锂电池用聚偏氟乙烯粘结剂

锂电池用粘结剂是制造锂电池的重要材料之一,可直接影响其性能.介绍了锂电池用粘结剂应具备的特性、种类及存在的问题;叙述了日本专利中,偏氟乙烯作为锂电池用粘结剂和用偏氟乙烯与第二及第三单体的共聚改性、聚偏氟乙烯与其他聚合物共混改性等的方法.     

The radiation-initiated solution polymerization of vinylidene fluoride

The radiation-initiated solution polymerization of vinylidene fluoride was examined in an effort to determine the effect of polymerization conditions on the head-to-head content of the resulting poly(vinylidene fluoride). No appreciable change was observed in the head-to-head content when this new type of polymerization was utilized. However, the polymers which resulted had melting points 10–15°C higher than those of the suspension-polymerized poly(vinylidene fluoride), higher crystallinity, and, when trifluoroacetic acid was used as a solvent, a higher molecular weight.     

Hydrogen bonding in PMMA-fluorinated polymer blends: FTi.r. investigations using ester model molecules

The sensitivity of the carbonyl stretching vibration of methyl acetate to interactions with the surroundings is re-examined through FTi.r. analyses and Fourier self deconvolution. The relevant conclusions permit a study of the mixtures of methyl acetate and methyl pivalate with various fluorinated polymers. Evidence is given for the existence of hydrogen bonding between poly(vinylidene fluoride) and these model compounds of poly(methylmethacrylate). Arguments are put forward in favour of a similar behaviour in poly(vinylidene fluoride)/poly(methylmethacrylate) blends.     

Phase behavior of polycarbonate blends with selected halogenated polymers

Bisphenol A polycarbonate is shown to be miscible with a vinylidene chloride based polymer containing 13.5% by weight of vinyl chloride. On the other hand, polycarbonate is found to be immiscible with poly(vinyl chloride), poly(vinylidene fluoride), and polyepichlorohydrin.     

Thermal transitions,microstructure and miscibility in ternary polyblends based on poly(vinylidene fluoride)

The morphology, microstructure and compatibility of binary and ternary polyblends based on poly(vinylidene fluoride) have been studied by means of glass transition temperature, isothermal crystallization kinetics analysis and scanning electron microscopy in order to determine the possibilities offered by poly(vinyl acetate) for compatibilizing poly(vinylidene fluoride) and polystyrene. Calorimetric and dynamic mechanical analyses demonstrate that poly(vinyl acetate) tends to ‘compatibilize’ blends of PVF₂/PS, although the results of the two analyses do not agree with each other; we presume that this is due to differences in the techniques employed.     

Compatibilization of semicrystalline polymeric alloys through sepiolite addition

This study was conducted to examine the possibilities offered by sepiolite as a compatibilizing agent in the incompatible blend consisting of poly(vinylidene fluoride) and polystyrene. The effect of sepiolite on the crystalline microstructure and morphology was determined through isothermal crystallization and spherulite growth of the system under study. The effect of sepiolite on the compatibility of the system was also studied. The glass-transition temperature was determined, as well as the Flory–Huggins thermodynamic interaction parameter through two different routes: differential scanning calorimetry and inverse gas chromatography. A parallel study was conducted for the compatible system poly(vinylidene fluoride)/poly(methyl methacrylate). © 1994 John Wiley & Sons, Inc.     

Stress corrosion cracking of poly(vinylidene fluoride) in sodium hydroxide

Stress corrosion cracking of poly(vinylidene fluoride) in sodium hydroxide solution is investigated. Poly(vinylidene fluoride) (PVDF) is embrittled in the presence of solutions of sodium hydroxide. Cracks developed in specimens of PVDF subjected to load and solution of NaOH. Reddish-brown deposits appear before cracks can be seen. Straining the material slightly above its yield point retards the cracking activity. An explanation for this behavior is provided.     

Polymer blends containing poly(vinylidene fluoride). Part I: Poly(alkyl acrylates)

The transitional behavior of poly(vinylidene fluoride) (PVF₂) blends with poly(methyl acrylate) and with poly(ethyl acrylate) was examined by differential thermal analysis and dynamic mechanical testing. Both blend systems were judged to be miscible on the bases of the presence of single, composition dependent glass transitions and of the strong melting point depression of the PVF₂ component, Blends of poly(isopropyl acrylate) with poly(vinylidene fluoride) were found to be immiscible. These results suggest that miscibility of the acrylate series depends on a specific attractive interaction between the PVF₂ and oxygen within the acrylate and the effect of this interaction is diminished as the hydrocarbon content of the ester is increased.     

Enhancing Dielectric Properties of Poly(vinylidene fluoride)-Based Hybrid Nanocomposites by Synergic Employment of Hydroxylated BaTiO3 and Silanized Graphene

The poly(vinylidene fluoride)-based hybrid composites with a blended BaTiO₃–exfoliated graphene as filler were fabricated with the efficient method of solution casting and hot pressing and their dielectric properties were investigated in detail. In advance, both of the nanoparticles are functionalized to improve the interfacial bonding between fillers and matrix. Synergistic effects arising from blending zero-dimensional BaTiO₃ and two-dimensional exfoliated grapheneare identified by the improved distribution of nanoparticles in poly(vinylidene fluoride) host and mitigating the concomitant increase in dielectric loss while maintaining the high dielectric constant values of the composites.     

Effect of hydrostatic pressure and temperature on the mechanical loss properties of polymers: 2. Halogen polymers

The shear modulus, G′, and loss tangent, tan δ, of a number of halogen polymers have been measured as a function of temperature at various pressures. The polymers studied were various poly(vinyl chloride) (PVC) samples, poly(vinylidene chloride) (PVDC), poly(vinyl fluoride) (PVF), poly(vinylidene fluoride) (PVDF) and a tetrafluoroethylene-hexafluoropropylene copolymer. The glass transition temperatures are shifted upwards by pressure by amounts varying between about 11°C and 25°C/1000 atm. In the case of PVC it has proved possible to compare the results with theory and the observed shift is found to be considerably smaller than the predicted value. In PVDC and PVDF the secondary relaxations are also shifted upwards by the application of pressure.     

改性炭黑对复合材料介电性能的影响

为提高复合材料的介电性能,采用硅烷偶联剂KH550对炭黑表面进行改性,并与聚偏氟乙烯、钛酸钡制成复合材料,研究了复合材料介电性能.结果表明,硅烷偶联剂KH550改变了炭黑表面结构,使炭黑/聚偏氟乙烯复合材料的介电常数在104 Hz时提高了15％以上,填充钛酸钡后介电常数进一步增加,介电损耗可控制在较低的范围.     

The influence of sepiolite on the dynamic moduli and thermal transition of compatible and incompatible blends based on poly(vinylidene fluoride)

This paper reports on a study of dynamic moduli and thermal transitions of poly(vinylidene fluoride) in compatible blends with poly(methylmethacrylate) and in non-compatible blends with polystyrene. The effects of sepiolite on the compatibility of these blends have been studied.     

Preparation and anti-fouling property of carboxybetaine-based zwitterionic PVDF membrane

This work describes the synthesis and anti-fouling properties of poly(vinylidene fluoride) membrane, grafted with carboxybetaine-based zwitterions. An amphiphilic copolymer, poly(vinylidene fluoride)-graft- poly(N,N-dimethylamino-2-ethylmethacrylate) (PVDF-g-PDMAEMA), was synthesized by radical graft copolymerization, followed by casting the copolymer into a flat membrane, by an immersed phase inversion method. PVDF-g-PDMAEMA membrane was reacted with sodium chloroacetate (SCA) to yield a carboxybetaine-based zwitterionic surface. The membrane showed significantly enhanced hydrophilicity, due to the hydration ability of carboxybetaine-based zwitterions, which inhibited protein adsorption. Compared to pristine PVDF-g-PDMAEMA membrane, carboxybetaine-based zwitterionic membrane exhibited a higher flux recovery in the cyclic filtration.     

Kinetics of polymer surface fluorination: Elemental and plasma-enhanced reactions

E.s.c.a. spectra of surface fluorinated polyethylene, poly(vinyl fluoride), and poly(vinylidene fluoride) are reported. Two reaction environments were used in this study: exposure to elemental fluorine and immersion in a glow discharge plasma. The systematic variation of fluorine composition in the polymer phase is shown to have a dramatic effect on the kinetics of the elemental reaction and little effect in the plasma reaction.     

Comparison of gas permeation in vinyl and vinylidene polymers

The gas transport properties of several simple vinyl and vinylidene polymers are compared to examine the effect of pendant group type (H, CH₃, F, Cl) and symmetry of placement. The literature contains extensive information about these polymers, which has been critically reviewed to obtain consistent data for interpretation of the effect of structure on gas permeability. The gas transport data available for many of these polymers are quite variable because of differences in additives, thermal history, and crystallinity. The values used here are from studies where the physical properties of the film were reported along with the transport data. The appropriate data were not available for poly(vinyl fluoride) or poly(vinylidene chloride). For poly(vinyl fluoride), permeability measurements and thermal analysis were done to supply this information. Results for poly(vinylidene chloride) were obtained by extrapolation of copolymer permeation properties. Estimates of the permeability of oxygen in the amorphous phase of each polymer are discussed in terms of the estimated fractional free volume of that phase. In this way, the intrinsic effects of molecular structure on gas permeation exclusive of crystallinity effects have been evaluated.     

Mechanical relaxations of poly(vinylidene fluoride) and some of its copolymers

The dynamic mechanical properties of poly(vinylidene fluoride) have been studied under isochronal conditions and the effect of thermal treatment examined. The results are compared with a product of different molecular weight distribution. The study also included the mechanical relaxation spectra of copolymers of vinylidene fluoride and chlorotrifluoroethylene at four compositions and four frequencies as a function of temperature. The thermodynamic parameters associated with the main relaxations were determined and the results discussed on the basis of available information on the drgree of crystallinity, copolymer heterogeneity, and main chain flexibility.     

The Tribological Mechanism of Poly(Vinylidene Fluoride) Composites Reinforced with Carbon Fibers

The current study examines the tribological performance of poly(vinylidene fluoride) (PVDF) and carbon fiber-reinforced poly(vinylidene fluoride) (CF/PVDF) under dry sliding condition. Different contents of carbon fibers were employed as reinforcement. All filled and unfilled polyimide composites were tested against CGr15 ball and representative testing was performed. The effects of carbon fiber content on tribological properties of the composites were investigated. The worn surface morphologies of neat PVDF and its composites were examined by scanning electron microscopy (SEM) and the wear mechanisms were discussed. Moreover, all filled PVDFs have superior tribological characteristics to unfilled PVDFs. The optimum wear reduction was obtained when the content of carbon fiber is 20 vol%.     

氟树脂性能与加工应用(续12)

叙述了聚四氟乙烯悬浮树脂的螺杆挤出成型的原理、方法及设备。介绍了经过烧结后PTFE半制品的车削、压延及表面处理的方法、原理和设备。     

Preparation and tribological properties of carbon fibre reinforced poly(vinylidene fluoride) composites

Abstract

The current study examines the tribological performance of poly(vinylidene fluoride) (PVDF) and carbon fibre reinforced poly(vinylidene fluoride) (CF/PVDF) under dry sliding condition. Different contents of carbon fibres (CFs) were employed as reinforcement. All filled and unfilled polyimide composites were tested against CGr15 ball and representative testing was performed. The effects of CF content on tribological properties of the composites were investigated. The worn surface morphologies of neat PVDF and its composites were examined by scanning electron microscopy and the wear mechanisms were discussed. Moreover, all filled PVDFs have superior tribological characteristics to unfilled PVDFs. The optimum wear reduction was obtained when the content of CF is 20 vol.-%.     

Effects of macromolecular configuration of thermally sensitive binder in lithium‐ion battery

In order to suppress heat generation of nail‐penetrated lithium‐ion battery (LIB) cell, thermally sensitive binders (TSB) based on poly(vinylidene fluoride) (PVDF) and poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) were investigated. The testing data showed that with appropriate treatment, TSB could efficiently reduce the peak temperature associated with internal shorting, and did not influence the cycling performance of LIB. The molecular weight of TSB was not a vital factor, while crosslinking was critical. This technology can be used to mitigate thermal runaway of LIB, enabling safe and robust large‐scale energy storage. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45078.