrium water sorption of NPEL/TW and NPEF/TW composites for 14-day immersion was determined as 0.10 % and 0.21 %, respectively. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used for characterization of the composites

Influence of aromatic amine hardeners in the cure kinetics of an epoxy resin used in advanced composites

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Michelle Leali Costa

2005-03-01

Full Text Available Composite structures for aerospace applications are mainly made by the well-known prepreg technology. In order to achieve adequate prepreg processing schedules, and consequently maximum fiber strength utilization, one has to know in deep the cure kinetics of matrix, which held the fibers together. This work describes a procedure to study the cure kinetic and has as example how aromatic amine hardeners influence the cure kinetics of an epoxy resin used in advanced composites. The investigation was carried out by using the DSC technique and it was found that depending on the system used the cure kinetics of the formulation obeys order n or autocatalytic order.

Mobility restrictions and glass transition behaviour of an epoxy resin under confinement.

Science.gov (United States)

Djemour, A; Sanctuary, R; Baller, J

2015-04-07

Confinement can have a big influence on the dynamics of glass formers in the vicinity of the glass transition. Already 40 to 50 K above the glass transition temperature, thermal equilibration of glass formers can be strongly influenced by the confining substrate. We investigate the linear thermal expansion and the specific heat capacity cp of an epoxy resin (diglycidyl ether of bisphenol A, DGEBA) in a temperature interval of 120 K around the glass transition temperature. The epoxy resin is filled into controlled pore glasses with pore diameters between 4 and 111 nm. Since DGEBA can form H-bonds with silica surfaces, we also investigate the influence of surface silanization of the porous substrates. In untreated substrates a core/shell structure of the epoxy resin can be identified. The glass transition behaviours of the bulk phase and that of the shell phase are different. In silanized substrates, the shell phase disappears. At a temperature well above the glass transition, a second transition is found for the bulk phase - both in the linear expansion data as well as in the specific heat capacity. The cp data do not allow excluding the glass transition of a third phase as being the cause for this transition, whereas the linear expansion data do so. The additional transition temperature is interpreted as a separation between two regimes: above this temperature, macroscopic flow of the bulk phase inside the porous structure is possible to balance the mismatch of thermal expansion coefficients between DGEBA and the substrate. Below the transition temperature, this degree of freedom is hindered by geometrical constraints of the porous substrates. Moreover, this second transition could also be found in the linear expansion data of the shell phase.

The Effect of Ultrasonic Treatment on Thermal Stability of the Cured Epoxy/Layered Silicate Nanocomposite

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N. Y. Yuhana

2012-01-01

Full Text Available The effect of ultrasonic treatment on thermal stability of binary systems containing epoxy and organic chemically modified montmorillonite (Cloisite 30B was studied. Differential scanning calorimetry (DSC, thermal gravimetric analysis (TGA, transmission electron microscopy (TEM, and wide angle X-ray diffraction (WAXD analysis were utilized. The mixing of epoxy and Cloisite 30B nanocomposites was performed by mechanical stirring, followed by 1 or 3-hour ultrasonic treatment, and polyetheramine as the curing agent. Both XRD and TEM analyses confirmed that the intercalation of Cloisite 30B was achieved. The d0 spacings for silicate in cured sample prepared at 1- and 3-hour duration of ultrasonic treatment were about 21 and 18 Å, respectively. This shows that shorter duration or ultrasonic treatment may be preferable to achieve higher d0 spacing of clay. This may be attributed to the increase in viscosity as homopolymerization process occurred, which restricts silicate dispersion. The 1-hour sonicated samples seem to be more thermally stable during the glass transition, but less stable during thermal decomposition process.

Novel halogen-free flame retardant thermoset from a hybrid hexakis (methoxymethyl melamine/phosphorus-containing epoxy resin cured with phenol formaldehyde novolac

Directory of Open Access Journals (Sweden)

2009-12-01

Full Text Available This paper describes the curing behaviours, thermal properties and flame-resistance of a novel halogen-free epoxy hybrid thermoset, prepared by the curing reaction of hexakis (methoxymethyl melamine (HMMM, a phosphorouscontaining epoxy resin (EPN-D with 9, 10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO group and phenol formaldehyde novolac (n-PF. The resultant thermosets showed high glass-transition temperatures (Tg, 123–147°C as determined by thermal mechanical analysis (TMA, excellent thermal stability with high 5 wt% decomposition temperatures (Td,5% ≥308°C and high char yields (Yc ≥39.4 wt% from the thermogravimetric analysis (TGA. All the cured EPND/ HMMM/n-PF hybrid resins achieved the UL 94 V-0 grade with high limited oxygen indices (LOI > 45.7. It is found that phosphorous and nitrogen elements in the cured EPN-D/HMMM/n-PF hybrid resins had a positive synergistic effect on the improvement of the flame retardancy.

Radiation processing of carbon fiber-acrylated epoxy composites

International Nuclear Information System (INIS)

Singh, A.; Saunders, C.B.

1992-01-01

Advanced composites, specifically carbon fiber reinforced epoxies, are being used for a variety of demanding structural applications, primarily because of their high strength-to-weight and stiffness-to-weight ratios, corrosion resistance, and damage tolerance characteristics. For these composites the key advantages of using electron beam (EB), rather than thermal curing, are curing at ambient temperature, reduced curing times for individual components, improved resin stability, fewer volatiles, and better control of the profile of energy absorption. Epoxy compounds do, however, have to be modified to make them EB curable. The electron beam penetration limit, a function of beam energy, product density, and the thickness of any container required, must also be examined when considering EB processing. Research is being conducted to develop EB-curable carbon fiber-acrylated epoxy composites. The tensile properties of these laminates are comparable to those of thermally cured epoxy laminates. Research is continuing to develop suitable resin formulations and coupling agents to optimize the mechanical properties of EB-cured carbon fiber laminates. In this chapter the EB curing of epoxies, processing considerations, and typical properties of EB-cured carbon fiber-acrylated epoxy laminates are discussed. (orig.)

Preparación y caracterización de filmes epoxi basados en aceite de linaza para aplicación

OpenAIRE

Gómez Carrera, Marta

2015-01-01

En este proyecto se preparan diferentes composiciones de filmes epoxi basados en aceite de linaza químicamente epoxidado (Epoxidized Linseed Oil-ELO) y su posterior curado con dos tipos de endurecedores, una poliaminoamida comercial y una poli(etilenimina) con dos pesos moleculares distintos. El objetivo final es la preparación de una pintura epoxi menos tóxica para el ser humano, sustituyendo parcialmente la molécula de diglicidil éter de bisfenol A (DGEBA), de las formulaciones epoxi, por m...

Characterization and analysis of epoxy/clay nanotubes composites; Cacaterizacao e analise de compositos de epoxi, argila e nanotubos de carbono

Energy Technology Data Exchange (ETDEWEB)

NONE

2011-07-01

An DGEBA epoxy matrix was used aiming to achieve a nanocomposite material, through the dispersion of (CNT) via mechanical stirring followed by sonication. In this work the following characterization were performed: mechanical characterization, differential scanning calorimetry (DSC), wide angle X-ray diffraction (WXRD) and scanning electron microscopy (SEM). The addition of CNT and modified clays promoted the increase of modulus of the epoxy matrix, and a synergistic effect between CNT and both clays could be presumed. SEM images of the fracture surface show the difference between the fracture surface area and the presence of clusters among the samples, allowing a correlation with the modulus of elasticity. X-ray diffractograms from 2{Theta} = 5 deg showed no peaks for modified clay samples, however it is possible to affirm that modified clay platelets are forming a less organized structure compared to the structure of the clay as natural in epoxy. (author)

Controversial effects of fumed silica on the curing and thermomechanical properties of epoxy composites

Directory of Open Access Journals (Sweden)

2010-06-01

Full Text Available The effect of fumed silica on the curing of a trimethylolpropane epoxy resin was investigated by thermal analysis methods like Differential Scanning Calorimetry (DSC, and Dynamic Mechanical Analysis (DMA. The fumed silica used here is a by-product of the silicon and ferrosilicon industry, consisting of micro and nanosized particles. Both the curing reaction and the properties of the obtained composites were affected by the filler content. Different trends were observed for filler contents above and below the 30 wt%. Up to 30 wt%, the behaviour can be explained as a predominantly agglomeration effect. For 30 wt% and higher filler contents, single particles seem to play a more important role.

Characterization and analysis of epoxy/clay nanotubes composites

International Nuclear Information System (INIS)

Sene, Tarcisio S.; Kock, Thyago; Coelho, Luiz A.F.; Becker, Daniela

2011-01-01

An DGEBA epoxy matrix was used aiming to achieve a nanocomposite material, through the dispersion of (CNT) via mechanical stirring followed by sonication. In this work the following characterization were performed: mechanical characterization, differential scanning calorimetry (DSC), wide angle X-ray diffraction (WXRD) and scanning electron microscopy (SEM). The addition of CNT and modified clays promoted the increase of modulus of the epoxy matrix, and a synergistic effect between CNT and both clays could be presumed. SEM images of the fracture surface show the difference between the fracture surface area and the presence of clusters among the samples, allowing a correlation with the modulus of elasticity. X-ray diffractograms from 2Θ = 5 deg showed no peaks for modified clay samples, however it is possible to affirm that modified clay platelets are forming a less organized structure compared to the structure of the clay as natural in epoxy. (author)

Morphology and parameters of crystallization the blend PE/Epoxy/PE-co-PEG; Morfologia e parametros de cristalizacao da blenda PE/epoxi/PE-co-PEG

Energy Technology Data Exchange (ETDEWEB)

Becker, Daniela; Coelho, Luiz Antonio Ferreira; Nack, Fernanda; Silva, Bruna Louise, E-mail: dep2db@joinville.udesc.br [Universidade do Estado de Santa Catarina (UDESC), Joinville, SC (Brazil). Centro de Ciencias Tecnologicas

2014-07-01

This study aims to evaluate the morphology and crystallization parameters of high density polyethylene (HDPE) with different concentrations of epoxy (DGEBA / OTBG), and the compatibility of this system was used and the copolymer polyethylene-block-poly (ethylene glycol) (PEG-co-PE). The blends were obtained by mechanical mixing on a torque rheometer (Haake). Determined the crystallization parameters of the test matrix differential scanning calorimetry (DSC) and by X-ray diffraction (XRD). The morphology of the system was analyzed by transmission electron microscopy (TEM). It was observed by XRD analysis that the addition of compatibilizer and epoxy resins do not interfere with the crystal structure of HDPE, indicating that the increase in crystallinity associated with the crystallization kinetics. It was observed that the compatibilizing helped the adhesion, reducing the size of the dispersed phase becomes a more stable morphology and obtaining a distribution of the dispersed epoxy phase. (author)

Rapid microwave processing of epoxy nanocomposites using carbon nanotubes

OpenAIRE

Luhyna, Nataliia; Inam, Fawad; Winnington, Ian

2013-01-01

Microwave processing is one of the rapid processing techniques for manufacturing nanocomposites. There is very little work focussing on the addition of CNTs for shortening the curing time of epoxy nanocomposites. Using microwave energy, the effect of CNT addition on the curing of epoxy nanocomposites was researched in this work. Differential scanning calorimetry (DSC) was used to determine the degree of cure for epoxy and nanocomposite samples. CNT addition significantly reduced the duration ...

Positioning and aligning CNTs by external magnetic field to assist localised epoxy cure

Directory of Open Access Journals (Sweden)

Ariu G.

2016-01-01

Full Text Available This work focuses on the generation of conductive networks through the localised alignment of nano fillers, such as multi-walled carbon nanotubes (MWCNTs. The feasibility of alignment and positioning of functionalised MWCNTs by external DC magnetic fields was investigated. The aim of this manipulation is to enhance resin curing through AC induction heating due to hysteresis losses from the nanotubes. Experimental analyses focused on in-depth assessment of the nanotube functionalisation, processing and characterisation of magnetic, rheological and cure kinetics properties of the MWCNT solution. The study has shown that an external magnetic field has great potential for positioning and alignment of CNTs. The study demonstrated potential for creating well-ordered architectures with an unprecedented level of control of network geometry. Magnetic characterisation indicated cobalt-plated nanotubes to be the most suitable candidate for magnetic alignment due to their high magnetic sensitivity. Epoxy/metal-plated CNT nanocomposite systems were validated by thermal analysis as induction heating mediums. The curing process could therefore be optimised by the use of dielectric resins. This study offers a first step towards the proof of concept of this technique as a novel repair technology.

Positioning and aligning CNTs by external magnetic field to assist localised epoxy cure

Science.gov (United States)

Ariu, G.; Hamerton, I.; Ivanov, D.

2016-01-01

This work focuses on the generation of conductive networks through the localised alignment of nano fillers, such as multi-walled carbon nanotubes (MWCNTs). The feasibility of alignment and positioning of functionalised MWCNTs by external DC magnetic fields was investigated. The aim of this manipulation is to enhance resin curing through AC induction heating due to hysteresis losses from the nanotubes. Experimental analyses focused on in-depth assessment of the nanotube functionalisation, processing and characterisation of magnetic, rheological and cure kinetics properties of the MWCNT solution. The study has shown that an external magnetic field has great potential for positioning and alignment of CNTs. The study demonstrated potential for creating well-ordered architectures with an unprecedented level of control of network geometry. Magnetic characterisation indicated cobalt-plated nanotubes to be the most suitable candidate for magnetic alignment due to their high magnetic sensitivity. Epoxy/metal-plated CNT nanocomposite systems were validated by thermal analysis as induction heating mediums. The curing process could therefore be optimised by the use of dielectric resins. This study offers a first step towards the proof of concept of this technique as a novel repair technology.

Effect of mixing sequence on the curing of amine-hardened epoxy/ alumina nanocomposites as assessed by optical refractometry

Directory of Open Access Journals (Sweden)

2008-08-01

Full Text Available High performance refractometry has been proven to be a useful tool to elucidate the isothermal curing process of nanocomposites. As a model system an amine-hardening epoxy filled with non-surface-treated alumina nanoparticles was selected. The tremendous resolution of this experimental technique is used to study morphological changes within nanocomposites via the refractive index. It is shown that these morphological changes are not simply due to the curing process but also depend on the sequence of mixing the nanoparticles either first into the resin or first into the hardener. Independent of the resin/hardener composition, the type of the mixing sequence discriminates systematically between two distinct refractive index curves produced by the curing process. The difference between the two refractive index curves increases monotonically with curing time, which underlines the importance of the initial molecular environment of the nanoparticles.

Kinetic studies of chemical shrinkage and residual stress formation in thermoset epoxy adhesives under confined curing conditions

Science.gov (United States)

Schumann, M.; Geiß, P. L.

2015-05-01

Faultless processing of thermoset polymers in demanding applications requires a profound mastering of the curing kinetics considering both the physico-chemical changes in the transition from the liquid to the solid state and the consolidation of the polymers network in the diffusion controlled curing regime past the gel point. Especially in adhesive joints shrinkage stress occurring at an early state of the curing process under confined conditions is likely to cause defects due to local debonding and thus reduce their strength and durability1. Rheometry is considered the method of choice to investigate the change of elastic and viscous properties in the progress of curing. Drawbacks however relate to experimental challenges in accessing the full range of kinetic parameters of thermoset resins with low initial viscosity from the very beginning of the curing reaction to the post-cure consolidation of the polymer due to the formation of secondary chemical bonds. Therefore the scope of this study was to interrelate rheological data with results from in-situ measurements of the shrinkage stress formation in adhesive joints and with the change of refractive index in the progress of curing. This combination of different methods has shown to be valuable in gaining advanced insight into the kinetics of the curing reaction. The experimental results are based on a multi component thermoset epoxy-amine adhesive.

Stronger Fire-Resistant Epoxies

Science.gov (United States)

Fohlen, George M.; Parker, John A.; Kumar, Devendra

1988-01-01

New curing agent improves mechanical properties and works at lower temperature. Use of aminophenoxycyclotriphosphazene curing agents yields stronger, more heat- and fire-resistant epoxy resins. Used with solvent if necessary for coating fabrics or casting films.

A Study of Clay-Epoxy Nanocomposites Consisting of Unmodified Clay and Organo Clay

Directory of Open Access Journals (Sweden)

Graham Edward

2006-04-01

Full Text Available Clay-epoxy nanocomposites were synthesized from DGEBA resin and montmorillonite clay with an in-situ polymerization. One type of untreated clay and two types of organo clay were used to produce the nanocompsoites. The aims of this study were to examine the nanocomposite structure using different tools and to compare the results between the unmodified clay and modified clays as nanofillers. Although diffractogram in reflection mode did not show any apparent peak of both types of materials, the transmitted XRD (X-Ray Difraction graphs, DSC (Differential Scanning Calorimeter analysis and TEM (Transmission Electron Microscope images revealed that the modified clay-epoxy and unmodified clay-epoxy provides different results. Interestingly, the micrographs showed that some of the modified clay layers possessed non-exfoliated layers in the modified clay-epoxy nanocomposites. Clay aggregates and a hackle pattern were found from E-SEM images for both types of nanocomposite materials. It is shown that different tools should be used to determine the nanocomposite structure.

Epoxy Nanocomposites Containing Zeolitic Imidazolate Framework-8.

Science.gov (United States)

Liu, Cong; Mullins, Michael; Hawkins, Spencer; Kotaki, Masaya; Sue, Hung-Jue

2018-01-10

Zeolitic imidazole framework-8 (ZIF-8) is utilized as a functional filler and a curing agent in the preparation of epoxy nanocomposites. The imidazole group on the surface of the ZIF-8 initiates epoxy curing, resulting in covalent bonding between the ZIF-8 crystals and epoxy matrix. A substantial reduction in dielectric constant and increase in tensile modulus were observed. The implication of the present study for utilization of metal-organic framework to improve physical and mechanical properties of polymeric matrixes is discussed.

Degradation of epoxy coatings under gamma irradiation

International Nuclear Information System (INIS)

Djouani, F.; Zahra, Y.; Fayolle, B.; Kuntz, M.; Verdu, J.

2013-01-01

Epoxy networks based on Diglycidyl ether of bisphenol A (DGEBA) and cured with Jeffamine® (POPA) or polyamidoamine (PAA) were gamma irradiated at 25 °C in air. Dose rates of 50, 200 or 2000 Gy h −1 for doses up 100 kGy were used. Structural changes were monitored by IR spectrophotometry, DSC and sol–gel analysis. Both networks display some common features: for I≥200 Gy h −1 , reaction products grow proportionally to time and the rate is a decreasing function of dose rate. The simplest explanation is that peroxy radicals are the main precursors of these products (in the dose rate domain under study), through a unimolecular rearrangement of which an hypothetical mechanism is proposed. DGEBA–POPA are more reactive then DGEBA–PAA networks (according to IR criteria), that can be attributed to the high reactivity of tertiary CH bands in polyoxypropylene segments. The oxidation of these sites leads to methyl ketones. A simple kinetic model in which methyl ketones result from rearrangements of tertiary peroxyls and from tertiary alkoxyls was proposed. It leads to an expression of the radiochemical yield of methyl ketones (G(MK)) of the form G(MK)=a+bI −1/2 where a and b are parameters depending of elementary rate constants. Experimental G(MK) values are reasonably well fitted by this equation. In DGEBA–PAA networks, a wide variety of oxidation products, among which amides predominate, can be observed. In these networks, chain scissions predominate over crosslinking, whereas a slight predominance of crosslinking was observed, at least for the lowest dose rate, in DGEBA–POPA. - Highlights: ► The effects of irradiation at three distinct dose rates have been studied on two epoxy networks. ► DGEBA–polyamidoamine networks appear more stable than DGEBA–polyoxypropylene diamine ones. ► A simple kinetic model involving methyl ketones is proposed.

Influence of Al2O3 nanoparticles on the isothermal cure of an epoxy resin

International Nuclear Information System (INIS)

Sanctuary, R; Baller, J; Zielinski, B; Becker, N; Krueger, J K; Philipp, M; Mueller, U; Ziehmer, M

2009-01-01

The influence of Al 2 O 3 nanoparticles on the curing of an epoxy thermoset based on diglycidyl ether of bisphenol A was investigated using temperature-modulated differential scanning calorimetry (TMDSC) and rheology. Diethylene triamine was used as a hardener. TMDSC not only allows for a systematic study of the kinetics of cure but simultaneously gives access to the evolution of the specific heat capacities of the thermosets. The technique thus provides insight into the glass transition behaviour of the nanocomposites and hence makes it possible to shed some light on the interaction between the nanoparticles and the polymer matrix. The Al 2 O 3 fillers are shown to accelerate the growth of macromolecules upon isothermal curing. Several mechanisms which possibly could be responsible for the acceleration are described. As a result of the faster network growth chemical vitrification occurs at earlier times in the filled thermosets and the specific reaction heat decreases with increasing nanoparticle concentration. Rheologic measurements of the zero-shear viscosity confirm the faster growth of the macromolecules in the presence of the nanoparticles.

Isothermal curing of polymer layered silicate nanocomposites based upon epoxy resin by means of anionic homopolymerisation

International Nuclear Information System (INIS)

Román, Frida; Calventus, Yolanda; Colomer, Pere; Hutchinson, John M.

2013-01-01

Highlights: • The nanocomposite with low content of clay displayed improved thermal properties. • The vitrification was observed in the isothermal curing. • Dielectric relaxations outside and inside of the clay galleries were detected. - Abstract: The use of an initiator, 4-(dimethylamino) pyridine (DMAP), to promote an anionic homopolymerisation reaction for the isothermal cure of polymer layered silicate (PLS) nanocomposites based on an epoxy resin, as well as the effect of the nanoclay content, have been studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dielectric relaxation spectroscopy (DRS) and transmission electron microscopy (TEM). The vitrification phenomenon was observed during the isothermal cure process, and it was found that the nanocomposite with a low clay content (2 wt%), denoted EDM2, shows improved thermal properties with respect to the unreinforced resin (denoted ED), while the nanocomposite with a higher clay content (5 wt%), denoted EDM5, displayed inferior properties. The cure kinetics were analysed by different methods, and it was observed that the activation energy and kinetic parameters of EDM2 were lower compared to the other two systems. Examination of the nanostructure of the cured EDM2 nanocomposite showed partial exfoliation, while the EDM5 system retains an intercalated nanostructure. In the DRS studies of the curing process of the EDM2 system, two dielectric relaxations were detected, which are associated with the molecular mobility in the curing reaction which takes place both outside and inside the clay galleries

Optical emission behavior and radiation resistance of epoxy resins

International Nuclear Information System (INIS)

Kawanishi, Shunichi; Udagawa, Akira; Hagiwara, Miyuki

1987-11-01

To make clear a mechanism of radiation resistance of epoxy resin systems, a role of energy trapping site induced in bisphenol A type epoxy resins cured with 4 kinds of aromatic amines (Φ N ) was studied in comparison with the case of aliphatic amine curing system through a measurement of optical emission. In the system of the epoxy resin cured with DETA, the optical emission from an excited state of bisphenol A unit of epoxy resin and a charge transfer complex was observed. On the other hand, the optical emission from Φ N was observed in the aromatic amine curing system. Their excitation spectrum consists of peaks of absorption spectrum of BA and those of Φ N , showing that the excited state of Φ N is formed through the excitation of both BA and Φ N . Therefore, the excited energy of BA transfers to the excited state of Φ N . Emission intensity of Φ N band was 20 ∼ 100 times as large as that of BA. These results indicate that the radiation energy is effectively released as an optical emission from excited state of Φ N in the epoxy resin when cured with aromatic amine. It can be concluded from the above results that aromatic amine hardeners contribute to enhancement of the radiation resistance of epoxy resin by acting as an energy transfer agent. (author)

Morphology and parameters of crystallization the blend PE/Epoxy/PE-co-PEG

International Nuclear Information System (INIS)

Becker, Daniela; Coelho, Luiz Antonio Ferreira; Nack, Fernanda; Silva, Bruna Louise

2014-01-01

This study aims to evaluate the morphology and crystallization parameters of high density polyethylene (HDPE) with different concentrations of epoxy (DGEBA / OTBG), and the compatibility of this system was used and the copolymer polyethylene-block-poly (ethylene glycol) (PEG-co-PE). The blends were obtained by mechanical mixing on a torque rheometer (Haake). Determined the crystallization parameters of the test matrix differential scanning calorimetry (DSC) and by X-ray diffraction (XRD). The morphology of the system was analyzed by transmission electron microscopy (TEM). It was observed by XRD analysis that the addition of compatibilizer and epoxy resins do not interfere with the crystal structure of HDPE, indicating that the increase in crystallinity associated with the crystallization kinetics. It was observed that the compatibilizing helped the adhesion, reducing the size of the dispersed phase becomes a more stable morphology and obtaining a distribution of the dispersed epoxy phase. (author)

Fabrication of tough epoxy with shape memory effects by UV-assisted direct-ink write printing.

Science.gov (United States)

Chen, Kaijuan; Kuang, Xiao; Li, Vincent; Kang, Guozheng; Qi, H Jerry

2018-03-07

3D printing of epoxy-based shape memory polymers with high mechanical strength, excellent thermal stability and chemical resistance is highly desirable for practical applications. However, thermally cured epoxy in general is difficult to print directly. There have been limited numbers of successes in printing epoxy but they suffer from relatively poor mechanical properties. Here, we present an ultraviolet (UV)-assisted 3D printing of thermally cured epoxy composites with high tensile toughness via a two-stage curing approach. The ink containing UV curable resin and epoxy oligomer is used for UV-assisted direct-ink write (DIW)-based 3D printing followed by thermal curing of the part containing the epoxy oligomer. The UV curable resin forms a network by photo polymerization after the 1st stage of UV curing, which can maintain the printed architecture at an elevated temperature. The 2nd stage thermal curing of the epoxy oligomer yields an interpenetrating polymer network (IPN) composite with highly enhanced mechanical properties. It is found that the printed IPN epoxy composites enabled by the two-stage curing show isotropic mechanical properties and high tensile toughness. We demonstrated that the 3D-printed high-toughness epoxy composites show good shape memory properties. This UV-assisted DIW 3D printing via a two-stage curing method can broaden the application of 3D printing to fabricate thermoset materials with enhanced tensile toughness and tunable properties for high-performance and functional applications.

Synthesis and characterization of optically transparent epoxy matrix nanocomposites

International Nuclear Information System (INIS)

Esposito Corcione, C.; Manera, M.G.; Maffezzoli, A.; Rella, R.

2009-01-01

In this work optically transparent nanocomposites were prepared and characterized from an optical and morphological point of view. An organically modified boehmite was added at different concentrations in a diglycidyl ether of bisphenol A (DGEBA) epoxy matrix, hardened with a polyether diamine. Nanocomposites were characterized structurally by X-ray diffraction (XRD), optically by UV-Vis-NIR spectrophotometry and their morphology was investigated by Atomic Force Microscopy (AFM). Morphological investigation reveals the presence of boehmite particles dispersed in the epoxy matrix in different dimensions ranging from ten to hundreds of nanometers; some aggregation in the particles is the tendency noticed in the AFM images. The acquisition of multiple AFM images in different areas of the sample was used for a statistical analysis of the volumetric distribution of boehmite aggregates. The obtained result, (3.6 ± 0.3)%vol, is well comparable to thermogravimetric analysis.

Novel epoxy-benzoxazine water-based emulsions with reactive benzoxazine surfactants for coatings

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M. Krajnc

2014-08-01

Full Text Available Novel epoxy-benzoxazine emulsions designed for water-based coatings were prepared and investigated. Bisphenol A-based epoxy resins with molar weights of 340, 377 and 1750 g/mol along with epoxidized soybean oil were emulsified using mono- and bi-functional benzoxazine surfactants, which are able to react with epoxy resins at their cure temperature. The structure of synthesized surfactants carrying one or two polyether chains was confirmed using Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance and differential scanning calorimetry. Stability of emulsions was verified by particle diameters measurements. Coatings, made directly from emulsions, were dried and cured at elevated temperature using 3,3'-dimetoxybenzidine as curing agent to ensure a highly cross-linked structure of thermosetting films. Curing process, thermal properties and hardness of cured films were investigated. It was found that benzoxazine molecules were well incorporated into the epoxy network upon curing, which ensures no void structure of cured copolymer and enhanced coating properties.

Electron beam induced cationic polymerization of epoxy resins. Dependence of Tg on conversion

International Nuclear Information System (INIS)

Degrand, H.; Cazaux, F.; Coqueret, X.

2002-01-01

Complete text of publication follows. The high-energy radiation curing of monomer blends polymerizing by a free radical or by a cationic mechanism receives increasing attention in the perspective of high performance composite materials. In the present work, we have focused our attention on epoxy formulations as models of the matrices polymerizing by a cationic mechanism that could be used in fiber-reinforced composites for aerospace applications. We have examined the progress of the electron beam (EB) induced polymerization of diglycidylether of bisphenol A (DGEBA) in the presence of a diaryliodonium salt (DAIS) by FTIR spectroscopy and by dynamic mechanical thermal analysis (DMA). The obtained results allow to draw the gradual increase of the temperature for the network thermomechanical transition (T a , associated with the glass transition temperature T g ) over a broad range of conversion (p) and reveal a peculiar behavior at high conversion. In this domain (p > 0.90), the material's T g is shown to decrease when conversion approaches unity. Moreover, the post-irradiation thermal treatment of the materials, that generally yields effective 'dark curing', appears to induce a decrease of T g , with an amplitude correlated with the amount of DAIS in the formulation. Owing to the particular nature of the propagating centers in cationic polymerisation, the thermal relaxation of ionic clusters trapped in the glassy matrix can be reasonably invoked as a possible cause for this behavior

Viscoelastic properties of graphene-based epoxy resins

Science.gov (United States)

Nobile, Maria Rossella; Fierro, Annalisa; Rosolia, Salvatore; Raimondo, Marialuigia; Lafdi, Khalid; Guadagno, Liberata

2015-12-01

In this paper the viscoelastic properties of an epoxy resin filled with graphene-based nanoparticles have been investigated in the liquid state, before curing, by means of a rotational rheometer equipped with a parallel plate geometry. Exfoliated graphite was prepared using traditional acid intercalation followed by a sudden treatment at high temperature (900°C). The percentage of exfoliated graphite was found to be 56%. The epoxy matrix was prepared by mixing a tetrafunctional precursor with a reactive diluent which produces a significant decrease in the viscosity of the epoxy precursor so that the dispersion step of nanofillers in the matrix can easily occur. The hardener agent, the 4,4-diaminodiphenyl sulfone (DDS), was added at a stoichiometric concentration with respect to all the epoxy rings. The inclusion of the partially exfoliated graphite (pEG) in the formulated epoxy mixture significantly modifies the rheological behaviour of the mixture itself. The epoxy mixture, indeed, shows a Newtonian behaviour while, at 3 wt % pEG content, the complex viscosity of the nanocomposite clearly shows a shear thinning behaviour with η* values much higher at the lower frequencies. The increase in complex viscosity with the increasing of the partially exfoliated graphite content was mostly caused by a dramatic increase in the storage modulus. All the graphene-based epoxy mixtures were cured by a two-stage curing cycles: a first isothermal stage was carried out at the lower temperature of 125°C for 1 hour while the second isothermal stage was performed at the higher temperature of 200°C for 3 hours. The mechanical properties of the cured nanocomposites show high values in the storage modulus and glass transition temperature.

Novel epoxy-silicone thermolytic transparent packaging adhesives chemical modified by ZnO nanowires for HB LEDs

International Nuclear Information System (INIS)

He Ying; Wang Junan; Pei Changlong; Song Jizhong; Zhu Di; Chen Jie

2010-01-01

A novel high transparent thermolytic epoxy-silicone for high-brightness light-emitting diode (HB-LED) is introduced, which was synthesized by polymerization using silicone matrix via diglycidyl ether bisphenol-A epoxy resin (DGEBA) as reinforcing agent, and filling ZnO nanowires to modify thermal conductivity and control refractive index of the hybrid material. The interactions of ZnO nanowires with polymers are mediated by the ligands attached to the nanoparticles. Thus, the ligands markedly influence the properties of ZnO nanowires/epoxy-silicone composites. The refractive indices of the prepared hybrid adhesives can be tuned by the ZnO nanowires from 1.4711 to 1.5605. Light transmittance can be increased by 20% from 80 to 95%. The thermal conductivity of the transparent packaging adhesives is 0.89-0.90 W/mK.

Application of a silver–olefin coordination polymer as a catalytic curing agent for self-healing epoxy polymers

International Nuclear Information System (INIS)

Everitt, D T; Coope, T S; Trask, R S; Bond, I P; Wass, D F

2015-01-01

A silver–olefin based coordination polymer was prepared in a simple, one step process to act as an initiator to facilitate the ring-opening polymerization of epoxides. Thermal analysis found the complex to be capable of curing a range of commercially available epoxy resins used in the manufacture of conventional composite materials. Curing of the oligomeric diglycidyl ether bisphenol A resin, Epon 828, in combination with a non-toxic solvent, ethyl phenylacetate, was studied by differential scanning calorimetry. The mechanical characterization of the resultant cured polymers was conducted by single lap shear tests. Tapered double cantilever beam (TDCB) test specimens containing 2.5 pph of silver–olefin initiator, both with and without embedded microcapsules, were analyzed for their healing performance. Healing efficiency values were found to be strongly dependent on the applied healing temperature. A mean recovery of 74% fracture load was found in TDCB samples after being healed at 70 °C for 48 h. (paper)

Preparation of a bio-based epoxy with comparable properties to those of petroleum-based counterparts

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X. Q. Liu

2012-04-01

Full Text Available In this paper a bio-based epoxy with outstanding thermal and mechanical properties was synthesized using a rosin-based epoxy monomer and a rosin-based curing agent. The chemical structures of rosin based epoxy monomer and curing agent were confirmed by Nuclear Magnetic Resonance (NMR and Fourier Transform Infrared (FT-IR spectra. The flexural mechanical and dynamic mechanical properties as well as thermal stability of the cured epoxy were investigated. The results showed that the cured epoxy exhibited a glass transition temperature (Tg of 164°C and its flexural strength and modulus were as high as 70 and 2200 MPa, respectively. This indicated that a wholly bio-based epoxy resin possessing high performance was successfully obtained.

Multi-step cure kinetic model of ultra-thin glass fiber epoxy prepreg exhibiting both autocatalytic and diffusion-controlled regimes under isothermal and dynamic-heating conditions

Science.gov (United States)

Kim, Ye Chan; Min, Hyunsung; Hong, Sungyong; Wang, Mei; Sun, Hanna; Park, In-Kyung; Choi, Hyouk Ryeol; Koo, Ja Choon; Moon, Hyungpil; Kim, Kwang J.; Suhr, Jonghwan; Nam, Jae-Do

2017-08-01

As packaging technologies are demanded that reduce the assembly area of substrate, thin composite laminate substrates require the utmost high performance in such material properties as the coefficient of thermal expansion (CTE), and stiffness. Accordingly, thermosetting resin systems, which consist of multiple fillers, monomers and/or catalysts in thermoset-based glass fiber prepregs, are extremely complicated and closely associated with rheological properties, which depend on the temperature cycles for cure. For the process control of these complex systems, it is usually required to obtain a reliable kinetic model that could be used for the complex thermal cycles, which usually includes both the isothermal and dynamic-heating segments. In this study, an ultra-thin prepreg with highly loaded silica beads and glass fibers in the epoxy/amine resin system was investigated as a model system by isothermal/dynamic heating experiments. The maximum degree of cure was obtained as a function of temperature. The curing kinetics of the model prepreg system exhibited a multi-step reaction and a limited conversion as a function of isothermal curing temperatures, which are often observed in epoxy cure system because of the rate-determining diffusion of polymer chain growth. The modified kinetic equation accurately described the isothermal behavior and the beginning of the dynamic-heating behavior by integrating the obtained maximum degree of cure into the kinetic model development.

Atomistic Modeling of Thermal Conductivity of Epoxy Nanotube Composites

Science.gov (United States)

Fasanella, Nicholas A.; Sundararaghavan, Veera

2016-05-01

The Green-Kubo method was used to investigate the thermal conductivity as a function of temperature for epoxy/single wall carbon nanotube (SWNT) nanocomposites. An epoxy network of DGEBA-DDS was built using the `dendrimer' growth approach, and conductivity was computed by taking into account long-range Coulombic forces via a k-space approach. Thermal conductivity was calculated in the direction perpendicular to, and along the SWNT axis for functionalized and pristine SWNT/epoxy nanocomposites. Inefficient phonon transport at the ends of nanotubes is an important factor in the thermal conductivity of the nanocomposites, and for this reason discontinuous nanotubes were modeled in addition to long nanotubes. The thermal conductivity of the long, pristine SWNT/epoxy system is equivalent to that of an isolated SWNT along its axis, but there was a 27% reduction perpendicular to the nanotube axis. The functionalized, long SWNT/epoxy system had a very large increase in thermal conductivity along the nanotube axis (~700%), as well as the directions perpendicular to the nanotube (64%). The discontinuous nanotubes displayed an increased thermal conductivity along the SWNT axis compared to neat epoxy (103-115% for the pristine SWNT/epoxy, and 91-103% for functionalized SWNT/epoxy system). The functionalized system also showed a 42% improvement perpendicular to the nanotube, while the pristine SWNT/epoxy system had no improvement over epoxy. The thermal conductivity tensor is averaged over all possible orientations to see the effects of randomly orientated nanotubes, and allow for experimental comparison. Excellent agreement is seen for the discontinuous, pristine SWNT/epoxy nanocomposite. These simulations demonstrate there exists a threshold of the SWNT length where the best improvement for a composite system with randomly oriented nanotubes would transition from pristine SWNTs to functionalized SWNTs.

Curing characteristics of an epoxy resin in the presence of functional graphite oxide with amine-rich surface

Energy Technology Data Exchange (ETDEWEB)

Li, Le [The State Key Lab of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065 (China); Zeng, Zhong [Safety Environment Quality Surveillance and Inspection Research Institute of CNPC Chuanqing Drilling & Exploration Corporation, Chengdu 618300 (China); Zou, Huawei, E-mail: hwzou@163.com [The State Key Lab of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065 (China); Liang, Mei, E-mail: liangmeiww@163.com [The State Key Lab of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065 (China)

2015-08-20

Highlights: • Functional graphite oxide with amine-rich surface was prepared and characterized. • Kinetic parameters were calculated by Kissinger method and autocatalytic model. • The incorporation of GO and DGO brings in an effect of inhibition on curing. • The inhibition effect weakens for its good compatibility and catalytic effect of DGO. - Abstract: Functional graphite oxide (DGO) with amine-rich surface was successfully prepared through the amidation reaction and characterized by X-ray diffraction analyses (XRD), Fourier transform infrared spectra (FTIR) and Raman spectra. The effects of functional graphite oxide on the curing kinetics of epoxy (EP) were investigated by means of differential scanning calorimetry (DSC). The curing kinetic parameters of EP, EP/graphite oxide (GO) and EP/functional graphite oxide were obtained. There was not much difference in total heat of reaction ΔH and peak temperature T{sub p} with the incorporation of GO or DGO. However, the activation energy, E{sub a}, and the overall order of reaction m + n were enhanced. Comprehensive kinetic analyses indicated that the incorporation of GO sheets brought in an effect of inhibition on curing process. While the inhibition effect weaken when the GO is modified with amine-rich surface. The possible curing mechanism and reaction pathways were proposed to provide a reasonable explanation.

Curing characteristics of an epoxy resin in the presence of functional graphite oxide with amine-rich surface

International Nuclear Information System (INIS)

Li, Le; Zeng, Zhong; Zou, Huawei; Liang, Mei

2015-01-01

Highlights: • Functional graphite oxide with amine-rich surface was prepared and characterized. • Kinetic parameters were calculated by Kissinger method and autocatalytic model. • The incorporation of GO and DGO brings in an effect of inhibition on curing. • The inhibition effect weakens for its good compatibility and catalytic effect of DGO. - Abstract: Functional graphite oxide (DGO) with amine-rich surface was successfully prepared through the amidation reaction and characterized by X-ray diffraction analyses (XRD), Fourier transform infrared spectra (FTIR) and Raman spectra. The effects of functional graphite oxide on the curing kinetics of epoxy (EP) were investigated by means of differential scanning calorimetry (DSC). The curing kinetic parameters of EP, EP/graphite oxide (GO) and EP/functional graphite oxide were obtained. There was not much difference in total heat of reaction ΔH and peak temperature T p with the incorporation of GO or DGO. However, the activation energy, E a , and the overall order of reaction m + n were enhanced. Comprehensive kinetic analyses indicated that the incorporation of GO sheets brought in an effect of inhibition on curing process. While the inhibition effect weaken when the GO is modified with amine-rich surface. The possible curing mechanism and reaction pathways were proposed to provide a reasonable explanation

Multi-wall carbon nanotubes/epoxy resin composites characterization of the starting materials and evaluation of thermal and electrical conductivity

International Nuclear Information System (INIS)

Silva, Wellington Marcos da

2009-01-01

In this study we investigate the electrical and thermal properties of I) composite materials fabricated with O, I, 0,5 and I wt% of concentric multi-wall carbon nanotubes/epoxy resin (MWNT) dispersed randomly in the resin; 2) MWNT buckypaper/resin composite materials; 3) and neat MWNT buckypaper. Initially, we use the techniques of thermogravimetry, infrared spectroscopy, nuclear magnetic resonance, energy dispersive spectroscopy, x-ray fluorescence, scanning and transmission electron microscopy for a broadening characterization of the starting materials, to evaluate its morphology, purity, chemical composition and structure, in order to optimize the properties of crosslinked resin and, consequently, of the composite systems. Important parameters such as the average molecular mass and the equivalent weight of epoxy resin (DGEBA) were determined by 1 H-NMR analysis and, after that, resin/curing agent relations with Phr 10, 15, 20 and 53,2 were elaborated and investigated by thermogravimetry, the resin/curing agent relation with Phr 10 showed to be the most thermally stable. This stoichiometric relation was used to elaborate the composites. We have evaluated that the effect of adding 10 wt% of the solvent acetone to the epoxy resin preparation does not alter its properties so we have adopted two routes to fabricate the composites. In the first route we used 10 wt% of acetone and, in the second the MWNT were dispersed in the matrix without using the solvent. However, no significant difference was observed for the dispersion of the bundle tubes in both systems. The electrical conductivity of the composites and buckypapers was evaluated by impedance spectroscopy and the thermal conductivity by the flash laser flash method. Only the buckypapers presented high values for electrical conductivity (10 3 S.m -1 ). The composite systems presented values of 10 -3 S.m -1 , only a bit different from the value of the crosslinked resin. For thermal conductivity, the values for the

Proton conductive membranes based on poly (styrene-co-allyl alcohol semi-IPN

Directory of Open Access Journals (Sweden)

Felipe Augusto Moro Loureiro

2014-01-01

Full Text Available The optimization of fuel cell materials, particularly polymer membranes, for PEMFC has driven the development of methods and alternatives to achieve systems with more adequate properties to this application. The sulfonation of poly (styrene-co-allyl alcohol (PSAA, using sulfonating agent:styrene ratios of 2:1, 1:1, 1:2, 1:4, 1:6, 1:8 and 1:10, was previously performed to obtain proton conductive polymer membranes. Most of those membranes exhibited solubility in water with increasing temperature and showed conductivity of approximately 10-5 S cm-1. In order to optimize the PSAA properties, especially decreasing its solubility, semi-IPN (SIPN membranes are proposed in the present study. These membranes were obtained from the diglycidyl ether of bisphenol A (DGEBA, curing reactions in presence of DDS (4,4-diaminodiphenyl sulfone and PSAA. Different DGEBA/PSAA weight ratios were employed, varying the PSAA concentration between 9 and 50% and keeping the mass ratio of DGEBA:DDS as 1:1. The samples were characterized by FTIR and by electrochemical impedance spectroscopy. Unperturbed bands of PSAA were observed in the FTIR spectra of membranes, suggesting that chemical integrity of the polymer is maintained during the synthesis. In particular, bands involving C-C stretching (1450 cm-1, C=C (aromatic, ~ 3030 cm-1 and C-H (2818 and 2928 cm-1 were observed, unchanged after the synthesis. The disappearance or reduction of the intensity of the band at 916 cm-1, attributed to the DGEBA epoxy ring, is evidenced for all samples, indicating the epoxy ring opening and the DGEBA crosslinking. Conductivity of H3PO4 doped membranes increases with temperature, reaching 10-4 S cm-1.

Mechanical Reinforcement of Epoxy Composites with Carbon Fibers and HDPE

Science.gov (United States)

He, R.; Chang, Q.; Huang, X.; Li, J.

2018-01-01

Silanized carbon fibers (CFs) and a high-density polyethylene with amino terminal groups (HDPE) were introduced into epoxy resins to fabricate high-performance composites. A. mechanical characterization of the composites was performed to investigate the effect of CFs in cured epoxy/HDPE systems. The composites revealed a noticeable improvement in the tensile strength, elongation at break, flexural strength, and impact strength in comparison with those of neat epoxy and cured epoxy/HDPE systems. SEM micrographs showed that the toughening effect could be explained by yield deformations, phase separation, and microcracking.

Fatigue life extension of epoxy materials using ultrafast epoxy-SbF5 healing system introduced by manual infiltration

Directory of Open Access Journals (Sweden)

X. J. Ye

2015-03-01

Full Text Available The present paper is devoted to the verification of the capability of epoxy-SbF5 system as a healing chemistry for rapidly retarding and/or arresting fatigue cracks in epoxy materials at room temperature. Owing to the very fast curing speed of epoxy catalyzed by SbF5, epoxy monomer and the hardener (ethanol solution of SbF5–ethanol complex are successively infiltrated into the fracture plane under cyclic loading during the tension-tension fatigue test. As a result, the mechanisms including hydrodynamic pressure crack tip shielding, polymeric wedge and adhesive bonding of the healing agent are revealed. It is found that the healing agent forms solidified wedge at the crack tip within 20 s after start of polymerization of the epoxy monomer, so that the highest healing effect is offered at the moment. The epoxy-SbF5 system proves to be effective in rapidly obstructing fatigue crack propagation (despite that its cured version has lower fracture toughness than the matrix, and satisfies the requirement of constructing fast self-healing polymeric materials.

Facile fabrication of superhydrophobic films with fractal structures using epoxy resin microspheres

Energy Technology Data Exchange (ETDEWEB)

Quan, Yun-Yun; Zhang, Li-Zhi, E-mail: lzzhang@scut.edu.cn

2014-02-15

A simple method has been developed to fabricate superhydrophobic surfaces with fractal structures with epoxy resin microspheres (ERMs). The ERMs is produced by phase separation in an epoxy-amine curing system with a silica sol (SS) dispersant. The transparent epoxy solution becomes cloudy and turns into epoxy suspension (ES) in this process. The fractal structure (two tier structure) generated by synthetic epoxy resin microspheres (ERMs) and deposited nanoincrutations on the surfaces of these ERMs, which have been observed by scanning electron microscope (SEM). The curing time of ES is an important condition to obtain films with good comprehensive performances. Superhydrophobic films can be prepared by adding extra SS into ES with a curing time longer than 5 h. The optimal curing time is 10 h to fabricate a film with good mechanical stability and high superhydrophobicity. In addition, a surface with anti-wetting property of impacting microdroplets can be fabricated by prolonging the curing time of ES to 24 h. The gradually decreased hydrophilic groups resulted from a longer curing time enable the surface to have smaller surface adhesions to water droplets, which is the main reason to keep its superhydrophobicity under impacting conditions. The coated surface is highly hydrophobic and the impacting water droplets are bounced off from the surface.

Facile fabrication of superhydrophobic films with fractal structures using epoxy resin microspheres

Science.gov (United States)

Quan, Yun-Yun; Zhang, Li-Zhi

2014-02-01

A simple method has been developed to fabricate superhydrophobic surfaces with fractal structures with epoxy resin microspheres (ERMs). The ERMs is produced by phase separation in an epoxy-amine curing system with a silica sol (SS) dispersant. The transparent epoxy solution becomes cloudy and turns into epoxy suspension (ES) in this process. The fractal structure (two tier structure) generated by synthetic epoxy resin microspheres (ERMs) and deposited nanoincrutations on the surfaces of these ERMs, which have been observed by scanning electron microscope (SEM). The curing time of ES is an important condition to obtain films with good comprehensive performances. Superhydrophobic films can be prepared by adding extra SS into ES with a curing time longer than 5 h. The optimal curing time is 10 h to fabricate a film with good mechanical stability and high superhydrophobicity. In addition, a surface with anti-wetting property of impacting microdroplets can be fabricated by prolonging the curing time of ES to 24 h. The gradually decreased hydrophilic groups resulted from a longer curing time enable the surface to have smaller surface adhesions to water droplets, which is the main reason to keep its superhydrophobicity under impacting conditions. The coated surface is highly hydrophobic and the impacting water droplets are bounced off from the surface.

Optical storage in azobenzene-containing epoxy polymers processed as Langmuir Blodgett films

International Nuclear Information System (INIS)

Fernández, Raquel; Mondragon, Iñaki; Sanfelice, Rafaela C.; Pavinatto, Felippe J.; Oliveira, Osvaldo N.; Oyanguren, Patricia; Galante, María J.

2013-01-01

In this study, azocopolymers containing different main-chain segments have been synthesized with diglycidyl ether of bisphenol A (DGEBA, DER 332, n = 0.03) and the azochromophore Disperse Orange 3 (DO3) cured with two monoamines, viz. benzylamine (BA) and m-toluidine (MT). The photoinduced birefringence was investigated in films produced with these azopolymers using the spin coating (SC) and Langmuir Blodgett (LB) techniques. In the LB films, birefringence increased with the content of azochromophore and the film thickness, as expected. The nanostructured nature of the LB films led to an enhanced birefringence and faster dynamics in the writing process, compared to the SC films. In summary, the combination of azocopolymers and the LB method may allow materials with tuned properties for various optical applications, including in biological systems were photoisomerization may be used to trigger actions such as drug delivery. Highlights: ► Langmuir Blodgett (LB) films of epoxy-based azopolymers were obtained and analyzed. ► Optical properties of LB and spin coated (SC) films were compared. ► Azo content, structure, laser power and number of layers were main factors studied. ► LB films had larger free volume for the azobenzenes isomerization than SC. ► LB films led to higher birefringence and faster dynamics compared to SC

Optical storage in azobenzene-containing epoxy polymers processed as Langmuir Blodgett films

Energy Technology Data Exchange (ETDEWEB)

Fernández, Raquel; Mondragon, Iñaki [‘Materials - Technologies’ Group, Department of Chemical and Environmental Engineering, Polytechnic School, Universidad País Vasco/Euskal Herriko Unibertsitatea, Pza Europa 1, 20018 Donostia-San Sebastián (Spain); Sanfelice, Rafaela C.; Pavinatto, Felippe J.; Oliveira, Osvaldo N. [Instituto de Física de São Carlos, Universidade de São Paulo, Av. Trabalhador São Carlense, 400, Centro, CEP 13560-970, São Carlos (Brazil); Oyanguren, Patricia [Institute of Materials Science and Technology (INTEMA), University of Mar del Plata and National Research Council (CONICET), J. B. Justo 4302, 7600 Mar del Plata (Argentina); Galante, María J., E-mail: galant@fi.mdp.edu.ar [Institute of Materials Science and Technology (INTEMA), University of Mar del Plata and National Research Council (CONICET), J. B. Justo 4302, 7600 Mar del Plata (Argentina)

2013-04-01

In this study, azocopolymers containing different main-chain segments have been synthesized with diglycidyl ether of bisphenol A (DGEBA, DER 332, n = 0.03) and the azochromophore Disperse Orange 3 (DO3) cured with two monoamines, viz. benzylamine (BA) and m-toluidine (MT). The photoinduced birefringence was investigated in films produced with these azopolymers using the spin coating (SC) and Langmuir Blodgett (LB) techniques. In the LB films, birefringence increased with the content of azochromophore and the film thickness, as expected. The nanostructured nature of the LB films led to an enhanced birefringence and faster dynamics in the writing process, compared to the SC films. In summary, the combination of azocopolymers and the LB method may allow materials with tuned properties for various optical applications, including in biological systems were photoisomerization may be used to trigger actions such as drug delivery. Highlights: ► Langmuir Blodgett (LB) films of epoxy-based azopolymers were obtained and analyzed. ► Optical properties of LB and spin coated (SC) films were compared. ► Azo content, structure, laser power and number of layers were main factors studied. ► LB films had larger free volume for the azobenzenes isomerization than SC. ► LB films led to higher birefringence and faster dynamics compared to SC.

Critical parameters for electron beam curing of cationic epoxies and property comparison of electron beam cured cationic epoxies versus thermal cured resins and composites

International Nuclear Information System (INIS)

Janke, C.J.; Norris, R.E.; Yarborough, K.; Lopata, V.J.

1997-01-01

Electron beam curing of composites is a nonthermal, nonautoclave curing process offering the following advantages compared to conventional thermal curing: substantially reduced manufacturing costs and curing times; improvements in part quality and performance; reduced environmental and health concerns; and improvements in material handling. In 1994 a Cooperative Research and Development Agreement (CRADA), sponsored by the Department of Energy Defense Programs and 10 industrial partners, was established to advance electron beam curing of composites. The CRADA has successfully developed hundreds of new toughened and untoughened resins, offering unlimited formulation and processing flexibility. Several patent applications have been filed for this work. Composites made from these easily processable, low shrinkage material match the performance of thermal cured composites and exhibit: low void contents comparable to autoclave cured composites (less than 1%); superb low water absorption values in the same range as cyanate esters (less than 1%); glass transition temperatures rivaling those of polyimides (greater than 390 C); mechanical properties comparable to high performance, autoclave cured composites; and excellent property retention after cryogenic and thermal cycling. These materials have been used to manufacture many composite parts using various fabrication processes including hand lay-up, tow placement, filament winding, resin transfer molding and vacuum assisted resin transfer molding

Influence of Al{sub 2}O{sub 3} nanoparticles on the isothermal cure of an epoxy resin

Energy Technology Data Exchange (ETDEWEB)

Sanctuary, R; Baller, J; Zielinski, B; Becker, N; Krueger, J K; Philipp, M; Mueller, U; Ziehmer, M [University of Luxembourg, 162a avenue de la Faiencerie, L-1511 (Luxembourg)], E-mail: roland.sanctuary@uni.lu

2009-01-21

The influence of Al{sub 2}O{sub 3} nanoparticles on the curing of an epoxy thermoset based on diglycidyl ether of bisphenol A was investigated using temperature-modulated differential scanning calorimetry (TMDSC) and rheology. Diethylene triamine was used as a hardener. TMDSC not only allows for a systematic study of the kinetics of cure but simultaneously gives access to the evolution of the specific heat capacities of the thermosets. The technique thus provides insight into the glass transition behaviour of the nanocomposites and hence makes it possible to shed some light on the interaction between the nanoparticles and the polymer matrix. The Al{sub 2}O{sub 3} fillers are shown to accelerate the growth of macromolecules upon isothermal curing. Several mechanisms which possibly could be responsible for the acceleration are described. As a result of the faster network growth chemical vitrification occurs at earlier times in the filled thermosets and the specific reaction heat decreases with increasing nanoparticle concentration. Rheologic measurements of the zero-shear viscosity confirm the faster growth of the macromolecules in the presence of the nanoparticles.

Synthesis and electrical characterization of low-temperature thermal-cured epoxy resin/functionalized silica hybrid-thin films for application as gate dielectrics

Energy Technology Data Exchange (ETDEWEB)

Na, Moonkyong, E-mail: nmk@keri.re.kr [HVDC Research Division, Korea Electrotechnology Research Institute, Changwon, 642-120 (Korea, Republic of); System on Chip Chemical Process Research Center, Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 790-784 (Korea, Republic of); Kang, Young Taec [Creative and Fundamental Research Division, Korea Electrotechnology Research Institute, Changwon, 642-120 (Korea, Republic of); Department of Polymer Science and Engineering, Pusan National University, Busan, 609-735 (Korea, Republic of); Kim, Sang Cheol [HVDC Research Division, Korea Electrotechnology Research Institute, Changwon, 642-120 (Korea, Republic of); Kim, Eun Dong [Creative and Fundamental Research Division, Korea Electrotechnology Research Institute, Changwon, 642-120 (Korea, Republic of)

2013-07-31

Thermal-cured hybrid materials were synthesized from homogenous hybrid sols of epoxy resins and organoalkoxysilane-functionalized silica. The chemical structures of raw materials and obtained hybrid materials were characterized using Fourier transform infrared spectroscopy. The thermal resistance of the hybrids was enhanced by hybridization. The interaction between epoxy matrix and the silica particles, which caused hydrogen bonding and van der Waals force was strengthened by organoalkoxysilane. The degradation temperature of the hybrids was improved by approximately 30 °C over that of the parent epoxy material. The hybrid materials were formed into uniformly coated thin films of about 50 nm-thick using a spin coater. An optimum mixing ratio was used to form smooth-surfaced hybrid films. The electrical property of the hybrid film was characterized, and the leakage current was found to be well below 10{sup −6} A cm{sup −2}. - Highlights: • Preparation of thermal-curable hybrid materials using epoxy resin and silica. • The thermal stability was enhanced through hybridization. • The insulation property of hybrid film was investigated as gate dielectrics.

Influence of the silica fillers on the ageing of epoxy resins under irradiations

International Nuclear Information System (INIS)

Benard, F.

2004-01-01

Various studies were carried out on the ageing of epoxy resins under irradiations. In all cases, pure polymers were studied. The aim of our work managed by the CEA and the CNRS consists on studying the part of fillers and particularly the part of silica on ageing process under electron beam irradiations. Because of their wide use in industrial applications and especially in nuclear environment, the DGEBA-TETA resins (Diglycidylether of Bisphenol A - Triethylenetetramine) were chosen. Those epoxy resins are difficult to analyse because of their insolubility. Some pure and nano-metric silica filled chemical models which chemical structure very close to the one the DGEBA/TETA resin were synthesized and analysed with classical methods in organic chemistry. A major phenomenon of rupture of the C-O and C-N chemical bonds with creation of phenolic extremities, methylketone extremities, of primary and tertiary amines and notably enamine functions were revealed by the analyses. The quantitative 1 H and 13 C NMR analyses revealed the screen effect due to the silica and the reactions between the chemical species created by the irradiations and the silica surface. Thermic and thermodynamic analyses of the different epoxy resins in function of the irradiation dose and of the kind of silica showed the decrease of the glass transition temperature, of the relaxation temperature and of the crosslink density confirming the major phenomenon of bond ruptures during irradiations. With silica, the decrease of the crosslink density is slowed. This phenomenon can be explained with interactions between the nano-metric silica surface and the epoxy resin offsetting the effect of the chain rupture on the resin mechanical properties. The 13 C solid state NMR analyses confirmed the choice of the chemical models and permitted to detect the chemical species created by the irradiations. The analyse of the polarization transfers with 13 C CP-MAS NMR spectroscopy revealed the stiffening of the nano

Shape memory polymers from benzoxazine-modified epoxy

International Nuclear Information System (INIS)

Rimdusit, Sarawut; Lohwerathama, Montha; Dueramae, Isala; Hemvichian, Kasinee; Kasemsiri, Pornnapa

2013-01-01

Novel shape memory polymers (SMPs) were prepared from benzoxazine-modified epoxy resin. Specimens consisting of aromatic epoxy (E), aliphatic epoxy (N), Jeffamine D230 (D) and BA-a benzoxazine monomer (B) were evaluated. The mole ratio of D/B was used as a mixed curing agent for an epoxy system with a fixed E/N. The effects of BA-a content on the thermal, mechanical and shape memory properties of epoxy-based shape memory polymers (SMPs) were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), flexural test and shape recovery test. The results revealed that the obtained SMPs exhibited a higher flexural strength and flexural modulus than those of the unmodified epoxy-based SMP at room temperature and at 20 ° C above glass transition temperature (T g ). The presence of 1 mol BA-a as a curing agent provided the specimen with the highest T g , i.e. about 72 ° C higher than that of epoxy-based SMP cured by Jeffamine D230. All SMP samples needed only a few minutes to fully recover to their original shape. The samples exhibited high shape fixity (98–99%) and shape recovery ratio (90–100%). In addition, the recovery stress values increased with increasing BA-a mole ratio from 20 to 38 kPa, when BA-a up to 1 mol ratio was added. All of the SMP samples exhibited only minimum change in their flexural strength at the end of a 100 recovery cycles test. (paper)

Characterization of fracture toughness of epoxy resin after hygrothermal aging

KAUST Repository

Quispe, Gustavo Q.

2013-07-01

Characterization of fracture toughness of epoxy resin after hygrothermal ageing Gustavo Quino Quispe The aim of this work is to characterize the e ects of hygrothermal aging in the plain strain fracture toughness of the epoxy system composed by cycloaliphatic epoxy resin and diglycidyl ether of bisphenol-A (DGEBA). For this, after having been under hygrothermal aging in a climatic chamber, epoxy samples were studied using ASTM D5045 fracture toughness test, and micrography and roughness measurements of the fracture surface. It is reported a rapid decrease of GIc and KIc during the rst 2 days. Moreover, a numerical model [13] was used to simulate and see with more detail the water absorption in the aged samples. From that, it was observed the heterogeneous distribution of water. Accordingly, it was proposed that the results should be correlated with the water content at the vicinity of the crack tip. Consequently, it was possible to obtain, by quasi-static simulations, the ideal load-displacement curves of crack propagation in the heterogeneous samples. Finally, another contribution of this work is the study of the fracture surface, that gives a clue of the relationship among the fracture energy, the appearance of microcracks in the fracture surface, and the roughness (Ra).

Rubber-like Quasi-thermosetting Polyetheramine-cured Epoxy Asphalt Composites Capable of Being Opened to Traffic Immediately.

Science.gov (United States)

Kang, Yang; Wu, Qiang; Jin, Rui; Yu, Pengfei; Cheng, Jixiang

2016-01-06

This paper reports the facile preparation, mechanical performance and linear viscoelasticity of polyetheramine-cured rubber-like epoxy asphalt composites (EACs) with different asphalt contents. Compared with previous EACs prepared via complex chemical reactions and time-consuming high-temperature curing, the EACs reported here were obtained by using a compatible, bi-functional polyetheramine and a simple physical co-blend process, which make the EACs feasibly scalable for production at a lower cost. The EACs were cured for 1 h at 160 °C and 3 d at 60 °C; therefore, these composites can be opened to traffic immediately. The EACs have a much greater temperature stability than common thermoplastic polymer-modified asphalt composites from -30 °C to 120 °C, but their complex shear moduli at higher temperatures slightly decrease instead of remaining constant when temperatures are greater than 80 °C, especially for the higher asphalt content composites; that is, these composites are quasi-thermosetting. Wicket plots illustrate that the EACs reported here are thermorheological simple materials, and the master curves are constructed and well-fitted by generalized logistic sigmoidal model functions. This research provides a facile, low-cost method for the preparation of polyetheramine-cured EACs that can be opened to traffic immediately, and the concept of quasi-thermosetting may facilitate the development of cheaper EACs for advanced applications.

Rubber-like Quasi-thermosetting Polyetheramine-cured Epoxy Asphalt Composites Capable of Being Opened to Traffic Immediately

Science.gov (United States)

Kang, Yang; Wu, Qiang; Jin, Rui; Yu, Pengfei; Cheng, Jixiang

2016-01-01

This paper reports the facile preparation, mechanical performance and linear viscoelasticity of polyetheramine-cured rubber-like epoxy asphalt composites (EACs) with different asphalt contents. Compared with previous EACs prepared via complex chemical reactions and time-consuming high-temperature curing, the EACs reported here were obtained by using a compatible, bi-functional polyetheramine and a simple physical co-blend process, which make the EACs feasibly scalable for production at a lower cost. The EACs were cured for 1 h at 160 °C and 3 d at 60 °C therefore, these composites can be opened to traffic immediately. The EACs have a much greater temperature stability than common thermoplastic polymer-modified asphalt composites from -30 °C to 120 °C, but their complex shear moduli at higher temperatures slightly decrease instead of remaining constant when temperatures are greater than 80 °C, especially for the higher asphalt content composites; that is, these composites are quasi-thermosetting. Wicket plots illustrate that the EACs reported here are thermorheological simple materials, and the master curves are constructed and well-fitted by generalized logistic sigmoidal model functions. This research provides a facile, low-cost method for the preparation of polyetheramine-cured EACs that can be opened to traffic immediately, and the concept of quasi-thermosetting may facilitate the development of cheaper EACs for advanced applications.

Thermally activated, single component epoxy systems

KAUST Repository

Unruh, David A.; Pastine, Stefan J.; Moreton, Jessica C.; Frechet, Jean

2011-01-01

A single component epoxy system in which the resin and hardener components found in many two-component epoxies are combined onto the same molecule is described. The single molecule precursor to the epoxy resin contains both multiple epoxide moieties and a diamine held latent by thermally degradable carbamate linkages. These bis-carbamate "single molecule epoxies" have an essentially infinite shelf life and access a significant range in curing temperatures related to the structure of the carbamate linkages used. © 2011 American Chemical Society.

Thermally activated, single component epoxy systems

KAUST Repository

Unruh, David A.

2011-08-23

A single component epoxy system in which the resin and hardener components found in many two-component epoxies are combined onto the same molecule is described. The single molecule precursor to the epoxy resin contains both multiple epoxide moieties and a diamine held latent by thermally degradable carbamate linkages. These bis-carbamate "single molecule epoxies" have an essentially infinite shelf life and access a significant range in curing temperatures related to the structure of the carbamate linkages used. © 2011 American Chemical Society.

Latent Hardeners for the Assembly of Epoxy Composites

Science.gov (United States)

Palmieri, Frank; Wohl, Christopher J.; Connell, John W.; Mercado, Zoar; Galloway, Jordan

2016-01-01

Large-scale composite structures are commonly joined by secondary bonding of molded-and-cured thermoset components. This approach may result in unpredictable joint strengths. In contrast, assemblies made by co-curing, although limited in size by the mold, result in stable structures, and are certifiable for commercial aviation because of structural continuity through the joints. Multifunctional epoxy resins were prepared that should produce fully-cured subcomponents with uncured joining surfaces, enabling them to be assembled by co-curing in a subsequent out-of-autoclave process. Aromatic diamines were protected by condensation with a ketone or aldehyde to form imines. Properties of the amine-cured epoxy were compared with those of commercially available thermosetting epoxy resins and rheology and thermal analysis were used to demonstrate the efficacy of imine protection. Optimum conditions to reverse the protecting chemistry in the solid state using moisture and acid catalysis were determined. Alternative chemistries were also investigated. For example, chain reaction depolymerization and photoinitiated catalysts would be expected to minimize liberation of volatile organic content upon deprotection and avoid residual reactive species that could damage the resin. Results from the analysis of protected and deprotected resins will be presented.

Cure Behavior and Thermal Properties of Diepoxidized Cardanol Resin Cured by Electron Beam Process

International Nuclear Information System (INIS)

Cho, Donghwan; Cheon, Jinsil

2013-01-01

Thermal curing of epoxy resin requires high temperature, time-consuming process and the volatilization of hardener. It has known that electron beam curing of epoxy resin is a fast process and occurs at low or room temperature that help reduce residual mechanical stresses in thermosetting polymers. Diepoxidized cardanol (DEC) can be synthesized by an enzymatic method from cashew nut shell liquid (CNSL), that constitutes nearly one-third of the total nut weight. A large amount of CNSL can be formed as a byproduct of the mechanical processes used to render the cashew kerneledible and its total production approaches one million tons annually, which can be bio-degradable and replace the industrial thermosetting plastics. It is expected that DEC may be cured as in an epoxy resin, which was constituted on two epoxide group and long alkyl chain, and two-types of onium salts (cationic initiator) were used as a photo-initiator. The experimental variables of this study are type and concentration of photo-initiators and electron beam dosage. In this study, the effects of initiator type and concentration on the cure behavior and the thermal properties of DEC resin processed by using electron beam technology were studied using FT-IR, TGA, TMA, DSC, and DMA. Figure 1 is the FT-IR results, showing the change of chemical structure of pure DEC and electron beam cured DEC. The characteristic absorption peak of epoxide group appeared at 850cm -1 . The shape and the height were reduced when the sample was irradiated with electron beam. From this result, the epoxide groups is DEC were opened by electron beam and cured. After then, electron beam cured DEC was investigated the effect of forming 3-dimensional network

Cure Behavior and Thermal Properties of Diepoxidized Cardanol Resin Cured by Electron Beam Process

Energy Technology Data Exchange (ETDEWEB)

Cho, Donghwan; Cheon, Jinsil [Kumoh National Institute of Technology, Gumi (Korea, Republic of)

2013-07-01

Thermal curing of epoxy resin requires high temperature, time-consuming process and the volatilization of hardener. It has known that electron beam curing of epoxy resin is a fast process and occurs at low or room temperature that help reduce residual mechanical stresses in thermosetting polymers. Diepoxidized cardanol (DEC) can be synthesized by an enzymatic method from cashew nut shell liquid (CNSL), that constitutes nearly one-third of the total nut weight. A large amount of CNSL can be formed as a byproduct of the mechanical processes used to render the cashew kerneledible and its total production approaches one million tons annually, which can be bio-degradable and replace the industrial thermosetting plastics. It is expected that DEC may be cured as in an epoxy resin, which was constituted on two epoxide group and long alkyl chain, and two-types of onium salts (cationic initiator) were used as a photo-initiator. The experimental variables of this study are type and concentration of photo-initiators and electron beam dosage. In this study, the effects of initiator type and concentration on the cure behavior and the thermal properties of DEC resin processed by using electron beam technology were studied using FT-IR, TGA, TMA, DSC, and DMA. Figure 1 is the FT-IR results, showing the change of chemical structure of pure DEC and electron beam cured DEC. The characteristic absorption peak of epoxide group appeared at 850cm{sup -1}. The shape and the height were reduced when the sample was irradiated with electron beam. From this result, the epoxide groups is DEC were opened by electron beam and cured. After then, electron beam cured DEC was investigated the effect of forming 3-dimensional network.

Interaction of water with epoxy.

Energy Technology Data Exchange (ETDEWEB)

Powers, Dana Auburn

2009-07-01

The chemistries of reactants, plasticizers, solvents and additives in an epoxy paint are discussed. Polyamide additives may play an important role in the absorption of molecular iodine by epoxy paints. It is recommended that the unsaturation of the polyamide additive in the epoxy cure be determined. Experimental studies of water absorption by epoxy resins are discussed. These studies show that absorption can disrupt hydrogen bonds among segments of the polymers and cause swelling of the polymer. The water absorption increases the diffusion coefficient of water within the polymer. Permanent damage to the polymer can result if water causes hydrolysis of ether linkages. Water desorption studies are recommended to ascertain how water absorption affects epoxy paint.

Fiber-Reinforced Epoxy Composites and Methods of Making Same Without the Use of Oven or Autoclave

Science.gov (United States)

Barnell, Thomas J. (Inventor); Rauscher, Michael D. (Inventor); Stienecker, Rick D. (Inventor); Nickerson, David M. (Inventor); Tong, Tat H. (Inventor)

2016-01-01

Method embodiments for producing a fiber-reinforced epoxy composite comprise providing a mold defining a shape for a composite, applying a fiber reinforcement over the mold, covering the mold and fiber reinforcement thereon in a vacuum enclosure, performing a vacuum on the vacuum enclosure to produce a pressure gradient, insulating at least a portion of the vacuum enclosure with thermal insulation, infusing the fiber reinforcement with a reactive mixture of uncured epoxy resin and curing agent under vacuum conditions, wherein the reactive mixture of uncured epoxy resin and curing agent generates exothermic heat, and producing the fiber-reinforced epoxy composite having a glass transition temperature of at least about 100.degree. C. by curing the fiber reinforcement infused with the reactive mixture of uncured epoxy resin and curing agent by utilizing the exothermically generated heat, wherein the curing is conducted inside the thermally insulated vacuum enclosure without utilization of an external heat source or an external radiation source.

Comparison of structural health assessment capabilities in epoxy – carbon black and epoxy – carbon nanotube nanocomposites

OpenAIRE

F. Inam; B. R. Bhat; N. Luhyna; T. Vo

2014-01-01

A novel method for comparing structural health of different types of brittle epoxy nanocomposites filled with carbon nanostructured fillers is presented. Epoxy – 0.2 vol% carbon black (CB) and epoxy – 0.2 vol% carbon nanotube (CNT) nanocomposite bars were prepared by calendering and thermal curing. Nanocomposite bars were subjected to Vickers diamond indentation to produce sub-surface damage. Electrical conductivities were analysed by 4-point method to estimate the structural damage caused by...

Estudio cinético del efecto de polifenilsulfona sobre el curado de una resina epoxi/amina mediante calorimetría diferencial de barrido convencional y modulada con temperatura: parte II Kinetic study on the effect of curing polyphenylsulfone epoxy resin/amina by differential calorimetry scanning conventional and modulated temperature: part II

Directory of Open Access Journals (Sweden)

Asdrúbal J. Cedeño

2010-01-01

Full Text Available En este trabajo se estudió el efecto de la adición del termoplástico lineal polifenilsulfona (PPSU, sobre la cinética de reacción y las propiedades térmicas de una resina epoxídica basada en diglicidil éter de bisfenol - A (DGEBA, curada con diaminodifenilsulfona (DDS. El estudio cinético y la caracterización se realizaron mediante calorimetría diferencial de barrido, DSC estándar y modulado, bajo condiciones isotérmicas y dinámicas. La cinética del curado se discutió en el marco de tres modelos cinéticos: Kissinger, Flynn-Wall-Ozawa y el modelo cinético de orden n. Para describir la reacción de curado en su última etapa, se usó la relación semiempírica propuesta por Chern y Poehlein para considerar la influencia de la difusión sobre la rapidez de reacción. El mecanismo de curado, para todos los sistemas, se ajustó a una cinética de orden n, a pesar del contenido de PPSU, y se observó que éste se hace muy controlado por la difusión conforme aumenta el contenido de PPSU y conforme la temperatura de curado disminuye. El tiempo de vitrificación de los sistemas exhibió una fuerte dependencia con el contenido de PPSU.In this work we studied the effect of the addition of the linear thermoplastic polyphenyl sulfone (PPSU on the cure kinetics and the thermal properties of a resin based on diglycidyl ether of bisphenol-A (DGEBA, cured with 4,4´-diaminodiphenyl sulfone (DDS. The kinetic study and the characterization process have been carried out by using differential scanning calorimetry, DSC, and temperature modulated DSC (TMDSC, under isothermal and dynamic conditions. The curing kinetics was discussed in the framework of three kinetic models: Kissinger, Flynn-Wall-Ozawa, and the model of reaction of order n. To describe the cured reaction in its last stage, we have used the semiempirical relationship proposed by Chern and Poehlein to take into account the influence of diffusion on the reaction rate. The cure mechanism

UV curing of teak veneers for decorative panel

International Nuclear Information System (INIS)

Gatot Trimulyadi Rekso; Darsono

1999-01-01

The radiation curing of surface coating of teak veneers for decorative panels has been conducted by using ultra violet (UV) as radiation source. In this experiment teak wood veneer was use as a substrate. Epoxy acrylate (import product,) and unsaturated polyester (locally product) were used as coating materials after being added with difunctional monomer TPGDA, and photo-initiator darocur 1173 or irgacure 184. Irradiation was conducted using 80 watt/cm LTV source at conveyor speed of 3,0 m/min. Parameters observed were viscosity of coating materials, hardness, adhesion, appearance, abrasion and chemical resistance of cured films. In general the results showed that viscosity of the formulations based on epoxy acrylate and unsaturated polyester resin were effected by the storage. Film cured by LTV made of epoxy acrylate and unsaturated polyester on the teak veneer wood have the same adhesion and abrasion resistant properties but the hardness and chemical resistant of epoxy acrylate are better than unsaturated polyester. From the experiment result it can be concluded the unsaturated polyester (locally product) can be used as radiation curable material for coating teak veneer panels

Plant Oil-Derived Epoxy Polymers toward Sustainable Biobased Thermosets.

Science.gov (United States)

Wang, Zhongkai; Yuan, Liang; Ganewatta, Mitra S; Lamm, Meghan E; Rahman, Md Anisur; Wang, Jifu; Liu, Shengquan; Tang, Chuanbing

2017-06-01

Epoxy polymers (EPs) derived from soybean oil with varied chemical structures are synthesized. These polymers are then cured with anhydrides to yield soybean-oil-derived epoxy thermosets. The curing kinetic, thermal, and mechanical properties are well characterized. Due to the high epoxide functionality per epoxy polymer chain, these thermosets exhibit tensile strength over an order of magnitude higher than a control formulation with epoxidized soybean oil. More importantly, thermosetting materials ranging from soft elastomers to tough thermosets can be obtained simply by using different EPs and/or by controlling feed ratios of EPs to anhydrides. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and characterisation of epoxy resins reinforced with carbon nanotubes and nanofibers.

Science.gov (United States)

Prolongo, S G; Gude, M R; Ureña, A

2009-10-01

Epoxy nanocomposites were fabricated using two kinds of nanofiller, amino-functionalized multi-walled carbon nanotubes (CNTs) and non-treated long carbon nanofibers (CNFs). The non-cured mixtures were analysed through viscosity measurements. The effect of the nanoreinforcement on the curing process was determined by differential scanning calorimetry. Finally, the characterisation of cured nanocomposites was carried out studying their thermo-mechanical and electrical behaviour. At room temperature, the addition of CNTs causes a viscosity increase of epoxy monomer much more marked than the introduction of CNFs due to their higher specific area. It was probed that in that case exists chemical reaction between amino-functionalized CNTs and the oxirane rings of epoxy monomer. The presence of nanoreinforcement induces a decrease of curing reaction rate and modifies the epoxy conversion reached. The glass transition temperature of the nanocomposites decreases with the contents of CNTs and CNFs added, which could be related to plasticization phenomena of the nanoreinforcements. The storage modulus of epoxy resin significantly increases with the addition of CNTs and CNFs. This augment is higher with amino-functionalized CNTs due, between other reasons, to the stronger interaction with the epoxy matrix. The electrical conductivity is greatly increased with the addition of CNTs and CNFs. In fact, the percolation threshold is lower than 0.25 wt% due to the high aspect ratio of the used nanoreinforcements.

On the epoxy moulding compound aging effect on package reliability

NARCIS (Netherlands)

Noijen, S.P.M.; Engelen, R.A.B.; Martens, J.; Opran, A.; Sluis, van der O.

2009-01-01

Most semi-conductor devices are encapsulated by epoxy moulding compound (EMC) material. Even after curing at the prescribed temperature and time in accordance with the supplier's curing specifications often the product is not yet 100% fully cured. As a consequence, the curing process of a product

Strain development in a filled epoxy resin curing under constrained and unconstrained conditions as assessed by Fibre Bragg Grating sensors

Directory of Open Access Journals (Sweden)

2007-04-01

Full Text Available The influence of adhesion to the mould wall on the released strain of a highly filled anhydride cured epoxy resin (EP, which was hardened in an aluminium mould under constrained and unconstrained condition, was investigated. The shrinkage-induced strain was measured by fibre optical sensing technique. Fibre Bragg Grating (FBG sensors were embedded into the curing EP placed in a cylindrical mould cavity. The cure-induced strain signals were detected in both, vertical and horizontal directions, during isothermal curing at 75 °C for 1000 minutes. A huge difference in the strain signal of both directions could be detected for the different adhesion conditions. Under non-adhering condition the horizontal and vertical strain-time traces were practically identical resulting in a compressive strain at the end of about 3200 ppm, which is a proof of free or isotropic shrinking. However, under constrained condition the horizontal shrinkage in the EP was prevented due to its adhesion to the mould wall. So, the curing material shrunk preferably in vertical direction. This resulted in much higher released compressive strain signals in vertical (10430 ppm than in horizontal (2230 ppm direction. The constrained cured EP resins are under inner stresses. Qualitative information on the residual stress state in the molding was deduced by exploiting the birefringence of the EP.

Anhydrides-Cured Bimodal Rubber-Like Epoxy Asphalt Composites: From Thermosetting to Quasi-Thermosetting

Directory of Open Access Journals (Sweden)

Yang Kang

2016-03-01

Full Text Available The present engineering practices show the potential that epoxy asphalt composites (EACs would be a better choice to obtain long life for busy roads. To understand the service performance–related thermorheological properties of prepared bimodal anhydrides-cured rubber-like EACs (REACs, a direct tensile tester, dynamic shear rheometer and mathematical model were used. Tensile tests demonstrate that all the REACs reported here are more flexible than previously reported anhydrides-cured REACs at both 20 and 0 °C. The better flexibility is attributed to the change of bimodal networks, in which cross-linked short chains decreased and cross-linked long chains increased, relatively. Strain sweeps show that all the REACs have linear viscoelastic (LVE properties when their strains are smaller than 1.0% from −35 to 120 °C. Temperature sweeps illustrate that the thermorheological properties of REACs evolve from thermosetting to quasi-thermosetting with asphalt content, and all the REACs retain solid state and show elastic properties in the experimental temperature range. A Cole–Cole plot and Black diagram indicate that all the REACs are thermorheologically simple materials, and the master curves were constructed and well-fitted by the Generalized Logistic Sigmoidal models. This research provides a facile approach to tune the thermorheological properties of the REACs, and the cheaper quasi-thermosetting REAC facilitates their advanced applications.

Thermal-mechanical properties of a graphitic-nanofibers reinforced epoxy.

Science.gov (United States)

Salehi-Khojin, Amin; Jana, Soumen; Zhong, Wei-Hong

2007-03-01

We previously developed a series of reactive graphitic nanofibers (r-GNFs) reinforced epoxy (nano-epoxy) as composite matrices, which have shown good wetting and adhesion properties with continuous fiber. In this work, the thermal-mechanical properties of the nano-epoxy system containing EponTM Resin 828 and Epi-cure Curing Agent W were characterized. Results from three-point bending tests showed that the flexural strength and flexural modulus of this system with 0.30 wt% of reactive nanofibers were increased by 16%, and 21% respectively, over pure epoxy. Fracture toughness increased by ca. 40% for specimens with 0.50 wt% of r-GNFs. By dynamic mechanical analysis (DMA) test, specimens with 0.30 wt% of r-GNFs showed a significant increase in storage modulus E' (by ca. 122%) and loss modulus E" (by ca. 111%) with respect to that of pure epoxy. Also thermo-dilatometry analysis (TDA) was used to measure dimensional change of specimens as a function of temperature, and then, coefficients of thermal expansion (CTE) before and after glass transition temperature (Tg) were obtained. Results implied that nano-epoxy materials had good dimensional stability and reduced CTE values when compared to those of pure epoxy.

Silane coupling agent for attaching fusion-bonded epoxy to steel.

Science.gov (United States)

Tchoquessi Diodjo, Madeleine R; Belec, Lénaïk; Aragon, Emmanuel; Joliff, Yoann; Lanarde, Lise; Perrin, François-Xavier

2013-07-24

We describe the possibility of using γ-aminopropyltriethoxysilane (γ-APS) to increase the durability of epoxy powder coating/steel joints. The curing temperature of epoxy powder coatings is frequently above 200 °C, which is seen so far as a major limitation for the use of the heat-sensitive aminosilane coupling agent. Despite this limitation, we demonstrate that aminosilane is a competitive alternative to traditional chromate conversion to enhance the durability of epoxy powder coatings/steel joints. Fourier-transform reflection-absorption infrared spectroscopy (FT-RAIRS), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) were used to identify the silane deposition conditions that influence the adhesion of epoxy powder coatings on steel. We show that AFM analysis provides highly sensitive measurements of mechanical property development and, as such, the degree of condensation of the silane. The joint durability in water at 60 °C was lower when the pH of the γ-APS solution was controlled at 4.6 using formic acid, rather than that at natural pH (10.6). At the curing temperature of 220 °C, oxidation of the carbon adjacent to the amine headgroup of γ-APS gives amide species by a pseudofirst-order kinetics. However, a few amino functionalities remain to react with oxirane groups of epoxy resin and, thus, strengthen the epoxy/silane interphase. The formation of ammonium formate in the acidic silane inhibits the reaction between silane and epoxy, which consequently decreases the epoxy/silane interphase cohesion. We find that the nanoroughness of silane deposits increases with the cure temperature which is beneficial to the wet stability of the epoxy/steel joints, due to increased mechanical interlocking.

Epoxy modified bitumen : Chemical hardening and its interpretation

NARCIS (Netherlands)

Apostolidis, P.; Pipintakos, G.; van de Ven, M.F.C.; Liu, X.; Erkens, Sandra; Scarpas, Athanasios

2018-01-01

Epoxy modified bitumen (EMB) is a promising technology for long lasting paving materials ensuring higher resistance to rutting, oxygen- and moisture-induced damage. In this paper, an analysis of the chemical reactions that take place during the chemical hardening process (curing) of epoxy modified

A novel calorimetry technique for monitoring electron beam curing of polymer resins

International Nuclear Information System (INIS)

Chen, J.H.; Johnston, A.; Petrescue, L.; Hojjati, M.

2006-01-01

This paper describes the development of a calorimetry-based technique for monitoring of the curing of electron beam (EB) curable resins, including design of the calorimeter hardware and the development of an analytical model for calculating resin cure rates and radiation dose. Factors affecting the performance of the calorimeter were investigated. Experimental trials monitoring the curing of epoxy resin were conducted under single pass and multiple passes of EB irradiation. Results show that the developed calorimeter is a simple, inexpensive and reasonably accurate technique for monitoring the EB curing of cationic epoxies

Epoxy-Based Shape-Memory Actuators Obtained via Dual-Curing of Off-Stoichiometric “Thiol–Epoxy” Mixtures

Directory of Open Access Journals (Sweden)

Alberto Belmonte

2017-03-01

Full Text Available In this work, epoxy-based shape-memory actuators have been developed by taking advantage of the sequential dual-curing of off-stoichiometric “thiol–epoxy” systems. Bent-shaped designs for flexural actuation were obtained thanks to the easy processing of these materials in the intermediate stage (after the first curing process, and successfully fixed through the second curing process. The samples were programmed into a flat temporary-shape and the recovery-process was analyzed in unconstrained, partially-constrained and fully-constrained conditions using a dynamic mechanical analyzer (DMA. Different “thiol–epoxy” systems and off-stoichiometric ratios were used to analyze the effect of the network structure on the actuation performance. The results evidenced the possibility to take advantage of the flexural recovery as a potential actuator, the operation of which can be modulated by changing the network structure and properties of the material. Under unconstrained-recovery conditions, faster and narrower recovery-processes (an average speed up to 80%/min are attained by using materials with homogeneous network structure, while in partially- or fully-constrained conditions, a higher crosslinking density and the presence of crosslinks of higher functionality lead to a higher amount of energy released during the recovery-process, thus, increasing the work or the force released. Finally, an easy approach for the prediction of the work released by the shape-memory actuator has been proposed.

Thermoset epoxy polymers from renewable resources

Science.gov (United States)

East, Anthony [Madison, NJ; Jaffe, Michael [Maplewood, NJ; Zhang, Yi [Harrison, NJ; Catalani, Luiz H [Carapicuiba, BR

2009-11-17

Novel thermoset epoxy polymers using the bisglycidyl ethers of anhydrosugars, such as isosorbide, isomannide, and isoidide, are disclosed. The bisglycidyl ethers are useful as substitutes for bisphenol A in the manufacture of thermoset epoxy ethers. The anhydrosugars are derived from renewable sources and the bisglycidyl ethers are not xenoestrogenic and the thermoset curing agents are likewise derived form renewable resources.

Epoxy resin systems for FGD units

International Nuclear Information System (INIS)

Brytus, V.; Puglisi, J.S.

1984-01-01

This paper discusses ongoing research work which is directed towards epoxy resins and curing agents which are designed to withstand aggressive environments. This work includes not only a chemical description of the materials involved, but the application testing necessary to verify the usefulness of these systems. It demonstrates that new high performance epoxy systems are superior to those which traditionally come to mind when one thinks epoxy. Finally, it discusses the results of testing designed specifically to screen candidates for use in FGD units

Synthesis of Polyurethane/Silica Modified Epoxy Polymer Based on 1,3-Propanediol for Coating Application

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Lutviasari Nuraini

2017-11-01

Full Text Available Studies on the synthesis of polyurethane/silica modified epoxy polymer using 1,3-propanediol has been conducted. Synthesis of polymers made by reaction of tolonate and 1,3-propanediol (ratio NCO/OH=2.5 as the building blocks of polyurethane with diglycidyl ether bisphenol A (DGEBA epoxy and catalyst dibutyltin dilaurate (DBTL.The total weight of the polyurethane used was 20% (w/w of the total epoxy. Based on Fourier Transform Infrared (FTIR and 1H-Nuclear Magnetic Resonance (1H-NMR spectra indicated the existence of a new bond that is formed from the reaction of isocyanate group and hydroxyl group, where the hydroxyl groups derived from epoxy and 1,3-propanediol. The addition of silica (5, 10, and 15% w/w to epoxy into the epoxy-modified polyurethane has been carried out through sol-gel reaction of tetraethyl orthosilicate (TEOS. The isocyanate conversion rate for the addition of silica 5, 10, and 15% are 95.69; 100, and 100%, respectively. The morphology and element identification by Scanning Electron Microscopy/Energy Dispersive X-Ray Analysis (SEM/EDX, showed that Si element has been successfully added in the polymer. From the tensile strength and elongation analysis, also thermal stability analysis using Thermal Gravimetric Analyzer (TGA, the increase of silica amount into the polyurethane modified epoxy did not significantly affect to thermal properties, but decrease the tensile strength of the polymer.

Molecular Modeling of Aerospace Polymer Matrices Including Carbon Nanotube-Enhanced Epoxy

Science.gov (United States)

Radue, Matthew S.

Carbon fiber (CF) composites are increasingly replacing metals used in major structural parts of aircraft, spacecraft, and automobiles. The current limitations of carbon fiber composites are addressed through computational material design by modeling the salient aerospace matrix materials. Molecular Dynamics (MD) models of epoxies with and without carbon nanotube (CNT) reinforcement and models of pure bismaleimides (BMIs) were developed to elucidate structure-property relationships for improved selection and tailoring of matrices. The influence of monomer functionality on the mechanical properties of epoxies is studied using the Reax Force Field (ReaxFF). From deformation simulations, the Young's modulus, yield point, and Poisson's ratio are calculated and analyzed. The results demonstrate an increase in stiffness and yield strength with increasing resin functionality. Comparison between the network structures of distinct epoxies is further advanced by the Monomeric Degree Index (MDI). Experimental validation demonstrates the MD results correctly predict the relationship in Young's moduli for all epoxies modeled. Therefore, the ReaxFF is confirmed to be a useful tool for studying the mechanical behavior of epoxies. While epoxies have been well-studied using MD, there has been no concerted effort to model cured BMI polymers due to the complexity of the network-forming reactions. A novel, adaptable crosslinking framework is developed for implementing 5 distinct cure reactions of Matrimid-5292 (a BMI resin) and investigating the network structure using MD simulations. The influence of different cure reactions and extent of curing are analyzed on the several thermo-mechanical properties such as mass density, glass transition temperature, coefficient of thermal expansion, elastic moduli, and thermal conductivity. The developed crosslinked models correctly predict experimentally observed trends for various properties. Finally, the epoxies modeled (di-, tri-, and tetra

Prediction of the epoxy moulding compound aging effect on package reliability

NARCIS (Netherlands)

Noijen, S.P.M.; Engelen, R.A.B.; Martens, J.; Opran, A.; Sluis, van der O.; Silfhout, van R.B.R.

2010-01-01

Most semi-conductor devices are encapsulated by epoxy moulding compound (EMC) material. Even after curing at the prescribed temperature and time in accordance with the supplier’s curing specifications often the product is not yet 100% fully cured. As a consequence, the curing process of a product

Aliphatic amine cured PDMS–epoxy interpenetrating network ...

Indian Academy of Sciences (India)

Unknown

Tg, heat-distortion temperature and reduced the percentage weight loss with ... The siliconized epoxy IPN, with better impact and thermal resistance, ... However, these materials also deteriorate ... the method of compounding remains the state of the art. ... geneity and to ascertain any chemical change during storage.

High Temperature Epoxy Foam: Optimization of Process Parameters

Directory of Open Access Journals (Sweden)

Samira El Gazzani

2016-06-01

Full Text Available For many years, reduction of fuel consumption has been a major aim in terms of both costs and environmental concerns. One option is to reduce the weight of fuel consumers. For this purpose, the use of a lightweight material based on rigid foams is a relevant choice. This paper deals with a new high temperature epoxy expanded material as substitution of phenolic resin, classified as potentially mutagenic by European directive Reach. The optimization of thermoset foam depends on two major parameters, the reticulation process and the expansion of the foaming agent. Controlling these two phenomena can lead to a fully expanded and cured material. The rheological behavior of epoxy resin is studied and gel time is determined at various temperatures. The expansion of foaming agent is investigated by thermomechanical analysis. Results are correlated and compared with samples foamed in the same temperature conditions. The ideal foaming/gelation temperature is then determined. The second part of this research concerns the optimization of curing cycle of a high temperature trifunctional epoxy resin. A two-step curing cycle was defined by considering the influence of different curing schedules on the glass transition temperature of the material. The final foamed material has a glass transition temperature of 270 °C.

Multivariate curve resolution using a combination of mid-infrared and near-infrared spectra for the analysis of isothermal epoxy curing reaction

Science.gov (United States)

Yamasaki, Hideki; Morita, Shigeaki

2018-05-01

Multivariate curve resolution (MCR) was applied to a hetero-spectrally combined dataset consisting of mid-infrared (MIR) and near-infrared (NIR) spectra collected during the isothermal curing reaction of an epoxy resin. An epoxy monomer, bisphenol A diglycidyl ether (BADGE), and a hardening agent, 4,4‧-diaminodiphenyl methane (DDM), were used for the reaction. The fundamental modes of the Nsbnd H and Osbnd H stretches were highly overlapped in the MIR region, while their first overtones could be independently identified in the NIR region. The concentration profiles obtained by MCR using the hetero-spectral combination showed good agreement with the results of calculations based on the Beer-Lambert law and the mass balance. The band assignments and absorption sites estimated by the analysis also showed good agreement with the results using two-dimensional (2D) hetero-correlation spectroscopy.

Effection of UV-LED Illuminant on the Curation of Photolatent-amidine Mixed with Bisphenol A Epoxy Acrylate under Printing Conditions

Directory of Open Access Journals (Sweden)

Duan Huawei

2016-01-01

Full Text Available In order to make photocuring ink or coating cured by UV-LED illuminant, we synthesized (4-((hexahydropyrrolo[1,2-a]pyrimidin-1 (2H-ylmethylphenyl(phenylmethanone(PL -DBN and (4-((octahydropyrimido[1,2-a]azepin-1(2H-ylmethylphenyl(phenylmet hanone(PL -DBU as photoinitiators. Different mass fraction of the photoinitiators was mixed with bisphenol A epoxy acrylate, cured by different wavelengths and power of UV-LED illuminant,and investigated the curing effects of photoinitiators on bisphenol A epoxy acrylate. The results show that the conversion of C=C double bonds of bisphenol A epoxy acrylate will increase as the mass fraction of the photoinitiators or the power of UV-LED illuminant increase. In the same conditions, the curing effect of using 365nm UV-LED illuminant on bisphenol A epoxy acrylate is better than using 395nm UV-LED illuminant. PL-DBU has a better curing effect on the bisphenol A epoxy acrylate rather than PL-DBN. When using the 8W/cm2 of 365nm UV-LED illuminant to cure a mixture of 3% PL-DBU and 97% bisphenol A epoxy acrylate, it will be dry completely in 2 seconds, moreover, the conversion reach 79%.

Positron lifetime study of electron-irradiated epoxy resins

International Nuclear Information System (INIS)

Suevegh, K.; Vertes, A.; Wojnarovits, L.; Foeldiak, G.; Liszkai, L.; Kajcsos, Zs.

1990-01-01

Two bisphenol-A type epoxy resins were irradiated by electron beam and studied afterwards by positron lifetime spectroscopy. An interesting result is that despite of the considerable amount of free-radicals, no inhibition of positronium formation was observed in the two epoxies. Nevertheless, several serious differences were detected between the studied polymers. The results suggest that the radiation-resistant properties of epoxies depend strongly on the amount of the curing agent. (author) 8 refs.; 2 figs

Flame retardancy and thermal properties of epoxy acrylate resin/alpha-zirconium phosphate nanocomposites used for UV-curing flame retardant films

International Nuclear Information System (INIS)

Xing Weiyi; Jie Ganxin; Song Lei; Wang Xin; Lv Xiaoqi; Hu Yuan

2011-01-01

This paper reported the UV-curing flame retardant film, which consisted of epoxy acrylate resin (EA) used as an oligomer, tri(acryloyloxyethyl) phosphate (TAEP) and triglycidyl isocyanurate acrylate (TGICA) used as flame retardant (FR). The flame retardancy and thermal properties of films were reinforced by using alpha-zirconium phosphate (α-Zr (HPO 4 ) 2 H 2 O, α-ZrP). The morphology of nanocomposite film was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results showed that the organophilic α-ZrP (OZrP) layers were dispersed well in epoxy acrylate resin. Microscale Combustion Calorimeter (MCC), thermogravimetric analysis (TGA) and thermogravimetric analysis/infrared spectrometry (TGA-IR) were used to characterize the flame retardant property and thermal stability. It was found that the incorporation of TAEP and TGICA can reduce the flammability of EA. Moreover, further reductions were observed due to the addition of OZrP. The char residue for systems with or without OZrP was also explored by scanning electron microscopy (SEM).

Aging in CTBN modified epoxy resin stocks

International Nuclear Information System (INIS)

Creed, K.E. Jr.

1979-01-01

The cause of degradation in the glass transition temperature (T/sub G/) of a partially crystallized polymer was investigated. Sample epoxy resin filled capacitors were cured at 90 0 C for 24 hours, then stored at room atmospheric conditions. These showed typical degradation in T/sub G/ after storage for one month. One set of epoxy resin castings was stored at room atmosphere and another set was stored in a dry box at 0% relative humidity and 27 0 C. The samples at room atmospheric conditions showed typical degradation in T/sub G/, while the T/sub G/ for those stored in the dry box increased. Further tests were then made on epoxy resin castings at various curing temperatures and times at both room atmosphere and 0% humidity. Resulting data indicated that absorption of moisture during storage was the predominant cause of T/sub G/ degradation, with stress relaxation another, though smaller, contributing factor

Biobased Epoxy Nanocomposites Derived from Lignin-Based Monomers.

Science.gov (United States)

Zhao, Shou; Abu-Omar, Mahdi M

2015-07-13

Biobased epoxy nanocomposites were synthesized based on 2-methoxy-4-propylphenol (dihydroeugenol, DHE), a molecule that has been obtained from the lignin component of biomass. To increase the content of hydroxyl groups, DHE was o-demethylated using aqueous HBr to yield propylcatechol (DHEO), which was subsequently glycidylated to epoxy monomer. Optimal conditions in terms of yield and epoxy equivalent weight were found to be 60 °C with equal NaOH/phenolic hydroxyl molar ratio. The structural evolution from DHE to cured epoxy was followed by (1)H NMR and Fourier transform infrared spectroscopy. The nano-montmorillonite modified DHEO epoxy exhibited improved storage modulus and thermal stability as determined from dynamic mechanical analysis and thermogravimetric analysis. This study widens the synthesis routes of biobased epoxy thermosets from lignin-based molecules.

The Effects of in Situ-Formed Silver Nanoparticles on the Electrical Properties of Epoxy Resin Filled with Silver Nanowires

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Gwang-Seok Song

2016-04-01

Full Text Available A novel method for preparing epoxy/silver nanocomposites was developed via the in situ formation of silver nanoparticles (AgNPs within the epoxy resin matrix while using silver nanowires (AgNWs as a conductive filler. The silver–imidazole complex was synthesized from silver acetate (AgAc and 1-(2-cyanoethyl-2-ethyl-4-methylimidazole (imidazole. AgNPs were generated in situ during the curing of the epoxy resin through the thermal decomposition of the AgAc–imidazole complex, which was capable of reducing Ag+ to Ag by itself. The released imidazole acted as a catalyst to cure the epoxy. Additionally, after the curing process, the in situ-generated AgNPs were stabilized by the formed epoxy network. Therefore, by using the thermal decomposition method, uniformly dispersed AgNPs of approximately 100 nm were formed in situ in the epoxy matrix filled with AgNWs. It was observed that the nanocomposites containing in situ-formed AgNPs exhibited isotropic electrical properties in the epoxy resins in the presence of AgNWs.

Radiation Supporting Synthezis and Curing of Composites Suitable for Practical Applications

International Nuclear Information System (INIS)

Przybytniak, G.; Antoniak, M.; Nowicki, A.; Mirkowski, K.; Walo, M.

2011-01-01

Epoxy resins (ER) due to favorable combination of superior mechanical and thermal properties with unusual radiation resistance play an important role in some nuclear and aerospace industries. They are also widely used as matrices of reinforced composites since the homogeneous dissipation of fillers in the non-cured material is uncomplicated and efficient. Curing procedure is a very important factor determining final features of the epoxy resin and its composite. It was confirmed that irradiation facilitates molecular mobility and decreases glass transition as a result of chain scission. On the other hand, the increase in local mobility accelerates crosslinking thus the total effect is dependent on the relation between these two processes. Larieva reported that the ratio between degradation and crosslinking is 0.43, thus under selected conditions yield of curing more than twice prevails over yield of decomposition. The nature of hardener and its radiosensitivity also significantly influence the radiation induced curing. During exposure to ionizing radiation the binders participate in the processes initiated both by radiation and by heating, as curing is highly exothermic and considerably increases temperature of the system. Application of radiation treatment lowers energy consumption, shortens curing time and decreases curing temperature enhancing dimensional stability. In the past some attempts were made to improve heat resistance and strength of epoxy resins by the incorporation of various particles, e.g. silica, carbon nanotubes, montmorillonite, etc, however the results were unambiguous. In the reported studies the effects of radiation and thermal curing were investigated for ER and its composites either in the presence of cationic initiator or amine hardener

Radiation Supporting Synthezis and Curing of Composites Suitable for Practical Applications

Energy Technology Data Exchange (ETDEWEB)

Przybytniak, G.; Antoniak, M.; Nowicki, A.; Mirkowski, K.; Walo, M. [Institute of Nuclear Chemistry and Technology, Dorodna 16 Str., 03-195 Warsaw (Poland)

2011-07-01

Epoxy resins (ER) due to favorable combination of superior mechanical and thermal properties with unusual radiation resistance play an important role in some nuclear and aerospace industries. They are also widely used as matrices of reinforced composites since the homogeneous dissipation of fillers in the non-cured material is uncomplicated and efficient. Curing procedure is a very important factor determining final features of the epoxy resin and its composite. It was confirmed that irradiation facilitates molecular mobility and decreases glass transition as a result of chain scission. On the other hand, the increase in local mobility accelerates crosslinking thus the total effect is dependent on the relation between these two processes. Larieva reported that the ratio between degradation and crosslinking is 0.43, thus under selected conditions yield of curing more than twice prevails over yield of decomposition. The nature of hardener and its radiosensitivity also significantly influence the radiation induced curing. During exposure to ionizing radiation the binders participate in the processes initiated both by radiation and by heating, as curing is highly exothermic and considerably increases temperature of the system. Application of radiation treatment lowers energy consumption, shortens curing time and decreases curing temperature enhancing dimensional stability. In the past some attempts were made to improve heat resistance and strength of epoxy resins by the incorporation of various particles, e.g. silica, carbon nanotubes, montmorillonite, etc, however the results were unambiguous. In the reported studies the effects of radiation and thermal curing were investigated for ER and its composites either in the presence of cationic initiator or amine hardener.

Out-of-Autoclave Cure Composites

Science.gov (United States)

Hayes, Brian S.

2015-01-01

As the size of aerospace composite parts exceeds that of even the largest autoclaves, the development of new out-of-autoclave processes and materials is necessary to ensure quality and performance. Many out-of-autoclave prepreg systems can produce high-quality composites initially; however, due to long layup times, the resin advancement commonly causes high void content and variations in fiber volume. Applied Poleramic, Inc. (API), developed an aerospace-grade benzoxazine matrix composite prepreg material that offers more than a year out-time at ambient conditions and provides exceptionally low void content when out-of-autoclave cured. When compared with aerospace epoxy prepreg systems, API's innovation offers significant improvements in terms of out-time at ambient temperature and the corresponding tack retention. The carbon fiber composites developed with the optimized matrix technology have significantly better mechanical performance in terms of hot-wet retention and compression when compared with aerospace epoxy matrices. These composites also offer an excellent overall balance of properties. This matrix system imparts very low cure shrinkage, low coefficient of thermal expansion, and low density when compared with most aerospace epoxy prepreg materials.

Development and characterization of woven kevlar reinforced epoxy matrix composite materials

International Nuclear Information System (INIS)

Imran, A.; Alam, S.; Irfan, S.; Iftikhar, F.; Raza, M.A.

2006-01-01

Composite materials are actually well established materials that have demonstrated their promising advantages among the light weight structural materials used for aerospace and advanced applications. A great effort is now being made to develop and characterize the Kevlar Epoxy Composite Materials by changing the % age composition of curing agent in epoxy matrix. In order to study the phenomenon; how the change in composition of curing agent effect the composite material and which optimum composition can give the optimum properties of the material, when Kevlar reinforced to Epoxy Matrix by Hand Lay-up process. It was ensured that factors which can .affect the experiment remained the same for each experiment. The composite produced were subjected to mechanical tests to analyze the performance, to optimize the material. (author)

Processing and properties of carbon nanofibers reinforced epoxy powder composites

International Nuclear Information System (INIS)

Palencia, C.; Mazo, M. A.; Nistal, A.; Rubio, F.; Rubio, J.; Oteo, J. L.

2011-01-01

Commercially available CNFs (diameter 30–300 nm) have been used to develop both bulk and coating epoxy nanocomposites by using a solvent-free epoxy matrix powder. Processing of both types of materials has been carried out by a double-step process consisting in an initial physical premix of all components followed by three consecutive extrusions. The extruded pellets were grinded into powder and sieved. Carbon nanofibers powder coatings were obtained by electrostatic painting of the extruded powder followed by a curing process based in a thermal treatment at 200 °C for 25 min. On the other hand, for obtaining bulk carbon nanofibers epoxy composites, a thermal curing process involving several steps was needed. Gloss and mechanical properties of both nanocomposite coatings and bulk nanocomposites were improved as a result of the processing process. FE-SEM fracture surface microphotographs corroborate these results. It has been assessed the key role played by the dispersion of CNFs in the matrix, and the highly important step that is the processing and curing of the nanocomposites. A processing stage consisted in three consecutive extrusions has reached to nanocomposites free of entanglements neither agglomerates. This process leads to nanocomposite coatings of enhanced properties, as it has been evidenced through gloss and mechanical properties. A dispersion limit of 1% has been determined for the studied system in which a given dispersion has been achieved, as the bending mechanical properties have been increased around 25% compared with the pristine epoxy resin. It has been also demonstrated the importance of the thickness in the nanocomposite, as it involves the curing stage. The complex curing treatment carried out in the case of bulk nanocomposites has reached to reagglomeration of CNFs.

Processing and properties of carbon nanofibers reinforced epoxy powder composites

Science.gov (United States)

Palencia, C.; Mazo, M. A.; Nistal, A.; Rubio, F.; Rubio, J.; Oteo, J. L.

2011-11-01

Commercially available CNFs (diameter 30-300 nm) have been used to develop both bulk and coating epoxy nanocomposites by using a solvent-free epoxy matrix powder. Processing of both types of materials has been carried out by a double-step process consisting in an initial physical premix of all components followed by three consecutive extrusions. The extruded pellets were grinded into powder and sieved. Carbon nanofibers powder coatings were obtained by electrostatic painting of the extruded powder followed by a curing process based in a thermal treatment at 200 °C for 25 min. On the other hand, for obtaining bulk carbon nanofibers epoxy composites, a thermal curing process involving several steps was needed. Gloss and mechanical properties of both nanocomposite coatings and bulk nanocomposites were improved as a result of the processing process. FE-SEM fracture surface microphotographs corroborate these results. It has been assessed the key role played by the dispersion of CNFs in the matrix, and the highly important step that is the processing and curing of the nanocomposites. A processing stage consisted in three consecutive extrusions has reached to nanocomposites free of entanglements neither agglomerates. This process leads to nanocomposite coatings of enhanced properties, as it has been evidenced through gloss and mechanical properties. A dispersion limit of 1% has been determined for the studied system in which a given dispersion has been achieved, as the bending mechanical properties have been increased around 25% compared with the pristine epoxy resin. It has been also demonstrated the importance of the thickness in the nanocomposite, as it involves the curing stage. The complex curing treatment carried out in the case of bulk nanocomposites has reached to reagglomeration of CNFs.

Electron beam curing of coatings

International Nuclear Information System (INIS)

Schmidt, J.; Mai, H.

1986-01-01

Modern low-energy electron beam processors offer the possibility for high-speed curing of coatings on paper, plastics, wood and metal. Today the electron beam curing gets more importance due to the increasing environmental problems and the rising cost of energy. For an effective curing process low-energy electron beam processors as well as very reactive binders are necessary. Generally such binders consist of acrylic-modified unsaturated polyester resins, polyacrylates, urethane acrylates or epoxy acrylates and vinyl monomers, mostly multifunctional acrylates. First results on the production of EBC binders on the base of polyester resins and vinyl monomers are presented. The aim of our investigations is to obtain binders with curing doses ≤ 50 kGy. In order to reduce the curing dose we studied mixtures of resins and acrylates. (author)

Electron beam processed plasticized epoxy coatings for surface protection

International Nuclear Information System (INIS)

Ibrahim, Mervat S.; Mohamed, Heba A.; Kandile, Nadia G.; Said, Hossam M.; Mohamed, Issa M.

2011-01-01

Highlights: · Coating formulations with EA 70%, HD 20%, and castor oil 10% under 1 Mrad pass -1 irradiation dose showed the best adhesion and passed bending tests. · The prepared EP-SF-An adduct improve anti-corrosion properties of coatings without any significant effect on physical, mechanical and chemical properties of the cured film. The optimum amount of aniline adduct as corrosion inhibitor was found to be 0.4 g for 100 g of coating formulation. · The corrosion inhibition efficiency of the prepared adduct competed the commercial efficiency. - Abstract: Epoxy acrylate oligomer (EA) was plasticized by adding different plasticizers such as epoxidized soybean oil, glycerol and castor oil and cured by electron beam (EB). Different irradiation doses (1, 2.5 and 5 Mrad pass -1 ) were used in the curing process. The effect of both different irradiation doses and plasticizers on the end use performance properties of epoxy acrylate coating namely, pencil hardness, bending test, adhesion test, acid and alkali resistance test were studied. It was observed that incorporation of castor oil in epoxy acrylate diluted by 1,6-hexanediol diacrylate (HD) monomer with a ratio (EA 70%, HD 20%, castor oil 10%) under 1 Mrad pass -1 irradiation dose improved the physical, chemical and mechanical properties of cured films than the other plasticizer. Sunflower free fatty acid was epoxidized in situ under well established conditions. The epoxidized sunflower free fatty acids (ESFA) were subjected to react with aniline in sealed ampoules under inert atmosphere at 140 deg. C. The produced adducts were added at different concentrations to epoxy acrylate coatings under certain EB irradiation dose and then evaluated as corrosion inhibitors for carbon steel surfaces in terms of weight loss measurements and corrosion resistance tests. It was found that, addition of 0.4 g of aniline adduct to 100 g epoxy acrylate formula may give the best corrosion protection for carbon steel and compete the

Development of sealed radioactive sources immobilized in epoxy resin for verification of detectors used in nuclear medicine

Energy Technology Data Exchange (ETDEWEB)

Tiezzi, Rodrigo; Rostelato, Maria Elisa C.M.; Nagatomi, Helio R.; Zeituni, Calos A.; Benega, Marcos A.G.; Souza, Daiane B. de; Costa, Osvaldo L. da; Souza, Carla D.; Rodrigues, Bruna T.; Souza, Anderson S. de; Peleias Junior, Fernando S.; Santos, Rafael Melo dos; Melo, Emerson Ronaldo de, E-mail: rktiezzi@gmail.com [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Karan Junior, Dib [Universidade de Sao Paulo (USP), Sao Paulo, SP (Brazil)

2015-07-01

The radioactive sealed sources are used in verification ionization chamber detectors, which measure the activity of radioisotopes used in several areas, such as in nuclear medicine. The measurement of the activity of radioisotopes must be made with accuracy, because it is administered to a patient. To ensure the proper functioning of the ionization chamber detectors, standardized tests are set by the International Atomic Energy Agency (IAEA) and the National Nuclear Energy Commission using sealed radioactive sources of Barium-133, Cesium-137 and Cobalt-57. The tests assess the accuracy, precision, reproducibility and linearity of response of the equipment. The focus of this work was the study and the development of these radioactive sources with standard Barium-133, Cesium-137 and Cobalt-57,using a polymer, in case commercial epoxy resin of diglycidyl ether of bisphenol A (DGEBA) and a curing agent based on modified polyamine diethylenetriamine (DETA), to immobilize the radioactive material. The polymeric matrix has the main function of fix and immobilize the radioactive contents not allowing them to leak within the technical limits required by the standards of radiological protection in the category of characteristics of a sealed source and additionally have the ability to retain the emanation of any gases that may be formed during the manufacture process and the useful life of this artifact. The manufacturing process of a sealed source standard consists of the potting ,into bottle standardized geometry, in fixed volume of a quantity of a polymeric matrix within which is added and dispersed homogeneously to need and exact amount in activity of the radioactive materials standards. Accordingly, a study was conducted for the choice of epoxy resin, analyzing its characteristics and properties. Studies and tests were performed, examining the maximum solubility of the resin in water (acidic solution, simulating the conditions of radioactive solution), loss of mechanical

Dielectric Cure Monitoring of Thermosetting Matrix Composites

Energy Technology Data Exchange (ETDEWEB)

Kim, Hyoung Geun [Agency for Defense Development, Daejeon (Korea, Republic of); Lee, Dae Gil [KAIST, Daejeon (Korea, Republic of)

2003-10-15

Cure monitoring can be used to improve the quality and productivity of thermosetting resin matrix composite products during their manufacturing process. In this work, the sensitivity of dielectrometry was improved by adequate separation the efforts of sensor and externals on the measured signal. A new algorithm to obtain the degree of cure during dielectric cure monitoring of glass/polyester and glass/epoxy composites was developed by employing a function of both temperature and dissipation factor, in which five cure monitoring parameters were used to calculate the degree of cure. The decreasing pattern of dissipation factor was compared with the relationships between the degree of cure and the resin viscosity. The developed algorithm might be employed for the in situ cure monitoring of thermosetting resin composites

Dielectric Cure Monitoring of Thermosetting Matrix Composites

International Nuclear Information System (INIS)

Kim, Hyoung Geun; Lee, Dae Gil

2003-01-01

Cure monitoring can be used to improve the quality and productivity of thermosetting resin matrix composite products during their manufacturing process. In this work, the sensitivity of dielectrometry was improved by adequate separation the efforts of sensor and externals on the measured signal. A new algorithm to obtain the degree of cure during dielectric cure monitoring of glass/polyester and glass/epoxy composites was developed by employing a function of both temperature and dissipation factor, in which five cure monitoring parameters were used to calculate the degree of cure. The decreasing pattern of dissipation factor was compared with the relationships between the degree of cure and the resin viscosity. The developed algorithm might be employed for the in situ cure monitoring of thermosetting resin composites

Comparison of structural health assessment capabilities in epoxy – carbon black and epoxy – carbon nanotube nanocomposites

Directory of Open Access Journals (Sweden)

F. Inam

2014-01-01

Full Text Available A novel method for comparing structural health of different types of brittle epoxy nanocomposites filled with carbon nanostructured fillers is presented. Epoxy – 0.2 vol% carbon black (CB and epoxy – 0.2 vol% carbon nanotube (CNT nanocomposite bars were prepared by calendering and thermal curing. Nanocomposite bars were subjected to Vickers diamond indentation to produce sub-surface damage. Electrical conductivities were analysed by 4-point method to estimate the structural damage caused by indentation. For comprehensive comparison, fracture toughness and percolation threshold were analysed as well. Because of the systematically induced indentation damage, a sharp decrease of 89% was observed in the electrical conductivity of epoxy – CNT nanocomposite as compared to 25% in the electrical conductivity of epoxy – CB nanocomposite. CNTs impart superior damage sensing capability in brittle nanocomposite structures, in comparison to CB, due to their high aspect ratio (fibrous nature and high electrical conductivity.

Addition effect of erbium(III) trifluoromethanesulfonate in the homopolymerization kinetics of a DGEBA resin

International Nuclear Information System (INIS)

Garcia, S.J.; Ramis, X.; Serra, A.; Suay, J.

2006-01-01

Solid bisphenol-A epoxy resin of medium molecular weight was cured using a Lewis acid initiator (erbium(III) trifluoromethanesulfonate) in three different proportions (0.5, 1 and 2 phr). A kinetic study was performed in a differential scanning calorimeter. The complete kinetic triplet was determined (activation energy, pre-exponential factor, and integral function of the deg.ree of conversion) for each system. A kinetic analysis was performed with an integral isoconversional procedure (model-free), and the kinetic model was determined both with the Coats-Redfern method (the obtained isoconversional E value being accepted as the effective activation energy) and through the compensation effect. All the systems followed the same isothermal curing model simulated from non-isothermal ones. The 'nucleation and growth' Avrami kinetic model A 3/2 has been proposed as the polymerization kinetic model. The addition of initiator accelerated the reaction having higher influence when low temperatures were applied

Study the scratch resistance of UV-cured epoxy acrylate in the presence of nano alumina particles via nano indentation

International Nuclear Information System (INIS)

Bastani, S.; Ebrahimi, M.; Kardar, P.

2007-01-01

In this research, an epoxy acrylate resin was synthesized, then the synthesized resin was used along with different multifunctional acrylate monomers and with a photoinitiator in different formulations and cured with UV radiation. The experiments were designed based on mixture method by using Design-Expert software. To investigate the effect of nano particles on the some of physical and mechanical properties of the UV cured resins, the suspension of nano alumina in TPGDA, was used in formulations. The hardness of prepared films was evaluated by using konig hardness tester and nano indentater. The scratch resistance and gloss of the films were also determined. The results showed that the visibility of scratch decreased when the nano particles were used. It seems that the self-healing property of the film improved in the presence of nano particles. The hardness of the samples with nano particles was found to be less than that the samples of without any nano particles. It was observed that the gloss of the films with the nano particles, almost was the same as the film without nano particles. (Author)

Experimental design applied optimization of a state in epoxy clay dispersion; Planejamento de experimentos aplicado a otimizacao do estado de dispersao de argilas em epoxi

Energy Technology Data Exchange (ETDEWEB)

Paz, Juliana D' Avila; Bertholdi, Jonas; Folgueras, Marilena Valadares; Pezin, Sergio Henrique; Coelho, Luiz Antonio Ferreira, E-mail: julianadpaz@yahoo.com.b [Universidade do Estado de Santa Catarina (UDESC), Joinville, SC (Brazil). Centro de Ciencias Tecnologicas

2010-07-01

This paper presents some analysis showed that the exfoliation / intercalation of a montmorillonite clay in epoxy resin such as viscosity, X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetry (TG). Increasing the viscosity of epoxy resin diglycidyl ether bisphenol A with the addition of clay associated with the sonification system at the time of dispersion is a good indication of exfoliation. The X-ray diffraction already cured composite shows a decrease of crystallinity of clay and EDS microanalysis of SEM, non-uniform dispersion of clay in epoxy resin. Thermal analysis TG composite clay / epoxy shows an increase in thermal stability relative to pure epoxy. (author)

A room temperature cured low dielectric hyperbranched epoxy ...

Indian Academy of Sciences (India)

carbon chain in its structure.2 In the present study, a .... The degree of branching, epoxy equivalent and hydroxyl value ... The physical properties and swelling value of the hardener were ... samples were studied by thermogravimetric analysis. (TGA) in ..... Nalwa H S 1999 Handbook of low and high dielectric constant ...

In situ measurement using FBGs of process-induced strains during curing of thick glass/epoxy laminate plate

DEFF Research Database (Denmark)

Nielsen, Michael Wenani; Schmidt, Jacob Wittrup; Hattel, Jesper Henri

2012-01-01

For large composite structures, such as wind turbine blades, thick laminates are required to withstand large in-service loads. During the manufacture of thick laminates, one of the challenges met is avoiding process-induced shape distortions and residual stresses. In this paper, embedded fibre...... Bragg grating sensors are used to monitor process-induced strains during vacuum infusion of a thick glass/epoxy laminate. The measured strains are compared with predictions from a cure hardening instantaneous linear elastic (CHILE) thermomechanical numerical model where different mechanical boundary...... conditions are employed. The accuracy of the CHILE model in predicting process-induced internal strains, in what is essentially a viscoelastic boundary value problem, is investigated. A parametric study is furthermore performed to reveal the effect of increasing the laminate thickness. The numerical model...

Epoxy resin/phosphonium ionic liquid/carbon nanofiller systems: Chemorheology and properties

Directory of Open Access Journals (Sweden)

H. Maka

2014-10-01

Full Text Available Epoxy nanocomposites with commercial carbon nanotubes (CNT or graphene (GN have been prepared using phosphonium ionic liquid [trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl phosphinate, IL-f]. IL-f served simultaneously as nanofiller dispersing medium and epoxy resin catalytic curing agent. An influence of IL-f/epoxy weight ratio (3, 6 and 9/100, phr, carbon nanofiller type and content on viscosity of epoxy compositions during storage at ambient temperature was evaluated. Curing process was controlled for neat and CNT or GN modified epoxy compositions (0.25-1.0 wt.% load using differential scanning calorimetry and rheometry. Epoxy nanocomposites exhibited slightly increased glass transition temperature values (146 to 149°C whereas tan δ and storage modulus decreased (0.30 to 0.27 and 2087 to 1070 MPa, respectively as compared to reference material. Crosslink density regularly decreased for composites with increasing CNT content (11 094 to 7 020 mol/m3. Electrical volume resistivity of the nanocomposites was improved in case of CNT to 4•101 Ω•m and GN to 2•105 Ω•m (nanofiller content 1 wt.%. Flame retardancy was found for modified epoxy materials with as low GN and phosphorus content as 0.25 and 0.7 wt.%, respectively (increase of limiting oxygen index to 26.5%.

Adhesion between coating layers based on epoxy and silicone

DEFF Research Database (Denmark)

Svendsen, Jacob R.; Kontogeorgis, Georgios; Kiil, Søren

2007-01-01

The adhesion between a silicon tie-coat and epoxy primers, used in marine coating systems, has been studied in this work. Six epoxy coatings (with varying chain lengths of the epoxy resins), some of which have shown problems with adhesion to the tie-coat during service life, have been considered....... The experimental investigation includes measurements of the surface tension of the tie-coat and the critical surface tensions of the epoxies, topographic investigation of the surfaces of cured epoxy coatings via atomic force microscopy (AFM), and pull-off tests for investigating the strength of adhesion...... to the silicon/epoxy systems. Calculations for determining the roughness factor of the six epoxy coatings (based on the AFM topographies) and the theoretical work of adhesion have been carried out. The coating surfaces are also characterized based on the van Oss-Good theory. Previous studies on the modulus...

Reinforcing styrene butadiene rubber with lignin-novolac epoxy resin networks

Directory of Open Access Journals (Sweden)

P. Yu

2015-01-01

Full Text Available In this study, lignin-novolac epoxy resin networks were fabricated in the styrene butadiene rubber (SBR matrix by combination of latex compounding and melt mixing. Firstly, SBR/lignin compounds were co-coagulated by SBR latex and lignin aqueous solution. Then the novolac epoxy resin (F51 was added in the SBR/lignin compounds by melt compounding method. F51 was directly cured by lignin via the ring-opening reaction of epoxy groups of F51 and OH groups (or COOH groups of lignin during the curing process of rubber compounds, as was particularly evident from Fourier transform infrared spectroscopy (FTIR studies and maximum torque of the curing analysis. The existence of lignin-F51 networks were also detected by scanning electron microscope (SEM and dynamic mechanical analysis (DMA. The structure of the SBR/lignin/F51 was also characterized by rubber process analyzer (RPA, thermogravimetric analysis (TGA and determination of crosslinking density. Due to rigid lignin-F51 networks achieved in SBR/lignin/F51 composites, it was found that the hardness, modulus, tear strength, crosslinking density, the temperature of 5 and 10% weight-loss were significantly enhanced with the loading of F51.

Fabrication and mechanical properties of multi-walled carbon nanotubes/epoxy nanocomposites

International Nuclear Information System (INIS)

Yeh, M.-K.; Hsieh, T.-H.; Tai, N.-H.

2008-01-01

Carbon nanotubes have better physical and mechanical behavior than the traditional materials. In this study, the multi-walled carbon nanotubes (MWNTs) were added to the epoxy resin as a reinforcement to fabricate MWNTs/epoxy nanocomposites. The pressure and temperature were applied to cure the MWNTs/epoxy compound by hot press method. Mechanical properties such as tensile strength, Young's modulus, and Poisson's ratio were measured. The effect of weight percentages of the MWNTs was investigated. Morphologies of the fracture surface of MWNTs/epoxy nanocomposites were observed by scanning electron microscope

Thermo-physical properties of epoxy nanocomposites reinforced by carbon nanotubes and vapor grown carbon fibers

International Nuclear Information System (INIS)

Miyagawa, Hiroaki; Rich, Michael J.; Drzal, Lawrence T.

2006-01-01

In this study, the thermo-physical properties of epoxy nanocomposites reinforced by fluorinated single wall carbon nanotubes (FSWCNT) and vapor grown carbon fibers (VGCF) were investigated. A sonication technique using a suspension of FSWCNT and VGCF in acetone was utilized to process nanocomposites in anhydride-cured epoxy. The viscoelastic properties of the nanocomposites were measured with dynamic mechanical analysis. The glass transition temperature decreased approximately 30 deg. C with an addition of 0.14 vol.% (0.2 wt.%) FSWCNT. The depression in T g is attributed to non-stoichiometric balance of the epoxy matrix caused by the fluorine on single wall carbon nanotubes. The correct amount of the anhydride curing agent needed to achieve stoichiometry was experimentally determined by DMA measurements. After adjusting the amount of the anhydride curing agent for stoichiometry, the storage modulus of the epoxy at room temperature increased 0.63 GPa with the addition of only 0.21 vol.% (0.30 wt.%) of FSWCNT, a 20% improvement compared with the anhydride-cured neat epoxy. For VGCF, the storage modulus at room temperature increased 0.48 GPa with the addition of only 0.94 vol.% (1.5 wt.%) and then reached a plateau for larger amounts of VGCF. To understand the influence of VGCF on thermo-physical properties, the microstructure of the nanocomposites was interrogated using transmission electron microscopy (TEM). This study discusses the chemical effects of fluorine on matrix properties and the effect of stoichiometric balance on the thermo-physical properties of nanocomposites

Epoxy matrix with triaromatic mesogenic unit in dielectric spectroscopy observation

Science.gov (United States)

Włodarska, Magdalena; Mossety-Leszczak, Beata; Bąk, Grzegorz W.; Kisiel, Maciej; Dłużniewski, Maciej; Okrasa, Lidia

2018-04-01

This paper describes the dielectric response of a selected liquid crystal epoxy monomer (plain and in curing systems) in a wide range of frequency and temperature. The dielectric spectroscopy, thanks to its sensitivity, is a very good tool for studying phase transitions, reaction progress, or material properties. This sensitivity is important in the case of liquid crystal epoxy resins, where properties of the final network depend on the choice of monomers, curing agents, curing conditions and post-curing treatment, or applying an external electric or magnetic field during the reaction. In most of the obtained cured products, the collected dielectric data show two relaxation processes. The α-process is related to a structural reorientation; it can usually be linked with the glass transition and the mechanical properties of the material. The β-process can be identified as a molecular motion process, probably associated with the carboxyl groups in the mesogen. A transient Maxwell-Wagner relaxation observed in one of the compositions after the initial curing is removed by post-curing treatment at elevated temperatures. Post-curing is therefore necessary for obtaining uniformly cured products in those cases. In the investigated systems, the choice of a curing agent can change the glass transition temperature by at least 70 °C. The obtained results are in a good agreement with an earlier study employing other techniques. Finally, we assess the influence of the direction of mesogen alignment on the dielectric properties of one selected system, where a global order was induced by applying an external magnetic field in the course of curing.

Addition effect of erbium(III) trifluoromethanesulfonate in the homopolymerization kinetics of a DGEBA resin

Energy Technology Data Exchange (ETDEWEB)

Garcia, S.J. [Area de Ciencia de los Materiales, Departament d' Enginyeria de Sistemes Industrials i Disseny, Universitat Jaume I, Avda. Vicent Sos Baynat s/n, 12071 Castellon (Spain)]. E-mail: espallar@sg.uji.es; Ramis, X. [Laboratori de Termodinamica, Escola Tecnica Superior Enginyeria Industrial Barcelona, Universitat Politecnica de Catalunya, Diagonal 647, 08028 Barcelona (Spain); Serra, A. [Departament de Q. Analitica i Q. Organica, Facultat de Quimica, Universitat Rovira i Virgili, C/Marcel.li Domingo s/n, 43007 Tarragona (Spain); Suay, J. [Centro de Biomateriales, Universitat Politecnica de Valencia, Camino de Vera s/n, E-46071 Valencia (Spain)

2006-02-01

Solid bisphenol-A epoxy resin of medium molecular weight was cured using a Lewis acid initiator (erbium(III) trifluoromethanesulfonate) in three different proportions (0.5, 1 and 2 phr). A kinetic study was performed in a differential scanning calorimeter. The complete kinetic triplet was determined (activation energy, pre-exponential factor, and integral function of the deg.ree of conversion) for each system. A kinetic analysis was performed with an integral isoconversional procedure (model-free), and the kinetic model was determined both with the Coats-Redfern method (the obtained isoconversional E value being accepted as the effective activation energy) and through the compensation effect. All the systems followed the same isothermal curing model simulated from non-isothermal ones. The 'nucleation and growth' Avrami kinetic model A {sub 3/2} has been proposed as the polymerization kinetic model. The addition of initiator accelerated the reaction having higher influence when low temperatures were applied.

Experimental design applied optimization of a state in epoxy clay dispersion

International Nuclear Information System (INIS)

Paz, Juliana D'Avila; Bertholdi, Jonas; Folgueras, Marilena Valadares; Pezin, Sergio Henrique; Coelho, Luiz Antonio Ferreira

2010-01-01

This paper presents some analysis showed that the exfoliation / intercalation of a montmorillonite clay in epoxy resin such as viscosity, X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetry (TG). Increasing the viscosity of epoxy resin diglycidyl ether bisphenol A with the addition of clay associated with the sonification system at the time of dispersion is a good indication of exfoliation. The X-ray diffraction already cured composite shows a decrease of crystallinity of clay and EDS microanalysis of SEM, non-uniform dispersion of clay in epoxy resin. Thermal analysis TG composite clay / epoxy shows an increase in thermal stability relative to pure epoxy. (author)

Structural, mechanical and electrical characterization of epoxy-amine/carbon black nanonocomposites

Directory of Open Access Journals (Sweden)

2008-05-01

Full Text Available This work presents an insight into the effect of preparation procedure and the filler content on both electrical and mechanical properties of a nanocomposite system. For the preparation of the nanocomposites diglycidyl ether of bisphenol A (DGEBA was used with triethylenetetramine (TETA as a curing agent. As fillers carbon black (CB nanoparticles with size from 25 to 75 nm were used. The characterization was done using Dynamic Mechanical Analysis (DMA, Dielectric Relaxation Spectroscopy (DRS, Differential Scanning Calorimetry (DSC, Wide Angle X-ray Diffraction (WAXD and electrical conductivity measurements. The dependence of the dynamic mechanical and dielectric parameters (E′, E″, tanδ, ε', ε″, σ and Tg is associated with the filler content and is controlled by the employed curing conditions. An increase in electrical conductivity, which is observed at about 1% w/w of carbon black, indicates the creation of conducting paths and is associated with the Maxwell Wagner Sillars (MWS relaxation, probably due to the formation of aggregated microstructures in the bulk composite..

Polymer chain dynamics in epoxy based composites as investigated by broadband dielectric spectroscopy

Directory of Open Access Journals (Sweden)

Mohammad K. Hassan

2016-03-01

Full Text Available Epoxy networks of the diglycidyl ether of bisphenol A (DGEBA were prepared using 3,3′- and 4,4′-diaminodiphenyl sulfone isomer crosslinkers. Secondary relaxations and the glass transitions of resultant networks were probed using broadband dielectric spectroscopy (BDS. A sub-Tg γ relaxation peak for both networks shifts to higher frequencies (f with increasing temperature in Arrhenius fashion, both processes having the same activation energy and being assigned to phenyl ring flipping in DGEBA chains. A β relaxation is assigned to local motions of dipoles that were created during crosslinking reactions. 4,4′-based networks exhibited higher Tg relative to 3,3′-based networks as per dynamic mechanical as well as BDS analyses. The Vogel–Fulcher–Tammann–Hesse equation fitted well to relaxation time vs. temperature data and comparison of Vogel temperatures suggests lower free volume per mass for the 3,3′-based network. The Kramers–Krönig transformation was used to directly calculate dc-free ɛ″ vs. f data from experimental ɛ′ vs. f data. Distribution of relaxation times (DRT curves are bi-modal for the 3,3′-crosslinked resin suggesting large-scale microstructural heterogeneity as opposed to homogeneity for the 4,4′-based network whose DRT consists of a single peak.

Higher-order-structure formation in liquid crystal epoxy thermosets investigated by synchrotron radiation-wide-angle X-ray diffraction

International Nuclear Information System (INIS)

Maeda, Rina; Okuhara, Kenta; Nakamura, Akihiro; Hayakawa, Teruaki; Uehara, Yasushi; Motoya, Tsukasa; Nobutoki, Hideharu

2016-01-01

We report the investigation of the mesophase transformations of a liquid crystalline molecule with terminal epoxy groups from the initial stages of curing with a diamine compound. The ordered arrangement of molecules within the smectic layers in the thermoset formed at the end of the curing process was characterized by synchrotron radiation-wide-angle X-ray diffraction (SR-WAXD). Data from this experiment helps us understand the phase transitions from the nematic to smectic phases of curing liquid crystalline epoxies. (author)

Improvement in electrical, thermal and mechanical properties of epoxy by filling carbon nanotube

Directory of Open Access Journals (Sweden)

2008-01-01

Full Text Available In this study, electrical, thermal and mechanical properties of multi-walled carbon nanotubes (CNTs reinforced Epon 862 epoxy have been evaluated. Firstly, 0.1, 0.2, 0.3, and 0.4 wt% CNT were infused into epoxy through a high intensity ultrasonic liquid processor and then mixed with EpiCure curing agent W using a high speed mechanical agitator. Electric conductivity, dynamic mechanical analysis (DMA, three point bending tests and fracture tests were then performed on unfilled, CNT-filled epoxy to identify the loading effect on the properties of materials. Experimental results show significant improvement in electric conductivity. The resistivity of epoxy decreased from 1014 Ω•m of neat epoxy to 10 Ω•m with 0.4% CNT. The experimental results also indicate that the frequency dependent behavior of CNT/epoxy nanocomposite can be modeled by R-C circuit, permittivity of material increase with increasing of CNT content. DMA studies revealed that filling the carbon nanotube into epoxy can produce a 90% enhancement in storage modulus and a 17°C increase in Tg. Mechanical test results showed that modulus increased with higher CNT loading percentages, but the 0.3 wt% CNT-infusion system showed the maximum strength and fracture toughness enhancement. The decrease in strength and fracture toughness in 0.4% CNT/epoxy was attributed to poor dispersions of nanotubes in the composite.

Thiol-yne/thiol-epoxy hybrid crosslinked materials based on propargyl modified hyperbranched poly(ethyleneimine) and diglycidylether of bisphenol A resins

OpenAIRE

Acebo Gorostiza, Cristina; Fernández Francos, Xavier; Ramis Juan, Xavier; Serra Albet, Àngels

2016-01-01

A novel curing methodology based on the combination of thiol-yne and thiol-epoxy click reactions has been developed. The curing process consists of a first photoinitiated thiol-yne reaction, followed by a thermal thiol-epoxy process. As alkyne substrate a new propargyl terminated hyperbranched poly(ethyleneimine) (PEIyne) has been synthesized from the reaction of commercial poly(ethylenimine) (PEI) and glycidyl propargyl ether. The evolution of the curing of different mixtures of PEIyne and d...

Differences in interfacial bond strengths of graphite fiber-epoxy resin composites

Science.gov (United States)

Needles, H. L.

1985-01-01

The effect of epoxy-size and degree of cure on the interfacial bonding of an epoxy-amine-graphite fiber composite system is examined. The role of the fiber-resin interface in determining the overall mechanical properties of composites is poorly understood. A good interfacial adhesive bond is required to achieve maximum stress transfer to the fibers in composites, but at the same time some form of energy absorbing interfacial interaction is needed to achieve high fracture toughening. The incompatibility of these two processes makes it important to understand the nature and basic factors involved at the fiber-resin interface as stress is applied. The mechanical properties including interlaminar shear values for graphite fiber-resin composites are low compared to glass and boron-resin composites. These differences have been attributed to poor fiber-matrix adhesion. Graphite fibers are commonly subjected to post-treatments including application of organic sizing in order to improve their compatibility with the resin matrix and to protect the fiber tow from damage during processing and lay-up. In such processes, sized graphite fiber tow is impregnated with epoxy resin and then layed-up i nto the appropriate configuration. Following an extended ambient temperature cure, the graphite-resin composite structure is cured at elevated temperature using a programmed temperature sequence to cure and then cool the product.

Epoxy resin casting of trim coils for superconducting cyclotron

International Nuclear Information System (INIS)

Hajra, D.P.; Sarkar, S.C.; Saha, Subimal; Chaudhuri, J.; Bhandari, R.K.

2006-01-01

The life of any magnet depends on the soundness of the coil insulation, its aging properties and initial and final endurance limitations. The insulation of water-cooled trim coils for superconducting cyclotron is made of glass fibre tape with heat cured unfilled epoxy resin combination. This type of insulation has been selected to achieve excellent stability against thermal and electromagnetic stresses, tight dimensional control, good dielectric strength, non-hygroscopic and considerably low vapour-pressure as it will be inside rough vacuum. The process development and the difficulties encountered for appropriate selection of epoxy resin combination, potting, vacuum process, curing cycle, control of coil dimension to achieve a sound coil absolutely free from cracks, trapped air and voids has been discussed. (author)

Self-healing woven glass fabric/epoxy composites with the healant consisting of micro-encapsulated epoxy and latent curing agent

International Nuclear Information System (INIS)

Yin Tao; Zhou Lin; Rong Minzhi; Zhang Mingqiu

2008-01-01

This paper reports a study of self-healing woven glass fabric reinforced epoxy composites. The healing agent was a two-component one synthesized in the authors' laboratory, which consisted of epoxy-loaded urea-formaldehyde microcapsules as the polymerizable binder and CuBr 2 (2-methylimidazole) 4 (CuBr 2 (2-MeIm) 4 ) as the latent hardener. Both the microcapsules and the matching catalyst were pre-embedded and pre-dissolved in the composites' matrix, respectively. When the microcapsules are split by propagating cracks, the uncured epoxy can be released into the damaged areas and then consolidated under the catalysis of CuBr 2 (2-MeIm) 4 that was homogeneously distributed in the composites' matrix on a molecular scale. As a result, the cracked faces can be bonded together. The influence of the content of the self-healing agent on the composites' tensile properties, interlaminar fracture toughness and healing efficiency was evaluated. It was found that a healing efficiency over 70% relative to the fracture toughness of virgin composites was obtained in the case of 30 wt% epoxy-loaded microcapsules and 2 wt% latent hardener

The Role of Multi-wall Carbon Nanotubes on Fracture Mechanism of Epoxy Nanocomposite

Directory of Open Access Journals (Sweden)

M. Hooshiar Sadegian

2008-12-01

Full Text Available In order to investigate the role of multi-wall carbon nanotubes (MWCNTs on fracture mechanism of epoxy nanocomposites, a series of tensile standard specimens reinforced with different carbon nanotube contents (0, 0.3, 0.6 and 1 wt% were produced. The fracture surfaces of the produced nanocomposites were evaluated using scanning electron microscope (SEM. The results show that the surface fracture of epoxy nanocomposites comprised of three regions, i.e. mirror, transition and final propagation zones. The extension of all zones depends strongly on curing agent as well asMWCNTs content. The mirror zone is disappeared as curing agent and MWCNTs content increases, while the transition zone depends on the nucleation rate of secondary microcrack. The pattern of final propagation zone becomes coarser as MWCNTs are added to epoxy system.

Fracture surface analysis on nano-SiO{sub 2}/epoxy composite

Energy Technology Data Exchange (ETDEWEB)

Zhao Rongguo [Institute of Fundamental Mechanics and Material Engineering, Xiangtan University, Hunan 411105 (China); Key Laboratory of Low Dimensional Materials and Application Technology, Xiangtan University, Ministry of Education, Hunan 411105 (China)], E-mail: zhaorongguo@xtu.edu.cn; Luo Wenbo [Institute of Fundamental Mechanics and Material Engineering, Xiangtan University, Hunan 411105 (China); Key Laboratory of Low Dimensional Materials and Application Technology, Xiangtan University, Ministry of Education, Hunan 411105 (China)

2008-06-15

Fracture surface morphologies of nano-SiO{sub 2}/epoxy composite with different weight percentage of SiO{sub 2} are investigated using scanning electron microscopy. Two types of curing agent, dimethylbenzanthracene (DMBA) and methyltetrahydrophthalic anhydride (MeTHPA), are individually used for preparing the composites. It is found that the fracture surface morphology of the composite cured by DMBA shows as radial striations, which suggests a rapid brittle fracture mode, while the fracture surface morphology of the composite cured by MeTHPA shows as regularly spaced 'rib' markings, which indicates a stick-slip motion during the fracture process. Furthermore, the uniaxial tensile behavior under constant loading rate and ambient temperature are investigated. It is shown that the elastic modulus of the composite cured by DMBA firstly increases, and then decreases with the mass fraction of nano-SiO{sub 2} particles, but the elongation of the composite cured by MeTHPA is reversed with increasing fraction of nano-SiO{sub 2} particles. For nano-SiO{sub 2}/epoxy composite cured with MeTHPA that possesses a suitable fraction of nano-SiO{sub 2}, an excellent synthetic mechanical property on elastic modulus and elongation is obtained.

Nanostructure of tetrafunctional epoxy resins and composites: Correlation to moisture absorption properties

Science.gov (United States)

Bolan, Brett Andrew

The effect that changes in network topology, while maintaining a constant network polarity (i.e. thermodynamic driving force was kept constant), had upon the moisture absorption properties of an aerospace grade tetrafunctional epoxy (TGMDA) cured with multifunctional amines were investigated. Utilizing Positron Annihilation Lifetime Spectroscopy (PALS) to characterize the nanoscale structure of these epoxies, it was found that as the "static" hole volume (a measurement of packing defects at 0K) increased so did the equilibrium uptake. PALS studies of one of these resins cured to varying extents, found that this static amount increased with degree of cure indicating that the network becomes more open as a direct consequence of crosslinking. Polar groups, which are the attractive force for diffusion, are in the vicinity of these crosslinks, therefore it is believed that the increase in static hole volume results in exposing more polar groups for absorption. The diffusion coefficient, which is representative of the kinetic aspect of diffusion, was also investigated. It was discovered that the amount of nanohole volume in the polymer; whether the total, the static, or dynamic (i.e. thermally activated) does not correlate to the diffusion coefficient in anyway. Furthermore, at an isotherm the diffusion coefficients for all these materials were relatively constant. From this it is hypothesized that it is the similar sub-Tsb{g} motions of these resins which is the rate limiting step in diffusion. This was bolstered by the fact that the activation energy for diffusion and for the sub-Tsb{g} motions for these epoxies are of the same order of magnitude. The nanostructure of fiber reinforced epoxy composites (i.e. a boron/epoxy and a graphite/epoxy) were probed with the bulk PALS technique as well. It was observed that for the graphite/epoxy composite and its flash (i.e. no fibers present) cured under identical conditions, that the nanoholes in the composite were larger than

Paramagnetic epoxy resin

Directory of Open Access Journals (Sweden)

E. C. Vazquez Barreiro

2017-01-01

Full Text Available This work illustrates that macrocycles can be used as crosslinking agents for curing epoxy resins, provided that they have appropriate organic functionalities. As macrocycles can complex metal ions in their structure, this curing reaction allows for the introduction of that metal ion into the resin network. As a result, some characteristic physical properties of the metallomacrocycle could be transferred to the new material. The bisphenol A diglycidyl ether (BADGE, n = 0 and hemin (a protoporphyrin IX containing the Fe(III ion, and an additional chloride ligand have been chosen. The new material has been characterized by differential scanning calorimetry (DSC, thermogravimetric analysis (TGA, Fourier Transform Infrared (FT-IR, Nuclear Magnetic Resonance (NMR, Transmission Electron Microscopy (TEM, and magnetic susceptibility measurements. Fe(III remains in the high-spin state during the curing process and, consequently, the final material exhibits the magnetic characteristics of hemin. The loss of the chlorine atom ligand during the cure of the resin allows that Fe(III can act as Lewis acid, catalyzing the crosslinking reactions. At high BADGE n = 0/hemin ratios, the formation of ether and ester bonds occurs simultaneously during the process.

High-Speed 3D Printing of High-Performance Thermosetting Polymers via Two-Stage Curing.

Science.gov (United States)

Kuang, Xiao; Zhao, Zeang; Chen, Kaijuan; Fang, Daining; Kang, Guozheng; Qi, Hang Jerry

2018-04-01

Design and direct fabrication of high-performance thermosets and composites via 3D printing are highly desirable in engineering applications. Most 3D printed thermosetting polymers to date suffer from poor mechanical properties and low printing speed. Here, a novel ink for high-speed 3D printing of high-performance epoxy thermosets via a two-stage curing approach is presented. The ink containing photocurable resin and thermally curable epoxy resin is used for the digital light processing (DLP) 3D printing. After printing, the part is thermally cured at elevated temperature to yield an interpenetrating polymer network epoxy composite, whose mechanical properties are comparable to engineering epoxy. The printing speed is accelerated by the continuous liquid interface production assisted DLP 3D printing method, achieving a printing speed as high as 216 mm h -1 . It is also demonstrated that 3D printing structural electronics can be achieved by combining the 3D printed epoxy composites with infilled silver ink in the hollow channels. The new 3D printing method via two-stage curing combines the attributes of outstanding printing speed, high resolution, low volume shrinkage, and excellent mechanical properties, and provides a new avenue to fabricate 3D thermosetting composites with excellent mechanical properties and high efficiency toward high-performance and functional applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Curing reaction of bisphenol-A based benzoxazine with cyanate ester resin and the properties of the cured thermosetting resin

Directory of Open Access Journals (Sweden)

H. Kimura

2011-12-01

Full Text Available Curing reaction of bisphenol-A based benzoxazine with cyanate ester resin and the properties of the cured thermosetting resin were investigated. The cure behavior of benzoxazine with cyanate ester resin was monitored by model reaction using nuclear magnetic resonance (NMR. As a result of the model reaction, the ring opening reaction of benzoxazine ring and thermal self-cyclotrimerization of cyanate ester group occurred, and then the phenolic hydoroxyl group generated by the ring opening reaction of benzoxazine ring co-reacted with cyanate ester group. The properties of the cured thermosetting resin were estimated by mechanical properties, electrical resistivity, water resistance and heat resistance. The cured thermosetting resin from benzoxazine and cyanate ester resin showed good heat resistance, high electrical resistivity and high water resistance, compared with the cured thermosetting resin from benzoxazine and epoxy resin.

Analysis of sulphone based organic–inorganic hybrid epoxy nanocomposites for advanced engineering applications—Study of the mechanical, thermomechanical, XRD, EDS and physical properties

International Nuclear Information System (INIS)

Shree Meenakshi, K.; Pradeep Jaya Sudhan, E.; Menon, Prathibha G.

2012-01-01

Highlights: ► Novel sulphone based tetraglycidyl epoxy nanocomposites were developed for aerospace applications. ► Nano-reinforcements were incorporated and curing was done. ► Excellent results were obtained in the mechanical studies. The nanocomposites developed were flame retardant and hydrophobic. - Abstract: A study was made in the present investigation on sulphone containing tetraglycidyl epoxy nanocomposites to find its suitability for use in high performance applications. The synthesis and characterization of the sulphone tetraglycidyl epoxy resin denoted as ‘B’ was done as reported in our previous study. Nanoclay and POSS-amine nano-reinforcements denoted as N1 and N2 were incorporated into the synthesized epoxy resin. Curing was done with diaminodiphenylmethane (DDM) and bis(3-aminophenyl) phenylphosphine oxide (BAPPO) curing agents denoted as X and Y respectively. In our current research, we continue this research and study the mechanical, thermo-mechanical, X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), viscosity, epoxy equivalent weight (EEW) and gel permeation chromatography (GPC) studies.

Modification of bifunctional epoxy resin using CO2 fixation process and nanoclay

International Nuclear Information System (INIS)

Khoshkish, Morteza; Bouhendi, Hosein; Vafayan, Mehdi

2014-01-01

A bifunctional epoxy resin was modified by using a CO 2 fixation solution process in the presence of tetra n-butyl ammonium bromide (TBAB) as catalyst and the modified treated resin was treated by cloisite 30B as nano additive. The Unmodified epoxy resin (UME), CO 2 fixated modified epoxy resin (CFME), and CFME/clay nano composite (CFMEN), were cured by diethylenetriamine (DETA). A cycloaliphatic compound as a reactive diluent was used to control the viscosity of high viscose CFME. The exfoliation of organoclay in UME and CFME was investigated by X-ray diffraction and activation energy was computed using the advanced integral isoconversional method. The activation energy dependency demonstrated that the mechanism of UME curing did not change in the presence of nanoclay. In contrast, the CO 2 fixation results showed a significant change in the activation energy dependency. The Thermal stability parameters include the initial degradation temperature (IDT), the temperature at the maximum rate of weight loss (T max ), and the decomposition activation energy (E d ) were determined by thermal gravimetry analysis. Dynamic mechanical thermal analysis measurements showed that the presence of organoclay in CFME increases the T g of nano composite in contrast to UME. The fracture roughness of UME, CFME and CFNE were determined by scanning electron microscope. The exfoliated UME/1%clay nanocomposite was confirmed by TEM image. - Highlights: • A new epoxy resin was synthesized using CO 2 fixation reaction. • The synthesized epoxy resin was modified by an organo nano-clay. • CO 2 fixation noticeably changed the curing mechanism. • CO 2 fixation reaction consumes CO 2 which is a harmful greenhouse gas

Study on epoxy/BaTiO3 composite embedded capacitor films (ECFs) for organic substrate applications

International Nuclear Information System (INIS)

Cho, Sung-Dong; Lee, Joo-Yeon; Hyun, Jin-Gul; Paik, Kyung-Wook

2004-01-01

Embedded capacitor films (ECFs) were newly designed for high dielectric constant and low capacitance tolerance (less than ±5%) embedded capacitor fabrication for organic substrates. ECFs are transferable and B-stage films which can be coated on a releasing film. In terms of materials formulation, ECFs are composed of high dielectric constant BaTiO 3 (BT) powder, specially formulated epoxy resin, and latent curing agent. And in terms of coating process, a roll coating method is used for obtaining film thickness uniformity in a large area. Differential scanning calorimeter (DSC) thermal analysis was conducted to determine the optimum amount of curing agent, curing temperature, and curing time. Changes in the dielectric constant of epoxy/BaTiO 3 composite ECFs with BT particle sizes and contents were investigated. Dielectric constant of 90 was obtained using two different size BaTiO 3 powders mixture. Typically, capacitors of 12 μm thick film with 8 nF/cm 2 with less than ±5% capacitance tolerance and low leakage current (less than 10 -7 A/cm 2 at 10 V) were successfully demonstrated on PCBs using epoxy/BaTiO 3 composite embedded capacitor films

Enhancement of mechanical and electrical properties of continuous-fiber-reinforced epoxy composites with stacked graphene

OpenAIRE

Naveh, Naum; Shepelev, Olga; Kenig, Samuel

2017-01-01

Impregnation of expandable graphite (EG) after thermal treatment with an epoxy resin containing surface-active agents (SAAs) enhanced the intercalation of epoxy monomer between EG layers and led to further exfoliation of the graphite, resulting in stacks of few graphene layers, so-called “stacked” graphene (SG). This process enabled electrical conductivity of cured epoxy/SG composites at lower percolation thresholds, and improved thermo-mechanical properties were measured with either Kevlar, ...

Study on epoxy resin modified by polyether ionic liquid

Science.gov (United States)

Jin, X. C.; Guo, L. Y.; Deng, L. L.; Wu, H.

2017-06-01

Chloride 1-carboxyl polyether-3-methyl imidazole ionic liquid (PIIL) was synthesized. Then blended with epoxy resin(EP) to prepare the composite materials of PIIL/EP, which cured with aniline curing agent. The structure and curing performance of PIIL/EP were determined by FT-IR and DSC. The effects of the content of PIIL on strength of EP were studied. The results show that the PIIL was the target product. The strength was improved significantly with increase of the PIIL content. The obvious rubber elasticity of PIIL/EP after cured was showed when the content of PIIL accounts for 40% and the impact strength was up to 15.95kJ/m2.

Investigation of the Residual Stress State in an Epoxy Based Specimen

DEFF Research Database (Denmark)

Baran, Ismet; Jakobsen, Johnny; Andreasen, Jens Henrik

2015-01-01

Abstract. Process induced residual stresses may play an important role under service loading conditions for fiber reinforced composite. They may initiate premature cracks and alter the internal stress level. Therefore, the developed numerical models have to be validated with the experimental...... observations. In the present work, the formation of the residual stresses/strains are captured from experimental measurements and numerical models. An epoxy/steel based sample configuration is considered which creates an in-plane biaxial stress state during curing of the resin. A hole drilling process...... material models, i.e. cure kinetics, elastic modulus, CTE, chemical shrinkage, etc. together with the drilling process using the finite element method. The measured and predicted in-plane residual strain states are compared for the epoxy/metal biaxial stress specimen....

Increasing the electrical discharge endurance of acid anhydride cured DGEBA epoxy resin by dispersion of nanoparticle silica. High Perform. Polym. 11 (1999) pp 281-296 by IOP Publishing Ltd

DEFF Research Database (Denmark)

Henk, Peter O; Kortsen, T.W.; Kvarts, T.

1999-01-01

combinations were used: (a) fumed nanoparticle silicon dioxide referred to as Aerosil, (b) equal volumes of Aerosil and nanoparticle anatase, and (c) Aerosil plus anatase in combination with coarse-particle filler grade calcium-magnesium carbonate dolomite. A test for endurance using the CIGRE method II...... electrode arrangement was applied, the test comprising the establishment of partial discharges running perpendicularly onto one face of a plate specimen for a period measured until breakdown.Our results show that the endurance of the pure polymer is low. Increased loading with Aerosil increases...... the endurance by a factor of up to 20 as the Aerosil content goes from zero to 5.4 vol%. Aerosil mixed with anatase has a similar effect. The high level of endurance is maintained with an additional high-volume (35 vol.%) filling of coarse-particle dolomite to an epoxy system already containing Aerosil...

Effect of silane coupling agent on interfacial adhesion of copper/glass fabric/epoxy composites

International Nuclear Information System (INIS)

Langroudi, A. E.; Yousefi, A. A.; Kabiri, Kourosh

2003-01-01

The effect of silane coupling agent on the peel strength of copper/prep reg/copper composites was investigated. The composite consisted of one or two sheets of prepress covered by two copper plates. The prep reg was prepared by hand dry-lay-up technique using an epoxy resin and an electrical resistant glass fabric (e-glass style 2165). 4,4'-methylene dianiline. An aromatic amine, was used as curing agent. curing times for prep reg and composite at 120 d ig C and 170 d ig C were 15 min and 1 h, respectively. γ-aminopropyl trimethoxy silane was used as coupling agent. The effect of aminopropyl trimethoxy silane on the adhesion of epoxy/glass and epoxy/copper interfaces was investigated by two methods. In the first method, the surface of the glass fabric and/or the copper plates were treated by aminopropyl trimethoxy silane. In the second method, aminopropyl trimethoxy silane was directly added to epoxy resin. In addition, the effect of additional resin on the adhesion strength was also studied by the latter method

Volume changes at macro- and nano-scale in epoxy resins studied by PALS and PVT experimental techniques

Energy Technology Data Exchange (ETDEWEB)

Somoza, A. [IFIMAT-UNCentro, Pinto 399, B7000GHG Tandil (Argentina) and CICPBA, Pinto 399, B7000GHG Tandil (Argentina)]. E-mail: asomoza@exa.unicen.edu.ar; Salgueiro, W. [IFIMAT-UNCentro, Pinto 399, B7000GHG Tandil (Argentina); Goyanes, S. [LPMPyMC, Depto. de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon I, 1428 Buenos Aires (Argentina); Ramos, J. [Materials and Technology Group, Departamento de Ingenieria Quimica y M. Ambiente, Escuela University Politecnica, Universidad Pais Vasco/Euskal Herriko Unibertsitatea, Pz. Europa 1, 20018 Donostia/San Sebastian (Spain); Mondragon, I. [Materials and Technology Group, Departamento de Ingenieria Quimica y M. Ambiente, Escuela University Politecnica, Universidad Pais Vasco/Euskal Herriko Unibertsitatea, Pz. Europa 1, 20018 Donostia/San Sebastian (Spain)

2007-02-15

A systematic study on changes in the volumes at macro- and nano-scale in epoxy systems cured with selected aminic hardeners at different pre-cure temperatures is presented. Free- and macroscopic specific-volumes were measured by PALS and pressure-volume-temperature techniques, respectively. An analysis of the relation existing between macro- and nano-scales of the thermosetting networks developed by the different chemical structures is shown. The result obtained indicates that the structure of the hardeners governs the packing of the molecular chains of the epoxy network.

Study on an amine-containing benzoxazine: Homo- and copolymerization with epoxy resin

Directory of Open Access Journals (Sweden)

L. Zhang

2016-07-01

Full Text Available An amine-containing benzoxazine (P-deta based homopolymer and its epoxy (Ep copolymers are investigated in this study. The structure of benzoxazine, prepared from phenol, diethylenetriamine and formalin, is confirmed by Fourier transform infrared spectroscopy (FT-IR and nuclear magnetic resonance spectroscopy (NMR. The viscosity of P-deta is much lower than that of commercialized benzoxazine monomers. The curing profiles of P-deta with various Ep ratios are studied by deconvolution and the related mechanism is clarified. Epoxy will not increase the curing temperature of P-deta, instead, it helps P-deta overcome the conversion limitation and promotes the curing rate. The thermal and viscoelastic properties were determined and compared. The copolymer of P-deta/Ep = 50/50 (wt/wt shows the highest glass transition temperature, higher than both individual homopolymers and other copolymers. Increasing benzoxazine fraction enhances modulus at room temperature but deteriorates the crosslink density. It can also enhances the char yield, but deteriorates the thermal stability of the copolymers.

Development of sealed radioactive sources immobilized in epoxy resin for verification of detectors used in nuclear medicine; Desenvolvimento de fontes radioativas seladas imobilizadas em resina epoxi para verificacao de detectores utilizados em medicina nuclear

Energy Technology Data Exchange (ETDEWEB)

Tiezzi, Rodrigo

2016-07-01

The radioactive sealed sources are used in verification ionization chamber detectors, which measure the activity of radioisotopes used in several areas, such as in nuclear medicine. The measurement of the activity of radioisotopes must be made with accuracy, because it is administered to a patient. To ensure the proper functioning of the ionization chamber detectors, standardized tests are set by the International Atomic Energy Agency (IAEA) and the National Nuclear Energy Commission using sealed radioactive sources of Barium-133, Cesium-137 and Cobalt-57. The tests assess the accuracy, precision, reproducibility and linearity of response of the equipment. The focus of this work was the study and the development of these radioactive sources with standard Barium-133 and Cesium-137,using a polymer, in case commercial epoxy resin of diglycidyl ether of bisphenol A (DGEBA) and a curing agent based on modified polyamine diethylenetriamine (DETA), to immobilize the radioactive material. The polymeric matrix has the main function of fix and immobilize the radioactive contents not allowing them to leak within the technical limits required by the standards of radiological protection in the category of characteristics of a sealed source and additionally have the ability to retain the emanation of any gases that may be formed during the manufacture process and the useful life of this artifact. The manufacturing process of a sealed source standard consists of the potting ,into bottle standardized geometry, in fixed volume of a quantity of a polymeric matrix within which is added and dispersed homogeneously to need and exact amount in activity of the radioactive materials standards. Accordingly, a study was conducted for the choice of epoxy resin, analyzing its characteristics and properties. Studies and tests were performed, examining the maximum miscibility of the resin with the water (acidic solution, simulating the conditions of radioactive solution), loss of mechanical and

Colorless triphenylamine-based aliphatic thermoset epoxy for multicolored and near-infrared electrochromic applications.

Science.gov (United States)

Chuang, Ya-Wen; Yen, Hung-Ju; Wu, Jia-Hao; Liou, Guey-Sheng

2014-03-12

In this study, two novel colorless thermoset epoxy resins with anodically electrochromism were prepared from the thermal curing of two triphenylamine-based diamine monomers, 4,4'-diamino-4″-methoxytriphenylamine (1) and N,N'-bis(4-aminophenyl)-N,N'-di(4-methoxylphenyl)-1,4-phenylenediamine (2) with aliphatic epoxy triglycidyl isocyanurate, respectively. The resulting thermoset epoxy resins showed excellent softening temperature (Ts, 270 and 280 °C) due to the rigid structure and highly crosslinking density. In addition, novel colorless epoxy resin films revealed good reversible electrochemical oxidation and interesting multi-electrochromic behavior with high contrast ratio both in visible and near-infrared regions. The aliphatic thermoset epoxy resins also exhibited high transparency in visible region as colorless and great potential for practical electrochromic applications.

Composite Materials With Uncured Epoxy Matrix Exposed in Stratosphere During NASA Stratospheric Balloon Flight

Science.gov (United States)

Kondyurin, Alexey; Kondyurina, Irina; Bilek, Marcela; de Groh, Kim K.

2013-01-01

A cassette of uncured composite materials with epoxy resin matrixes was exposed in the stratosphere (40 km altitude) over three days. Temperature variations of -76 to 32.5C and pressure up to 2.1 torr were recorded during flight. An analysis of the chemical structure of the composites showed, that the polymer matrix exposed in the stratosphere becomes crosslinked, while the ground control materials react by way of polymerization reaction of epoxy groups. The space irradiations are considered to be responsible for crosslinking of the uncured polymers exposed in the stratosphere. The composites were cured on Earth after landing. Analysis of the cured composites showed that the polymer matrix remains active under stratospheric conditions. The results can be used for predicting curing processes of polymer composites in a free space environment during an orbital space flight.

Influence of curing profile and fibre architecture on the fatigue resistance of composite materials for wind turbine blades

DEFF Research Database (Denmark)

Mikkelsen, Lars Pilgaard

been investigated during a variety of curing profiles of the used epoxy material system. Thereby, it is possible to observe that even though the overall chemical shrinkage of the epoxy material system is independent on the chosen curing profile, the location of the gel-point and thereby the amount......The fatigue performance of unidirectional glass fibre reinforced epoxy is found to be highly dependent on the manufacturing conditions, where a low manufacturing temperature, for the investigated wind turbine relevant composite material system, is found to improve the tension/tension fatigue life....... It is a failure mechanism which is judge to be highly influenced by the magnitude of the residual stresses exhibit in the matrix material and therefore also in the secondary oriented backing bundles. Using fibre Bragg grated optical fibres2; the build-up of the cure-induced strains in the fibre-reinforcement has...

Treatment of high-latency microcapsules containing an aluminium complex with an epoxy-functionalised trialkoxysilane.

Science.gov (United States)

Kamiya, Kazunobu; Suzuki, Noboru

2016-12-01

Some aluminium complexes are excellent catalysts of cationic polymerisation and are used for low-temperature and fast-curing adhesive, used in electronic part mounting. Microencapsulation is a suitable technique for getting high latency of the catalysts and long shelf life of the adhesives. For the higher latency in a cycloaliphatic epoxy compound, the microcapsule surface which retained small amount of aluminium complex was coated with epoxy polymer and the effect was examined. From the X-ray photoelectron spectroscopic results, the surface was recognised to be sufficiently coated and the differential scanning calorimetric analyses showed that the coating did not significantly affect the low-temperature and fast-curing properties of adhesive. After storing the mixture of cycloaliphatic epoxy compound, coated microcapsules, triphenylsilanol and silane coupling agent for 48 h at room temperature, the increase in viscosity was only 0.01 Pa s, resulting in the excellent shelf life.

DEGRADATION OF MAGNET EPOXY AT NSLS X-RAY RING.

Energy Technology Data Exchange (ETDEWEB)

HU,J.P.; ZHONG,Z.; HAAS,E.; HULBERT,S.; HUBBARD,R.

2004-05-24

Epoxy resin degradation was analyzed for NSLS X-ring magnets after two decades of 2.58-2.8 GeV continuous electron-beam operation, based on results obtained from thermoluminescent dosimeters irradiated along the NSLS ring and epoxy samples irradiated at the beamline target location. A Monte Carlo-based particle transport code, MCNP, was utilized to verify the dose from synchrotron radiation distributed along the axial- and transverse-direction in a ring model, which simulates the geometry of a ring quadrupole magnet and its central vacuum chamber downstream of the bending-magnet photon ports. The actual life expectancy of thoroughly vacuum baked-and-cured epoxy resin was estimated from radiation tests on similar polymeric materials using a radiation source developed for electrical insulation and mechanical structure studies.

Effects of benzoxazine resin on property enhancement of shape memory epoxy: A dual function of benzoxazine resin as a curing agent and a stable network segment

Directory of Open Access Journals (Sweden)

T. Tanpitaksit

2015-09-01

Full Text Available An ability of bisphenol-A/aniline based benzoxazine resin (BA-a to simultaneously acts as a curing agent and a stable or rigid network segment for shape memory epoxy, i.e. a two component system, is demonstrated. This significantly simplifies a formulation of present shape memory epoxy systems, i.e. a three or four component system. A suitable content of BA-a in the aliphatic epoxy (NGDE/polybenzoxazine (PBA-a samples for good shape memory performance is in a range of 30 to 50 mol%. The storage modulus of the obtained NGDE/PBA-a shape memory polymers (SMPs was increased from 3.57 GPa for 30 mol% BA-a content to 4.50 GPa for 50 mol% BA-a content. Glass transition temperature of the sample was also substantially increased with increasing BA-a fraction, i.e. from 51°C to 140°C. Flexural modulus and strength at room temperature of the samples at 50 mol% BA-a were found to be as high as 3.97 GPa and 132 MPa compared to the maximum values of 2.54 GPa and 100 MPa of SMP based on cyanate ester-epoxy. All samples exhibited a high value of shape fixity close to 100%. A presence of the BA-a in the samples also imparted a greater recovery stress ranging from 0.25 to 1.59 MPa. Consequently, the obtained NGDE/PBA-a copolymers are highly attractive for shape memory materials to be used in a broader range of applications particularly at elevated temperature and a higher recovery stress value.

Modification of bifunctional epoxy resin using CO{sub 2} fixation process and nanoclay

Energy Technology Data Exchange (ETDEWEB)

Khoshkish, Morteza; Bouhendi, Hosein, E-mail: H.boohendi@ippi.ac.ir; Vafayan, Mehdi

2014-10-15

A bifunctional epoxy resin was modified by using a CO{sub 2} fixation solution process in the presence of tetra n-butyl ammonium bromide (TBAB) as catalyst and the modified treated resin was treated by cloisite 30B as nano additive. The Unmodified epoxy resin (UME), CO{sub 2} fixated modified epoxy resin (CFME), and CFME/clay nano composite (CFMEN), were cured by diethylenetriamine (DETA). A cycloaliphatic compound as a reactive diluent was used to control the viscosity of high viscose CFME. The exfoliation of organoclay in UME and CFME was investigated by X-ray diffraction and activation energy was computed using the advanced integral isoconversional method. The activation energy dependency demonstrated that the mechanism of UME curing did not change in the presence of nanoclay. In contrast, the CO{sub 2} fixation results showed a significant change in the activation energy dependency. The Thermal stability parameters include the initial degradation temperature (IDT), the temperature at the maximum rate of weight loss (T{sub max}), and the decomposition activation energy (E{sub d}) were determined by thermal gravimetry analysis. Dynamic mechanical thermal analysis measurements showed that the presence of organoclay in CFME increases the T{sub g} of nano composite in contrast to UME. The fracture roughness of UME, CFME and CFNE were determined by scanning electron microscope. The exfoliated UME/1%clay nanocomposite was confirmed by TEM image. - Highlights: • A new epoxy resin was synthesized using CO{sub 2} fixation reaction. • The synthesized epoxy resin was modified by an organo nano-clay. • CO{sub 2} fixation noticeably changed the curing mechanism. • CO{sub 2} fixation reaction consumes CO{sub 2} which is a harmful greenhouse gas.

Electron-beam curing of epoxy resins: effect of alcohols on cationic ...

Indian Academy of Sciences (India)

Unknown

Electron-beam (e-beam) induced polymerization of epoxy resins proceeds via cationic mechanism in presence of suitable ... generate ionic species, free radicals, and/or molecules in .... bisphenol A) and the effect of presence of different OH.

Modified silyl-terminated polyether polymer blends with bisphenol A diglycidyl ether epoxy for adhesive applications

International Nuclear Information System (INIS)

Bitenieks, J; Meri, R Merijs; Zicans, J; Berzins, R; Umbraško, J; Rekners, U

2016-01-01

Modified silyl-terminated polyether polymer (MS Polymer) was blended with bisphenol A diglycidyl ether (DGEBPA) epoxy at MS Polymer/epoxy ratio from 30/70 to 70/30. MS Polymer/epoxy systems were examined for two-component adhesive formulation with additional fillers. Applicability of the MS Polymer/epoxy system at the ratio of the components 60/40 is demonstrated for the development of adhesive formulation. Rheological analysis of the components A and B shows suitable viscosity values for development of two- component adhesives formulation. Curing dynamics as well as tensile stress-strain properties and Shore A hardness of the chosen adhesive formulation are reasonable for the development of MS Polymer/epoxy type adhesive. (paper)

Residual Stress Developed During the Cure of Thermosetting Polymers: Optimizing Cure Schedule to Minimize Stress.

Energy Technology Data Exchange (ETDEWEB)

Kropka, Jamie Michael; Stavig, Mark E.; Jaramillo, Rex

2016-06-01

When thermosetting polymers are used to bond or encapsulate electrical, mechanical or optical assemblies, residual stress, which often affects the performance and/or reliability of these devices, develops within the structure. The Thin-Disk-on-Cylinder structural response test is demonstrated as a powerful tool to design epoxy encapsulant cure schedules to reduce residual stress, even when all the details of the material evolution during cure are not explicitly known. The test's ability to (1) distinguish between cohesive and adhesive failure modes and (2) demonstrate methodologies to eliminate failure and reduce residual stress, make choices of cure schedules that optimize stress in the encapsulant unambiguous. For the 828/DEA/GMB material in the Thin-Disk-on-Cylinder geometry, the stress associated with cure is significant and outweighs that associated with cool down from the final cure temperature to room temperature (for measured lid strain, Scure I > I I e+h erma * II) * The difference between the final cure temperature and 1 1 -- the temperature at which the material gels, Tf-T ge i, was demonstrated to be a primary factor in determining the residual stress associated with cure. Increasing T f -T ge i leads to a reduction in cure stress that is described as being associated with balancing some of the 828/DEA/GMB cure shrinkage with thermal expansion. The ability to tune residual stress associated with cure by controlling T f -T ge i would be anticipated to translate to other thermosetting encapsulation materials, but the times and temperatures appropriate for a given material may vary widely.

Influence on the anticorrosive properties of the use of erbium (III) trifluoromethanesulfonate as initiator in an epoxy powder clearcoat

International Nuclear Information System (INIS)

Garcia, S.J.; Suay, J.

2007-01-01

New low curing temperature epoxy powder coatings cured cationically by the use of erbium (III) trifluoromethanesulfonate as initiator have been formulated. Their curing kinetics and anticorrosive properties have been studied and compared with a system commonly used in industry (o-tolylbiguanide/epoxy resin). Three different tests of anticorrosive properties (EIS, AC/DC/AC, and salt fog spray) have been used together with an adherence test, in order to establish the optimal system. Results show that a system employing 1 phr of erbium triflate presents good anticorrosive properties. The technique AC/DC/AC has shown its ability to evaluate properly, much faster, and in accordance to anticorrosive properties results' of powder coatings obtained by other techniques

Influence on the anticorrosive properties of the use of erbium (III) trifluoromethanesulfonate as initiator in an epoxy powder clearcoat

Energy Technology Data Exchange (ETDEWEB)

Garcia, S.J. [Centro de Biomateriales, Universitat Politecnica de Valencia, Camino de Vera s/n, E-46071 Valencia (Spain)]. E-mail: sangares@upvnet.upv.es; Suay, J. [Centro de Biomateriales, Universitat Politecnica de Valencia, Camino de Vera s/n, E-46071 Valencia (Spain)

2007-08-15

New low curing temperature epoxy powder coatings cured cationically by the use of erbium (III) trifluoromethanesulfonate as initiator have been formulated. Their curing kinetics and anticorrosive properties have been studied and compared with a system commonly used in industry (o-tolylbiguanide/epoxy resin). Three different tests of anticorrosive properties (EIS, AC/DC/AC, and salt fog spray) have been used together with an adherence test, in order to establish the optimal system. Results show that a system employing 1 phr of erbium triflate presents good anticorrosive properties. The technique AC/DC/AC has shown its ability to evaluate properly, much faster, and in accordance to anticorrosive properties results' of powder coatings obtained by other techniques.

High performance, rapid thermal/UV curing epoxy resin for additive manufacturing of short and continuous carbon fiber epoxy composites

Science.gov (United States)

Lewicki, James

2018-04-17

An additive manufacturing resin system including an additive manufacturing print head; a continuous carbon fiber or short carbon fibers operatively connected to the additive manufacturing print head; and a tailored resin operatively connected to the print head, wherein the tailored resin has a resin mass and wherein the tailored resin includes an epoxy component, a filler component, a catalyst component, and a chain extender component; wherein the epoxy component is 70-95% of the resin mass, wherein the filler component is 1-20% of the resin mass, wherein the catalyst component is 0.1-10% of the resin mass, and wherein the chain extender component is 0-50% of the resin mass.

Epoxy coatings for anticorrosion challenges: a link between chemistry and performance?

Energy Technology Data Exchange (ETDEWEB)

Sauvant-Moynot, Valerie; Schweitzer, Sylvie; Grenier, Jacky; Duval, Sebastien [Institut Francais du Petrole, 1 et 4 avenue Bois Preau, 92450 Rueil-Malmaison (France)

2004-07-01

Epoxy coatings have been used extensively for pipeline protection in the oil and gas industries over the past decades. Thank to their outstanding adhesive properties, epoxy resins are classically used for external coating of offshore pipelines although cathodic protection is applied. They provide corrosion protection while being used as neat coating or as primer layer in a three-layer coating. Protection of internal pipelines devoted to gas transport is another application of epoxy coatings. Whatever the case, the choice of the right epoxy formulation should be adapted to the service conditions, namely exposition medium and temperature, in order to provide efficient and sustainable corrosion protection. Epoxy resins constitute a wide family and classical formulations may not fulfill the requirements of today's challenges: as pipelines are require d to operate in more and more difficult conditions, coatings are expected to function in higher temperature conditions; additionally, practical conditions such as temporary injection of methanol make the environmental exposure of the epoxy coating harsher. Therefore, there is a need of a better knowledge of technical performance and limitations of high temperature epoxy resins. This paper examined the influence of the epoxy network architecture on their protection properties and durability while exposed to distilled / sea water at 110 deg. C and to methanol at room temperature. The objective was to investigate the link between resin chemistry and final performance with respect to anticorrosion applications. Five epoxy resin formulations mixed in stoichiometric proportions were cured and post-cured to infinite extent in order to achieve densely cross-linked networks exhibiting controlled and reproducible architectures. Gravimetric and pressurised differential scanning calorimetry (DSC) measurements were performed to evaluate the plasticization effect of both water and methanol on formulations under study. The related

Photoelastic stress analysis assisted evaluation of fracture toughness in hydrothermally aged epoxies

Directory of Open Access Journals (Sweden)

G. Pitarresi

2014-10-01

Full Text Available The present work has investigated the fracture toughness of a model DGEBA epoxy system subject to Hidro-Thermal aging. A Photoelastic Stress Analysis technique has been implemented, showing the evolution of stresses arising throughout the water uptake process due to the non-uniform swelling of the material. Gravimetric and Dynamic Mechanical Thermal Analyses have further complemented the characterization, showing the onset of plasticization effects with aging. The correlation of all previous characterizations has allowed to conclude that an increase of KIC fracture toughness is obtained at the fully saturated condition. In particular Photoelasticity has also revealed the onset of relevant swelling induced stresses during the first stages of water absorption, leading to an increase of fracture toughness due to compressive stresses settling near the crack tip. A stress free condition is instead reestablished at the later stages of absorption, suggesting that the increased toughness of the saturated material is an effect of the modifications induced by aging on the polymer structure.

Spall Strength Measurements in Transparent Epoxy Polymers

Science.gov (United States)

Pepper, Jonathan; Rahmat, Meysam; Petel, Oren

2017-06-01

Polymer nanocomposites are seeing more frequent use in transparent armour applications. The role of the microstructure on the performance of these materials under dynamic tensile loading conditions is of particular interest. In the present study, a series of plate impact experiments was conducted in order to evaluate the dynamic response of an epoxy (EPON 828) cured with two differed hardeners. The purpose was to compare the role of these hardeners on the dynamic performance of the resulting transparent epoxy. The material response was resolved with a multi-channel photonic Doppler velocimeter. This system was used to determine the shock Hugoniot and dynamic tensile (spall) strength of the materials. The experimental results are presented in reference to spall theory and are evaluated against results predicted by an analytical model of the impacts. While varying the hardener did not change the shock Hugoniot of the epoxy, it did have an effect on the measured spall strengths.

Bio-Based Aromatic Epoxy Monomers for Thermoset Materials

Directory of Open Access Journals (Sweden)

Feifei Ng

2017-01-01

Full Text Available The synthesis of polymers from renewable resources is a burning issue that is actively investigated. Polyepoxide networks constitute a major class of thermosetting polymers and are extensively used as coatings, electronic materials, adhesives. Owing to their outstanding mechanical and electrical properties, chemical resistance, adhesion, and minimal shrinkage after curing, they are used in structural applications as well. Most of these thermosets are industrially manufactured from bisphenol A (BPA, a substance that was initially synthesized as a chemical estrogen. The awareness on BPA toxicity combined with the limited availability and volatile cost of fossil resources and the non-recyclability of thermosets implies necessary changes in the field of epoxy networks. Thus, substitution of BPA has witnessed an increasing number of studies both from the academic and industrial sides. This review proposes to give an overview of the reported aromatic multifunctional epoxide building blocks synthesized from biomass or from molecules that could be obtained from transformed biomass. After a reminder of the main glycidylation routes and mechanisms and the recent knowledge on BPA toxicity and legal issues, this review will provide a brief description of the main natural sources of aromatic molecules. The different epoxy prepolymers will then be organized from simple, mono-aromatic di-epoxy, to mono-aromatic poly-epoxy, to di-aromatic di-epoxy compounds, and finally to derivatives possessing numerous aromatic rings and epoxy groups.

Surface and buried interfacial structures of epoxy resins used as underfills studied by sum frequency generation vibrational spectroscopy.

Science.gov (United States)

Vázquez, Anne V; Holden, Brad; Kristalyn, Cornelius; Fuller, Mike; Wilkerson, Brett; Chen, Zhan

2011-05-01

Flip chip technology has greatly improved the performance of semiconductor devices, but relies heavily on the performance of epoxy underfill adhesives. Because epoxy underfills are cured in situ in flip chip semiconductor devices, understanding their surface and interfacial structures is critical for understanding their adhesion to various substrates. Here, sum frequency generation (SFG) vibrational spectroscopy was used to study surface and buried interfacial structures of two model epoxy resins used as underfills in flip chip devices, bisphenol A digylcidyl ether (BADGE) and 1,4-butanediol diglycidyl ether (BDDGE). The surface structures of these epoxies were compared before and after cure, and the orientations of their surface functional groups were deduced to understand how surface structural changes during cure may affect adhesion properties. Further, the effect of moisture exposure, a known cause of adhesion failure, on surface structures was studied. It was found that the BADGE surface significantly restructured upon moisture exposure while the BDDGE surface did not, showing that BADGE adhesives may be more prone to moisture-induced delamination. Lastly, although surface structure can give some insight into adhesion, buried interfacial structures more directly correspond to adhesion properties of polymers. SFG was used to study buried interfaces between deuterated polystyrene (d-PS) and the epoxies before and after moisture exposure. It was shown that moisture exposure acted to disorder the buried interfaces, most likely due to swelling. These results correlated with lap shear adhesion testing showing a decrease in adhesion strength after moisture exposure. The presented work showed that surface and interfacial structures can be correlated to adhesive strength and may be helpful in understanding and designing optimized epoxy underfill adhesives.

Development of sealed radioactive sources immobilized in epoxy resin for verification of detectors used in nuclear medicine

International Nuclear Information System (INIS)

Tiezzi, Rodrigo

2016-01-01

The radioactive sealed sources are used in verification ionization chamber detectors, which measure the activity of radioisotopes used in several areas, such as in nuclear medicine. The measurement of the activity of radioisotopes must be made with accuracy, because it is administered to a patient. To ensure the proper functioning of the ionization chamber detectors, standardized tests are set by the International Atomic Energy Agency (IAEA) and the National Nuclear Energy Commission using sealed radioactive sources of Barium-133, Cesium-137 and Cobalt-57. The tests assess the accuracy, precision, reproducibility and linearity of response of the equipment. The focus of this work was the study and the development of these radioactive sources with standard Barium-133 and Cesium-137,using a polymer, in case commercial epoxy resin of diglycidyl ether of bisphenol A (DGEBA) and a curing agent based on modified polyamine diethylenetriamine (DETA), to immobilize the radioactive material. The polymeric matrix has the main function of fix and immobilize the radioactive contents not allowing them to leak within the technical limits required by the standards of radiological protection in the category of characteristics of a sealed source and additionally have the ability to retain the emanation of any gases that may be formed during the manufacture process and the useful life of this artifact. The manufacturing process of a sealed source standard consists of the potting ,into bottle standardized geometry, in fixed volume of a quantity of a polymeric matrix within which is added and dispersed homogeneously to need and exact amount in activity of the radioactive materials standards. Accordingly, a study was conducted for the choice of epoxy resin, analyzing its characteristics and properties. Studies and tests were performed, examining the maximum miscibility of the resin with the water (acidic solution, simulating the conditions of radioactive solution), loss of mechanical and

Physical and chemical durability of cement impregnated epoxy resin

International Nuclear Information System (INIS)

Suryantoro

1997-01-01

Immobilization of simulation radioactive waste contains Cs and Sr with cement impregnated epoxy resin has been done. Low level liquid waste in 30% weight mixed cement homogeneously and then set in its curing time about 28 days. Waste from was impregnated with epoxy resin (Bisphenol-A-diglycidylether) and use Triethylenteramin as catalyst. the sample of cement impregnated epoxy resin 2.5 cm x 2.5 cm in diameter and length was tested by Paul Weber. The compressive strength was obtained of 4.08 kN.cm - 2. The sochxlet apparatus was run on flow rate of 300 ml/hour at 100 o C and during 24 hours. The leaching rate of Cs was round on 5.5 x 10 - 4 g.cm - 2.d - 1 and Sr was 6.1 x 10 - 4 g.cm - 2.d - 1 (author)

Fabrication and Characterization of Silicon Carbide Epoxy Composites

Science.gov (United States)

Townsend, James

Nanoscale fillers can significantly enhance the performance of composites by increasing the extent of filler-to-matrix interaction. Thus far, the embedding of nanomaterials into composites has been achieved, but the directional arrangement has proved to be a challenging task. Even with advances in in-situ and shear stress induced orientation, these methods are both difficult to control and unreliable. Therefore, the fabrication of nanomaterials with an ability to orient along a magnetic field is a promising pathway to create highly controllable composite systems with precisely designed characteristics. To this end, the goal of this dissertation is to develop magnetically active nanoscale whiskers and study the effect of the whiskers orientation in a polymer matrix on the nanocomposite's behavior. Namely, we report the surface modification of silicon carbide whiskers (SiCWs) with magnetic nanoparticles and fabrication of SiC/epoxy composite materials. The magnetic nanoparticles attachment to the SiCWs was accomplished using polyelectrolyte polymer-to-polymer complexation. The "grafting to" and adsorption techniques were used to attach the polyelectrolytes to the surface of the SiCWs and magnetic nanoparticles. The anchored polyelectrolytes were polyacrylic acid (PAA) and poly(2-vinylpyridine) (P2VP). Next, the SiC/epoxy composites incorporating randomly oriented and magnetically oriented whiskers were fabricated. The formation of the composite was studied to determine the influence of the whiskers' surface composition on the epoxy curing reaction. After curing, the composites' thermal and thermo-mechanical properties were studied. These properties were related to the dispersion and orientation of the fillers in the composite samples. The obtained results indicated that the thermal and thermo-mechanical properties could be improved by orienting magnetically-active SiCWs inside the matrix. Silanization, "grafting to", adsorption, and complexation were used to modify

Synthesis and Thermal Properties of a Novel Nitrogen-containing Epoxy Resin

Institute of Scientific and Technical Information of China (English)

Xing Hong ZHANG; Hong Mei WAN; Yu Qin MIN; Zuo FANG; Guo Rong QI

2005-01-01

A new nitrogen-containing epoxy resin (XT resin) was synthesized from chain extension of xylenephenolformaldehyde resin (XPF) and triglycidyl isocyanurate (TGIC) in the presence of base catalyst. FT-IR and 1H-NMR analysis confirmed the chemical structure of XT resin. It was cured with dicyandiamide (DICY) and diaminodiphenyl sulfone (DDS). Dynamic mechanical analysis (DMA) results showed that the introduction of triazine ring provides epoxy polymer with good thermal stability. Furthermore, high char yields at 800℃ in thermogravimetric (TGA)analysis indicated that XT resin had potential flame retardance.

1H, 19F and 11B nuclear magnetic resonance characterization of BF3:amine catalysts used in the cure of C fiber-epoxy prepregs

International Nuclear Information System (INIS)

Happe, J.A.; Morgan, R.J.; Walkup, C.M.

1983-12-01

The chemical composition of commercial BF 3 :amine complexes are variable and contain BF 4 - and BF 3 (OH) - salts together with other unidentified highly reactive species. The BF 3 :amine complexes, which are susceptible to hydrolysis, also partially convert to the BF 4 - salt (i.e. BF 4 - NH 3 + C 2 H 5 ) upon heating. This salt formation is accelerated in dimethyl sulfoxide solution and in the presence of the epoxides that are present in commercial prepregs. Commercial C fiber-epoxy prepregs are shown to contain either BF 3 :NH 2 C 2 H 5 or BF 3 :NHC 5 H 10 species together with their BF 4 - salts and a variety of boron-fluorine or carbon-fluorine prepreg species. Considerable variation in the relative quantities of BF 3 :amine to its BF 4 - salt was observed from prepreg lot to lot, which will cause variable viscosity-time-temperature prepreg cure profiles. It is concluded that the chemically stable and mobile BF 4 - salt is the pre-dominant catalytic species, acting as a cationic catalyst for the prepreg cure reactions. During the early stages of cure the BF 3 :amine catalyst converts to the BF 4 - salt in the presence of epoxides, whereas the BF 3 -prepreg species are susceptible to catalytic deactivation and immobilization

Optimization of the rheological properties of epoxy resins for glass and carbon reinforced plastics

Science.gov (United States)

Phyo Maung, Pyi; Malysheva, G.; Romanova, I.

2016-10-01

Vacuum assisted resin transfer moulding (VARTM) offers advantages such as simplicity, low cost of consumables, and the ability to carry out the impregnation process and curing without using expensive equipment and tooling. In the VARTM process, rheological properties of resin have a critical impact on the impregnation and curing process. In this article, the experimental results of viscosity are presented, including the glass transition temperature, and the tensile and bending strength of the epoxy binders with the amine hardener, which depend on the quantity of its active solvent composition. The active solvent used is diethylene glycol. It shows that for an increase in the content of the active solvent, a reduction in the viscosity and a reduction of the glass transition temperature and strength occurs. The optimum composition of the binder is selected by using the Pareto optimization criteria and the Cayley - Smorodinskaya method. By using the epoxy binder, the active solvent should not exceed 10-15% by weight. This approach helps to optimize the amount of active solvent added to the epoxy resins for the criterion of viscosity, strength, and heat resistance.

Multi function Finishing and Pigment Printing of UV Cured Cotton/Polyester Fabrics Coated with Plasticized Epoxy Resin/ZnO Formulation

International Nuclear Information System (INIS)

Hassan, M.S.; Mousaa, I.M.; Ali, N.M.

2015-01-01

Cotton/ Polyester fabrics were coated with epoxy acrylate (EA) formulations plasticized by castor oil (CO), in the presence of benzophenone as initiator, ZnO (antibacterial agent) and pigment printing. Ultra violet (UV) irradiation was used as a curing system. The effect of UV irradiation time and CO percentage on the mechanical and crease recovery properties were investigated. The effect of the coating process on the cross-section feature by using scanning electron microscope (SEM), the antibacterial properties, water retardance, colour difference and the durability for washing of the coated fabrics were also investigated. From the results, it was found that the crease recovery and antibacterial properties were enhanced. Also, the colour durability against multiple washing cycles gave adequate results after application of the investigated coating formulation. The most fitting castor oil per cent was found to be 45%, while the 3% ZnO recorded the best antibacterial and mechanical properties. The pigment per cent that gave the highest durability and adequate colour strength was 0.6%.

Mechanical properties of multi-walled carbon nanotube/epoxy polysulfide nanocomposite

International Nuclear Information System (INIS)

Shirkavand Hadavand, Behzad; Mahdavi Javid, Kimya; Gharagozlou, Mehrnaz

2013-01-01

Highlights: ► Preparation of epoxy polysulfide nanocomposite. ► Multi-walled carbon nanotubes have been modified and dispersed in epoxy polysulfide matrix. ► Mechanical properties of MWNT/epoxy polysulfide have been studied. - Abstract: In this research, multi-walled carbon nanotubes (MWCNTs) were modified by acid functionalization (H 2 SO 4 :HNO 3 = 1:3 by volume) and then mechanical properties of reinforced epoxy polysulfide resin by the both pure and treated MWNTs have been evaluated. For achieving this goal, different weight percentages of pure and treated MWCNT (0.1–0.3 wt%) were dispersed in the epoxy polysulfide resin separately and then mixed with curing agent. Experimental results have shown significant difference between acid treated and untreated MWCNTs in mechanical properties of epoxy polysulfide nanocomposites. In nanocomposite with 0.1–0.3% acid treated MWCNTs we observed increase of Young’s modulus from 458 to 723 MPa, tensile strength from 5.29 to 8.83 MPa and fracture strain from 0.16% to 0.25%. For understanding the structure and morphology of nanocomposite, the dispersion states were studied using scanning electron microscopy (SEM) and field emission electron microscopy (FESEM). The results showed better dispersion of modified carbon nanotube than unmodified in polymeric matrix

Curing of Thick Thermoset Composite Laminates: Multiphysics Modeling and Experiments

Science.gov (United States)

Anandan, S.; Dhaliwal, G. S.; Huo, Z.; Chandrashekhara, K.; Apetre, N.; Iyyer, N.

2017-11-01

Fiber reinforced polymer composites are used in high-performance aerospace applications as they are resistant to fatigue, corrosion free and possess high specific strength. The mechanical properties of these composite components depend on the degree of cure and residual stresses developed during the curing process. While these parameters are difficult to determine experimentally in large and complex parts, they can be simulated using numerical models in a cost-effective manner. These simulations can be used to develop cure cycles and change processing parameters to obtain high-quality parts. In the current work, a numerical model was built in Comsol MultiPhysics to simulate the cure behavior of a carbon/epoxy prepreg system (IM7/Cycom 5320-1). A thermal spike was observed in thick laminates when the recommended cure cycle was used. The cure cycle was modified to reduce the thermal spike and maintain the degree of cure at the laminate center. A parametric study was performed to evaluate the effect of air flow in the oven, post cure cycles and cure temperatures on the thermal spike and the resultant degree of cure in the laminate.

Thermodynamic and Mechanical Properties of Epon 862 With Curing Agent Detda by Molecular Simulation

National Research Council Canada - National Science Library

Tack, Jeremy L

2006-01-01

Fully atomistic molecular dynamics (MD) simulations were used to predict the properties of EPON 862 cross-linked with curing agent DETDA, a potentially useful epoxy resin for future applications of nanocomposites...

Improvement of fatigue resistance of epoxy composite with microencapsulated epoxy-SbF5 self-healing system

Directory of Open Access Journals (Sweden)

X. J. Ye

2017-11-01

Full Text Available Rapid retardation and arresting of fatigue crack are successfully realized in the epoxy composite containing microencapsulated epoxy and ethanol solution of antimony pentafluoride-ethanol complex (SbF5·HOC2H5/HOC2H5. The effects of (i microcapsules induced-toughening, (ii hydrodynamic pressure crack tip shielding offered by the released healing agent, and (iii polymeric wedge and adhesive bonding of cured healing agent account for extension of fatigue life of the material. The two components of the healing agent can quickly react with each other soon after rupture of the microcapsules, and reconnect the crack only 20 seconds as of the test. The applied stress intensity range not only affects the healing efficiency, but also can be used to evaluate the healing speed. The present work offers a very fast healing system, and sets up a framework for characterizing speed of self-healing.

Estimation of hardness and compressive strength of SP 100 aluminum powder epoxy

Energy Technology Data Exchange (ETDEWEB)

Han, Jeong Young [Pusan National Univ., Busan (Korea, Republic of); Kim, Myung Hun [Korea Institute of Footwear and Leather Technology, Busan (Korea, Republic of); Kang, Sung Soo [Jeonju Univ., Jeonju (Korea, Republic of)

2012-09-15

In this study, we performed experimental tests on five SP 100 aluminum powder epoxy specimens with several after curing conditions in order to estimate their hardness with temperature and compressive strength. In the surface hardness test, it was found that the higher the after curing temperature, the higher was the hardness. In particular, it was found that the hardness of the specimens in cases 3 and 4 was much higher than in the other cases. In addition, in the compression tests carried out to evaluate the compressive strength, it was found that the specimens showed relatively similar stiffness and strength with after curing, and specimens with no after curing showed compression stress strain curves similar to those of thermoplastic resins.

Estimation of hardness and compressive strength of SP 100 aluminum powder epoxy

International Nuclear Information System (INIS)

Han, Jeong Young; Kim, Myung Hun; Kang, Sung Soo

2012-01-01

In this study, we performed experimental tests on five SP 100 aluminum powder epoxy specimens with several after curing conditions in order to estimate their hardness with temperature and compressive strength. In the surface hardness test, it was found that the higher the after curing temperature, the higher was the hardness. In particular, it was found that the hardness of the specimens in cases 3 and 4 was much higher than in the other cases. In addition, in the compression tests carried out to evaluate the compressive strength, it was found that the specimens showed relatively similar stiffness and strength with after curing, and specimens with no after curing showed compression stress strain curves similar to those of thermoplastic resins

Effect of thermally reduced graphene oxide on dynamic mechanical properties of carbon fiber/epoxy composite

Science.gov (United States)

Adak, Nitai Chandra; Chhetri, Suman; Murmu, Naresh Chandra; Samanta, Pranab; Kuila, Tapas

2018-03-01

The Carbon fiber (CF)/epoxy composites are being used in the automotive and aerospace industries owing to their high specific mechanical strength to weight ratio compared to the other conventional metal and alloys. However, the low interfacial adhesion between fiber and polymer matrix results the inter-laminar fracture of the composites. Effects of different carbonaceous nanomaterials i.e., carbon nanotubes (CNT), graphene nanosheets (GNPs), graphene oxide (GO) etc. on the static mechanical properties of the composites were investigated in detail. Only a few works focused on the improvement of the dynamic mechanical of the CF/epoxy composites. Herein, the effect of thermally reduced grapheme oxide (TRGO) on the dynamic mechanical properties of the CF/epoxy composites was investigated. At first, GO was synthesized using modified Hummers method and then reduced the synthesized GO inside a vacuum oven at 800 °C for 5 min. The prepared TRGO was dispersed in the epoxy resin to modify the epoxy matrix. Then, a number of TRGO/CF/epoxy laminates were manufactured incorporating different wt% of TRGO by vacuum assisted resin transfer molding (VARTM) technique. The developed laminates were cured at room temperature for 24 h and then post cured at 120 °C for 2 h. The dynamic mechanical analyzer (DMA 8000 Perkin Elmer) was used to examine the dynamic mechanical properties of the TRGO/CF/epoxy composites according to ASTM D7028. The dimension of the specimen was 44×10×2.4 mm3 for the DMA test. This test was carried out under flexural loading mode (duel cantilever) at a frequency of 1 Hz and amplitude of 50 μm. The temperature was ramped from 30 to 200 °C with a heating rate of 5 °C min-1. The dynamic mechanical analysis of the 0.2 wt% TRGO incorporated CF/epoxy composites showed ~ 96% enhancement in storage modulus and ~ 12 °C increments in glass transition temperature (Tg) compared to the base CF/epoxy composites. The fiber-matrix interaction was studied by Cole

Static and Dynamic Mechanical Properties of Graphene Oxide-Incorporated Woven Carbon Fiber/Epoxy Composite

Science.gov (United States)

Adak, Nitai Chandra; Chhetri, Suman; Kim, Nam Hoon; Murmu, Naresh Chandra; Samanta, Pranab; Kuila, Tapas

2018-03-01

This study investigates the synergistic effects of graphene oxide (GO) on the woven carbon fiber (CF)-reinforced epoxy composites. The GO nanofiller was incorporated into the epoxy resin with variations in the content, and the CF/epoxy composites were manufactured using a vacuum-assisted resin transfer molding process and then cured at 70 and 120 °C. An analysis of the mechanical properties of the GO (0.2 wt.%)/CF/epoxy composites showed an improvement in the tensile strength, Young's modulus, toughness, flexural strength and flexural modulus by 34, 20, 83, 55 and 31%, respectively, when compared to the CF/epoxy composite. The dynamic mechanical analysis of the composites exhibited an enhancement of 56, 114 and 22% in the storage modulus, loss modulus and damping capacity (tan δ), respectively, at its glass transition temperature. The fiber-matrix interaction was studied using a Cole-Cole plot analysis.

Identification of nanostructural development in epoxy polymer layered silicate nanocomposites from the interpretation of differential scanning calorimetry and dielectric spectroscopy

International Nuclear Information System (INIS)

Román, Frida; Calventus, Yolanda; Colomer, Pere; Hutchinson, John M.

2012-01-01

Highlights: ► Comparison of DSC and DRS in the cure of epoxy nanocomposites. ► Dependence of exfoliation of nanocomposite on clay content. ► Anionically initiated homopolymerisation in PLS nanocomposites. - Abstract: The effect of nanoclay on the non-isothermal cure kinetics of polymer layered silicate nanocomposites based upon epoxy resin is studied by calorimetric techniques (DSC and TGA) and by dielectric relaxation spectroscopy (DRS) in non-isothermal cure at constant heating rate. The cure process takes place by homopolymerisation, initiated anionically using 3 wt% dimethylaminopyridine (DMAP), and the influence of the nanoclay content has been analysed. Interesting differences are observed between the nanocomposites with 2 wt% and 5 wt% clay content. At low heating rates, these samples vitrify and then devitrify during the cure. For the sample with 2 wt% clay, the devitrification is accompanied by a thermally initiated homopolymerisation, which can be identified by DRS but not by DSC. The effect of this is to improve the exfoliation of the nanocomposite with 2 wt% clay, as verified by transmission electron microscopy, with a corresponding increase in the glass transition temperature. These observations are interpreted in respect of the nanocomposite preparation method and the cure kinetics.

Off-Axis Ratcheting Behavior of Unidirectional Carbon/Epoxy Laminate under Asymmetric Cyclic Loading at High Temperature

Science.gov (United States)

2011-11-01

ply unidirectional carbon/epoxy laminates [0]12 were fabricated from the prepreg tape of P3252-20 (TORAY). They were laid up by hand and cured in...Off-Axis Ratcheting Behavior of Unidirectional Carbon/Epoxy Laminate under Asymmetric Cyclic Loading at High Temperature Takafumi Suzuki 1 and...Development of an engineering model for predicting the off-axis ratcheting behavior of a unidirectional CFRP laminate has been attempted. For this purpose

Electron beam curing of polymer matrix composites

International Nuclear Information System (INIS)

Janke, C.J.; Wheeler, D.; Saunders, C.

1998-01-01

The purpose of the CRADA was to conduct research and development activities to better understand and utilize the electron beam PMC curing technology. This technology will be used to replace or supplement existing PMC thermal curing processes in Department of Energy (DOE) Defense Programs (DP) projects and American aircraft and aerospace industries. This effort involved Lockheed Martin Energy Systems, Inc./Lockheed Martin Energy Research Corp. (Contractor), Sandia National Laboratories, and ten industrial Participants including four major aircraft and aerospace companies, three advanced materials companies, and three electron beam processing organizations. The technical objective of the CRADA was to synthesize and/or modify high performance, electron beam curable materials that meet specific end-use application requirements. There were six tasks in this CRADA including: Electron beam materials development; Electron beam database development; Economic analysis; Low-cost Electron Beam tooling development; Electron beam curing systems integration; and Demonstration articles/prototype structures development. The contractor managed, participated and integrated all the tasks, and optimized the project efforts through the coordination, exchange, and dissemination of information to the project participants. Members of the Contractor team were also the principal inventors on several electron beam related patents and a 1997 R and D 100 Award winner on Electron-Beam-Curable Cationic Epoxy Resins. The CRADA achieved a major breakthrough for the composites industry by having successfully developed high-performance electron beam curable cationic epoxy resins for use in composites, adhesives, tooling compounds, potting compounds, syntactic foams, etc. UCB Chemicals, the world's largest supplier of radiation-curable polymers, has acquired a license to produce and sell these resins worldwide

Carbon nanotube (CNT)–epoxy nanocomposites: a systematic investigation of CNT dispersion

International Nuclear Information System (INIS)

Chakraborty, Amit K.; Plyhm, Tiia; Barbezat, Michel; Necola, Adly; Terrasi, Giovanni P.

2011-01-01

A systematic investigation of the dispersion of carbon nanotubes (CNTs), 1–6 nm in diameter and a few microns in length, in a bisphenol F-based epoxy resin has been presented. Several dispersing techniques including high-speed dissolver, ultrasonic bath/horn, 3-roll mill, etc. have been employed. Optical microscopy has been extensively used to systematically characterise the state of CNT dispersion in the epoxy resin during the entire processing cycle from mixing CNT with resin to adding and curing with hardener. Complimentary viscosity measurements were also performed at various stages of nanocomposite processing. A method to produce a good CNT dispersion in resin was established, but the state of CNT dispersion was found to be extremely sensitive to its physical and chemical environments. The cured nanocomposites were further tested for their thermo-mechanical properties by dynamic mechanical thermal analysis (DMTA), and for flexural and compressive mechanical properties. The measured properties of various nanocomposite plates were then discussed in view of the corresponding CNT dispersion.

Impact of a novel phosphorus-nitrogen flame retardant curing agent on the properties of epoxy resin

Science.gov (United States)

Liu, Xiaoli; Liang, Bing

2017-12-01

A phosphorus-nitrogen flame retardant curing agent diethyl phosphonic p-Phenylenediamine diamide (DEPPPD) was synthesized. The chemical structure of the obtained compound was identified by Fourier transform infrared (FTIR), 1H nuclear magnetic resonance (1HNMR), and mass spectroscopies. A series of t hermosetting systems were prepared by conventional epoxy resins (E-44) and DEPPPD. The effects of DEPPPD on flame retardancy, thermal degradation behavior, mechanical properties and the morphologies of char residues of EP/DEPPPD thermosets were investigated. The results demonstrated that when the phosphorus content of 2.88 wt%, EP-3 successfully passed UL-94 V-0 flammability rating, the LOI value was as high as 31.1%, the impact strength and tensile strength of it was 6.50 KJ m-2 and 48.21 MPa, the adhesive strength could reach 14.61 MPa, respectively. The TGA results indicated that the introduction of DEPPPD promoted EP matrix decomposed at a lower temperature, the rate of the thermal decomposition also decreased compared with EP-0. The residual char ratio of 800 °C was increased whether in nitrogen or in the air. The morphological structures of char residue were more compact and homogeneous which could prevent the heat transmission and diffusion, limit the production of combustible gases and reduced the heat release rate.

Tailored SWCNT functionalization optimized for compatibility with epoxy matrices

International Nuclear Information System (INIS)

Martinez-Rubi, Y; Kingston, C T; Daroszewska, M; Barnes, M; Simard, B; Gonzalez-Dominguez, J M; Ansón-Casaos, A; Martinez, M T; Hubert, P; Cattin, C

2012-01-01

We have modified single walled carbon nanotubes (SWCNTs) with well defined matrix-based architectures to improve interface interaction in SWCNT/epoxy composites. The hardener and two pre-synthesized oligomers containing epoxy and hardener moieties were covalently attached to the SWCNT walls by in situ diazonium or carboxylic coupling reactions. In this way, SWCNTs bearing amine or epoxide-terminated fragments of different molecular weights, which resemble the chemical structure of the cured resin, were synthesized. A combination of characterization techniques such as Raman and infrared absorption (FTIR) spectroscopy, elemental analysis and coupled thermogravimetry-FTIR spectroscopy were used to identify both the functional groups and degree of functionalization of SWCNTs synthesized by the laser ablation and arc-discharge methods. Depending on the type of reaction employed for the chemical functionalization and the molecular weight of the attached fragment, it was possible to control the degree of functionalization and the electronic properties of the functionalized SWCNTs. Improved dispersion of SWCNTs in the epoxy matrix was achieved by direct integration without using solvents, as observed from optical microscopy and rheology measurements of the SWCNT/epoxy mixtures. Composite materials using these fillers are expected to exhibit improved properties while preserving the thermosetting architecture. (paper)

Evolution of carbon nanotube dispersion in preparation of epoxy-based composites: From a masterbatch to a nanocomposite

Directory of Open Access Journals (Sweden)

M. Aravand

2014-08-01

Full Text Available The state of carbon nanotube (CNT dispersion in epoxy is likely to change in the process of composite production. In the present work CNT dispersion is characterized at different stages of nanocomposite preparation: in the original masterbatch with high CNT concentration, after masterbatch dilution, in the process of curing and in the final nanocomposite. The evaluation techniques included dynamic rheological analysis of the liquid phases, optical, environmental and charge contrast scanning electron microscopy, electrochemical impedance spectroscopy and dynamic mechanical analysis. The evolution of the CNT dispersion was assessed for two CNT/epoxy systems with distinctly different dispersion states induced by different storage time. Strong interactions between CNT clusters were revealed in the masterbatch with a longer storage time. Upon curing CNT clusters in this material formed a network-like structure. This network enhanced the elastic behaviour and specific conductivity of the resulting nanocomposite, leading to a partial electrical percolation after curing.

CURADO NO-ISOTERMICO DE MEZCLAS EPOXI-ACEITE DE SOJA EPOXIDADO-ANHÍDRIDO

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Facundo I. Altuna

2011-01-01

Full Text Available Se estudió la cinética de curado no-isotérmico de mezclas de diglicidil éter de bisfenol A (DGEBA con aceite de soja epoxidado (ESO utilizando anhídrido metiltetrahidroftálico (MTHPA como agente de curado y 1-metil imidazol (1MI como iniciador. El sistema ESO/MTHPA exhibió valores de entalpía de reacción menores y temperaturas de pico exotérmico mayores que el sistema DGEBA/MTHPA debido a la menor reactividad de los grupos oxirano internos del ESO. Los parámetros cinéticos de los sistemas puros DGEBA/MTHPA y ESO/MTHPA se obtuvieron a partir de los datos calorimétricos mediante un análisis de regresión multiparamétrica utilizando un modelo cinético fenomenológico. La cinética de los sistemas puros fue utilizada para predecir la de las mezclas considerando las interacciones entre DGEBA y ESO. El modelo propuesto permitió predecir adecuadamente la cinética del proceso de curado utilizando parámetros independientes de la velocidad de calentamiento y de aplicación directa en el campo de procesamiento de estos materiales.

Effect of nanoclay on thermal, mechanical and liquid absorption properties of epoxy-clay nanocomposite

International Nuclear Information System (INIS)

Nguyen Cong Quyen; Nguyen Pham Duy Linh; Bui Chuong; Doan Thi Yen Oanh

2015-01-01

Composite materials based on epoxy DER 331 hot cured by MHHPA with several contents of nanoclay I28E were prepared and characterized by TEM and SEM. Results showed that the nanostructures were created in two levels: intercalated structure and nanoparticles (cluster). The interaction between nanoclay and epoxy matrix was evaluated by properties such as: liquid absorption, TGA and DMA. It was shown that nanostructures of cluster, as well as the hydrophobic behavior of material with the presence of nanoclay have dominant effect to liquid absorption. Otherwise, the thermal stability was affected mainly by intercalation structure. Results of DMA showed that the interaction of epoxy-clay was strongly destroyed at the temperature higher than material Tg. (author)

Applications of Fourier transform infrared spectroscopy to quality control of the epoxy matrix

Science.gov (United States)

Antoon, M. K.; Starkey, K. M.; Koenig, J. L.

1979-01-01

The object of the paper is to demonstrate the utility of Fourier transform infrared (FT-IR) difference spectra for investigating the composition of a neat epoxy resin, hardener, and catalysts. The composition and degree of cross-linking of the cured matrix is also considered.

Advanced Nanocomposite Coatings of Fusion Bonded Epoxy Reinforced with Amino-Functionalized Nanoparticles for Applications in Underwater Oil Pipelines

OpenAIRE

Patricia A. Saliba; Alexandra A. P. Mansur; Herman S. Mansur

2016-01-01

The performance of fusion-bonded epoxy coatings can be improved through advanced composite coatings reinforced with nanomaterials. Hence, in this study a novel organic-inorganic nanocomposite finish was designed, synthesized, and characterized, achieved by adding γ-aminopropyltriethoxysilane modified silica nanoparticles produced via sol-gel process in epoxy-based powder. After the curing process of the coating reinforced with nanoparticles, the formation of a homogenous novel nanocomposite w...

Cellulose whisker/epoxy resin nanocomposites.

Science.gov (United States)

Tang, Liming; Weder, Christoph

2010-04-01

New nanocomposites composed of cellulose nanofibers or "whiskers" and an epoxy resin were prepared. Cellulose whiskers with aspect ratios of approximately 10 and approximately 84 were isolated from cotton and sea animals called tunicates, respectively. Suspensions of these whiskers in dimethylformamide were combined with an oligomeric difunctional diglycidyl ether of bisphenol A with an epoxide equivalent weight of 185-192 and a diethyl toluenediamine-based curing agent. Thin films were produced by casting these mixtures and subsequent curing. The whisker content was systematically varied between 4 and 24% v/v. Electron microscopy studies suggest that the whiskers are evenly dispersed within the epoxy matrix. Dynamic mechanical thermoanalysis revealed that the glass transition temperature (T(g)) of the materials was not significantly influenced by the incorporation of the cellulose filler. Between room temperature and 150 degrees C, i.e., below T(g), the tensile storage moduli (E') of the nanocomposites increased modestly, for example from 1.6 GPa for the neat polymer to 4.9 and 3.6 GPa for nanocomposites comprising 16% v/v tunicate or cotton whiskers. The relative reinforcement was more significant at 185 degrees C (i.e., above T(g)), where E' was increased from approximately 16 MPa (neat polymer) to approximately 1.6 GPa (tunicate) or approximately 215 MPa (cotton). The mechanical properties of the new materials are well-described by the percolation model and are the result of the formation of a percolating whisker network in which stress transfer is facilitated by strong interactions between the whiskers.

Solving the problem of building models of crosslinked polymers: an example focussing on validation of the properties of crosslinked epoxy resins.

Science.gov (United States)

Hall, Stephen A; Howlin, Brendan J; Hamerton, Ian; Baidak, Alex; Billaud, Claude; Ward, Steven

2012-01-01

The construction of molecular models of crosslinked polymers is an area of some difficulty and considerable interest. We report here a new method of constructing these models and validate the method by modelling three epoxy systems based on the epoxy monomers bisphenol F diglycidyl ether (BFDGE) and triglycidyl-p-amino phenol (TGAP) with the curing agent diamino diphenyl sulphone (DDS). The main emphasis of the work concerns the improvement of the techniques for the molecular simulation of these epoxies and specific attention is paid towards model construction techniques, including automated model building and prediction of glass transition temperatures (T(g)). Typical models comprise some 4200-4600 atoms (ca. 120-130 monomers). In a parallel empirical study, these systems have been cast, cured and analysed by dynamic mechanical thermal analysis (DMTA) to measure T(g). Results for the three epoxy systems yield good agreement with experimental T(g) ranges of 200-220°C, 270-285°C and 285-290°C with corresponding simulated ranges of 210-230°C, 250-300°C, and 250-300°C respectively.

Grafting of polyethylenimine onto cellulose nanofibers for interfacial enhancement in their epoxy nanocomposites.

Science.gov (United States)

Zhao, Jiangqi; Li, Qingye; Zhang, Xiaofang; Xiao, Meijie; Zhang, Wei; Lu, Canhui

2017-02-10

Cellulose nanofibers (CNFs) were surface-modified with polyethyleneimine (PEI), which brought plentiful amine groups on the surface of CNFs, leading to a reduced hydrogen bond density between CNFs and consequently less CNFs agglomerates. The amine groups could also react with the epoxy as an effective curing agent that could increase the interfacial crosslinking density and strengthen interfacial adhesion. The tensile strength and Young's modulus of CNFs-PEI/Epoxy nanocomposites were 88.1% and 237.6% higher than those of neat epoxy, respectively. The tensile storage modulus of the nanocomposites also increased significantly at the temperature either below or above the Tg. The coefficient of thermal expansion for the CNFs-PEI/Epoxy nanocomposites was 22.2ppmK -1 , much lower than that of the neat epoxy (88.6ppmK -1 ). In addition, the thermal conductivity of the nanocomposites was observed to increase as well. The exceptional and balanced properties may provide the nanocomposites promising applications in automotive, construction and electronic devices. Copyright © 2016 Elsevier Ltd. All rights reserved.

Liquid crystal alignment in electro-responsive nanostructured thermosetting materials based on block copolymer dispersed liquid crystal

Energy Technology Data Exchange (ETDEWEB)

Tercjak, A; Garcia, I; Mondragon, I [Materials-Technologies Group, Departamento IngenierIa Quimica y M Ambiente, Escuela Politecnica, Universidad PaIs Vasco/Euskal Herriko Unibertsitatea, Plaza Europa 1, E-20018 Donostia-San Sebastian (Spain)], E-mail: scptesza@sc.ehu.es, E-mail: inaki.mondragon@ehu.es

2008-07-09

Novel well-defined nanostructured thermosetting systems were prepared by modification of a diglicydylether of bisphenol-A epoxy resin (DGEBA) with 10 or 15 wt% amphiphilic poly(styrene-b-ethylene oxide) block copolymer (PSEO) and 30 or 40 wt% low molecular weight liquid crystal 4'-(hexyl)-4-biphenyl-carbonitrile (HBC) using m-xylylenediamine (MXDA) as a curing agent. The competition between well-defined nanostructured materials and the ability for alignment of the liquid crystal phase in the materials obtained has been studied by atomic and electrostatic force microscopy, AFM and EFM, respectively. Based on our knowledge, this is the first time that addition of an adequate amount (10 wt%) of a block copolymer to 40 wt% HBC-(DGEBA/MXDA) leads to a well-organized nanostructured thermosetting system (between a hexagonal and worm-like ordered structure), which is also electro-responsive with high rate contrast. This behavior was confirmed using electrostatic force microscopy (EFM), by means of the response of the HBC liquid crystal phase to the voltage applied to the EFM tip. In contrast, though materials containing 15 wt% PSEO and 30 wt% HBC also form a well-defined nanostructured thermosetting system, they do not show such a high contrast between the uncharged and charged surface.

Liquid crystal alignment in electro-responsive nanostructured thermosetting materials based on block copolymer dispersed liquid crystal.

Science.gov (United States)

Tercjak, A; Garcia, I; Mondragon, I

2008-07-09

Novel well-defined nanostructured thermosetting systems were prepared by modification of a diglicydylether of bisphenol-A epoxy resin (DGEBA) with 10 or 15 wt% amphiphilic poly(styrene-b-ethylene oxide) block copolymer (PSEO) and 30 or 40 wt% low molecular weight liquid crystal 4'-(hexyl)-4-biphenyl-carbonitrile (HBC) using m-xylylenediamine (MXDA) as a curing agent. The competition between well-defined nanostructured materials and the ability for alignment of the liquid crystal phase in the materials obtained has been studied by atomic and electrostatic force microscopy, AFM and EFM, respectively. Based on our knowledge, this is the first time that addition of an adequate amount (10 wt%) of a block copolymer to 40 wt% HBC-(DGEBA/MXDA) leads to a well-organized nanostructured thermosetting system (between a hexagonal and worm-like ordered structure), which is also electro-responsive with high rate contrast. This behavior was confirmed using electrostatic force microscopy (EFM), by means of the response of the HBC liquid crystal phase to the voltage applied to the EFM tip. In contrast, though materials containing 15 wt% PSEO and 30 wt% HBC also form a well-defined nanostructured thermosetting system, they do not show such a high contrast between the uncharged and charged surface.

Liquid crystal alignment in electro-responsive nanostructured thermosetting materials based on block copolymer dispersed liquid crystal

International Nuclear Information System (INIS)

Tercjak, A; Garcia, I; Mondragon, I

2008-01-01

Novel well-defined nanostructured thermosetting systems were prepared by modification of a diglicydylether of bisphenol-A epoxy resin (DGEBA) with 10 or 15 wt% amphiphilic poly(styrene-b-ethylene oxide) block copolymer (PSEO) and 30 or 40 wt% low molecular weight liquid crystal 4'-(hexyl)-4-biphenyl-carbonitrile (HBC) using m-xylylenediamine (MXDA) as a curing agent. The competition between well-defined nanostructured materials and the ability for alignment of the liquid crystal phase in the materials obtained has been studied by atomic and electrostatic force microscopy, AFM and EFM, respectively. Based on our knowledge, this is the first time that addition of an adequate amount (10 wt%) of a block copolymer to 40 wt% HBC-(DGEBA/MXDA) leads to a well-organized nanostructured thermosetting system (between a hexagonal and worm-like ordered structure), which is also electro-responsive with high rate contrast. This behavior was confirmed using electrostatic force microscopy (EFM), by means of the response of the HBC liquid crystal phase to the voltage applied to the EFM tip. In contrast, though materials containing 15 wt% PSEO and 30 wt% HBC also form a well-defined nanostructured thermosetting system, they do not show such a high contrast between the uncharged and charged surface

Identification of nanostructural development in epoxy polymer layered silicate nanocomposites from the interpretation of differential scanning calorimetry and dielectric spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Roman, Frida, E-mail: roman@mmt.upc.edu [Laboratori de Termodinamica, Departament de Maquines i Motors Termics, ETSEIAT, Universitat Politecnica de Catalunya, Carrer Colom 11, 08222 Terrassa (Spain); Calventus, Yolanda, E-mail: calventus@mmt.upc.edu [Laboratori de Termodinamica, Departament de Maquines i Motors Termics, ETSEIAT, Universitat Politecnica de Catalunya, Carrer Colom 11, 08222 Terrassa (Spain); Colomer, Pere, E-mail: colomer@mmt.upc.edu [Laboratori de Termodinamica, Departament de Maquines i Motors Termics, ETSEIAT, Universitat Politecnica de Catalunya, Carrer Colom 11, 08222 Terrassa (Spain); Hutchinson, John M., E-mail: hutchinson@mmt.upc.edu [Laboratori de Termodinamica, Departament de Maquines i Motors Termics, ETSEIAT, Universitat Politecnica de Catalunya, Carrer Colom 11, 08222 Terrassa (Spain)

2012-08-10

Highlights: Black-Right-Pointing-Pointer Comparison of DSC and DRS in the cure of epoxy nanocomposites. Black-Right-Pointing-Pointer Dependence of exfoliation of nanocomposite on clay content. Black-Right-Pointing-Pointer Anionically initiated homopolymerisation in PLS nanocomposites. - Abstract: The effect of nanoclay on the non-isothermal cure kinetics of polymer layered silicate nanocomposites based upon epoxy resin is studied by calorimetric techniques (DSC and TGA) and by dielectric relaxation spectroscopy (DRS) in non-isothermal cure at constant heating rate. The cure process takes place by homopolymerisation, initiated anionically using 3 wt% dimethylaminopyridine (DMAP), and the influence of the nanoclay content has been analysed. Interesting differences are observed between the nanocomposites with 2 wt% and 5 wt% clay content. At low heating rates, these samples vitrify and then devitrify during the cure. For the sample with 2 wt% clay, the devitrification is accompanied by a thermally initiated homopolymerisation, which can be identified by DRS but not by DSC. The effect of this is to improve the exfoliation of the nanocomposite with 2 wt% clay, as verified by transmission electron microscopy, with a corresponding increase in the glass transition temperature. These observations are interpreted in respect of the nanocomposite preparation method and the cure kinetics.

Anisotropic Dielectric Properties of Carbon Fiber Reinforced Polymer Composites during Microwave Curing

Science.gov (United States)

Zhang, Linglin; Li, Yingguang; Zhou, Jing

2018-01-01

Microwave cuing technology is a promising alternative to conventional autoclave curing technology in high efficient and energy saving processing of polymer composites. Dielectric properties of composites are key parameters related to the energy conversion efficiency during the microwave curing process. However, existing methods of dielectric measurement cannot be applied to the microwave curing process. This paper presented an offline test method to solve this problem. Firstly, a kinetics model of the polymer composites under microwave curing was established based on differential scanning calorimetry to describe the whole curing process. Then several specially designed samples of different feature cure degrees were prepared and used to reflect the dielectric properties of the composite during microwave curing. It was demonstrated to be a feasible plan for both test accuracy and efficiency through extensive experimental research. Based on this method, the anisotropic complex permittivity of a carbon fiber/epoxy composite during microwave curing was accurately determined. Statistical results indicated that both the dielectric constant and dielectric loss of the composite increased at the initial curing stage, peaked at the maximum reaction rate point and decreased finally during the microwave curing process. Corresponding mechanism has also been systematically investigated in this work.

Magnetic alignment of SWCNTs decorated with Fe3O4 to enhance mechanical properties of SC-15 epoxy

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O. Malkina

2013-04-01

Full Text Available We report significant improvement in mechanical properties of SC-15 epoxy when reinforced with decorated nanotubes and cured in a modest magnetic field. The chemical synthesis and field curing process is a low cost and relatively easy technique to impose strong magnetic anisotropy into the system without the need of a superconducting magnet. SWCNT(COOHs were decorated with Fe3O4 nanoparticles through a sonochemical oxidation process and then dispersed into SC-15 epoxy at 0.5 wt% loading. The admixture was cured for 6 hours in a magnetic field of 10 kOe followed by an additional 24 hours of post curing at room temperature. Control samples were prepared in a similar manner but without the application of the magnetic field. Mechanical tests performed on field-cured samples indicated that tensile strength and modulus increased by 62% and 40%. Most importantly, modulus of toughness, fracture strain, and modulus of resilience improved by 346%, 165%% and 170%, respectively. Such enhancement in mechanical properties was attributed to changes in polymer morphology, partial alignment of nanotubes in the field direction, and sliding at the polymer-nanotube interface. Detailed characterization of the system with XRD, TEM, DMA, and Magnetometry are described in the paper.

Imidazolium Ionic Liquid Modified Graphene Oxide: As a Reinforcing Filler and Catalyst in Epoxy Resin

Directory of Open Access Journals (Sweden)

Qing Lyu

2017-09-01

Full Text Available Surface modification of graphene oxide (GO is one of the most important issues to produce high performance GO/epoxy composites. In this paper, the imidazole ionic liquid (IMD-Si was introduced onto the surface of GO sheets by a cheap and simple method, to prepare a reinforcing filler, as well as a catalyst in epoxy resin. The interlayer spacing of GO sheets was obviously increased by the intercalation of IMD-Si, which strongly facilitated the dispersibility of graphene oxide in organic solvents and epoxy matrix. The addition of 0.4 wt % imidazolium ionic liquid modified graphene oxide (IMD-Si@GO, yielded a 12% increase in flexural strength (141.3 MPa, a 26% increase in flexural modulus (4.69 GPa, and a 52% increase in impact strength (18.7 kJ/m2, compared to the neat epoxy. Additionally the IMD-Si@GO sheets could catalyze the curing reaction of epoxy resin-anhydride system significantly. Moreover, the improved thermal conductivities and thermal stabilities of epoxy composites filled with IMD-Si@GO were also demonstrated.

Formulation of eb-curable epoxy resin : some important parameters

International Nuclear Information System (INIS)

Dahlan bin Haji Mohd; Hosoi, Fumio; Sasaki, Takashi

1989-01-01

The works on the electron-beam curing of surface coatings using epoxy acrylic-based resins were discussed. The works covered among other things the effect of molecular weights of the resins on the physical properties of coatings and their physical and chemical characterizations. The emphasis was given to formulating the resins applicable to surface coatings. Curings were done on a low-energy electron beam accelerator operating at 250 kV. A number of parameters deemed important to formulations, such as the molecular weights of the oligomers and monomers, monomer ratios, and HEA additions were explored. It was found that one could modify the physical properties of the coatings by changing or adjusting those parameters. (author)

Toughening Mechanisms in Silica-Filled Epoxy Nanocomposites

Science.gov (United States)

Patel, Binay S.

and modeled fracture energy results. Furthermore, the contribution of microcracking was most prevalent at lower filler contents which suggests that the presence of microcracking may account for the previously unexplained improvements in fracture behavior attained in silica-filled epoxy nanocomposites at low filler contents. Secondly, surface modification through the application of three different propriety surface treatments ("A", "B" and "C") was found to greatly influence the processibility and fracture behavior of silica-filled epoxy nanocomposites. B-treated silica nanoparticles were found to readily form micron-scale agglomerates, settled during nanocomposite curing and showed no improvement in fracture toughness with increasing filler content. In contrast, the nanocomposites consisting of A-treated and C-treated silica nanoparticles yielded morphologies primarily containing well-dispersed nanoparticles. Therefore, fracture toughness improved with increasing filler content. Finally, particle porosity was found to have no significant effect on fracture behavior for the range of silica-filled epoxy nanocomposites investigated. Lower density porous silica nanoparticles were just as effective toughening agents as higher density non-porous silica nanoparticles. Consequently, the potential exists for the use of toughened-epoxies in lightweight structural applications.

Effect of Montmorillonite Nanogel Composite Fillers on the Protection Performance of Epoxy Coatings on Steel Pipelines.

Science.gov (United States)

Atta, Ayman M; El-Saeed, Ashraf M; Al-Lohedan, Hamad A; Wahby, Mohamed

2017-06-02

Montmorillonite (MMT) clay mineral is widely used as filler for several organic coatings. Its activity is increased by exfoliation via chemical modification to produce nanomaterials. In the present work, the modification of MMT to form nanogel composites is proposed to increase the dispersion of MMT into epoxy matrices used to fill cracks and holes produced by the curing exotherms of epoxy resins. The dispersion of MMT in epoxy improved both the mechanical and anti-corrosion performance of epoxy coatings in aggressive marine environments. In this respect, the MMT surfaces were chemically modified with different types of 2-acrylamido-2-methyl propane sulfonic acid (AMPS) nanogels using a surfactant-free dispersion polymerization technique. The effect of the chemical structure, nanogel content and the interaction with MMT surfaces on the surface morphology, surface charges and dispersion in the epoxy matrix were investigated for use as nano-filler for epoxy coatings. The modified MMT nanogel epoxy composites showed excellent resistance to mechanical damage and salt spray resistance up to 1000 h. The interaction of MMT nanogel composites with the epoxy matrix and good response of AMPS nanogel to sea water improve their ability to act as self-healing materials for epoxy coatings for steel.

A critical evaluation of the enhancement of mechanical properties of epoxy modified using CNTs

Science.gov (United States)

Bedsole, Robert W.; Park, Cheol; Bogert, Philip B.; Tippur, Hareesh V.

2015-09-01

Carbon nanotubes (CNTs) have been widely shown in the literature to improve mechanical properties of epoxy, such as tensile strength, elastic modulus, strain to failure, and fracture toughness. These improvements in nanocomposite properties have been attributed to the extraordinary properties of the nanotubes, as well as the quality of their dispersion within and adhesion to the epoxy matrix. However, many authors have also struggled to show significant mechanical improvements using similar methodologies and despite, in some cases, showing qualitative improvements in dispersion with optical microscopy. These authors have frequently resorted to other methods for improving the mechanical properties of CNT/epoxy, such as electrically aligning CNTs, using different types of CNTs, or modifying the stoichiometry. The current work examines many different dispersion techniques, types of CNTs, types of epoxies, curing cycles, and other variables in an attempt to improve the mechanical properties of neat epoxy with CNTs. Despite seeing significant changes in the microscopy, no significant improvements in tensile or fracture properties have been attributed to CNTs in this work.

Studies on cationic UV curing of epoxidised palm oil (EPO) for surface coatings

International Nuclear Information System (INIS)

Mek Zah Salleh; Mohd Hilmi Mahmood; Wan Rosli Wan Daud; Kumar, R.N.

2000-01-01

Epoxidised palm oil (EPO) resin can be cured by ultraviolet (UV) radiation either by radical, cationic or hybrid system. Cationic curing system has been chosen in this study due to the fact that epoxy groups present in EPO can be utilised directly to form crosslinking. Curing was done by means of a 20 cm wide UV IST machine with the conditions of 7.5 A current and 4 m/min conveyor speed. Sulphonium and ferrocenium salts were used as cationic photoinitiator. A formulations study was performed on the selected grades of EPO with other materials. These include types and concentration of photoinitiator, monomers, concentration of EPO and post-cure. The properties of the cured film such as pendulum hardness, percentage of gel content and tensile strength were determined. It was found that triarylsulphonium hexafluorophosphate has a very low solubility in EPO. Addition of vinyl ether monomer to the formulation did not enhance pendulum hardness and gel content of the cured films. It is also found that the post cure temperature has no significant effect on the cured film

Nanosilica reinforced epoxy floor coating composites: preparation and thermophysical characterization

Directory of Open Access Journals (Sweden)

Mir Mohammad Alavi Nikje

2012-01-01

Full Text Available In this study, flooring grade epoxy/nanoSiO2 nanocomposites were prepared by in-situ polymerization method. Nano silica was treated by coupling agent in order to surface treating and introducing of reactive functional groups to achieving adequate bonding between polar inorganic nano particles and epoxy organic polymer. γ-Aminopropyltriethoxysilane (Amino A-100 was used as an effective and commercially available coupling agent and nano silica treated in acetone media. SEM observations of cured samples revealed that the nano silica was completely dispersed into polymer matrix into nanoscale particles. Thermal and physical properties of prepared samples were investigated and data showed improvements in physical and mechanical properties of the flooring samples in comparison with unfilled resin.

Additive effects in radiation grafting and curing

International Nuclear Information System (INIS)

Viengkhou, V.; Ng, L.

1996-01-01

Full text: Detailed studies on the accelerative effect of novel additives in radiation grafting and curing using acrylated monomer/oligomer systems have been performed in the presence of ionising radiation and UV as sources. Methyl methacrylate (MMA) is used as typical monomer for these grafting studies in the presence of the additives with model backbone polymers, cellulose and propropylene. Additives which have been found to accelerate these grafting processes are: mineral acid, occlusion compounds like urea, thermal initiators and photoinitiators as well as multifunctional monomers such as multifunctional acrylates. The results from irradiation with gamma rays have also been compared with irradiation from a 90W UV lamp. The role of the above additives in accelerating the analogous process of radiation curing has been investigated. Acrylated urethanes, epoxies and polyesters are used as oligomers together with acrylated monomers in this work with uv lamps of 300 watts/inch as radiation source. In the UV curing process bonding between film and substrate is usually due to physical forces. In the present work the presence of additives are shown to influence the occurrence of concurrent grafting during cure thus affecting the nature of the bonding of the cured film. The conditions under which concurrent grafting with UV can occur will be examined. A mechanism for accelerative effect of these additives in both grafting and curing processes has been proposed involving radiation effects and partitioning phenomena

Solving the problem of building models of crosslinked polymers: an example focussing on validation of the properties of crosslinked epoxy resins.

Directory of Open Access Journals (Sweden)

Stephen A Hall

Full Text Available The construction of molecular models of crosslinked polymers is an area of some difficulty and considerable interest. We report here a new method of constructing these models and validate the method by modelling three epoxy systems based on the epoxy monomers bisphenol F diglycidyl ether (BFDGE and triglycidyl-p-amino phenol (TGAP with the curing agent diamino diphenyl sulphone (DDS. The main emphasis of the work concerns the improvement of the techniques for the molecular simulation of these epoxies and specific attention is paid towards model construction techniques, including automated model building and prediction of glass transition temperatures (T(g. Typical models comprise some 4200-4600 atoms (ca. 120-130 monomers. In a parallel empirical study, these systems have been cast, cured and analysed by dynamic mechanical thermal analysis (DMTA to measure T(g. Results for the three epoxy systems yield good agreement with experimental T(g ranges of 200-220°C, 270-285°C and 285-290°C with corresponding simulated ranges of 210-230°C, 250-300°C, and 250-300°C respectively.

The ionic conductivity, mechanical performance and morphology of two-phase structural electrolytes based on polyethylene glycol, epoxy resin and nano-silica

Energy Technology Data Exchange (ETDEWEB)

Feng, Qihang; Yang, Jiping, E-mail: jyang08@163.com; Yu, Yalin; Tian, Fangyu; Zhang, Boming; Feng, Mengjie; Wang, Shubin

2017-05-15

Highlights: • Structural electrolytes based on PEG-epoxy resins were prepared. • Factors of influencing ionic conductivity and mechanical properties were studied. • Co-continuous morphology was benefit for improved structural electrolyte property. • Efficiently optimized multifunctional electrolyte performance was achieved. - Abstract: As one of significant parts of structural power composites, structural electrolytes have desirable mechanical properties like structural resins while integrating enough ionic conductivity to work as electrolytes. Here, a series of polyethylene glycol (PEG)-epoxy-based electrolytes filled with nano-silica were prepared. The ionic conductivity and mechanical performance were studied as functions of PEG content, lithium salt concentration, nano-silica content and different curing agents. It was found that, PEG-600 and PEG-2000 content in the epoxy electrolyte system had a significant effect on their ionic conductivity. Furthermore, increasing the nano-silica content in the system induced increased ionic conductivity, decreased glass transition temperature and mechanical properties, and more interconnected irregular network in the cured systems. The introduction of rigid m-xylylenediamine resulted in enhanced mechanical properties and reasonably decreased ionic conductivity. As a result, these two-phase epoxy structural electrolytes have great potential to be used in the multifunctional energy storage devices.

Relationships between nanostructure and dynamic-mechanical properties of epoxy network containing PMMA-modified silsesquioxane

Directory of Open Access Journals (Sweden)

2009-06-01

Full Text Available A new class of organic-inorganic hybrid nanocomposites was obtained by blending PMMA-modified silsesquioxane hybrid materials with epoxy matrix followed by curing with methyl tetrahydrophthalic anhydride. The hybrid materials were obtained by sol-gel method through the hydrolysis and polycondensation of the silicon species of the hybrid precursor, 3-methacryloxypropyltrimethoxysilane (MPTS, simultaneously to the polymerization of the methacrylate (MMA groups covalently bonded to the silicon atoms. The nanostructure of these materials was investigated by small angle X-ray scattering (SAXS and correlated to their dynamic mechanical properties. The SAXS results revealed a hierarchical nanostructure consisting on two structural levels. The first level is related to the siloxane nanoparticles spatially correlated in the epoxy matrix, forming larger hybrid secondary aggregates. The dispersion of siloxane nanoparticles in epoxy matrix was favored by increasing the MMA content in the hybrid material. The presence of small amount of hybrid material affected significantly the dynamic mechanical properties of the epoxy networks.

Synthesis and properties of a novel UV-cured fluorinated siloxane graft copolymer for improved surface, dielectric and tribological properties of epoxy acrylate coating

International Nuclear Information System (INIS)

Yan, Zhenlong; Liu, Weiqu; Gao, Nan; Wang, Honglei; Su, Kui

2013-01-01

A novel functional fluorinated siloxane graft copolymer bearing with vinyl end-groups was synthesized from dihydroxypropyl-terminated poly(dimethylsiloxane) (PDMS), dicarboxyl terminated poly(2,2,3,4,4,4-hexafluorobutyl acrylate) oligomer (CTHFA), 2,4-toluene diissocyanate (TDI) and 2-hydroxyethyl methacrylate (HEMA). The chemical structure was characterized by FT-IR and GPC. The effect of concentration of the vinyl-capped fluorosilicone graft copolymer (Vi-PFSi) on the surface, thermal properties, dielectric and tribological properties of UV-cured films was investigated. Contact angles and surface energies showed that the high hydrophobic and oleophobic surfaces were obtained by incorporation of Vi-PFSi at very low amount (0.5 wt%). X-ray photoelectron spectroscopy (XPS) evidenced that the fluorinated and siloxane moiety selectively migrated to the outermost surface of UV-cured film, thus reduced its surface energy from 45.42 to 15.40 mN/m 2 without affecting its bulk properties. The morphology of fracture surface of modified film exhibited rough fracture surface only at the outermost surface, revealing fluorinated and siloxane groups migrated toward air-side surface. The dielectric constants decreased from 5.32 (1 MHz) for bisphenol-A epoxy methacrylate (EMA) to 2.82 (1 MHz) for modified film when the Vi-PFSi copolymer concentration increased from 0 to 0.8 wt%. Tribological results from abrasion tester suggested that the Vi-PFSi could obviously reduce the abrasion weight loss of modified films.

Aspects of the Fracture Toughness of Carbon Nanotube Modified Epoxy Polymer Composites

Science.gov (United States)

Mirjalili, Vahid

Epoxy resins used in fibre reinforced composites exhibit a brittle fracture behaviour, because they show no sign of damage prior to a catastrophic failure. Rubbery materials and micro-particles have been added to epoxy resins to improve their fracture toughness, which reduces strength and elastic properties. In this research, carbon nanotubes (CNTs) are investigated as a potential toughening agent for epoxy resins and carbon fibre reinforced composites, which can also enhance strength and elastic properties. More specifically, the toughening mechanisms of CNTs are investigated theoretically and experimentally. The effect of aligned and randomly oriented carbon nanotubes (CNTs) on the fracture toughness of polymers was modelled using Elastic Plastic Fracture Mechanics. Toughening from CNT pull-out and rupture were considered, depending on the CNTs critical length. The model was used to identify the effect of CNTs geometrical and mechanical properties on the fracture toughness of CNT-modified epoxies. The modelling results showed that a uniform dispersion and alignment of a high volume fraction of CNTs normal to the crack growth plane would lead to the maximum fracture toughness enhancement. To achieve a uniform dispersion, the effect of processing on the dispersion of single walled and multi walled CNTs in epoxy resins was investigated. An instrumented optical microscope with a hot stage was used to quantify the evolution of the CNT dispersion during cure. The results showed that the reduction of the resin viscosity at temperatures greater than 100 °C caused an irreversible re-agglomeration of the CNTs in the matrix. The dispersion quality was then directly correlated to the fracture toughness of the modified resin. It was shown that the fine tuning of the ratio of epoxy resin, curing agent and CNT content was paramount to the improvement of the base resin fracture toughness. For the epoxy resin (MY0510 from Hexcel), an improvement of 38% was achieved with 0.3 wt

Ytterbium triflate as a new catalyst on the curing of epoxy-isocyanate based thermosets

Energy Technology Data Exchange (ETDEWEB)

Flores, Marjorie; Fernandez-Francos, Xavier [Departament de Quimica Analitica i Quimica Organica, Universitat Rovira i Virgili, Marcelli Domingo s/n, 43007 Tarragona (Spain); Morancho, Josep M. [Laboratori de Termodinamica, ETSEIB, Universitat Politecnica de Catalunya, Diagonal 647, 08028 Barcelona (Spain); Serra, Angels [Departament de Quimica Analitica i Quimica Organica, Universitat Rovira i Virgili, Marcelli Domingo s/n, 43007 Tarragona (Spain); Ramis, Xavier, E-mail: ramis@mmt.upc.es [Laboratori de Termodinamica, ETSEIB, Universitat Politecnica de Catalunya, Diagonal 647, 08028 Barcelona (Spain)

2012-09-10

Highlights: Black-Right-Pointing-Pointer Ytterbium triflate is an active catalyst for diepoxides/diisocyanate formulations. Black-Right-Pointing-Pointer Ytterbium triflate promotes the formation of oxazolidone, isocyanurate, urethane and allophanate groups and the polyetherification of epoxides. Black-Right-Pointing-Pointer Diepoxides/diisocyanate formulations catalyzed by ytterbium triflate show higher pot-life than equivalent formulations catalyzed by benzyldimethylamine. - Abstract: Networks containing oxazolidone, isocyanurate, urethane, allophanate and ether groups were prepared by copolymerization of mixtures of diglycidylether of bisphenol A and toluene-2,4-diisocyanate in presence of ytterbium triflate. It has been demonstrated that ytterbium triflate promotes six elemental reactions that coexist during curing and yield the aforementioned groups. Changes during curing, fraction of different groups present in the network and final properties of the cured materials were investigated by thermal analysis and infrared spectroscopy. The influence of the molar ratio of isocyanate to epoxide groups on the properties and curing has been studied. The curing kinetics were analyzed by means of an integral isoconversional non-isothermal procedure. The results obtained were compared with those obtained by using a common catalyst such as the benzyldimethylamine. The structure and the properties of the resulting thermosets are controlled by the initial composition of the formulation and the catalyst used.

Thermoplastic impact property improvement in hybrid natural fibre epoxy composite bumper beam

International Nuclear Information System (INIS)

Davoodi, M M; Sapuan, S M; Ali, Aidy; Ahmad, D; Khalina, A

2010-01-01

Utilization of thermoset resin as a bumper beam composite matrix is currently more dominated in car manufacturer suppliers, because of availability, easy processing, low material cost and production equipment investment. Moreover, low viscosity, shrinkage and excellent flow facilitate better fibre impregnation and proper surface resin wetting. Three-dimensional cross linking curing increase impact, creep and environmental stress cracking resistance properties. Low impact properties of natural fibre epoxy composite, are main issues in its employment for automotive structural components. Impact properties in epoxy composite bumper beam could be increased by modifying the resin, reinforcement and manufacturing process as well as geometry parameters such as cross section, thickness, added ribs and fixing method optimizations could strengthen impact resistance. There are two main methods, flexibilisation and toughening, as modifying the resin in order to improve the impact properties of epoxy composite, which form single phase or two-phase morphology to make modifier as epoxy or from separate phase to keep the thermo-mechanical properties. Liquid rubber, thermoplastic, core shell particle and rigid particle are different methods of toughening improvements. In this research, thermoplastic toughening has used to improve impact properties in hybrid natural fibre epoxy composite for automotive bumper beam and has achieved reasonable impact improvements.

Warpage of QFN Package in Post Mold Cure Process of integrated circuit packaging

Science.gov (United States)

Sriwithoon, Nattha; Ugsornrat, Kessararat; Srisuwitthanon, Warayoot; Thonglor, Panakamon

2017-09-01

This research studied about warpage of QFN package in post mold cure process of integrated circuit (IC) packages using pre-plated (PPF) leadframe. For IC package, epoxy molding compound (EMC) are molded by cross linking of compound stiffness but incomplete crosslinked network and leading the fully cured thermoset by post mold cure (PMC) process. The cure temperature of PMC can change microstructure of EMC in term of stress inside the package and effect to warpage of the package due to coefficient of thermal expansion (CTE) between EMC and leadframe. In experiment, cure temperatures were varied to check the effect of internal stress due to different cure temperature after completed post mold cure for TDFN 2×3 8L. The cure temperature were varied with 180 °C, 170 °C, 160 °C, and 150°C with cure time 4 and 6 hours, respectively. For analysis, the TDFN 2×3 8L packages were analyzed the warpage by thickness gauge and scanning acoustic microscope (SAM) after take the test samples out from the oven cure. The results confirmed that effect of different CTE between EMC and leadframe due to different cure temperature resulting to warpage of the TDFN 2×3 8L packages.

Curing of polymer thermosets via click reactions and on demand processes

Science.gov (United States)

Brei, Mark Richard

In the first project, an azide functional resin and tetra propargyl aromatic diamines were fabricated for use as a composite matrix. These systems take already established epoxy/amine matrices and functionalize them with click moieties. This allows lower temperatures to be used in the production of a thermoset part. These new systems yield many better mechanical properties than their epoxy/amine derivatives, but their Tgs are low in comparison. The second project investigates the characterization of a linear system based off of the above azide functional resin and a difunctional alkyne. Through selectively choosing catalyst, the linear system can show regioselectivity to either a 1,4-disubstituted triazole, or a 1,5-disubstituted triazole. Without the addition of catalyst, the system produces both triazoles in almost an equal ratio. The differently catalyzed systems were cured and then analyzed by 1H and 13C NMR to better understand the structure of the material. The third project builds off of the utility of the aforementioned azide/alkyne system and introduces an on-demand aspect to the curing of the thermoset. With the inclusion of copper(II) within the azide/alkyne system, UV light is able to catalyze said reaction and cure the material. It has been shown that the copper(II) loading levels can be extremely small, which helps in reducing the copper's effect on mechanical properties The fourth project takes a look at polysulfide-based sealants. These sealants are normally cured via an oxidative reaction. This project took thiol-terminated polysulfides and fabricated alkene-terminated polysulfides for use as a thiol-ene cured material. By changing the mechanism for cure, the polysulfide can be cured via UV light with the use of a photoinitiator within the thiol/alkene polysulfide matrix. The final chapter will focus on a characterization technique, MALDI-TOF, which was used to help characterize the above materials as well as many others. By using MALDI-TOF, the

Study by dynamic light scattering of an o/w emulsion of an epoxi resin dispersed in water by means of a triblock copolymer of type PEO-PPO-PEO

International Nuclear Information System (INIS)

Uscanga, E. H.; Rio, J. M. del; Avendano-Gomez, J. R.

2009-01-01

The curing epoxy resins are widely used in various fields of chemical industry, such as adhesives, automotive, coatings, etc. The process operation consisting of flow and mixing of epoxy resins become difficult due to their high viscosity. One solution is to dissolve the epoxy resin in volatile organic solvents (VOS) such as toluene, xylene or benzene. However, the use of VOS is not only expensive but harmful to the environment. (Author)

Epoxy elastomers reinforced with functionalized multi-walled carbon nanotubes as stimuli-responsive shape memory materials

International Nuclear Information System (INIS)

Lama, G. C.; Nasti, G.; Cerruti, P.; Gentile, G.; Carfagna, C.; Ambrogi, V.

2014-01-01

In this work, the incorporation of multiwalled carbon nanotubes (MWCNT) into epoxy-based elastomers was carried out in order to obtain nanocomposite systems with shape memory effect. For the preparation of elastomeric matrices, p-bis(2,3-epoxypropoxy)-α-methylstilbene (DOMS) was cured with sebacic acid. DOMS was synthesized in our laboratory and it is characterized by a rigid-rod, potentially liquid crystalline structure. A lightly cross-linked liquid crystalline elastomer was obtained. As for nanocomposites, variable amounts (0.75, 1.50, 3.0, 6.0, 12.0 wt.%) of COOH-MWCNTs were employed. In order to improve the nanotubes dispersibility and the interfacial adhesion with the epoxy matrix, an optimized two-step procedure was developed, which consisted in grafting the epoxy monomer onto the nanotube surface and then curing it in presence of crosslinking agent. DOMS-functionalized MWCNT were characterized through solvent dispersion experiments, FTIR spectroscopy and TGA analysis, which demonstrated the occurred covalent functionalization of the nanotubes with the epoxy monomers. The morphological analysis through electron microscopy demonstrated that this was an efficient strategy to improve the dispersion of nanotubes within the matrix. The second part of the work was devoted to the structural, thermal, mechanical and electric characterization of elastomeric nanocomposites. The results indicated a general improvement of properties of nanocomposites. Also, independently of the nanotube content, a smectic phase formed. Shape memory features of LC systems were also evaluated. It was demonstrated the shape could be recovered through heating, solvent immersion, as well as upon the application of an electrical field

Thermosetting epoxy resin/thermoplastic system with combined shape memory and self-healing properties

International Nuclear Information System (INIS)

Yao, Yongtao; Wang, Jingjie; Lu, Haibao; Liu, Yanju; Leng, Jinsong; Xu, Ben; Fu, Yongqing

2016-01-01

A novel and facile strategy was proposed to construct a thermosetting/thermoplastic system with both shape memory and self-healing properties based on commercial epoxy resin and poly(ϵ-caprolactone)-PCL. Thermoplastic material is capable of re-structuring and changing the stiffness/modulus when the temperature is above melting temperature. PCL microfiber was used as a plasticizer in epoxy resin–based blends, and served as a ‘hard segment’ to fix a temporary shape of the composites during shape memory cycles. In this study, the electrospun PCL membrane with a porous network structure enabled a homogenous PCL fibrous distribution and optimized interaction between fiber and epoxy resin. The self-healing capability is achieved by phase transition during curing of the composites. The mechanism of the shape memory effect of the thermosetting (rubber)/thermoplastic composite is attributed to the structural design of the thermoplastic network inside the thermosetting resin/rubber matrix. (paper)

Enhanced microwave shielding and mechanical properties of high loading MWCNT–epoxy composites

International Nuclear Information System (INIS)

Singh, B. P.; Prasanta; Choudhary, Veena; Saini, Parveen; Pande, Shailaja; Singh, V. N.; Mathur, R. B.

2013-01-01

Dispersion of high loading of carbon nanotubes (CNTs) in epoxy resin is a challenging task for the development of efficient and thin electromagnetic interference (EMI) shielding materials. Up to 20 wt% of multiwalled carbon nanotubes (MWCNTs) loading in the composite was achieved by forming CNT prepreg in the epoxy resin as a first step. These prepreg laminates were then compression molded to form composites which resulted in EMI shielding effectiveness of −19 dB for 0.35 mm thick film and −60 dB at for 1.75 mm thick composites in the X-band (8.2–12.4 GHz). One of the reasons for such high shielding is attributed to the high electrical conductivity of the order of 9 S cm −1 achieved in these composites which is at least an order of magnitude higher than previously reported results at this loading. In addition, an improvement of 40 % in the tensile strength over the neat resin value is observed. Thermal conductivity of the MWCNTs–epoxy composite reached 2.18 W/mK as compared to only 0.14 W/mK for cured epoxy.

Enhanced microwave shielding and mechanical properties of high loading MWCNT-epoxy composites

Science.gov (United States)

Singh, B. P.; Prasanta; Choudhary, Veena; Saini, Parveen; Pande, Shailaja; Singh, V. N.; Mathur, R. B.

2013-04-01

Dispersion of high loading of carbon nanotubes (CNTs) in epoxy resin is a challenging task for the development of efficient and thin electromagnetic interference (EMI) shielding materials. Up to 20 wt% of multiwalled carbon nanotubes (MWCNTs) loading in the composite was achieved by forming CNT prepreg in the epoxy resin as a first step. These prepreg laminates were then compression molded to form composites which resulted in EMI shielding effectiveness of -19 dB for 0.35 mm thick film and -60 dB at for 1.75 mm thick composites in the X-band (8.2-12.4 GHz). One of the reasons for such high shielding is attributed to the high electrical conductivity of the order of 9 S cm-1 achieved in these composites which is at least an order of magnitude higher than previously reported results at this loading. In addition, an improvement of 40 % in the tensile strength over the neat resin value is observed. Thermal conductivity of the MWCNTs-epoxy composite reached 2.18 W/mK as compared to only 0.14 W/mK for cured epoxy.

Advanced Nanocomposite Coatings of Fusion Bonded Epoxy Reinforced with Amino-Functionalized Nanoparticles for Applications in Underwater Oil Pipelines

Directory of Open Access Journals (Sweden)

Patricia A. Saliba

2016-01-01

Full Text Available The performance of fusion-bonded epoxy coatings can be improved through advanced composite coatings reinforced with nanomaterials. Hence, in this study a novel organic-inorganic nanocomposite finish was designed, synthesized, and characterized, achieved by adding γ-aminopropyltriethoxysilane modified silica nanoparticles produced via sol-gel process in epoxy-based powder. After the curing process of the coating reinforced with nanoparticles, the formation of a homogenous novel nanocomposite with the development of interfacial reactions between organic-inorganic and inorganic-inorganic components was observed. These hybrid nanostructures produced better integration between nanoparticles and epoxy matrix and improved mechanical properties that are expected to enhance the overall performance of the system against underwater corrosion.

Acrylated Palm Oil Resins for Radiation (UV) Curing of Over Print Varnish (OPV)

International Nuclear Information System (INIS)

Norshamsul Arif; Mohd Hilmi Mahmood; Khairul Zaman Mohd Dahlan; Rosley Che Ismail; Flora Sim; Sharilla Muhammad Faizal

2010-01-01

The purpose of this project was to determine the effects of Acrylated Epoxidized Palm Oil (EPOLA) on a radiation (UV) curing Over Print Varnish (OPV) application. The initial target was to produce an environmentally friendly resin (non-VOC) and reduce the dependence on petroleum (hydrocarbon) based products which are more toxic. Toxicity was determined via Acute Oral Toxicity (LD50), OECD 401 and Acute Toxicity (Dermal), OECD 402 technique whilst the reactivity, chemical resistance and other physical properties were obtained from actual printing application test. The developed EPOLA resin was combined with acrylated monomers, photo initiator(s) and additives in typical OPV formulation before being chemically converted into protective glossy printed film under Ultra Violet (UV-C) light. The gloss, flexibility and adhesion effects are significantly greater than conventional OPV epoxy based coupled with further extremely low irritancy to skin. The contributions of this project are twofold. First, the toxicity of developed acrylated Palm Oil resin is certainly lower than conventional epoxy acrylates resin. Secondly, the benefits towards radiation curing OPV applications were significantly demonstrated. (author)

A Comparison of gel point for a Glass/Epoxy Composite and a Neat Epoxy Material during Isothermal Curing

DEFF Research Database (Denmark)

Jakobsen, Johnny; Andreasen, Jens H.; Thomsen, Ole Thybo

2014-01-01

Determination of gel point is important for a modelling assessment of residual stresses developed during curing of composite materials. Residual stresses in a composite structure may have a detrimental effect on its mechanical performance and compromise its integrity. In this article, the evoluti...

Monitoring cure properties of out-of-autoclave BMI composites using IFPI sensor

Science.gov (United States)

Kaur, Amardeep; Anandan, Sudharshan; Yuan, Lei; Watkins, Steve E.; Chandrashekhara, K.; Xiao, Hai; Phan, Nam

2016-04-01

A non-destructive technique for inspection of a Bismaleimide (BMI) composite is presented using an optical fiber sensor. High performance BMI composites are used for Aerospace application for their mechanical strength. They are also used as an alternative to toughened epoxy resins. A femtosecond-laser-inscribed Intrinsic Fabry-Perot Interferometer (IFPI) sensor is used to perform real time cure monitoring of a BMI composite. The composite is cured using the out-of-autoclave (OOA) process. The IFPI sensor was used for in-situ monitoring; different curing stages are analyzed throughout the curing process. Temperature-induced-strain was measured to analyze the cure properties. The IFPI structure comprises of two reflecting mirrors inscribed on the core of the fiber using a femtosecond-laser manufacturing process. The manufacturing process makes the sensor thermally stable and robust for embedded applications. The sensor can withstand very high temperatures of up to 850 °C. The temperature and strain sensitivities of embedded IFPI sensor were measured to be 1.4 pm/μepsilon and 0.6 pm/μepsilon respectively.

Relationship between the mechanical properties of epoxy/PMMA-b-PnBA-b-PMMA block copolymer blends and their three-dimensional nanostructures

Directory of Open Access Journals (Sweden)

H. Kishi

2017-10-01

Full Text Available Nanostructures of diglycidyl ether of bisphenol-A epoxy/poly(methyl methacrylate-b-poly(n-butyl acrylate-b-poly(methyl methacrylate (PMMA-b-PnBA-b-PMMA triblock copolymer (BCP blends were studied in relation to their mechanical properties. Three types of self-assembled nanostructures, such as spheres, random cylinders, and curved lamella, were controlled in phenol novolac-cured epoxy blends with a wide range of BCP content. Three types of nanostructures were observed using two-dimensional and three-dimensional transmission electron microscopy (TEM. The 3D-TEM, dynamic viscoelastic analyses, and theoretical model on the elastic modulus clarified that the spheres and the random cylinders, consisted of epoxy-immiscible PnBA phases, were discontinuously dispersed in the epoxy matrix. In contrast, the curved lamella formed co-continuous nanostructure, in which both the PnBA and epoxy phases formed continuous channels. The fracture toughness (critical strain energy release rate, GIC and the flexural moduli of elasticity (E of the cured blends were evaluated for various amounts of BCP content. The highest GIC was obtained from the random cylindrical nanostructured blends in the three types of nanostructures with the same PnBA content. The lowest E was obtained for the curved lamella with co-continuous nanostructures. The details of deformation and fracture events were observed using optical and electron microscopy, and the mechanical properties are discussed in relation to the nanostructures.

Strong composition dependence of adhesive properties of ultraviolet curing adhesives with modified acrylates

Science.gov (United States)

Feng, Yefeng; Li, Yandong; Wang, Fupeng; Peng, Cheng; Xu, Zhichao; Hu, Jianbing

2018-05-01

Ultraviolet (UV) curable adhesives have been widely researched in fields of health care and electronic components. UV curing systems with modified acrylic ester prepolymers have been frequently employed. In order to clarify composition dependence of adhesive properties of adhesives containing modified acrylates, in this work, several UV curing adhesives bearing urethane and epoxy acrylates were designed and fabricated. The effects of prepolymer, diluent, feed ratio, initiator and assistant on adhesive performances were investigated. This work might offer a facile route to gain promising high-performance UV curable adhesives with desired adhesive traits through regulating their compositions.

Beam radiation curing of adhesives for flocking on heat-sensitive substrates

International Nuclear Information System (INIS)

Nablo, S.V.; Fussa, A.D.

1979-01-01

A process is described for curing the adhesive used to hold flock fiber material to a heat-sensitive substrate consisting of temperature-sensitive plastic, natural fibers, wood, paper, or paper-foil laminates. An electron-curable adhesive layer (acrylic, epoxy, epoxy esters, acrylic latex, or urethane) a few mils thick is applied to the substrate and a layer of texturing material is attached to the adhesive layer with fibers substantially perpendicular to the layer. The assembly of substrate and adhesively secured material is passed at a rate of about 20 to 80 meters per minute under an unscanned electron curtain beam which possesses an energy of 150 keV +- 30 percent and delivers an electron dose of 2 megarads +- 50 percent to the adhesive layer. (LL)

Effects of the curing pressure on the torsional fatigue characteristics of adhesively bonded joints

International Nuclear Information System (INIS)

Hwang, Hui Yun; Kim, Byung Jung; Lee, Dai Gil

2004-01-01

Adhesive joints have been widely used for fastening thin adherends because they can distribute the load over a larger area than mechanical joints, require no hole, add very little weight to the structure and have superior fatigue resistance. However, the fatigue characteristics of adhesive joints are much affected by applied pressure during curing operation because actual curing temperature is changed by applied pressure and the adhesion characteristics of adhesives are very sensitive to manufacturing conditions. In this study, cure monitoring and torsional fatigue tests of adhesive joints with an epoxy adhesive were performed in order to investigate the effects of the applied pressure during curing operation. From the experiments, it was found that the actual curing temperature increased as the applied pressure increased, which increased residual thermal stress in the adhesive layer. Therefore, the fatigue life decreased as the applied pressure increased because the mean stress during fatigue tests increased due to the residual thermal stress

Improving Fracture Toughness of Epoxy Nanocomposites by Silica Nanoparticles

Directory of Open Access Journals (Sweden)

Seyed Reza Akherati Sany

2017-04-01

Full Text Available An epoxy resin was modified by silica nanoparticles and cured with an anhydride. The particles with different batches of 12, 20, and 40 nm sizes were each distributed into the epoxy resin ultrasonically. Electron microscopy images showed that the silica particles were well dispersed throughout the resin. Tensile test results showed that Young’s modulus and tensile strength increased with the volume fraction and surface area of the silica particles. The simultaneous use of two average sizes of 20 and 40 nm diameter silica particles still increased these mechanical properties but other combinations of silica particles were unsuccessful. A three-point bending test on each pre-cracked specimen was performed to measure the mode I fracture toughness energy. The fracture energy increased from 283 J/m2 for the unmodified epoxy to about 740 J/m2 for the epoxy with 4.5 wt% of 12 nm diameter silica nanoparticles. The fracture energy of smaller particles was greater because of their higher surface to volume ratio. The fracture energy results showed also that the combined nanoparticles has a synergic effect on the fracture toughness of nanocomposites. Simultaneous use of 10 and 20 nm particles increased the fracture energy to about 770 J/m2. Finally, crack-opening displacement was calculated and found to be in the range of several micrometers which was much larger than the sizes of particles studied. Thus, the toughening mechanisms of crack pinning and crack deflection have a negligible effect on improvement of toughness, nevertheless, the plastic deformation and plastic void growth are dominant mechanisms in epoxy toughening by nanoparticles.

Epoxy Adhesives for Stator Magnet Assembly in Stirling Radioisotope Generators (SRG)

Science.gov (United States)

Cater, George M.

2004-01-01

As NASA seeks to fulfill its goals of exploration and understanding through missions planned to visit the moons of Saturn and beyond, a number of challenges arise from the idea of deep space flight. One of the first problems associated with deep space travel is electrical power production for systems on the spacecraft. Conventional methods such as solar power are not practical because efficiency decreases substantially as the craft moves away from the Sun. The criterion for power generation during deep space missions are very specific, the main points requiring high reliability, low mass, minimal vibration and a long lifespan. A Stirling generator, although fairly old in concept, is considered to be a potential solution for electrical power generation for deep space flight. A Stirling generator works on the same electromagnetic principles of a standard generator, using the linear motion of the alternator through the stationary stator which produces electric induction. The motion of the alternator, however, is produced by the heating and cooling dynamics of pressurized gases. Essentially heating one end and cooling another of a contained gas will cause a periodic expansion and compression of the gas from one side to the other, which a displacer translates into linear mechanical motion. NASA needs to confirm that the materials used in the generator will be able to withstand the rigors of space and the life expectancy of the mission. I am working on the verification of the epoxy adhesives used to bond magnets to the steel lamination stack to complete the stator; in terms of in-service performance and durability under various space environments. Understanding the proper curing conditions, high temperature properties, and degassing problems as well as production difficulties are crucial to the long term success of the generator. system and steel substrate used in the stator. To optimize the curing conditions of the epoxies, modulated differential scanning calorimetry

The Effects of UV Light on the Chemical and Mechanical Properties of a Transparent Epoxy-Diamine System in the Presence of an Organic UV Absorber

Directory of Open Access Journals (Sweden)

Saeid Nikafshar

2017-02-01

Full Text Available Despite several excellent properties including low shrinkage, good chemical resistance, curable at low temperatures and the absence of byproducts or volatiles, epoxy resins are susceptible to ultra violet (UV damage and their durability is reduced substantially when exposed to outdoor environments. To overcome this drawback, UV absorbers have been usually used to decrease the rate of UV degradation. In this present study, the effects of UV light on the chemical, mechanical and physical properties of cured epoxy structure, as well as the effect of an organic UV absorber, Tinuvin 1130, on the epoxy properties were investigated. Chemical changes in a cured epoxy system as a result of the presence and absence of Tinuvin 1130 were determined using Fourier transform infrared spectroscopy (FT-IR analyses. The effect of Tinuvin 1130 on the surface morphology of the epoxy systems was also investigated by scanning electron microscopy (SEM imaging. Additionally, the glass transition temperatures (Tg before and during UV radiation were measured. After an 800 h UV radiation, mechanical test results revealed that the lack of the UV absorber can lead to a ~30% reduction in tensile strength. However, in the presence of Tinuvin 1130, the tensile strength was reduced only by ~11%. It was hypothesized that the use of Tinuvin 1130, as an organic UV absorber in the epoxy-amine system, could decrease the undesirable effects, arising from exposure to UV light.

Influence of the reaction stoichiometry on the mechanical and thermal properties of SWCNT-modified epoxy composites

International Nuclear Information System (INIS)

Ashrafi, Behnam; Johnston, Andrew; Martinez-Rubi, Yadienka; Kingston, Christopher T; Simard, Benoit; Khoun, Lolei; Yourdkhani, Mostafa; Hubert, Pascal

2013-01-01

Previous studies suggest that carbon nanotubes (CNTs) have a considerable influence on the curing behavior and crosslink density of epoxy resins. This invariably has an important effect on different thermal and mechanical properties of the epoxy network. This work focuses on the important role of the epoxy/hardener mixing ratio on the mechanical and thermal properties of a high temperature aerospace-grade epoxy (MY0510 Araldite as an epoxy and 4,4′-diaminodiphenylsulfone as an aromatic hardener) modified with single-walled carbon nanotubes (SWCNTs). The effects of three different stoichiometries (stoichiometric and off-stoichiometric) on various mechanical and thermal properties (fracture toughness, tensile properties, glass transition temperature) of the epoxy resin and its SWCNT-modified composites were obtained. The results were also supported by Raman spectroscopy and scanning electron microscopy (SEM). For the neat resin, it was found that an epoxy/hardener molar ratio of 1:0.8 provides the best overall properties. In contrast, the pattern in property changes with the reaction stoichiometry was considerably different for composites reinforced with unfunctionalized SWCNTs and reduced SWCNTs. A comparison among composites suggests that a 1:1 molar ratio considerably outperforms the other two ratios examined in this work (1:0.8 and 1:1.1). This composition at 0.2 wt% SWCNT loading provides the highest overall mechanical properties by improving fracture toughness, ultimate tensile strength and ultimate tensile strain of the epoxy resin by 40%, 34%, 54%, respectively. (paper)

Lap shear strength of selected adhesives (epoxy, varnish, B-stage glass cloth) in liquid nitrogen and at room temperature

International Nuclear Information System (INIS)

Froelich, K.J.; Fitzpatrick, C.M.

1976-12-01

The adhesives included several epoxy resins, a varnish, and a B-stage glass cloth (a partially cured resin in a fiberglass cloth matrix). Several parameters critical to bond strength were varied: adhesive and adherend differences, surface preparation, coupling agents, glass cloth, epoxy thickness, fillers, and bonding pressure and temperature. The highest lap shear strengths were obtained with the B-shear glass cloth at both liquid nitrogen and room temperatures with values of approximately 20 MPa (3000 psi) and approximately 25.5 MPa (3700 psi) respectively

Properties of halloysite nanotube-epoxy resin hybrids and the interfacial reactions in the systems

Energy Technology Data Exchange (ETDEWEB)

Liu Mingxian; Guo Baochun; Du Mingliang; Cai Xiaojia; Jia Demin [Department of Polymer Materials and Engineering, South China University of Technology, Guangzhou 510640 (China)

2007-11-14

A naturally occurred microtubullar silicate, halloysite nanotubes (HNTs), was co-cured with epoxy/cyanate ester resin to form organic-inorganic hybrids. The coefficient of thermal expansion (CTE) of the hybrids with low HNT concentration was found to be substantially lower than that of the plain cured resin. The moduli of the hybrids in the glassy state and rubbery state were significantly higher than those for the plain cured resin. The dispersion of HNTs in the resin matrix was very uniform as revealed by the transmission electron microscopy (TEM) results. The interfacial reactions between the HNTs and cyanate ester (CE) were revealed by the results of Fourier transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS). The substantially increased properties of the hybrids were attributed to the covalent bonding between the nanotubes and the matrix.

Properties of halloysite nanotube-epoxy resin hybrids and the interfacial reactions in the systems

International Nuclear Information System (INIS)

Liu Mingxian; Guo Baochun; Du Mingliang; Cai Xiaojia; Jia Demin

2007-01-01

A naturally occurred microtubullar silicate, halloysite nanotubes (HNTs), was co-cured with epoxy/cyanate ester resin to form organic-inorganic hybrids. The coefficient of thermal expansion (CTE) of the hybrids with low HNT concentration was found to be substantially lower than that of the plain cured resin. The moduli of the hybrids in the glassy state and rubbery state were significantly higher than those for the plain cured resin. The dispersion of HNTs in the resin matrix was very uniform as revealed by the transmission electron microscopy (TEM) results. The interfacial reactions between the HNTs and cyanate ester (CE) were revealed by the results of Fourier transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS). The substantially increased properties of the hybrids were attributed to the covalent bonding between the nanotubes and the matrix

Mechanical properties and environmental effects of epoxy resins in the neat state and in composites

International Nuclear Information System (INIS)

Yang, C.M.P.

1984-01-01

The dynamic mechanical properties of graphite fiber reinforced, epoxy matrix composite laminates subjected to loading perpendicular to the plane of lamination and of neat epoxy resin are reported. The centrosymmetric deformation (CSD) test geometry provides an accurate and convenient test mode for the study of the viscoelastic behavior of very stiff graphite-epoxy laminates. It is found that the in-phase and out-of-phase stiffness superpose to form master curves covering a frequency range of 12 decades. By a suitable scaling procedure of the master curves, it is found that the in-phase stiffness has the same shape and the out-of-phase has the same dispersion for all laminates irrespective of the stacking sequence. The dispersion characteristics of in-situ and neat resin epoxy were nearly identical, but with the neat resin having a lower glass-transition temperature. The graphite/epoxy composites and neat resin epoxy have been shown to be sensitive to hygrothermal environment. For postcured specimens the plasticization and inhomogeneous swelling effects due to the moisture absorbed are found to be reversible, in the sense that the initially dry properties of the laminate are recovered after redrying the wet specimen. On the other hand, for as cured specimens, the plasticization and inhomogeneous swelling effects are found to be irreversible under the same hygrothermal environment

Influence of particle surface properties on the dielectric behavior of silica/epoxy nanocomposites

International Nuclear Information System (INIS)

Cheng Lihong; Zheng Liaoying; Li Guorong; Zeng Jiangtao; Yin Qingrui

2008-01-01

Silica/epoxy composites have been widely used in functional electric device applications. Silica nanoparticles, both unmodified and modified with the coupling agent KH-550, were used to prepare epoxy composites. Dielectric measurements showed that nanocomposites exhibit a higher dielectric constant than the control sample, and had more obvious dielectric relaxation characteristics. Results showed that particle surface properties have a profound effect on the dielectric behavior of the nanocomposites. These characteristics are attributed to the local ununiformity of the microstructure caused by the large interface area and the interaction between the filler and the matrix. This phenomenon is explained in terms of prolonging chemical chains created during the curing process. The mechanism is discussed with measurements of X-ray diffraction (XRD) and Fourier transform infrared (FTIR)

Epoxy cracking in the epoxy-impregnated superconducting winding: nonuniform dissipation of stress energy in a wire-epoxy matrix model

International Nuclear Information System (INIS)

Tsukamoto, O.; Iwasa, Y.

1985-01-01

The authors present the epoxy-crack-induced temperature data of copper wires imbedded in wire-epoxy resin composite model at 4.2 K. The experimental results show that the epoxy-crackinduced temperature rise is higher in the copper wires than in the epoxy matrix, indicating that in stress-induced wire-epoxy failure, stress energy stored in the wire-epoxy matrix is preferrentially dissipated in the wire. A plausible mechanism of the nonuniform dissipation is presented

Influence of surface modification of halloysite nanotubes on their dispersion in epoxy matrix: Mesoscopic DPD simulation

Science.gov (United States)

Komarov, P.; Markina, A.; Ivanov, V.

2016-06-01

The problems of constructing of a meso-scale model of composites based on polymers and aluminosilicate nanotubes for prediction of the filler's spatial distribution at early stages of material formation have been considered. As a test system for the polymer matrix, the mixture of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate as epoxy resin monomers and 4-methylhexahydrophthalic anhydride as curing agent has been used. It is shown that the structure of a mixture of uncured epoxy resin and nanotubes is (mainly) determined by the surface functionalization of nanotubes. The results indicate that only nanotubes with maximum functionalization can preserve a uniform distribution in space.

Corrosion Protection of Phenolic-Epoxy/Tetraglycidyl Metaxylediamine Composite Coatings in a Temperature-Controlled Borax Environment

Science.gov (United States)

Xu, Wenhua; Wang, Zhenyu; Han, En-Hou; Liu, Chunbo

2017-12-01

The failure behavior for two kinds of phenolic-epoxy/tetraglycidyl metaxylediamine composite coatings in 60 °C borax aqueous solution was evaluated using electrochemical methods (EIS) combined with scanning electron microscopy, confocal laser scanning microscope, water immersion test, and Raman spectrum. The main focus was on the effect of curing agent on the corrosion protection of coatings. Results revealed that the coating cured by phenolic modified aromatic amine possessed more compact cross-linked structure, better wet adhesion, lower water absorption (0.064 mg h-1 cm-2) and its impedance values was closed to 108 Ω cm2 after immersion for 576 h, while the coating cured by modified aromatic ring aliphatic amine was lower than 105 Ω cm2. The corrosion mechanism of the two coatings is discussed.

Modification of a Phenolic Resin with Epoxy- and Methacrylate-Functionalized Silica Sols to Improve the Ablation Resistance of Their Glass Fiber-Reinforced Composites

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Yu Hu

2014-01-01

Full Text Available Functionalized silica sols were obtained by the hydrolytic condensation of (γ-methacryloxypropyltrimethoxysilane (MPMS, (γ-glycidyloxypropyltrimethoxysilane (GPMS and tetraethoxysilane (TEOS. Three different sols were obtained: MPS (derived from MPMS and TEOS, GPS-MPS (derived from GPMS, MPMS and TEOS, and GPSD (derived from GPMS, TEOS and diglycidyl ether of bisphenol A, DGEBA. These silica sols were mixed with a phenolic resin (PR. Ethylenediamine was used as a hardener for epoxy-functionalized sols and benzoyl peroxide was used as an initiator of the free-radical polymerization of methacrylate-functionalized silica sols. Glass fiber-reinforced composites were obtained from the neat PR and MPS-PR, GPS-MPS-PR and GPSD-PR. The resulting composites were evaluated as ablation resistant materials in an acetylene-oxygen flame. A large increase in the ablation resistance was observed when the PR was modified by the functionalized silica sols. The ablation resistance of the composites decreased as follows: GPSD-PR > MPS-PR > GPS-MPS-PR > PR.

Determining the effects of thermal conductivity on epoxy molds using profiled cooling channels with metal inserts

International Nuclear Information System (INIS)

Altaf, Khurram; Rani, Abdul Ahmad Majdi; Ahmad, Faiz; Baharom, Masri; Raghavan, Vijay R.

2016-01-01

Polymer injection molds are generally manufactured with metallic materials, such as tool steel, which provide reliable working of molds and extended service life. The manufacture of injection molds with steel is a prolonged process because of the strength of steel. For a short prototype production run, one of the suitable choices could be the use of aluminum-filled epoxy material, which can produce a functional mold in a short time as compared with a conventionally machined tool. Aluminum-filled epoxy tooling is a good choice for short production runs for engineering applications, yet works best for relatively simple shapes. The advantages in relation to the fabrication of injection molds with epoxy-based materials include time saving in producing the mold, epoxy curing at ambient temperature, and ease of machining and post processing. Nevertheless, one major drawback of epoxy material is its poor thermal conductivity, which results in a relatively longer cooling time for epoxy injection molds. This study investigates some of the innovative ideas for enhancing the thermal conductivity for epoxy molds. The basic concept behind these ideas was to embed a highly thermally conductive metal insert within the mold between cavities with an innovative design of cooling channels called profiled cooling channels. This technique will increase the effective thermal conductivity of the epoxy mold, leading to the reduction in cooling time for the injection molded polymer part. Experimental analysis conducted in the current study also verified that the mold with profiled cooling channels and embedded metal insert has significantly reduced the cooling time

Determining the effects of thermal conductivity on epoxy molds using profiled cooling channels with metal inserts

Energy Technology Data Exchange (ETDEWEB)

Altaf, Khurram; Rani, Abdul Ahmad Majdi; Ahmad, Faiz; Baharom, Masri [Mechanical Engineering Dept., Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Perak (Malaysia); Raghavan, Vijay R. [OYL Manufacturing, Sungai Buloh (Malaysia)

2016-11-15

Polymer injection molds are generally manufactured with metallic materials, such as tool steel, which provide reliable working of molds and extended service life. The manufacture of injection molds with steel is a prolonged process because of the strength of steel. For a short prototype production run, one of the suitable choices could be the use of aluminum-filled epoxy material, which can produce a functional mold in a short time as compared with a conventionally machined tool. Aluminum-filled epoxy tooling is a good choice for short production runs for engineering applications, yet works best for relatively simple shapes. The advantages in relation to the fabrication of injection molds with epoxy-based materials include time saving in producing the mold, epoxy curing at ambient temperature, and ease of machining and post processing. Nevertheless, one major drawback of epoxy material is its poor thermal conductivity, which results in a relatively longer cooling time for epoxy injection molds. This study investigates some of the innovative ideas for enhancing the thermal conductivity for epoxy molds. The basic concept behind these ideas was to embed a highly thermally conductive metal insert within the mold between cavities with an innovative design of cooling channels called profiled cooling channels. This technique will increase the effective thermal conductivity of the epoxy mold, leading to the reduction in cooling time for the injection molded polymer part. Experimental analysis conducted in the current study also verified that the mold with profiled cooling channels and embedded metal insert has significantly reduced the cooling time.

Influência da Estrutura química do co-monômero nas propriedades mecânicas e adesivas de redes epoxídicas Influence of chemical structure of co-monomer on mechanical and adhesive properties of epoxy networks

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Filiberto González Garcia

2010-06-01

Full Text Available As propriedades mecânicas e adesivas de formulações à base do prepolímero do éter diglicidílico do bisfenol A curadas com várias aminas alifáticas foram avaliadas no estado vítreo. Ensaios de impacto do tipo Izod e compressão uniaxial foram usados para determinar a energia de impacto, o módulo de elasticidade e a tensão de escoamento. Ensaios de adesão usando substrato de aço para uniões de simples sobreposição, descascamento em T, e de impacto foram realizados. O melhor comportamento mecânico e adesivo dos polímeros foi obtido quando existe alta flexibilidade entre as cadeias e/ou alto módulo elástico. O sistema DGEBA/AEP mostrou as melhores propriedades adesivas, alta flexibilidade e maior energia de impacto nos ensaios mecânicos. No entanto, apresentou baixo modulo elástico e tensão de escoamento. Além disso, exibe incremento nos ensaios de adesão de descascamento em T e nas uniões de impacto, por outro lado, apresenta uma redução na resistência das uniões de simples sobreposição.The mechanical and adhesive properties of epoxy formulations based on diglycidyl ether of bisphenol A cured with various aliphatic amines were evaluated in the glass state. Impact and uniaxial compression tests were used to determine the impact energy, elastic modulus and yield stress, respectively. The adhesion tests were carried out in steel-steel joints using single lap shear, T-peel and impact adhesive joints geometry. The better mechanical and adhesive behavior of the networks is obtained for highly flexible chains and/or a high elastic modulus. The 1-(2-aminoethylpiperazine epoxy network presents the best adhesive properties, high flexibility, and the largest impact energy. However, it possesses low elastic modulus and yield stress. Also, it exhibits increased peel strength and impact energy with a reduction in the lap shear strength.

Enhancement of mechanical and electrical properties of continuous-fiber-reinforced epoxy composites with stacked graphene.

Science.gov (United States)

Naveh, Naum; Shepelev, Olga; Kenig, Samuel

2017-01-01

Impregnation of expandable graphite (EG) after thermal treatment with an epoxy resin containing surface-active agents (SAAs) enhanced the intercalation of epoxy monomer between EG layers and led to further exfoliation of the graphite, resulting in stacks of few graphene layers, so-called "stacked" graphene (SG). This process enabled electrical conductivity of cured epoxy/SG composites at lower percolation thresholds, and improved thermo-mechanical properties were measured with either Kevlar, carbon or glass-fiber-reinforced composites. Several compositions with SAA-modified SG led to higher dynamic moduli especially at high temperatures, reflecting the better wetting ability of the modified nanoparticles. The hydrophilic/hydrophobic nature of the SAA dictates the surface energy balance. More hydrophilic SAAs promoted localization of the SG at the Kevlar/epoxy interface, and morphology seems to be driven by thermodynamics, rather than the kinetic effect of viscosity. This effect was less obvious with carbon or glass fibers, due to the lower surface energy of the carbon fibers or some incompatibility with the glass-fiber sizing. Proper choice of the surfactant and fine-tuning of the crosslink density at the interphase may provide further enhancements in thermo-mechanical behavior.

Enhancement of mechanical and electrical properties of continuous-fiber-reinforced epoxy composites with stacked graphene

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Naum Naveh

2017-09-01

Full Text Available Impregnation of expandable graphite (EG after thermal treatment with an epoxy resin containing surface-active agents (SAAs enhanced the intercalation of epoxy monomer between EG layers and led to further exfoliation of the graphite, resulting in stacks of few graphene layers, so-called “stacked” graphene (SG. This process enabled electrical conductivity of cured epoxy/SG composites at lower percolation thresholds, and improved thermo-mechanical properties were measured with either Kevlar, carbon or glass-fiber-reinforced composites. Several compositions with SAA-modified SG led to higher dynamic moduli especially at high temperatures, reflecting the better wetting ability of the modified nanoparticles. The hydrophilic/hydrophobic nature of the SAA dictates the surface energy balance. More hydrophilic SAAs promoted localization of the SG at the Kevlar/epoxy interface, and morphology seems to be driven by thermodynamics, rather than the kinetic effect of viscosity. This effect was less obvious with carbon or glass fibers, due to the lower surface energy of the carbon fibers or some incompatibility with the glass-fiber sizing. Proper choice of the surfactant and fine-tuning of the crosslink density at the interphase may provide further enhancements in thermo-mechanical behavior.

A contribution from dielectric analysis to the study of the formation of multi-wall carbon nanotubes percolated networks in epoxy resin under an electric field

International Nuclear Information System (INIS)

Risi, Celso L.S.; Hattenhauer, Irineu; Ramos, Airton; Coelho, Luiz A.F.; Pezzin, Sérgio H.

2015-01-01

The formation of percolation networks in epoxy matrix nanocomposites reinforced with multi-wall carbon nanotubes (MWNT) during the curing process, at different MWNT contents, was studied by using a parallel plate cell subjected to a 300 V/cm AC electric field at 1 kHz. The percolation was verified by the electrical current output measured during and after the resin curing. The behavior of electric dipoles was characterized by impedance spectroscopy and followed the Debye first order dispersion model, by which an average relaxation time of 6.0 × 10 −4 s and a cut-off frequency of 1.7 kHz were experimentally found. By applying the theory of percolation, a critical probability, p c , equal to 0.038 vol% and an exponent of conductivity of 2.0 were found. Both aligned and random samples showed dipole relaxation times typical of interfacial and/or charge-hopping polarization, while the permittivity exhibited an exponential decrease with frequency. This behavior can be related to the increased ability to trap electrical charges due to the formation of the carbon nanotubes network. Optical and electron microscopies confirm the theoretical prediction that the application of an electric field during cure helps the process of MWNT debundling in epoxy resin. - Highlights: • We report the formation of percolating networks of MWNTs under AC electric field. • MWNT/epoxy dielectric properties were measured by impedance spectroscopy. • Lower percolation thresholds were obtained for composites with aligned CNTs. • Application of AC electric field helps the debundling of CNTs. • CNT/Epoxy with percolated networks presents interfacial and hopping polarizations

Effect of an organoclay on the reaction-induced phase-separation in a dynamically asymmetric epoxy/PCL system

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J. Rotrekl

2013-12-01

Full Text Available The addition of layered silicates can significantly affect the phase behaviour of both immiscible thermoplastic blends and partially miscible thermoset systems that undergo reaction-induced phase separation (RIPS during curing. This study focuses on the phase behaviour of polycaprolactone (PCL/epoxy in the presence of organically modified montmorillonite (oMMT. Due to the high dynamic asymmetry caused by the differences in the molecular weights and viscosities of the PCL and the uncured epoxy, the critical point is localised at low PCL concentrations, as indicated by the pseudophase diagram. The addition of oMMT to the system led to the marked shift of the critical point towards higher concentrations of PCL, with an increase in the oMMT content occurring as a consequence of the preferential localisation of the clay in the epoxy phase, making this phase more dynamically slow. Significant changes in morphology, including phase inversion of the PCL/epoxy systems caused by the presence of oMMT, were recorded for PCL concentrations ranging from 10 to 30%.

Organic materials for semiconductor. Epoxy molding compound for IC encapsulation; Handotai kanren no yuki zairyo. Handotai fushiyo epoxy seikei zairyo ni tsuite

Energy Technology Data Exchange (ETDEWEB)

Kusuhara, A. [Sumitomo Bakelite Co. Ltd., Tokyo (Japan)

1998-11-05

This paper describes organic materials for semiconductor. Based on the composition and raw material, typical materials are epoxy resins, curing agents including phenol-novolak resins, fillers including silica and alumina, flame retardants including brominated epoxy resin and antimony oxide, hardening accelerators including amine compounds and phosphorus compounds, coupling agents including silane compounds and titanate compounds, and the others including colorants and mold lubricants. Raw materials are heated and kneaded after mixing, and produced as tablets after cooling and crushing. Recently, the packages have changed from insertion type to surface mounting type for the small thin IC package and for improving the efficiency of soldering during the incorporation of IC package on the print circuit substrate. High temperature of 260degC has been employed from the conventional limit of 100degC. Reduction of water absorption, improvement of adhesion, reduction of thermal expansion coefficient, and reduction of elastic modulus during heating are promoted for avoiding the peeling and cracking due to the sudden evaporation of adsorbed moisture. This paper also describes the organic materials for BGA. 10 figs., 4 tabs.

Surface Modifier-Free Organic-Inorganic Hybridization To Produce Optically Transparent and Highly Refractive Bulk Materials Composed of Epoxy Resins and ZrO2 Nanoparticles.

Science.gov (United States)

Enomoto, Kazushi; Kikuchi, Moriya; Narumi, Atsushi; Kawaguchi, Seigou

2018-04-25

Surface modifier-free hybridization of ZrO 2 nanoparticles (NPs) with epoxy-based polymers is demonstrated for the first time to afford highly transparent and refractive bulk materials. This is achieved by a unique and versatile hybridization via the one-pot direct phase transfer of ZrO 2 NPs from water to epoxy monomers without any aggregation followed by curing with anhydride. Three types of representative epoxy monomers, bisphenol A diglycidyl ether (BADGE), 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexane carboxylate (CEL), and 1,3,5-tris(3-(oxiran-2-yl)propyl)-1,3,5-triazinane-2,4,6-trione (TEPIC), are used to produce transparent viscous dispersions. The resulting ZrO 2 NPs are thoroughly characterized using dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), and solid-state 13 C CP/MAS NMR measurements. The results from DLS and TEM analyses indicate nanodispersion of ZrO 2 into epoxy monomers as a continuous medium. A surface modification mechanism and the binding fashion during phase transfer are proposed based on the FT-IR and solid-state 13 C CP/MAS NMR measurements. Epoxy-based hybrid materials with high transparency and refractive index are successfully fabricated by heat curing or polymerizing a mixture of monomers containing epoxy-functionalized ZrO 2 NPs and methylhexahydrophthalic anhydride in the presence of a phosphoric catalyst. The TEM and small-angle X-ray scattering measurements of the hybrids show a nanodispersion of ZrO 2 in the epoxy networks. The refractive index at 594 nm ( n 594 ) increases up to 1.765 for BADGE-based hybrids, 1.667 for CEL-based hybrids, and 1.693 for TEPIC-based hybrids. Their refractive indices and Abbe's numbers are quantitatively described by the Lorentz-Lorenz effective medium expansion theory. Their transmissivity is also reasonably explained using Fresnel refraction, Rayleigh scattering, and the Lambert-Beer theories. This surface modifier-free hybridization

Comparison of the Nanostructure and Mechanical Performance of Highly Exfoliated Epoxy-Clay Nanocomposites Prepared by Three Different Protocols

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Fatemeh Shiravand

2014-05-01

Full Text Available Three different protocols for the preparation of polymer layered silicate nanocomposites based upon a tri-functional epoxy resin, triglycidyl para-amino phenol (TGAP, have been compared in respect of the cure kinetics, the nanostructure and their mechanical properties. The three preparation procedures involve 2 wt% and 5 wt% of organically modified montmorillonite (MMT, and are: isothermal cure at selected temperatures; pre-conditioning of the resin-clay mixture before isothermal cure; incorporation of an initiator of cationic homopolymerisation, a boron tri-fluoride methyl amine complex, BF3·MEA, within the clay galleries. It was found that features of the cure kinetics and of the nanostructure correlate with the measured impact strength of the cured nanocomposites, which increases as the degree of exfoliation of the MMT is improved. The best protocol for toughening the TGAP/MMT nanocomposites is by the incorporation of 1 wt% BF3·MEA into the clay galleries of nanocomposites containing 2 wt% MMT.

Comparison of the Nanostructure and Mechanical Performance of Highly Exfoliated Epoxy-Clay Nanocomposites Prepared by Three Different Protocols.

Science.gov (United States)

Shiravand, Fatemeh; Hutchinson, John M; Calventus, Yolanda; Ferrando, Francesc

2014-05-30

Three different protocols for the preparation of polymer layered silicate nanocomposites based upon a tri-functional epoxy resin, triglycidyl para -amino phenol (TGAP), have been compared in respect of the cure kinetics, the nanostructure and their mechanical properties. The three preparation procedures involve 2 wt% and 5 wt% of organically modified montmorillonite (MMT), and are: isothermal cure at selected temperatures; pre-conditioning of the resin-clay mixture before isothermal cure; incorporation of an initiator of cationic homopolymerisation, a boron tri-fluoride methyl amine complex, BF₃·MEA, within the clay galleries. It was found that features of the cure kinetics and of the nanostructure correlate with the measured impact strength of the cured nanocomposites, which increases as the degree of exfoliation of the MMT is improved. The best protocol for toughening the TGAP/MMT nanocomposites is by the incorporation of 1 wt% BF₃·MEA into the clay galleries of nanocomposites containing 2 wt% MMT.

Separação de fases induzida por meio de reação química no sistema éter diglicidílico do bisfenol A e piperidina com poli(metacrilato de metila Phase separation induced by chemical reaction in the system of diglycidyl ether of bisphenol A and piperidine with poly(methyl methacrylate

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Filiberto González Garcia

2003-12-01

Full Text Available O comportamento da separação de fases e da gelificação do sistema epoxídico, constituído pelo éter diglicidílico do bisfenol A (DGEBA e a piperidina, modificado com poli(metacrilato de metila (PMMA, foi estudado na faixa de temperatura de 60 °C - 120 °C. A concentração de PMMA e a temperatura de cura causam mudanças significativas na morfologia gerada. A massa molecular de PMMA provoca ligeiras mudanças para a observação da separação de fases e não afeta a velocidade da reação. O sistema modificado com PMMA mostra o efeito de retardação cinético e a velocidade de separação de fases é maior que a velocidade de polimerização.The phase separation and gelification behavior of epoxy system based on diglycidyl ether of bisphenol-A (DGEBA and piperidine modified with poly(methyl methacrylate (PMMA were studied in the range between 60 °C and 120 °C. The morphology is influenced by the PMMA content in the blend and also by the cure temperature. The molecular weight of PMMA provokes slight changes on cloud point and does not affect the reaction rate. The systems modified by PMMA exhibited kinetic retardation effect but the cloud point rate was higher than the polymerization rate.

Applications of Blue Light-curing Acrylic Resin to Forensic Sample Preparation and Microtomy.

Science.gov (United States)

Groves, Ethan; Palenik, Christopher S

2016-03-01

This study discusses the results of an evaluation of a one-part blue light-curing acrylic resin for embedding trace evidence prior to the preparation of thin sections with a microtome. Through a comparison to several epoxy resins, the physical properties relevant to both trace evidence examination and analytical microscopy in general, including as viscosity, clarity, color, hardness, and cure speed, were explored. Finally, thin sections from paint samples embedded in this acrylic resin were evaluated to determine if, through smearing or impregnation, the resin contributed to the infrared spectra. The results of this study show that blue light-curing acrylic resins provide the desired properties of an embedding medium, generate high-quality thin sections, and can significantly simplify the preparation of paint chips, fibers and a multitude of other types of microscopic samples in the forensic trace evidence laboratory. © 2015 American Academy of Forensic Sciences.

Biphenyl liquid crystalline epoxy resin as a low-shrinkage resin-based dental restorative nanocomposite.

Science.gov (United States)

Hsu, Sheng-Hao; Chen, Rung-Shu; Chang, Yuan-Ling; Chen, Min-Huey; Cheng, Kuo-Chung; Su, Wei-Fang

2012-11-01

Low-shrinkage resin-based photocurable liquid crystalline epoxy nanocomposite has been investigated with regard to its application as a dental restoration material. The nanocomposite consists of an organic matrix and an inorganic reinforcing filler. The organic matrix is made of liquid crystalline biphenyl epoxy resin (BP), an epoxy resin consisting of cyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (ECH), the photoinitiator 4-octylphenyl phenyliodonium hexafluoroantimonate and the photosensitizer champhorquinone. The inorganic filler is silica nanoparticles (∼70-100 nm). The nanoparticles were modified by an epoxy silane of γ-glycidoxypropyltrimethoxysilane to be compatible with the organic matrix and to chemically bond with the organic matrix after photo curing. By incorporating the BP liquid crystalline (LC) epoxy resin into conventional ECH epoxy resin, the nanocomposite has improved hardness, flexural modulus, water absorption and coefficient of thermal expansion. Although the incorporation of silica filler may dilute the reinforcing effect of crystalline BP, a high silica filler content (∼42 vol.%) was found to increase the physical and chemical properties of the nanocomposite due to the formation of unique microstructures. The microstructure of nanoparticle embedded layers was observed in the nanocomposite using scanning and transmission electron microscopy. This unique microstructure indicates that the crystalline BP and nanoparticles support each other and result in outstanding mechanical properties. The crystalline BP in the LC epoxy resin-based nanocomposite was partially melted during exothermic photopolymerization, and the resin expanded via an order-to-disorder transition. Thus, the post-gelation shrinkage of the LC epoxy resin-based nanocomposite is greatly reduced, ∼50.6% less than in commercialized methacrylate resin-based composites. This LC epoxy nanocomposite demonstrates good physical and chemical properties and good biocompatibility

A self-crosslinking thermosetting monomer with both epoxy and anhydride groups derived from Tung oil fatty acids: Synthesis and properties

Science.gov (United States)

A self-crosslinking compound with epoxy groups and anhydride groups (GEMA) has been successfully synthesized from Tung oil fatty acid by reacting with maleic anhydride via the Diels-Alder reaction. GEMA has very good storage stability and can be cured with trace amounts of tertiary amine. This advan...

Evaluation of mechanical properties of four different carbon/epoxy composites used in aeronautical field

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Jane Maria Faulstich de Paiva

2005-03-01

Full Text Available Four families of carbon fiber reinforced composites (CFRC used in aeronautical industry were evaluated by flexural and interlaminar shear tests. It is also characterized three families of non-conditioned and conditioned CFRC by compression test. The composites were obtained by hand lay-up process in autoclave by using prepregs based on epoxy matrices (F155 and F584 and carbon fiber fabric reinforcements (PW-"Plain Weave" and 8HS-"Eight Harness Satin". The F155-epoxy matrix was cured at 121 °C and the F584-epoxy type at 177 °C. After molding, the laminates were cut in specimens attending the ASTM D790 for the flexural test, the ASTM D2344 for the interlaminar shear test (ILSS and the ASTM D3410 for the compressive test. The compressive tests were performed for testing the specimens before and after hygrothermal conditioning. The results show that the F584-epoxy matrix laminates present higher mechanical properties when compared to the F155-epoxy ones. The shear-tested samples observed by scanning electron microscopy and that ones tested in flexural, analyzed by stereoscopy, revealed that the fractured surfaces present typical aspects. The compressive results show that the hygrothermal conditioning caused the decrease of the compressive strength in, approximately, 8-20% depending on the laminate type. The failure modes of the tested specimens were evaluated showing good agreement with the literature.

Functionalization of Nanodiamond with Four Kinds of Expoxies.

Science.gov (United States)

Ma, Weijia; Liu, Ruojin; Yu, Xiaoyan; Naito, Kimiyoshi; Qu, Xiongwei; Zhang, Qingxin

2017-01-01

In this work, a simple and effective method for the covalent functionalization of nanodiamond (ND) with four epoxies has been developed. After homogenization by mixed acids and thionyl chlorides, the surface of ND was modified with triethylenetetramine (TETA) to possess amine groups, which were used as active points to react with epoxy by ring opening reaction. Four different epoxies used are bifunctional diglycidyl ether of bisphenol-A (DGEBA), trifunctional triglycidyl p-amino phenol (TGAP), tetrafunctional tetraglycidyldiamino diphenylmethane (TGDDM) and bisphenol-A novolac epoxy resin (BAEPN). FT-IR spectra revealed that the epoxy was covalently attached to the ND (ND-g-epoxy). In addition, functionalized ND particles were characterized with WAXD and UV-Vis spectra to confirm the result. The weight gains as a result of the epoxy-functionalized ND were determined by TGA analysis. The ND-g-epoxy particles were better dispersed in common organic solvents and the average diameters were characterized. The better dispersion and of the modified ND were identified from the SEM images.

In-situ monitoring of curing and ageing effects in FRP plates using embedded FBG sensors

Science.gov (United States)

Xian, Guijun; Wang, Chuan; Li, Hui

2010-04-01

In recent years, fiber reinforced polymer (FRP) composites have been widely applied in civil engineering for retrofitting or renewal of existing structures. Since FRP composite may degrade when exposed to severe outdoor environments, a serious concern has been raised on its long term durability. In the present study, fiber Bragg grating (FBG) sensors were embedded in glass-, carbon- and basalt-fiber reinforced epoxy based FRP plates with wet lay-up technology, to in-situ monitor the stain changes in FRPs during the curing, and water immersion and freeze-thaw ageing processes. The study demonstrates that the curing of epoxy resin brings in a slight tension strain (e.g., 10 ~ 30 μɛ) along the fiber direction and a high contraction (e.g., ~ 1100μɛ) in the direction perpendicular to the fibers, mainly due to the resin shrinkage. The cured FRP strips were then subjected to distilled water immersion at 80oC and freeze-thaw cycles from -30°C to 30°C. Remarkable strain changes of FRPs due to the variation of the temperatures during freeze-thaw cycles indicate the potential property degradation from fatigue. The maximum strain change is dependent on the fiber types and directions to the fiber. Based on the monitored strain values with temperature change and water uptake content, CTE (coefficient of thermal expansion) and CME (coefficient of moisture expansion) are exactly determined for the FRPs.

Biocompatible high performance hyperbranched epoxy/clay nanocomposite as an implantable material.

Science.gov (United States)

Barua, Shaswat; Dutta, Nipu; Karmakar, Sanjeev; Chattopadhyay, Pronobesh; Aidew, Lipika; Buragohain, Alak K; Karak, Niranjan

2014-04-01

Polymeric biomaterials are in extensive use in the domain of tissue engineering and regenerative medicine. High performance hyperbranched epoxy is projected here as a potential biomaterial for tissue regeneration. Thermosetting hyperbranched epoxy nanocomposites were prepared with Homalomena aromatica rhizome oil-modified bentonite as well as organically modified montmorillonite clay. Fourier transformed infrared spectroscopy, x-ray diffraction and scanning and transmission electron microscopic techniques confirmed the strong interfacial interaction of clay layers with the epoxy matrix. The poly(amido amine)-cured thermosetting nanocomposites exhibited high mechanical properties like impact resistance (>100 cm), scratch hardness (>10 kg), tensile strength (48-58 MPa) and elongation at break (11.9-16.6%). Cytocompatibility of the thermosets was found to be excellent as evident by MTT and red blood cell hemolytic assays. The nanocomposites exhibited antimicrobial activity against Staphylococcus aureus (ATCC 11632), Escherichia coli (ATCC 10536), Mycobacterium smegmatis (ATCC14468) and Candida albicans (ATCC 10231) strains. In vivo biocompatibility of the best performing nanocomposite was ascertained by histopathological study of the brain, heart, liver and skin after subcutaneous implantation in Wistar rats. The material supported the proliferation of dermatocytes without induction of any sign of toxicity to the above organs. The adherence and proliferation of cells endorse the nanocomposite as a non-toxic biomaterial for tissue regeneration.

Polymerization of epoxy resins studied by positron annihilation

Energy Technology Data Exchange (ETDEWEB)

Suzuki, T. [Radiation Science Center, High Energy Accelerator Research Organization (KEK), Tsukuba (Japan); Hayashi, T. [Fine Chemical Research Lab., Sumitomo Chemical, Tsukuba (Japan); Ito, Y. [Research Center for Nuclear Science and Technology, Univ. of Tokyo (Japan)

2001-04-01

Positron annihilation lifetime spectroscopy (PALS) has been applied to study polymerization of epoxy resins of cresole novolac with a hardener of phenol novolac. PALS uses positrons to probe the microstructure of a nanometer (nm) size. Using PALS polymerization can be followed through three states: powder (monomer), liquid and solid. PALS is a unique method for the detection of intermolecular spaces, hence polymerization was followed from the point of view of free spaces (inter-molecular spaces) between polymer networks. The glass transition temperature (T{sub g}) was determined from the temperature dependence of the positronium (Ps) lifetime. Although Tg determined by PALS is usually lower than that determined by a mechanical analysis (TMA), it was observed that T{sub g} approached the value determined by TMA after long curing. Ps can form bubbles in a liquid, and the surface tension of a mixture of the resin and the hardener was calculated from a simple empirical formula using the Ps lifetime; the resulting value is similar to that of the bisphenol-A epoxy resin. Gelation was observed as an increase in the intensity of Ps and a sharp decrease in the lifetime. (orig.)

Mechanical properties of hybrid SiC/CNT filled toughened epoxy nanocomposite

Science.gov (United States)

Ratim, S.; Ahmad, S.; Bonnia, N. N.; Yahaya, Sabrina M.

2018-01-01

Mechanical properties of epoxy nanocomposites filled single filler have been extensively studied by various researchers. However, there are not much discovery on the behavior of hybrid nanocomposite. In this study, single and hybrid nanocomposites of toughened epoxy filled CNT/SiC nanoparticles were investigated. The hybrid nanocomposites samples were prepared by combining CNT and SiC nanoparticles in toughened epoxy matrix via mechanical stirring method assisted with ultrasonic cavitations. Epoxy resin and liquid epoxidized natural rubber (LENR) mixture were first blend prior to the addition of nanofillers. Then, the curing process of the nanocomposite samples were conducted by compression molding technique at 130°C for 2 hours. The purpose of this study is to investigate the hybridization effect of CNT and SiC nanoparticles on mechanical properties toughened epoxy matrix. The total loading of single and hybrid nanofillers were fixed to 4% volume are 0, 4C, 4S, 3S1C, 2S2C, and 1S3C. Mechanical properties of hybrid composites show that the highest value of tensile strength achieved by 3S1C sample at about 7% increment and falls between their single composite values. Meanwhile, the stiffness of the same sample is significantly increased at about 31% of the matrix. On the other hand, a highest flexural property is obtained by 1S3C sample at about 20% increment dominated by CNT content. However, the impact strength shows reduction trend with the addition of SiC and CNT into the matrix. The hybridization of SiC and CNT show highest value in sample 1S3C at about 3.37 kJ/m2 of impact energy absorbed. FESEM micrograph have confirmed that better distributions and interaction observed between SiC nanoparticles and matrix compared to CNT, which contributed to higher tensile strength and modulus.

The used epoxy matrix in immobilization sludge process of alpha emitter radioactive waste

International Nuclear Information System (INIS)

Walman, E.; Salimin, Z.; Johan, B.

1998-01-01

Immobilization of alpha emitter radioactive waste containing of ion complex of uranyl carbonate on uranium concentration ≤ 50 mg/l has been carried out using epoxy matrix. The first step of process is the coagulation of uranium with 1.3 mole/l of Ca(OH) 2 coagulant concentration on pH 8 to precipitate the calcium uranyl carbonate on uranium concentration ≤ g/l. The immobilization of calcium uranyl carbonate with epoxy matrix was done on variation of the ratio of resin epoxy and hardener of 1 : 1 (giving the maximum value of density and compressive strength), the increasing of precipitate loading capacity give the decreasing of compressive strength of embedded waste. The test of compressive strength and leaching was done for the embedded waste after its curing time using Paul Weber equipment and 7 days immersion of samples in normal water. On the precipitate loading capacity of 70%, the quality of embedded waste still conform to the standard quality value i.e. density 1.2 g/cm 3 , compressive strength 10 kN/cm 2 and there is not any release of radionuclide during leaching test (undetectable).. (author)

Formation of interfacial network structure via photo-crosslinking in carbon fiber/epoxy composites

Directory of Open Access Journals (Sweden)

S. H. Deng

2014-07-01

Full Text Available A series of diblock copolymers (poly(n-butylacrylate-co-poly(2-hydroxyethyl acrylate-b-poly(glycidyl methacrylate ((PnBA-co-PHEA-b-PGMA, containing a random copolymer block PnBA-co-PHEA, were successfully synthesized by atom transfer radical polymerization (ATRP. After being chemically grafted onto carbon fibers, the photosensitive methacrylic groups were introduced into the random copolymer, giving a series of copolymers (poly(n-butylacrylate-co-poly(2-methacryloyloxyethyl acrylate-b-poly(glycidyl methacrylate((PnBA-co-PMEA-b-PGMA. Dynamic mechanical analysis indicated that the random copolymer block after ultraviolet (UV irradiation was a lightly crosslinked polymer and acted as an elastomer, forming a photo-crosslinked network structure at the interface of carbon fiber/epoxy composites. Microbond test showed that such an interfacial network structure greatly improved the cohesive strength and effectively controlled the deformation ability of the flexible interlayer. Furthermore, three kinds of interfacial network structures, i physical crosslinking by H-bonds, ii chemical crosslinking by photopolymerization, and iii interpenetrating crosslinked network by photopolymerization and epoxy curing reaction were received in carbon fiber/epoxy composite, depending on the various preparation processes.

Hierarchically rough, mechanically durable and superhydrophobic epoxy coatings through rapid evaporation spray method

International Nuclear Information System (INIS)

Simovich, Tomer; Wu, Alex H.; Lamb, Robert N.

2015-01-01

A mechanically durable and scalable superhydrophobic coating was fabricated by combining the advantages of both bottom-up and top-down approaches into a one-pot, one-step application method. This is achieved by spray coating a solution consisting of silica nanoparticles, which are embedded within epoxy resin, onto a heated substrate to rapidly drive both solvent evaporation and curing simultaneously. By maintaining a high substrate temperature, the arrival of spray-delivered micrometer-sized droplets are rapidly cured onto the substrate to form surface microroughness, while simultaneously, rapid solvent evaporation within each droplet results in the formation of a nanoporous structure. SEM, dual-beam FIB, and cross-sectional TEM/EDAX elemental mapping were used to confirm both the chemistry and the requisite micro- and nano-porosity within the coating structure requisite for superhydrophobicity. The resultant coatings exhibit contact angles greater than 150° (153.8° ± 0.8°) and roll-off angles of 8° ± 2°, with a coating hardness of 6H on the pencil hardness scale, and a rating of 5 on an ASTM crosshatch test. - Highlights: • A highly superhydrophobic coating was fabricated utilizing epoxy and nanoparticles. • The coating was demonstrated to be very durable and abrasion resistant. • The fabrication involves a novel, scalable one-pot synthesis technique

Hierarchically rough, mechanically durable and superhydrophobic epoxy coatings through rapid evaporation spray method

Energy Technology Data Exchange (ETDEWEB)

Simovich, Tomer; Wu, Alex H.; Lamb, Robert N., E-mail: rnlamb@unimelb.edu.au

2015-08-31

A mechanically durable and scalable superhydrophobic coating was fabricated by combining the advantages of both bottom-up and top-down approaches into a one-pot, one-step application method. This is achieved by spray coating a solution consisting of silica nanoparticles, which are embedded within epoxy resin, onto a heated substrate to rapidly drive both solvent evaporation and curing simultaneously. By maintaining a high substrate temperature, the arrival of spray-delivered micrometer-sized droplets are rapidly cured onto the substrate to form surface microroughness, while simultaneously, rapid solvent evaporation within each droplet results in the formation of a nanoporous structure. SEM, dual-beam FIB, and cross-sectional TEM/EDAX elemental mapping were used to confirm both the chemistry and the requisite micro- and nano-porosity within the coating structure requisite for superhydrophobicity. The resultant coatings exhibit contact angles greater than 150° (153.8° ± 0.8°) and roll-off angles of 8° ± 2°, with a coating hardness of 6H on the pencil hardness scale, and a rating of 5 on an ASTM crosshatch test. - Highlights: • A highly superhydrophobic coating was fabricated utilizing epoxy and nanoparticles. • The coating was demonstrated to be very durable and abrasion resistant. • The fabrication involves a novel, scalable one-pot synthesis technique.

Measurement of glass transition temperature, residual heat of reaction and mixing ratio of epoxy resins using near infrared spectroscopy: a preliminary study

DEFF Research Database (Denmark)

Houmøller, Lars Plejdrup; Laursen, Peter Clemen

2003-01-01

As a measure of the degree of curing of epoxy resins, the glass transition temperature, Tg, and the residual heat of reaction, DeltaHr, are often used. In this study, near infrared spectroscopy and multivariate calibration (partial least squares regression (PLSR)) have been used to monitor the two...... variables, using differential scanning calorimetry (DSC) as the reference method. The epoxy under study was a commercial system consisting of the resin, trimethylolpropanetriglycidylether, and the hardener, 3-aminomethyl-3,5,5,-trimethylcyclohexylamine. Using samples cured under different conditions......, calibrations resulted in root mean square errors of cross-validation (RMSECV) of 18 J/g for DeltaHr (range for Hr: 6.1-231.3 J/g) and 7.2ºC for Tg (range for Tg: 41.5-98.8ºC). Also, a PLSR model for mixing ratio of hardener and resin was obtained, resulting in a RMSECV of 0.0040 (range for mixing ratio: 0.180-0.380)...

Hydrophobic Modification of Layered Clays and Compatibility for Epoxy Nanocomposites

Directory of Open Access Journals (Sweden)

Jiang-Jen Lin

2010-04-01

Full Text Available Recent studies on the intercalation and exfoliation of layered clays with polymeric intercalating agents involving poly(oxypropylene-amines and the particular uses for epoxy nanocomposites are reviewed. For intercalation, counter-ionic exchange reactions of clays including cationic layered silicates and anionic Al-Mg layered double hydroxide (LDH with polymeric organic ions afforded organoclays led to spatial interlayer expansion from 12 to 92 Å (X-ray diffraction as well as hydrophobic property. The inorganic clays of layered structure could be modified by the poly(oxypropyleneamine-salts as the intercalating agents with molecular weights ranging from 230 to 5,000 g/mol. Furthermore, natural montmorillonite (MMT clay could be exfoliated into thin layer silicate platelets (ca. 1 nm thickness in one step by using polymeric types of exfoliating agents. Different lateral dimensions of MMT, synthetic fluorinated Mica and LDH clays had been cured into epoxy nanocomposites. The hydrophobic amine-salt modification resulting in high spacing of layered or exfoliation of individual clay platelets is the most important factor for gaining significant improvements of properties. In particular, these modified clays were reported to gain significant improvements such as reduced coefficient of thermal expansion (CTE, enhanced thermal stability, and hardness. The utilization of these layered clays for initiating the epoxy self-polymerization was also reported to have a unique compatibility between clay and organic resin matrix. However, the matrix domain lacks of covalently bonded crosslink and leads to the isolation of powder material. It is generally concluded that the hydrophobic expansion of the clay inter-gallery spacing is the crucial step for enhancing the compatibility and the ultimate preparation of the advanced epoxy materials.

Hydrophobic Modification of Layered Clays and Compatibility for Epoxy Nanocomposites

Science.gov (United States)

Lin, Jiang-Jen; Chan, Ying-Nan; Lan, Yi-Fen

2010-01-01

Recent studies on the intercalation and exfoliation of layered clays with polymeric intercalating agents involving poly(oxypropylene)-amines and the particular uses for epoxy nanocomposites are reviewed. For intercalation, counter-ionic exchange reactions of clays including cationic layered silicates and anionic Al-Mg layered double hydroxide (LDH) with polymeric organic ions afforded organoclays led to spatial interlayer expansion from 12 to 92 Å (X-ray diffraction) as well as hydrophobic property. The inorganic clays of layered structure could be modified by the poly(oxypropylene)amine-salts as the intercalating agents with molecular weights ranging from 230 to 5,000 g/mol. Furthermore, natural montmorillonite (MMT) clay could be exfoliated into thin layer silicate platelets (ca. 1 nm thickness) in one step by using polymeric types of exfoliating agents. Different lateral dimensions of MMT, synthetic fluorinated Mica and LDH clays had been cured into epoxy nanocomposites. The hydrophobic amine-salt modification resulting in high spacing of layered or exfoliation of individual clay platelets is the most important factor for gaining significant improvements of properties. In particular, these modified clays were reported to gain significant improvements such as reduced coefficient of thermal expansion (CTE), enhanced thermal stability, and hardness. The utilization of these layered clays for initiating the epoxy self-polymerization was also reported to have a unique compatibility between clay and organic resin matrix. However, the matrix domain lacks of covalently bonded crosslink and leads to the isolation of powder material. It is generally concluded that the hydrophobic expansion of the clay inter-gallery spacing is the crucial step for enhancing the compatibility and the ultimate preparation of the advanced epoxy materials.

Influence of the curing cycles on the fatigue performance of unidirectional glass fiber reinforced epoxy composites

DEFF Research Database (Denmark)

Hüther, Jonas; Brøndsted, Povl

2016-01-01

During the manufacturing process of fiber reinforced polymers the curing reaction of the resin results in shrinkage of the resin and introduces internal stresses in the composites. When curing at higher temperatures in order to shorten up the processing time, higher curing stresses and thermal...... to different levels of internal stresses. The mechanical properties, static strength and fatigue life time, are measured in three different directions of the material, i.e. the fiber direction, 0°, the 30° off axis direction, and the 90° direction transverse to the fiber direction. It is experimentally...... demonstrated that the resulting residual stresses barely influences the quasi-static mechanical properties of reinforced glass-fiber composites. It is found that the fatigue performance in the 0° direction is significantly influenced by the internal stresses, whereas the fatigue performance in the off axes...

Efficient composite fabrication using electron-beam rapidly cured polymers engineered for several manufacturing processes

International Nuclear Information System (INIS)

Walton, T.C.; Crivello, J.V.

1995-01-01

Low cost, efficiently processed ultra high specific strength and stiffness graphite fiber reinforced polymeric composite materials are of great interest to commercial transportation, construction and aerospace industries for use in various components with enhanced degrees of weight reduction, corrosion/erosion resistance and fatigue resistance. 10 MeV Electron Beam cure processing has been found to increase the cure rate by an order of magnitude over thermally cured systems yet provide less molded in stresses and high T g s. However, a limited range of resins are available which are easily processed with low shrinkage and with performance properties equal or exceeding those of state of the art toughened epoxies and BMI's. The technology, introduced by an academia-industry partnership sparked by Langley Research Center utilizes a cost effective, rapid curing polymeric composite processing technique which effectively reduces the need for expensive tooling and energy inefficient autoclave processing and can cure the laminate in seconds (compared to hours for thermal curing) in ambient or sub-ambient conditions. The process is based on electron beam (E-Beam) curing of a new series of (65 to 1,000,000 cPs.) specially formulated resins that have been shown to exhibit excellent mechanical and physical properties once cured. Fabrication processes utilizing these specially formulated and newly commercialized resins, (e.g. including Vacuum Assist Resin Transfer molding (VARTM), vacuum bag prepreg layup, pultrusion and filament winding grades) are engineered to cure with low shrinkage, provide excellent mechanical properties, be processed solventless (environmentally friendly) and are inherently non toxic

Steady-shear rheological properties of graphene-reinforced epoxy resin for manufacturing of aerospace composite films

Science.gov (United States)

Clausi, Marialaura; Santonicola, M. Gabriella; Laurenzi, Susanna

2016-05-01

The aim of this work is to analyze the steady-shear rheological behavior and the absolute viscosity of epoxy matrix reinforced with graphene nanoplatelets (xGnP) before cure. Three different grades of xGnP (grades C, M and H) were dispersed homogenously at different weight percentages (wt%) into the epoxy matrix, ranging from 0.5 to 5 wt%. It is found that nanocomposite fluids with xGnP-C exhibit a Newtonian behavior at shear rate in the range 0.1-100 s-1, conversely, nanocomposite fluids with xGnP of grade M and H exhibit a shear-thinning behavior with the increase of nanoplatelet loading. Results from this analysis indicate how the steady shear rheological properties of the nano-reinforced polymer fluids depend on the geometrical characteristics of the graphene nanoplatelets.

Characterization of adhesion at carbon fiber-fluorinated epoxy interface and effect of environmental degradation

Science.gov (United States)

Dasgupta, Suman

2011-12-01

the unknown mechanical and physical properties of the resin, the relaxation modulus (determined using nano-indentation) and coefficient of thermal expansion (determined using coherent gradient sensing). The adhesional pressure for 6F TGMDA-carbon fiber interface was found to be 135.48 MPa compared to 138.47 MPa for the Diamino diphenyl sulphone (DDS) cured TGMDA-carbon fiber interface. The fact that the adhesional pressure does not show significant decrease upon fluorination of the epoxy system is an advantage. The hydrophobicity of fluorine can be utilized to manufacture environmentally resistant composites while keeping the level of interfacial adhesion the same as in the case of conventional epoxy system, DDS cured TGMDA.

Effect of heat treatment on carbon fiber surface properties and fibers/epoxy interfacial adhesion

International Nuclear Information System (INIS)

Dai Zhishuang; Zhang Baoyan; Shi Fenghui; Li Min; Zhang Zuoguang; Gu Yizhuo

2011-01-01

Carbon fiber surface properties are likely to change during the molding process of carbon fiber reinforced matrix composite, and these changes could affect the infiltration and adhesion between carbon fiber and resin. T300B fiber was heat treated referring to the curing process of high-performance carbon fiber reinforced epoxy matrix composites. By means of X-ray photoelectron spectroscopy (XPS), activated carbon atoms can be detected, which are defined as the carbon atoms conjunction with oxygen and nitrogen. Surface chemistry analysis shows that the content of activated carbon atoms on treated carbon fiber surface, especially those connect with the hydroxyl decreases with the increasing heat treatment temperature. Inverse gas chromatography (IGC) analysis reveals that the dispersive surface energy γ S d increases and the polar surface energy γ S sp decreases as the heat treatment temperature increases to 200. Contact angle between carbon fiber and epoxy E51 resin, which is studied by dynamic contact angle test (DCAT) increases with the increasing heat treatment temperature, indicating the worse wettability comparing with the untreated fiber. Moreover, micro-droplet test shows that the interfacial shear strength (IFSS) of the treated carbon fiber/epoxy is lower than that of the untreated T300B fiber which is attributed to the decrement of the content of reactive functional groups including hydrogen group and epoxy group.

Enhanced protective properties and UV stability of epoxy/graphene nanocomposite coating on stainless steel

Directory of Open Access Journals (Sweden)

H. Alhumade

2016-12-01

Full Text Available Epoxy-Graphene (E/G nanocomposites with different loading of graphene were prepared via in situ prepolymerization and evaluated as protective coating for Stainless Steel 304 (SS304. The prepolymer composites were spin coated on SS304 substrates and thermally cured. Transmission Electron Microscopy (TEM and Scanning Electron Microscopy (SEM were utilized to examine the dispersion of graphene in the epoxy matrix. Epoxy and E/G nanocomposites were characterized using X-ray diffraction (XRD and Fourier Transform Infrared (FTIR techniques and the thermal behavior of the prepared coatings is analyzed using Thermogravimetric analysis (TGA and Differential scanning calorimetry (DSC. The corrosion protection properties of the prepared coatings were evaluated using Electrochemical Impedance Spectroscopy (EIS and Cyclic Voltammetry (CV measurements. In addition to corrosion mitigation properties, the long-term adhesion performance of the coatings was evaluated by measuring the adhesion of the coatings to the SS304 substrate after 60 days of exposure to 3.5 wt% NaCl medium. The effects of graphene loading on the impact resistance, flexibility, and UV stability of the coating are analyzed and discussed. SEM was utilized to evaluate post adhesion and UV stability results. The results indicate that very low graphene loading up to 0.5 wt % significantly enhances the corrosion protection, UV stability, and impact resistance of epoxy coatings.

Study of matrix micro-cracking in nano clay and acrylic tri-block-copolymer modified epoxy/basalt fiber-reinforced pressure-retaining structures

Directory of Open Access Journals (Sweden)

2011-10-01

Full Text Available In fiber-reinforced polymer pressure-retaining structures, such as pipes and vessels, micro-level failure commonly causes fluid permeation due to matrix cracking. This study explores the effect of nano-reinforcements on matrix cracking in filament-wound basalt fiber/epoxy composite structures. The microstructure and mechanical properties of bulk epoxy nanocomposites and hybrid fiber-reinforced composite pipes modified with acrylic tri-block-copolymer and organophilic layered silicate clay were investigated. In cured epoxy, the tri-block-copolymer phase separated into disordered spherical micelle inclusions; an exfoliated and intercalated structure was observed for the nano-clay. Block-copolymer addition significantly enhanced epoxy fracture toughness by a mechanism of particle cavitation and matrix shear yielding, whereas toughness remained unchanged in nano-clay filled nanocomposites due to the occurrence of lower energy resistance phenomena such as crack deflection and branching.Tensile stiffness increased with nano-clay content, while it decreased slightly for block-copolymer modified epoxy. Composite pipes modified with either the organic and inorganic nanoparticles exhibited moderate improvements in leakage failure strain (i.e. matrix cracking strain; however, reductions in functional and structural failure strength were observed.

Biocompatible high performance hyperbranched epoxy/clay nanocomposite as an implantable material

International Nuclear Information System (INIS)

Barua, Shaswat; Dutta, Nipu; Karak, Niranjan; Karmakar, Sanjeev; Chattopadhyay, Pronobesh; Aidew, Lipika; Buragohain, Alak K

2014-01-01

Polymeric biomaterials are in extensive use in the domain of tissue engineering and regenerative medicine. High performance hyperbranched epoxy is projected here as a potential biomaterial for tissue regeneration. Thermosetting hyperbranched epoxy nanocomposites were prepared with Homalomena aromatica rhizome oil-modified bentonite as well as organically modified montmorillonite clay. Fourier transformed infrared spectroscopy, x-ray diffraction and scanning and transmission electron microscopic techniques confirmed the strong interfacial interaction of clay layers with the epoxy matrix. The poly(amido amine)-cured thermosetting nanocomposites exhibited high mechanical properties like impact resistance (>100 cm), scratch hardness (>10 kg), tensile strength (48–58 MPa) and elongation at break (11.9–16.6%). Cytocompatibility of the thermosets was found to be excellent as evident by MTT and red blood cell hemolytic assays. The nanocomposites exhibited antimicrobial activity against Staphylococcus aureus (ATCC 11632), Escherichia coli (ATCC 10536), Mycobacterium smegmatis (ATCC14468) and Candida albicans (ATCC 10231) strains. In vivo biocompatibility of the best performing nanocomposite was ascertained by histopathological study of the brain, heart, liver and skin after subcutaneous implantation in Wistar rats. The material supported the proliferation of dermatocytes without induction of any sign of toxicity to the above organs. The adherence and proliferation of cells endorse the nanocomposite as a non-toxic biomaterial for tissue regeneration. (paper)

Thermal analysis of in-situ curing for thermoset, hoop-wound structures using infrared heating: Part II. Dependent scattering effect

International Nuclear Information System (INIS)

Chern, B.C.; Moon, T.J.; Howell, J.R.

1995-01-01

The volume fraction of the fibers present in commercial filament wound structures, formed from either epoxy-impregnated tapes (open-quotes prepregclose quotes) or fiber strands pulled through an epoxy bath, approaches 60 percent. Such close-packed structures are near the region that may cause dependent scattering effects to be important; that is, the scattering characteristics of one fiber may be affected by the presence of nearby fibers. This dependent scattering may change the single-fiber extinction coefficient and phase function, and thus may change the radiative transfer in such materials. This effect is studied for unidirectional fibers dispersed in a matrix with nonunity refractive index, and with large size parameter (fiber diameter to wavelength ratio) typical of commercial fiber-matrix composites. Only the case of radiation incident normal to the cylinder axes is considered, as this maximizes the dependent effects. The dependent extinction efficiency is found by solving the dispersion relations for the complex effective propagation constant of the composites. An estimation of this dependent scattering effect on the infrared in-situ curing of thermoset-hoop-wound structures is also conducted. It is found that the wave interference effect is significant for S-glass/3501-6 composite, and neglect of this effect tends to overestimate the temperature and cure state within the materials during IR in-situ curing. 23 refs., 8 figs

Morphological and mechanical analyses of laminates manufactured from randomly positioned carbon fibre/epoxy resin prepreg scraps

Science.gov (United States)

Souza, Christiane S. R.; Cândido, Geraldo M.; Alves, Wellington; Marlet, José Maria F.; Rezende, Mirabel C.

2017-10-01

This study aims to contribute to sustainability by proposing the reuse of composite prepreg scrap as an added value from discards. The research evaluates the microstructure and mechanical properties of laminates processed by the reuse of uncured carbon fibre/F155-epoxy resin prepreg scraps, waste from the ply cutting area of an aeronautical industry. The composite scraps were used as collected and were randomly positioned to produce laminates to be cured at an autoclave. The mechanical characterization shows a decrease of 39% for the compression property due to the discontinuous fibres in the laminate and an increase of 34% for the interlaminar shear strength, when compared to continuous fibre laminates. This increase is attributed to the higher crosslink density of the epoxy resin, as a result of the cure temperature used in autoclave (60 °C higher than suggested by supplier) and also to the randomly positioned scraps. Microscopic analyses confirm the consolidation of laminates, although show resin rich areas with different sizes and shapes attributed to the overlapping of the scraps with different sizes and shapes. These resin rich areas may contribute to decrease the mechanical properties of laminates. The correlation between mechanical and morphological results shows potential to be used on non-critical structural application, as composite jigs, contributing to sustainability.

Evolution of carbon nanotube dispersion in preparation of epoxy-based composites: From a masterbatch to a nanocomposite

OpenAIRE

Aravand, Mohammadali; Lomov, Stepan Vladimirovitch; Verpoest, Ignace; Gorbatikh, Larissa

2014-01-01

The state of carbon nanotube (CNT) dispersion in epoxy is likely to change in the process of composite production. In the present work CNT dispersion is characterized at different stages of nanocomposite preparation: in the original masterbatch with high CNT concentration, after masterbatch dilution, in the process of curing and in the final nanocomposite. The evaluation techniques included dynamic rheological analysis of the liquid phases, optical, environmental and charge contrast scanning ...

Mechanical and morphological characterizations of carbon fiber fabric reinforced epoxy composites used in aeronautical field

Directory of Open Access Journals (Sweden)

Jane Maria Faulstich de Paiva

2009-09-01

Full Text Available Carbon fiber reinforced composites (CFRC have been used in aeronautical industry in the manufacture of different aircraft components that must attend tight mechanical requirements. This paper shows a study involving mechanical (flexural, shear, tensile and compressive tests and morphological characterizations of four different laminates based on 2 epoxy resin systems (8552TM and F584TM and 2 carbon fiber fabric reinforcements (Plain Weave (PW and Eight Harness Satin (8HS. All laminates were obtained by handing lay-up of prepregs plies (0º/90º and consolidation in an autoclave following an appropriate curing cycle with vacuum and pressure. The results show that the F584-epoxy matrix laminates present better mechanical properties in the tensile and compressive tests than 8552 composites. It is also observed that PW laminates for both matrices show better flexural and interlaminar shear properties.

CRADA Final Report for CRADA No. ORNL99-0544, Interfacial Properties of Electron Beam Cured Composites

Energy Technology Data Exchange (ETDEWEB)

Janke, C.J.

2005-10-17

Electron beam (EB) curing is a technology that promises, in certain applications, to deliver lower cost and higher performance polymer matrix composite (PMC) structures compared to conventional thermal curing processes. PMCs enhance performance by making products lighter, stronger, more durable, and less energy demanding. They are essential in weight- and performance-dominated applications. Affordable PMCs can enhance US economic prosperity and national security. US industry expects rapid implementation of electron beam cured composites in aircraft and aerospace applications as satisfactory properties are demonstrated, and implementation in lower performance applications will likely follow thereafter. In fact, at this time and partly because of discoveries made in this project, field demonstrations are underway that may result in the first fielded applications of electron beam cured composites. Serious obstacles preventing the widespread use of electron beam cured PMCs in many applications are their relatively poor interfacial properties and resin toughness. The composite shear strength and resin toughness of electron beam cured carbon fiber reinforced epoxy composites were about 25% and 50% lower, respectively, than those of thermally cured composites of similar formulations. The essential purpose of this project was to improve the mechanical properties of electron beam cured, carbon fiber reinforced epoxy composites, with a specific focus on composite shear properties for high performance aerospace applications. Many partners, sponsors, and subcontractors participated in this project. There were four government sponsors from three federal agencies, with the US Department of Energy (DOE) being the principal sponsor. The project was executed by Oak Ridge National Laboratory (ORNL), NASA and Department of Defense (DOD) participants, eleven private CRADA partners, and two subcontractors. A list of key project contacts is provided in Appendix A. In order to properly

Room temperature thin foil SLIM-cut using an epoxy paste: experimental versus theoretical results

International Nuclear Information System (INIS)

Bellanger, Pierre; Serra, Joao; Bouchard, Pierre-Olivier; Bernacki, Marc

2015-01-01

The stress induced lift-off method (SLIM) -cut technique allows the detachment of thin silicon foils using a stress inducing layer. In this work, results of SLIM-cut foils obtained using an epoxy stress inducing layer at room temperature are presented. Numerical analyses were performed in order to study and ascertain the important experimental parameters. The experimental and simulation results are in good agreement. Indeed, large area (5 × 5 cm 2 ) foils were successfully detached at room temperature using an epoxy thickness of 900 μm and a curing temperature of 150 °C. Moreover, three foils (5 × 3 cm 2 ) with thickness 135, 121 and 110 μm were detached from the same monocrystalline substrate. Effective minority carrier lifetimes of 46, 25 and 20 μs were measured using quasi-steady-state photoconductance technique in these foils after iodine ethanol surface passivation. (paper)

Robust synthesis of epoxy resin-filled microcapsules for application to self-healing materials.

Science.gov (United States)

Bolimowski, Patryk A; Bond, Ian P; Wass, Duncan F

2016-02-28

Mechanically and thermally robust microcapsules containing diglycidyl ether bisphenol A-based epoxy resin and a high-boiling-point organic solvent were synthesized in high yield using in situ polymerization of urea and formaldehyde in an oil-in-water emulsion. Microcapsules were characterized in terms of their size and size distribution, shell surface morphology and thermal resistance to the curing cycles of commercially used epoxy polymers. The size distribution of the capsules and characteristics such as shell thickness can be controlled by the specific parameters of microencapsulation, including concentrations of reagents, stirrer speed and sonication. Selected microcapsules, and separated core and shell materials, were analysed using thermogravimetric analysis and differential scanning calorimetry. It is demonstrated that capsules lose minimal 2.5 wt% at temperatures no higher than 120°C. These microcapsules can be applied to self-healing carbon fibre composite structural materials, with preliminary results showing promising performance. © 2016 The Author(s).

Novel thermal curing of cycloaliphatic resins by thiol-epoxy click process with several multifunctional thiols

OpenAIRE

Guzman, Dailyn; Mateu, Blai; Fernández Francos, Xavier; Ramis Juan, Xavier; Serra Albet, Àngels

2017-01-01

Novel thermosets were prepared by the base-catalysed reaction between a cycloaliphatic resin (ECC) and various thiol crosslinkers. 4-(N,N-Dimethylaminopyridine) (DMAP) was used as base catalyst for the thiol–epoxy reaction. A commercial tetrathiol (PETMP) and three different thiols synthesized by us, 6SH-SQ, 3SH-EU and 3SH-ISO, were tested. 6SH-SQ and 3SH-EU were prepared from vinyl or allyl compounds from renewable resources such as squalene and eugenol, respectively. Thiol 3SH-ISO was prepa...

Predictive Modeling of Fast-Curing Thermosets in Nozzle-Based Extrusion

Science.gov (United States)

Xie, Jingjin; Randolph, Robert; Simmons, Gary; Hull, Patrick V.; Mazzeo, Aaron D.

2017-01-01

This work presents an approach to modeling the dynamic spreading and curing behavior of thermosets in nozzle-based extrusions. Thermosets cover a wide range of materials, some of which permit low-temperature processing with subsequent high-temperature and high-strength working properties. Extruding thermosets may overcome the limited working temperatures and strengths of conventional thermoplastic materials used in additive manufacturing. This project aims to produce technology for the fabrication of thermoset-based structures leveraging advances made in nozzle-based extrusion, such as fused deposition modeling (FDM), material jetting, and direct writing. Understanding the synergistic interactions between spreading and fast curing of extruded thermosetting materials will provide essential insights for applications that require accurate dimensional controls, such as additive manufacturing [1], [2] and centrifugal coating/forming [3]. Two types of thermally curing thermosets -- one being a soft silicone (Ecoflex 0050) and the other being a toughened epoxy (G/Flex) -- served as the test materials in this work to obtain models for cure kinetics and viscosity. The developed models align with extensive measurements made with differential scanning calorimetry (DSC) and rheology. DSC monitors the change in the heat of reaction, which reflects the rate and degree of cure at different crosslinking stages. Rheology measures the change in complex viscosity, shear moduli, yield stress, and other properties dictated by chemical composition. By combining DSC and rheological measurements, it is possible to establish a set of models profiling the cure kinetics and chemorheology without prior knowledge of chemical composition, which is usually necessary for sophisticated mechanistic modeling. In this work, we conducted both isothermal and dynamic measurements with both DSC and rheology. With the developed models, numerical simulations yielded predictions of diameter and height of

Thermo-mechanical characterization of siliconized E-glass fiber/hematite particles reinforced epoxy resin hybrid composite

Energy Technology Data Exchange (ETDEWEB)

Arun Prakash, V.R., E-mail: vinprakash101@gmail.com; Rajadurai, A., E-mail: rajadurai@annauniv.edu.in

2016-10-30

Highlights: • Particles dimension have reduced using Ball milling process. • Importance of surface modification was explored. • Surface modification has been done to improve adhesion of fiber/particles with epoxy. • Mechanical properties has been increased by adding modified fiber and particles. • Thermal properties have been increased. - Abstract: In this present work hybrid polymer (epoxy) matrix composite has been strengthened with surface modified E-glass fiber and iron(III) oxide particles with varying size. The particle sizes of 200 nm and <100 nm has been prepared by high energy ball milling and sol-gel methods respectively. To enhance better dispersion of particles and improve adhesion of fibers and fillers with epoxy matrix surface modification process has been done on both fiber and filler by an amino functional silane 3-Aminopropyltrimethoxysilane (APTMS). Crystalline and functional groups of siliconized iron(III) oxide particles were characterized by XRD and FTIR spectroscopy analysis. Fixed quantity of surface treated 15 vol% E-glass fiber was laid along with 0.5 and 1.0 vol% of iron(III) oxide particles into the matrix to fabricate hybrid composites. The composites were cured by an aliphatic hardener Triethylenetetramine (TETA). Effectiveness of surface modified particles and fibers addition into the resin matrix were revealed by mechanical testing like tensile testing, flexural testing, impact testing, inter laminar shear strength and hardness. Thermal behavior of composites was evaluated by TGA, DSC and thermal conductivity (Lee’s disc). The scanning electron microscopy was employed to found shape and size of iron(III) oxide particles adhesion quality of fiber with epoxy matrix. Good dispersion of fillers in matrix was achieved with surface modifier APTMS. Tensile, flexural, impact and inter laminar shear strength of composites was improved by reinforcing surface modified fiber and filler. Thermal stability of epoxy resin was improved

Innovative Chemical Process for Recycling Thermosets Cured with Recyclamines® by Converting Bio-Epoxy Composites in Reusable Thermoplastic—An LCA Study

Directory of Open Access Journals (Sweden)

Angela D. La Rosa

2018-02-01

Full Text Available An innovative recycling process for thermoset polymer composites developed by Connora Technologies (Hayward, CA, USA was studied. The process efficacy has already been tested, and it is currently working at the plant level. The main aspect investigated in the present paper was the environmental impact by means of the Life Cycle Assessment (LCA method. Because of the need to recycle and recover materials at their end of life, the Connora process creates a great innovation in the market of epoxy composites, as they are notoriously not recyclable. Connora Technologies developed a relatively gentle chemical recycling process that induces the conversion of thermosets into thermoplastics. The LCA demonstrated that low environmental burdens are associated with the process itself and, furthermore, impacts are avoided due to the recovery of the epoxy-composite constituents (fibres and matrix. A carbon fibre (CF epoxy-composite panel was produced through Vacuum Resin Transfer Moulding (VRTM and afterwards treated using the Connora recycling process. The LCA results of both the production and the recycling phases are reported.

Microcapsules Filled with a Palm Oil-Based Alkyd as Healing Agent for Epoxy Matrix

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Nurshafiza Shahabudin

2016-04-01

Full Text Available One of the approaches to prolong the service lifespan of polymeric material is the development of self-healing ability by means of embedded microcapsules containing a healing agent. In this work, poly(melamine-urea-formaldehyde (PMUF microcapsules containing a palm oil-based alkyd were produced by polymerization of melamine resin, urea and formaldehyde that encapsulated droplets of the suspended alkyd particles. A series of spherical and free-flowing microcapsules were obtained. The chemical properties of core and shell materials were characterized by Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR and proton nuclear magnetic resonance spectroscopy (1H-NMR. Differential scanning calorimetry (DSC analysis showed a glass transition around −15 °C due to the alkyd, and a melting temperature at around 200 °C due to the shell. Thermogravimetric analysis (TGA results showed that the core and shell thermally degraded within the temperature range of 200–600 °C. Field emission scanning electron microscope (FESEM examination of the ruptured microcapsule showed smooth inner and rough outer surfaces of the shell. Flexural strength and microhardness (Vickers of the cured epoxy compound were not affected with the incorporation of 1%–3% of the microcapsules. The viability of the healing reactions was demonstrated by blending small amounts of alkyd with epoxy and hardener at different ratios. The blends could readily cure to non-sticky hard solids at room temperature and the reactions could be verified by ATR-FTIR.

Influence of filler alignment in the mechanical and electrical properties of carbon nanotubes/epoxy nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Felisberto, M. [LPyMC, FCEyN-UBA and IFIBA-CONICET, Pab I Ciudad Universitaria, Buenos Aires 1428 (Argentina); INQUIMAE-CONICET-UBA, Pab II Ciudad Universitaria, Buenos Aires 1428 (Argentina); Arias-Duran, A. [LPyMC, FCEyN-UBA and IFIBA-CONICET, Pab I Ciudad Universitaria, Buenos Aires 1428 (Argentina); Ramos, J.A.; Mondragon, I. [Dep. Ingenieria Quimica y M. Ambiente. Esc. Politecnica. UPV/EHU, Pza. Europa 1, Donostia-San Sebastian 20018 (Spain); Candal, R. [INQUIMAE-CONICET-UBA, Pab II Ciudad Universitaria, Buenos Aires 1428 (Argentina); Escuela de Ciencia y Tecnologia-UNSAM, San Martin, Prov. De Buenos Aires (Argentina); Goyanes, S. [LPyMC, FCEyN-UBA and IFIBA-CONICET, Pab I Ciudad Universitaria, Buenos Aires 1428 (Argentina); Rubiolo, G.H., E-mail: rubiolo@cnea.gov.ar [LPyMC, FCEyN-UBA and IFIBA-CONICET, Pab I Ciudad Universitaria, Buenos Aires 1428 (Argentina); Dep. Materiales, Comision Nacional de Energia Atomica (CNEA-CAC), Avda Gral Paz 1499, B1650KNA San Martin (Argentina)

2012-08-15

In this work, we report the mechanical and electrical properties of carbon nanotubes/epoxy composites prepared with aligned and randomly oriented nanotubes as filler. The samples are disks of 30 mm in diameter and 3 mm in thickness. To obtain the carbon nanotubes alignment, an external electric field (250 VAC; 50 Hz) was applied through the thickness of the sample during all the cure process. The AC electrical current was measured, during the cure, as a strategy to determine the optimum time in which the alignment reaches the maximum value. DC conductivity measured after the cure shows a percolation threshold in the filler content one order of magnitude smaller for composites with aligned nanotubes than for composites with randomly oriented filler (from 0.06 to 0.5 wt%). In the percolation threshold, the achieved conductivity was 1.4 Multiplication-Sign 10{sup -5} Sm{sup -1}. In both cases, aligned and randomly distributed carbon nanotube composites, the wear resistance increases with the addition of the filler while the Rockwell hardness decreases independently of the nanotubes alignment.

Investigation of a carbon fiber/epoxy prepreg curing behavior for thick composite materials production: An industrial case-study

Science.gov (United States)

Giorgini, Loris; Mazzocchetti, Laura; Minak, Giangiacomo; Dolcini, Enrico

2012-07-01

A case-study is presented, in cooperation with RI-BA Composites srl, where the industrial production of a thick part for primary structural application is analysed. The final product is a bulk carbon fiber reinforced object characterized by great dimensions, with thickness ranging between 10mm and 35mm and obtained by Hand-Lay-Up of prepregs. The study shows that prepregs age along the time required for the process work up. Moreover, the isothermal curing investigation of the prepreg used in the production gives some useful hint for the design of a new thermal curing cycle, in order to avoid exotherm problems along the thickness of the object. The effect of the applied curing cycle on thermal properties of the object are reported.

Preparation and Characterization of Epoxy Resin Cross-Linked with High Wood Pyrolysis Bio-Oil Substitution by Acetone Pretreatment

Directory of Open Access Journals (Sweden)

Yi Liu

2017-03-01

Full Text Available The use of cost effective solvents may be necessary to store wood pyrolysis bio-oil in order to stabilize and control its viscosity, but this part of the production system has not been explored. Conversely, any rise in viscosity during storage, that would occur without a solvent, will add variance to the production system and render it cost ineffective. The purpose of this study was to modify bio-oil with a common solvent and then react the bio-oil with an epoxy for bonding of wood without any loss in properties. The acetone pretreatment of the bio-oil/epoxy mixture was found to improve the cross-linking potential and substitution rate based on its mechanical, chemical, and thermal properties. Specifically, the bio-oil was blended with epoxy resin at weight ratios ranging from 2:1 to 1:5 and were then cured. A higher bio-oil substitution rate was found to lower the shear bond strength of the bio-oil/epoxy resins. However, when an acetone pretreatment was used, it was possible to replace the bio-oil by as much as 50% while satisfying usage requirements. Extraction of the bio-oil/epoxy mixture with four different solvents demonstrated an improvement in cross-linking after acetone pretreatment. ATR-FTIR analysis confirmed that the polymer achieved a higher cross-linked structure. DSC and TGA curves showed improved thermal stability with the addition of the acetone pretreatment. UV-Vis characterization showed that some functional groups of the bio-oil to epoxy system were unreacted. Finally, when the resin mixture was utilized to bond wood, the acetone pretreatment coupled with precise tuning of the bio-oil:epoxy ratio was an effective method to control cross-linking while ensuring acceptable bond strength.

Comportamento termomecânico de compósitos ativos preparados com nanocompósitos epóxi/argila organofílica e fios de liga Ni-Ti com memória de forma Thermomechanical behavior of active composites prepared with epoxy/organoclay nanocomposites and Ni-Ti shape memory alloy wires

Directory of Open Access Journals (Sweden)

Artur S. C. Leal

2012-01-01

Full Text Available Neste trabalho, nanocompósitos epóxi/argila organofílica foram selecionados como matriz por apresentarem valores de temperatura de transição vítrea (Tg e estabilidade térmica suficientemente alta para que fios de uma liga com memória de forma (LMF possam ser incorporados. Para tanto, quatro frações volumétricas de fios LMF de Ni-Ti (1,55, 2,56, 3,57 e 4,54% foram embebidas na matriz epoxídica diglicidil éter do bisfenol-A (DGEBA, reticulada com a amina aromática 4,4’-diamino difenil sulfona (DDS contendo 1 pcr da argila bentonita purificada organofiliada (APOC. A formação do nanocompósito foi confirmada por análise de difração de raio X, enquanto a transformação de fase dos fios de Ni-Ti foi determinada por análise dinâmico-mecânica (DMA. As amostras dos compósitos ativos preparados a partir da matriz de nanocompósito e fios de Ni-Ti foram caracterizadas principalmente por DMA. De acordo com os resultados obtidos foi constatada uma recuperação do módulo de armazenamento do compósito ativo durante o aquecimento na faixa de transformação de fase dos fios de Ni-Ti quando a fração volumétrica foi mantida em torno de 3,5%.In this work, epoxy/organoclay nanocomposites were selected as matrix for presenting high enough glass transition temperature (Tg and thermal stability values in order to be incorporated in shape memory alloys (SMA. Four volume fractions of SMA wires containing Ni-Ti (1.55, 2.56, 3.57 and 4.54% were embedded in diglycidyl ether of bisphenol A (DGEBA, cured with the aromatic amine 4,4’-diamino diphenyl sulfone (DDS and containing 1 phr of purified organobentonite (APOC. The formation of nanocomposite was confirmed by X ray diffraction analysis, while the phase transformation of Ni-Ti wires was determined by dynamic mechanical analysis (DMA. Samples of the active composites prepared from nanocomposite matrix and Ni-Ti wires were mainly characterized by DMA. A recovery of the storage modulus of

Cage and linear structured polysiloxane/epoxy hybrids for coatings: Surface property and film permeability.

Science.gov (United States)

Ma, Yanli; He, Ling; Jia, Mengjun; Zhao, Lingru; Zuo, Yanyan; Hu, Pingan

2017-08-15

Three polysiloxane/epoxy hybrids obtained by evolving cage- or linear-structured polysiloxane into poly glycidyl methacrylate (PGMA) matrix are compared used as coatings. One is the cage-structured hybrid of P(GMA/MA-POSS) copolymer obtained by GMA and methacrylisobutyl polyhedral oligomeric silsesquioxane (MA-POSS) via free radical polymerization, the other two are PGMA/NH 2 -POSS and PGMA/NH 2 -PDMS hybrids by cage-structured aminopropyllsobutyl POSS (NH 2 -POSS) or linear-structured diamino terminated poly(dimethylsiloxane) (NH 2 -PDMS) to cure PGMA. The effect of MA-POSS, NH 2 -POSS and NH 2 -PDMS on polysiloxane/epoxy hybrid films is characterized according to their surface morphology, transparency, permeability, adhesive strength and thermo-mechanical properties. Due to caged POSS tending to agglomerate onto the film surface, P(GMA/MA-POSS) and PGMA/NH 2 -POSS films exhibit much more heterogeneous surfaces than PGMA/NH 2 -PDMS film, but the well-compatibility between epoxy matrix and MA-POSS has provided P(GMA/MA-POSS) film with much higher transmittance (98%) than PGMA/NH 2 -POSS film (24%), PGMA/NH 2 -PDMS film (27%) and traditional epoxy resin film (5%). The introduction of polysiloxane into epoxy matrix is confirmed to create hybrids with strong adhesive strength (526-1113N) and high thermos-stability (T g =262-282°C), especially the cage-structured P(GMA/MA-POSS) hybrid (1113N and 282°C), but the flexible PDMS improves PGMA/NH 2 -PDMS hybrid with much higher storage modulus (519MPa) than PGMA/NH 2 -POSS (271MPa), which suggests that PDMS is advantage in improving the film stiffness than POSS cages. However, cage-structured P(GMA/MA-POSS) and PGMA/NH 2 -POSS indicate higher permeability than PGMA/NH 2 -PDMS and traditional epoxy resin. Comparatively, the cage-structured P(GMA/MA-POSS) hybrid is the best coating in transparency, permeability, adhesive strength and thermostability, but linear-structured PGMA/NH 2 -PDMS hybrid behaviors the best coating in

Mechanism of Particle Formation in Silver/Epoxy Nanocomposites Obtained through a Visible-Light-Assisted in Situ Synthesis.

Science.gov (United States)

dell'Erba, Ignacio E; Martínez, Francisco D; Hoppe, Cristina E; Eliçabe, Guillermo E; Ceolín, Marcelo; Zucchi, Ileana A; Schroeder, Walter F

2017-10-03

A detailed understanding of the processes taking place during the in situ synthesis of metal/polymer nanocomposites is crucial to manipulate the shape and size of nanoparticles (NPs) with a high level of control. In this paper, we report an in-depth time-resolved analysis of the particle formation process in silver/epoxy nanocomposites obtained through a visible-light-assisted in situ synthesis. The selected epoxy monomer was based on diglycidyl ether of bisphenol A, which undergoes relatively slow cationic ring-opening polymerization. This feature allowed us to access a full description of the formation process of silver NPs before this was arrested by the curing of the epoxy matrix. In situ time-resolved small-angle X-ray scattering investigation was carried out to follow the evolution of the number and size of the silver NPs as a function of irradiation time, whereas rheological experiments combined with near-infrared and ultraviolet-visible spectroscopies were performed to interpret how changes in the rheological properties of the matrix affect the nucleation and growth of particles. The analysis of the obtained results allowed us to propose consistent mechanisms for the formation of metal/polymer nanocomposites obtained by light-assisted one-pot synthesis. Finally, the effect of a thermal postcuring treatment of the epoxy matrix on the particle size in the nanocomposite was investigated.

Effect of high shear mixing parameters and degassing temperature on the morphology of epoxy-clay nanocomposites

KAUST Repository

Al-Qadhi, Muneer; Merah, N.; Mezghani, Khaled S.; Khan, Zafarullah; Gasem, Zuhair Mattoug Asad; Sougrat, Rachid

2013-01-01

Epoxy-clay nanocomposites were prepared by high shear mixing method using Nanomer I.30E nanoclay as nano-reinforcement in diglycidyl ether of bisphenol A (DGEBA). The effect of mixing speed and time on the nature and degree of clay dispersion were investigated by varying the mixing speed in the range of 500-8000 RPM and mixing time in the range of 15-90 minutes. The effect of degassing temperature on the morphology of the resultant nanocomposites was also studied. Scanning and transmission microscopy (SEM and TEM) along with x-ray diffraction (XRD) have been used to characterize the effect of shear mixing speed, mixing time and degassing temperature on the structure of the resultant nanocomposites. The SEM, TEM and XRD examinations demonstrated that the degree of clay dispersion was improved with increasing the high shear mixing speed and mixing time. The results showed that the optimum high shear mixing speed and mixing time were 6000 rpm and 60 min, respectively. It was observed that the structure of the nanocomposites that have been degassed at 65°C was dominated by ordered intercalated morphology while disordered intercalated with some exfoliated morphology was found for the sample degassed at 100°C for the first 2 hours of the degassing process. © (2013) Trans Tech Publications, Switzerland.

The epoxy resin variation effect on microstructure and physical properties to improve bonded NdFeB flux magnetic density

International Nuclear Information System (INIS)

Rusnaeni, N.; Sarjono, Priyo; Muljadi; Noer, Nasrudin

2016-01-01

NdFeB magnets have been fabricated from a mixture of powder NdFeB (MPQ-B+) and epoxy resins (ER) with a variation of 0% wt, 2% wt, 4% wt and 6% wt. The pellets samples were made by pressing 4 tons of the mixture powder at room temperature before curing at 100°C for 1 hour. The SEM-EDX results showed the microstructure with ER were evenly smeared the NdFeB magnetic particles due to higher percent C and lower transition metals value. Sample with 2% wt epoxy resin was able to achieve the highest density of 5.35 g/cm 3 and the highest magnetic flux of 2121 Gauss. The magnetic properties characterization using the permagraph indicates that the sample pellets with 2% wt epoxy resin has a value of remanence (Br) = 4.92 kG, coercivity (Hc) = 7.76 kOe, and energy product (Bhmax) = 4.58 MGOe. Despite low remanence value in the pellet samples, the resistance to demagnetization value was still acceptable. (paper)

The epoxy resin variation effect on microstructure and physical properties to improve bonded NdFeB flux magnetic density

Science.gov (United States)

Rusnaeni, N.; Sarjono, Priyo; Muljadi; Noer, Nasrudin

2016-11-01

NdFeB magnets have been fabricated from a mixture of powder NdFeB (MPQ-B+) and epoxy resins (ER) with a variation of 0% wt, 2% wt, 4% wt and 6% wt. The pellets samples were made by pressing 4 tons of the mixture powder at room temperature before curing at 100°C for 1 hour. The SEM-EDX results showed the microstructure with ER were evenly smeared the NdFeB magnetic particles due to higher percent C and lower transition metals value. Sample with 2% wt epoxy resin was able to achieve the highest density of 5.35 g/cm3 and the highest magnetic flux of 2121 Gauss. The magnetic properties characterization using the permagraph indicates that the sample pellets with 2% wt epoxy resin has a value of remanence (Br) = 4.92 kG, coercivity (Hc) = 7.76 kOe, and energy product (Bhmax) = 4.58 MGOe. Despite low remanence value in the pellet samples, the resistance to demagnetization value was still acceptable.

Mechanical Properties Analysis Of Composite Magnetic Base On hexa ferrite And Polyester Or Epoxy Matrix With Silane Additive Addition

International Nuclear Information System (INIS)

Sudirman; Ridwan; Mujamilah; K K, Aloma; Rembulan, Marisa; Fitriyanti

2003-01-01

Application of composite magnetic especially hexa ferrite magnet for industry and home industry in Indonesia has been used. Research purposes were making composite magnetic by mixing hexa ferrite powder with polyester or epoxy and studying the effect of coupling agent 3-aminopropyltriethoxysilane (3-APE) addition on mechanical properties of composite magnetic. The coupling agent may increase bonding properties between magnetic powder and matrix polymer, so that tensile strength of magnetic composite will increase without decreasing the magnetic properties. Magnetic powder (SrM or BaM) wich be coated by coupling agent were added to matrix polyester and mekpo or epoxy and versamid, mixed until homogen then pressing into to the dumbbell form molding. For epoxy matrix, pressing was done in hot press at 70 deg. C and 150 kg/cm 2 following by cooling in cold press, while for polyester matrix pressing was done in hydraulic press and following by curing at 70 deg. C in an oven for 1 hour. The composition of magnetic powder were varied to 30, 40 and 50% volume fraction and coupling agent were varied to 5, 10 and 15 ml for every volume fraction. The result showed that 10 ml added of coupling agent was give best mechanical properties both polyester and epoxy matrix. However generally, increasing of magnetic powder content decreased the tensile strength of magnetic composite. The properties of magnetic composite SrM was better than BaM either in polyester or epoxy matrix

Synthesis and characterization of a novel laser ablation sensitive triazene incorporated epoxy resin

KAUST Repository

Patole, Archana S.

2014-01-01

New triazene monomer was synthesized and further employed as a crosslinking agent partner with epoxy matrix using ethyl methyl imidazole as a curing agent in order to investigate the effect of triazene moieties on polymeric properties for laser ablation application. The synthesized triazene monomer was characterized by analytical and spectroscopic methods, while the surface morphology of resist after laser ablation was visualized by optical laser scanning images and scanning electron microscopy. Thermogravimetrical investigations indicate the loss of nitrogen being the initial thermal decomposition step and exhibit sufficient stabilities for the requirements for laser ablation application. Fourier transform infra-red, nuclear magnetic resonance, and gas chromatography analyses showed the successful synthesis of triazene. The ablation results from the optical laser scanning images revealed that the etching depth could be controlled by varying the concentration of triazene monomer in the formulation of epoxy. The shear strength analysis revealed that that the shear strength increased with increasing the amount of triazene in the formulation of direct ablation sensitive resist. © 2014 The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht.

Literature Review: An Overview of Epoxy Resin Syntactic Foams with Glass Microballoons

Energy Technology Data Exchange (ETDEWEB)

Keller, Jennie [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2014-03-12

Syntactic foams are an important category of composite materials that have abundant applications in a wide variety of fields. The bulk phase of syntactic foams is a three-part epoxy resin formulation that consists of a base resin, a curative (curing agent) and a modifier (diluent and/or accelerator) [12]. These thermoset materials [12] are used frequently for their thermal stability [9], low moisture absorption and high compressive strength [10]. The characteristic feature of a syntactic foam is a network of beads that forms pores within the epoxy matrix [3]. In this review, hollow glass beads (known as glass microballoons) are considered, however, solid beads or microballoons made from materials such as ceramic, polymer or metal can also be used [3M, Peter]. The network of hollow beads forms a closed-cell foam; the term closed-cell comes from the fact that the microspheres used in the resin matrix are completely closed and filled with gas (termed hollow). In contrast, the microspheres used in open-cell foams are either not completely closed or broken so that matrix material can fill the spheres [11]. Although closed foams have been found to possess higher densities than open cell foams, their rigid structures give them superior mechanical properties [12]. Past research has extensively studied the effects that changing the volume fraction of microballoons to epoxy will have on the resulting syntactic foam [3,4,9]. In addition, published literature also explores how the microballoon wall thickness affects the final product [4,9,10]. Findings detail that indeed both the mechanical and some thermal properties of syntactic foams can be tailored to a specific application by varying either the volume fraction or the wall thickness of the microballoons used [10]. The major trends in syntactic foam research show that microballoon volume fraction has an inversely proportionate relationship to dynamic properties, while microballoon wall thickness is proportional to those

PENGARUH PENAMBAHAN SILIKON TERHADAP SUDUT KONTAK HIDROPOBIK DAN KARAKTERISTIK ARUS BOCOR PERMUKAAN BAHAN RESIN EPOKSI

Directory of Open Access Journals (Sweden)

Abdul Syakur

2012-02-01

Full Text Available Currently, polymer materials such as epoxy resin have been used as an insulator in the distribution andtransmission line. Some advantages of using this epoxy resin material having the dielectric properties are betterthan porcelain and glass insulators. On the other side, epoxy resins are also disadvantage the surface ishygroscopic. For the repair was done by adding the surface properties of silicone rubber materialThis paper describes the effect of adding silicone rubber against contact angle of hidrophobicity and surfaceleakage current characteristics of epoxy resin materials ( Di-Glycidyl Ether of Bisphenol A (DGEBA andMethaphenilene Diamine (MPDA. The study was conducted in the laboratory using the electrode method IEC587:1984 with NH4Cl contaminants. The voltage applied to the epoxy resin sample at 3.5 kV and 50 HzfrequencyThe experimental results showed that the addition of silicon rubber in epoxy resin makes the surface materialcontact angle increases. The higher percentage of silicone rubber, the greater the contact angle and the longertime required for the occurrence of surface discharge.

Epoxy-based carbon nanotubes reinforced composites

CSIR Research Space (South Africa)

Kesavan Pillai, Sreejarani

2011-04-01

Full Text Available of the three major epoxy resin producers worldwide [May, 1987]. Epoxy resin is most commonly used as a matrix for advanced composites due to their superior thermal, mechanical and electrical properties; dimensional stability and chemical resistance. Epoxy... and modifiers to create products with an almost unlimited range and variety of performance properties [The epoxy book, 2000]. Epoxy resins are widely used as high-grade synthetic resins, for example, in the electronics, aeronautics and astronautic industries...

Thermal stability and fracture toughness of epoxy resins modified with epoxidized castor oil and Al2O3 nanoparticles

International Nuclear Information System (INIS)

Zhu, Lin; Jin, Fanlong; Park, Soojin

2012-01-01

This study examined the effects of the epoxidized castor oil (ECO) and Al 2 O 3 content on the thermal stability and fracture toughness of the diglycidylether of bisphenol-A (DGEBA)/ECO/Al 2 O 3 ternary composites using a range of techniques. The thermal stability of the composites was decreased by the addition of ECO and Al 2 O 3 nanoparticles. The fracture toughness of the composites was improved significantly by the addition of ECO and Al 2 O 3 nanoparticles. The composite containing 3 wt % Al 2 O 3 nanoparticles showed the maximum flexural strength. Scanning electron microscopy (SEM) revealed tortuous cracks in the DGEBA/ECO/Al 2 O 3 composites, which prevented deformation and crack propagation

Evaluation of Environmental Conditions on the Curing Of Commercial Fixative and Intumescent Coatings

Energy Technology Data Exchange (ETDEWEB)

Nicholson, J. C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2016-09-26

Performance metrics for evaluating commercial fixatives are often not readily available for important parameters that must be considered per the facility safety basis and the facility Basis for Interim Operations (BIO). One such parameter is the behavior of such materials in varied, “non-ideal” conditions where ideal is defined as 75 °F, 40% RH. Coupled with the inherent flammable nature of the fixative materials that can act to propagate flame along surfaces that are otherwise fireproof (concrete, sheet metal), much is left unknown when considering the safety basis implications for introducing these materials into nuclear facilities. Through SRNL’s efforts, three (3) fixatives, one (1) decontamination gel, and six (6) intumescent coatings were examined for their responses to environmental conditions to determine whether these materials were impervious to non-nominal temperatures and humidities that may be found in nuclear facilities. Characteristics that were examined included set-to-touch time, dust free time, and adhesion testing of the fully cured compounds. Of these ten materials, three were two-part epoxy materials while the other seven consisted of only one constituent. The results show that the epoxies tested are unable to cure in sub-freezing temperatures, with the low temperatures inhibiting crosslinking to a very significant degree. These efforts show significant inhibiting of performance for non-nominal environmental conditions, something that must be addressed both in the decision process for a fixative material to apply and per the safety basis to ensure the accurate flammability and material at risk is calculated.

Evaluation of Environmental Conditions on the Curing Of Commercial Fixative and Intumescent Coatings

Energy Technology Data Exchange (ETDEWEB)

Nicholson, J. C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2017-01-10

Performance metrics for evaluating commercial fixatives are often not readily available for important parameters that must be considered per the facility safety basis and the facility Basis for Interim Operations (BIO). One such parameter is the behavior of such materials in varied, “non-ideal” conditions where ideal is defined as 75 °F, 40% RH. Coupled with the inherent flammable nature of the fixative materials that can act to propagate flame along surfaces that are otherwise fireproof (concrete, sheet metal), much is left unknown when considering the safety basis implications for introducing these materials into nuclear facilities. Through SRNL’s efforts, three (3) fixatives, one (1) decontamination gel, and six (6) intumescent coatings were examined for their responses to environmental conditions to determine whether these materials were impervious to non-nominal temperatures and humidities that may be found in nuclear facilities. Characteristics that were examined included set-to-touch time, dust free time, and adhesion testing of the fully cured compounds. Of these ten materials, three were two-part epoxy materials while the other seven consisted of only one constituent. The results show that the epoxies tested are unable to cure in sub-freezing temperatures, with the low temperatures inhibiting crosslinking to a very significant degree. These efforts show significant inhibiting of performance for non-nominal environmental conditions, something that must be addressed both in the decision process for a fixative material to apply and per the safety basis to ensure the accurate flammability and material at risk is calculated.

Contact allergy to epoxy resin

DEFF Research Database (Denmark)

Bangsgaard, Nannie; Thyssen, Jacob Pontoppidan; Menné, Torkil

2012-01-01

Background. Epoxy resin monomers are strong skin sensitizers that are widely used in industrial sectors. In Denmark, the law stipulates that workers must undergo a course on safe handling of epoxy resins prior to occupational exposure, but the effectiveness of this initiative is largely unknown...... in an educational programme. Conclusion. The 1% prevalence of epoxy resin contact allergy is equivalent to reports from other countries. The high occurrence of epoxy resin exposure at work, and the limited use of protective measures, indicate that reinforcement of the law is required....

Recyclable epoxy resins: An example of green approach for advanced composite applications

Science.gov (United States)

Cicala, Gianluca; Rosa, Daniela La; Musarra, Marco; Saccullo, Giuseppe; Banatao, Rey; Pastine, Stefan

2016-05-01

Automotive composite applications are increasingly growing due to demand for lightweight structures to comply to the requirements for fuel reduction. HP-RTM is gaining relevance as one of the preferred production technologies for high volume applications. The BMW i3 life module being a notable example of HP-RTM application. The key aspects of HP-RTM are the short injection times (i.e. less than 1min) and the fast curing of the thermoset resins (i.e. less than 10min). The choice of using thermosets poses relevant issues for their limited recycling options. The standard recycling solution is the incineration but, this solution poses some concerns in terms of global environmental impact. Novel solutions are presented in this work based on the use of recyclable epoxy systems. In our work the results of experimentation carried out by our group with cleavable ammines by Connora Technologies and bioepoxy resins by Entropy Resins will be discussed. The multiple uses of recycled matrices obtained treating the recyclable epoxy resins are discussed in the framework of a "cradle" to "crave" approach. Finally, Life Cycle Assessment (LCA) is used to evaluate the environmental benefits of the proposed approach.

Synthesis of hydrazone functionalized epoxy polymers for non-linear optical device applications

Science.gov (United States)