Waller, Jess M.; Newton, Barry E.; Beeson, Harold D.
Guide for Evaluation Nonmetallic Materials for Oxygen Service (G 63). Attempts to uncover the origins of the observed dimensional instability were hindered by uncertainties about resin grade, process history, and post-process heat history introduced by machining, annealing, and sample preparation. An approach was therefore taken to monitor property changes before and after processing and machining using a single, well-characterized lot of Neoflon CTFE.1 M400H resin. A task group consisting of the current PCTFE resin supplier, two molders, and four valve seat manufacturers was formed, and phased testing on raw resin, intermediate rod stock, and finished valve seats initiated. The effect of processing and machining on the properties of PCTFE rod stock and oxygen gas cylinder valve seats was then determined. Testing focused on two types of extruded rod stock and one type of compression-molded rod stock. To accommodate valve seat manufacturer preferences for certain rod stock diameters, two representative diameters were used (4.8 mm (0.1875 in.) and 19.1 mm (0.75 in.)). To encompass a variety of possible sealing configurations, seven different valve seat types with unique geometries or machining histories were tested. The properties investigated were dimensional stability as determined by TMA, specific gravity, differential scanning calorimetry (DSC), compressive strength, zero strength time, and intrinsic viscosity. Findings are discussed in the context of polymer structure-process-property relationships whenever possible.
Full Text Available Photoinduced Cu(II-mediated reversible deactivation radical polymerization (RDRP was employed to synthesize poly(vinylidene fluoride-co-chlorotrifluoroethylene-graft-polyacrylonitrile (P(VDF-co-CTFE-g-PAN. The concentration of copper catalyst (CuCl2 loading was as low as 1/64 equivalent to chlorine atom in the presence of Me6-Tren under UV irradiation. The light-responsive nature of graft polymerization was confirmed by “off-on” impulsive irradiation experiments. Temporal control of the polymerization process and varied graft contents were achieved via this photoinduced Cu(II-mediated RDRP.
Zheng, Libing; Wu, Zhenjun; Zhang, Yong; Wei, Yuansong; Wang, Jun
Four common types of additives for polymer membrane preparation including organic macromolecule and micromolecule additives, inorganic salts and acids, and the strong non-solvent H2O were used to prepare poly (vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) hydrophobic flat-sheet membranes. Membrane properties including morphology, porosity, hydrophobicity, pore size and pore distribution were investigated, and the permeability was evaluated via direct contact membrane distillation (DCMD) of 3.5g/L NaCl solution in a DCMD configuration. Both inorganic and organic micromolecule additives were found to slightly influence membrane hydrophobicity. Polyethylene glycol (PEG), organic acids, LiCl, MgCl2, and LiCl/H2O mixtures were proved to be effective additives to PVDF-CTFE membranes due to their pore-controlling effects and the capacity to improve the properties and performance of the resultant membranes. The occurrence of a pre-gelation process showed that when organic and inorganic micromolecules were added to PVDF-CTFE solution, the resultant membranes presented a high interconnectivity structure. The membrane prepared with dibutyl phthalate (DBP) showed a nonporous surface and symmetrical cross-section. When H2O and LiCl/H2O mixtures were also used as additives, they were beneficial for solid-liquid demixing, especially when LiCl/H2O mixed additives were used. The membrane prepared with 5% LiCl+2% H2O achieved a flux of 24.53kg/(m(2)·hr) with 99.98% salt rejection. This study is expected to offer a reference not only for PVDF-CTFE membrane preparation but also for other polymer membranes. Copyright © 2016. Published by Elsevier B.V.
Robertson, A.B.; Schaffhauser, R.J.
Melt-processable, radiation cross-linkable ethylene/chlorotrifluoroethylene copolymer compositions are provided which contain about 0.1 to 5 percent by weight of the copolymer of a radiation cross-linking promoter, about 0.01 to 5 percent by weight of an anti-oxidant and about 0.1 to 30 precent by weight of an acid scavenger. Such compositions do not give off odors when irradiated to cross-link the copolymer and do not develop bubbles after irradiation. 15 claims, no drawings
Carloni, Raffaella; Lapp, Valerie I.; Cremonese, Andrea; Belcari, Juri; Zucchelli, Andrea
This letter presents a novel rotational variable stiffness joint that relies on one motor and a set of variable stiffness springs. The variable stiffness springs are leaf springs with a layered design, i.e., an electro-active layer of electrospun aligned nanofibers of poly(vinylidene
Xu, Meili; Xiang, Lanyi; Xu, Ting; Wang, Wei; Xie, Wenfa; Zhou, Dayu
Future flexible electronic systems require memory devices combining low-power operation and mechanical bendability. However, high programming/erasing voltages, which are universally needed to switch the storage states in previously reported ferroelectric organic field-effect transistor (Fe-OFET) nonvolatile memories (NVMs), severely prevent their practical applications. In this work, we develop a route to achieve a low-voltage operating flexible Fe-OFET NVM. Utilizing vertical phase separation, an ultrathin self-organized poly(styrene) (PS) buffering layer covers the surface of the ferroelectric polymer layer by one-step spin-coating from their blending solution. The ferroelectric polymer with a low coercive field contributes to low-voltage operation in the Fe-OFET NVM. The polymer PS contributes to the improvement of mobility, attributing to screening the charge scattering and decreasing the surface roughness. As a result, a high performance flexible Fe-OFET NVM is achieved at the low P/E voltages of ±10 V, with a mobility larger than 0.2 cm2 V-1 s-1, a reliable P/E endurance over 150 cycles, stable data storage retention capability over 104 s, and excellent mechanical bending durability with a slight performance degradation after 1000 repetitive tensile bending cycles at a curvature radius of 5.5 mm.
Full Text Available Dielectric materials with high electric energy density and low dielectric loss are critical for electric applications in modern electronic and electrical power systems. To obtain desirable dielectric properties and energy storage, nanocomposites using Ba0.5Sr0.5TiO3 (BST as the filler and poly(vinylidene fluoride-chlorotrifluoroethylene as the matrix material are prepared with a uniform microstructure by using a newly developed process that combines the bridge-linked action of a coupling agent, solution casting, and a hot-pressing method. When a proper amount of coupling agent is used to modify the surface of the nanoparticles, the composite exhibits a higher dielectric constant and a more uniform microstructure. A dielectric constant of 95, dielectric loss of 0.25, and energy density of 2.7 J/cm3 is obtained in the nanocomposite with 30 vol.% of BST and 15 wt.% of coupling agent. The results suggest that the energy storage ability of the composites could be improved by the surface modification of the fillers and from the interface compatibility between the fillers and the polymer matrix.
Linares, R.C.; Nienart, L.F.; Toelcke, G.A.
A process is described for preparing melt-processable nuclear shielding compositions from chloro-fluoro substituted ethylene polymers, particularly PCTFE and E-CTFE, containing 1 to 75 percent by weight of a gadolinium compound. 13 claims, no drawings
Full Text Available This study reports the fabrication and characterization of poly(ethylene oxide (PEO and poly(vinylidenefluoride-co-chlorotrifluoroethylene (PVDF-CTFE nanofibrous separators for lithium-ion batteries loaded with different amounts of fumed-silica and tin oxide nanoparticles. Membrane morphological characterization (SEM, TEM showed the presence of good-quality nanofibres containing nanoparticles. Thermal degradation and membrane mechanical properties were also investigated, and a remarkable effect of nanoparticle addition on membrane mechanical properties was found. In particular, PEO membranes were strengthened by the addition of metal oxide, whereas PVDF-CTFE membranes acquired ductility.
as follows, lungs, liver, right kidney, perirenal fat , right testicle, and brain Each tissue was weighed A sample of about 1 g was sectioned from each...and feces were collected for CTFE analysis from each animal group Kidney, lung, liver, testes, brain, and fat were taken at sacrifice for CTFE...concentrated sample below 500 pg/mL for calibration purposes Lung, liver, testes, and brain extracts were diluted 1:20, kidney 1, and fat 1.1000 49 Gas
Liu, H. Z.; Wang, M. H.; Wang, Z. F.; Bian, J. M.
Due to using gaseous fluorine monomer with toxicity, waterborne fluoropolymers are synthesized by semi-continuous high-pressure emulsion polymerization method which differs from free-pressure emulsion polymerization. To dates, the research on preparing process and kinetics for high-pressure emulsion polymerization is reported relatively less, which hinders researchers from understanding of mechanisms for monomer-fluorinated emulsion polymerization. The paper also provides a new method by element auxiliary analysis to calculate kinetics parameters of high-pressure emulsion polymerization. Based on aforementioned consideration, waterborne fluoropolymers were prepared by copolymerization of chlorotrifluoroethylene (CTFE), vinyl acetate (VAc), butyl acrylate (BA) and vinyl ester of versatic acid (Veova 10) using potassium persulfate as initiator and mixed surfactants. The kinetics of emulsion polymerization of waterborne fluoropolymers was then investigated. Effects of emulsifier concentration, initiator concentration, and polymerization temperature on polymerization rate (Rp) were evaluated, and relationship was described as Rp∝[I]0.10 and Rp∝[E]0.12. The apparent activation energy was determined to be 33.61 kJ·mol-1. Moreover, the relative conversion rate of CTFE with the other monomers was observed, and results indicated that CTFE monomer more uniformly copolymerized with the other monomers. The resulting emulsion properties and pressure change in an autoclave were evaluated at different stirring rates. The initial reaction time, defined as the beginning time of dropwise addition, was determined by the change in solid content and particle size of emulsion.
Ju, Woo-Eon; Moon, Yong-Ju; Park, Cheon-Ho; Choi, Seung Tae
To provide tactile feedback on flexible touch screens, transparent relaxor ferroelectric polymer film vibrators were designed and fabricated in this study. The film vibrator can be integrated underneath a transparent cover film or glass, and can also produce acoustic waves that cause a tactile sensation on human fingertips. Poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) [P(VDF-TrFE-CTFE)] polymer was used as the relaxor ferroelectric polymer because it produces a large strain under applied electric fields, shows a fast response, and has excellent optical transparency. The natural frequency of this tactile-feedback touch screen was designed to be around 200–240 Hz, at which the haptic perception of human fingertips is the most sensitive; therefore, the resonance of the touch screen at its natural frequency provides maximum haptic sensation. A multilayered relaxor ferroelectric polymer film vibrator was also demonstrated to provide the same vibration power at reduced voltage. The flexible P(VDF-TrFE-CTFE) film vibrators developed in this study are expected to provide tactile sensation not only in large-area flat panel displays, but also in flexible displays and touch screens. (papers)
Synthesis and Characterization of Waterborne Fluoropolymers Prepared by the One-Step Semi-Continuous Emulsion Polymerization of Chlorotrifluoroethylene, Vinyl Acetate, Butyl Acrylate, Veova 10 and Acrylic Acid
Full Text Available Waterborne fluoropolymer emulsions were synthesized using the one-step semi-continuous seed emulsion polymerization of chlorotrifluoroethylene (CTFE, vinyl acetate (VAc, n-butyl acrylate (BA, Veova 10, and acrylic acid (AA. The main physical parameters of the polymer emulsions were tested and analyzed. Characteristics of the polymer films such as thermal stability, glass transition temperature, film-forming properties, and IR spectrum were studied. Meanwhile, the weatherability of fluoride coatings formulated by the waterborne fluoropolymer and other coatings were evaluated by the quick ultraviolet (QUV accelerated weathering test, and the results showed that the fluoropolymer with more than 12% fluoride content possessed outstanding weather resistance. Moreover, scale-up and industrial-scale experiments of waterborne fluoropolymer emulsions were also performed and investigated.
Han, Kuo; Gadinski, Matthew; Wang, Qing
Numerous efforts have been made in the past decades to improve the energy storage capability of dielectric capacitors by incorporating ceramic addictives into polymers. Ferroelectric polymers have been particularly interesting as matrix for dielectric composites because of their highest dielectric permittivity and energy density. However, most polymer composites suffer from significantly reduced breakdown strength, which compromises the potential gain in energy density. In this work, various metallic alkoxide were introduced into the functionalized ferroelectric poly(vinylidene fluoride-co- chlorotrifluoroethylene), P(VDF-CTFE), via covalent bonding. The composite with the optimized composition exhibited the Weibull statistical breakdown strength of 504.8 MV/m, 67.6 % higher than the pristine polymer. The enhanced breakdown strength was mainly ascribed to the cross-linking and the formation of deep traps, which effectively reduced the conduction and further lowered the energy loss. Additionally, the homogeneous dispersion of the inorganic phase and the small contrast in permittivity between the polymer and amorphous oxides also contribute to the improved dielectric strength. The dielectric spectra of the composites have been recorded at varied temperatures and frequencies, which revealed the presence of the interfacial polarization layer in the composites.
Wang, Linyuan; Ma, Jie; He, Xudong; Ke, Hao; Liu, Jian; Zhang, Chaoyang
Learning the micro-mechanisms of fluorinated polymers during mechanical response is more difficult than that of common polymers due to the unique intrinsic characteristics of the fluorine element. In this paper, we applied molecular dynamics simulations to study deformation mechanisms of poly(vinylidine fluoride-co-chlorotrifluoroethylene) during uniaxial tension. We analyzed the variations of individual energy components and structural distribution curves versus strain in addition to the commonly used stress-strain curves and microstructure evolutions during stretching. The elastic limit is ɛ = 0.02, ɛ = 0.06 is the yield point, ɛ = 0.24 is the termination of the softening, necking occurs at 0.24 strain hardening occurs at 0.5 strain rate, the obvious effect of strain rate can be seen at the yield region and strain softening region, and the stress values are not influenced by strain rates at the softening and hardening stages. Overall, total potential energy is mainly correlated with non-bonded energy, and the proportion of ΔE coul overwhelms all the others. The energy components are ordered: ΔE coul > ΔE vdwl > > ΔE angle > ΔE dihed > ΔE bond . The chain conformation at yield point is almost unchanged compared with the pre-stretching conformation. The chain conformations at the end of strain softening changes more obviously than that at yield point. The molecular chains maintain random coil structure before strain hardening, and switch into a stretch chain conformation gradually during strain hardening. The maximum change in bond angle during the stretching process is F-C-H, the largest change in bond length is the C-Cl bond, and the largest change in dihedral angle is H-C-C-H. The change of non-bonded interaction in the poly(VDF-co-CTFE) system is much larger than the bonding interaction, and the main factor affecting bonding interaction is the change of angles. Graphical abstract Poly(vinylidine fluoride
Almadhoun, Mahmoud N.
Increasing demands for efficient energy storage in microelectronics has pushed the scientific community towards finding suitable materials that can effectively deliver high pulse power in miniaturized systems. Polymer-ceramic composites are considered to be one possible solution towards the fabrication of high energy density capacitors, whether as embedded capacitors or gate insulators in organic field effect transistors (OFETs). Selecting high permittivity ceramics mixed with polymers with high breakdown field strengths would be the wisest approach towards enhancing energy storage. As such, novel ferroelectric polymers such as P(VDF-TrFE-CTFE) are being developed and researched, all displaying record dielectric values (K > 50) as promising candidates for high energy density composite capacitors (> 25 J/cm3). However, much work is still needed to understand the interaction mechanisms between the phases. We aim to seek an understanding of the processing challenges, especially in terms of fabricating thin film ferroelectric polymers and their application in nanocomposite capacitors while effectively maintaining optimized performance when embedded in flexible electronics. A process for synthesizing high performance P(VDF-TrFE) thin films is developed realizing the importance of controlling several process parameters to achieve high quality devices. Electrical and physicochemical characterization demonstrate how the performance of the polymer films improves with prolonged annealing periods by allowing sufficient time for solvent evaporation, crystallization and preferential-orientation of the crystallites. The polymer P(VDF-TrFE) is then used as a host material with barium titanate (BTO) nanoparticles below 100 nm (K = 150) as a ceramic filler in nanocomposite films. Facile surface modification by hydroxylation proved to be essential in the performance of the devices in terms of leakage current. A decrease of approximately 2 orders of magnitude in current leakage is
Sigamani, Nirmal Shankar
electroactive polymers, the relatively high electrical conductivity and low breakdown limits their use for practical applications. So next step was to exploit the advantages of a conductive carbon nanostructure while controlling its network to better impact its electrical properties which could also lead to higher breakdown strength. Based on the promising impact of hybrid nanofillers on the ferroelectric polymer PVDF, a similar polymer with a relaxor ferroelectric character is considered owing to its higher inherent electroactive response and higher breakdown strength. Given that it is not broadly studied, there was a need to understand structure-property relationship of the PVDF TrFE CTFE terpolymer. Hence, the effect of processing conditions (such as annealing times and isothermal crystallization temperatures) on the microstructure and the subsequent electromechanical properties were analyzed. This structure-property analysis helped to understand the relation between the different types of crystalline phases and the degrees of crystallinity as well as to observe crystal sizes as they relate to the electric field induced strain. As a final step, the effect of the hybrid SWNT/GO on both microstructure and electromechanical properties of the terpolymer were studied. The hybrid nanofillers were chemically modified to form a covalent bond between them to improve their interaction. The morphology of the hybrid nanofillers after the chemical modification was studied for two different chemical modification routes: one using thionyl chloride, other using NHS and EDAC as catalysts. Of the two methods, the NHS and EDAC catalyst method showed a strong uniform interaction, confirmed by SEM images and FTIR results, with a shift in the peak to 1630 cm-1. Finally, the effect of hybrid SWNT and GO on the electromechanical properties were studied and, interestingly, the hybrid terpolymer nanocomposite film showed a lower electroactive strain compared to pure terpolymer at the same applied