PVDF-based polymers

All the ordinary extrusion and molding equipment and techniques can be used to process PVDF into different shapes ranging from pipes, fitting, parts, solid rods and sheets, to thin films. Longevity of equipment can be extended using special alloys on the surface that is in contact with molten PVDF, but usually it is not necessary. PVDF based polymers are available commercially in a wide range of melt flow index and with additives to enhance processing or end use properties. However, both homopolymers and copolymers may be shaped from the molten state without extrusion aids or thermal stabilizers. 

Guo, L., Liu, Y. H., Zhang, C., and Chen, J. 2011. Rreparation of PVDF-based polymer inclusion membrane using ionic liquid plasticizer and Cyphos IL 104 carrier for Cr(VI) transport. Journal of Membrane Science 372 314-321. 

Zhang ZC, Chung TC (2007) The stnicture-propeity relationship of PVDF-based polymers with energy storage and loss under applied electric fields. Macnnnolecules 2007 9391... 

The electrostrictive behavior of P(VDF-CTFE) copolymers was investigated (Li et al. 2004 Li et al. 2006). A high electromechanical response was obtained in these copolymer films. As other PVDF-based polymers, the processing condition plays a very critical role on its properties. For a well-stretched and annealed P (VDF-CTFE) 88/12 copolymer film, a longitudinal electrostrictive strain as much as 5.5 % was obtained. A linear relationship between the strain response and the was observed, which indicates the electrostrictive nature of the electromechanical response in P(VDF-CTFE) copolymers. The corresponding electric field-related electrostrictive coefficient for the copolymer film is obtained as Mss = —1.23 0.02 X 10 (m /V ) (Li et al. 2006). 

PVDF-based polymers dissolve easily in polar solvents such as N-methyl pyrrolidone (NMP) and N,N-dimethylformamide (DMF). Their affinity for solvents with polar groups such as the carbonyl group is high, and they do not swell easily in solvents such as ethanol or hydrocarbons. Their solubility in different solvents and the performance of the solutions are related to the polymerization method. The viscosity of the PVDF obtained by suspension polymerization and its solubility in NMP are higher than those of a product such as Kynar, which is obtained by emulsion polymerization. For some as-yet unknown reason, the PVDF solution obtained by suspension... 

MUNiYANDi, N., KALAisELVi, N., PERiYASAMY, p., et al. Optimisation of PVdF-based polymer electrolytes,/. Power Sources, 2001,96(1), 14-9. 

The most common piezoelectric polymers are PVDF, based on the monomer CH2 CF2 and copolymers of PVDF with C2F3H. Although there are many sources for materials that are nominally piezoelectric, sources for reproducible materials are limited. 

Gel polymer lithium-ion batteries replace the conventional liquid electrolytes with an advanced polymer electrolyte membrane. These cells can be packed in lightweight plastic packages as they do not have any free electrolytes and they can be fabricated in any desired shape and size. They are now increasingly becoming an alternative to liquid-electrolyte lithium-ion batteries, and several battery manufacturers. such as Sanyo. Sony, and Panasonic have started commercial production.Song et al. have recently reviewed the present state of gel-type polymer electrolyte technology for lithium-ion batteries. They focused on four plasticized systems, which have received particular attention from a practical viewpoint, i.e.. poly(ethylene oxide) (PEO). poly (acrylonitrile) (PAN). ° poly (methyl methacrylate) (PMMA). - and poly(vinylidene fluoride) (PVdF) based electrolytes. ... 

One particular version of the lithium-ion gel polymer cells, also known as plastic lithium-ion cell (PLION). was developed by Bellcore (now Telcordia Technologies).In this case. Gozdz et al. developed a microporous plasticized PVdF—HFP based polymer electrolyte which served both as separator and electrolyte. In PLION cells, the anode and cathode are laminated onto either side of the gellable membrane. Good adhesion between the electrodes and the membranes is possible because all three sheets contain significant amounts of a PVdF copolymer that can be melted and bonded during the lamination step. 

Considering all the above criteria, PSf, PES, PAN, PVDF and cellulose-based polymers (cellulose acetates/CA/and regenerated cellulose) are mostly used for commercial UF membranes (see also Section 2.6.1). 

Reddy, Ch.V.S., Zhu, Q.-Y, and Mai, L.-Q. 2007. Electrochemical studies on PVC/PVdF blend-based polymer electrolytes. Journal of Solid State Electrochemistry 11, 543-548. Reinen, D., Kohl, P, and Muller, C. 2004. The nature of the colour centres in Maya blue —... 

The effects of simultaneous AO/VUV exposure of the two vinylidene fluoride based polymers were also examined. In both cases significant weight loss and surface erosion resulted from AO attack. Erosion yields were 2.8xl0 24 cm3/atom for PVDF and 2.5x1 O 24 cm3/atom for P(VDF-TrFE), consistent with previous literature data for similar materials. The film orientation of PVDF samples was reflected in the surface topology features after exposure, while the less orientated P(VDF-TrFE) samples had less regular surface patterning after exposure. Significantly, neither AO nor VUV irradiation dramatically altered the piezoelectric properties and we propose that these materials should perform satisfactorily under moderate LEO conditions. 

Recent advances in PVDF-based materials have led to the elimination of the hysteretic behavior characteristic of ferroelectrics. For this reason, these PVDF-based materials are classified as relaxor ferroelectric polymers they will be discussed under the Electrostrictive Polymers heading. 

Poly(vinylidene fluoride) (PVDF) has been recently tested as the base polymer in ionic liquid (IL)-based PIMs [13-15]. PVDF is a thermoplastic fluoropolymer with high hydrophobicity, good chemical resistance, and excellent thamal and mechanical stability making it attractive as a base polymer for PIMs. 

The common base polymers used in PMs are PVC and CTA, and each of these has some limitations such as instability caused by acidity or alkalinity of the aqueous phase. CTA suffers from hydrolysis reactions in strongly acidic solutions, and PVC undergoes dehydrochlorination under alkaline conditions and gradually turns brittle and black. Thus, alternative base polymers may be of use, and one such example is PVDF and its copolymers that are relatively inert under most conditions. 

The base polymer film type and its properties (such as film thickness, extent of orientation, and molar mass) have significant effect on both the degree of grafting and resultant membrane properties [64,65]. Walsby et al. [65] have reported that under identical conditions, grafting of styrene onto different base polymers yielded different graft levels. The authors indicated that graft levels were 5% for PTFE, 56% for PVDF, 28% for FEP, and 62% for ETFE. It... 

Mattsson, B., Ericson, H., ToreU, L. M., Simdhohn. F., (1999) Micro-Raman Investigations of PVDF-Based Proton-Conducting Membranes. Polymer Science Part A Polymer Chemistry, Vol. 37, pp.3317-3327, ISSN 1099-0518. 

The significant contribution of Nafion or perfluorosulfonic membranes to the cost of the fuel cells stacks and the high alcohol crossover levels that affect the fuel efficiency, prompted the development of radiation grafted proton exchange membranes based on poly(ethylene-tetrafluoroethylene) (ETFE) [172-178], PVdF [175], andPTFE [179]. The peroxy radicals produced on the base polymer by y-ray, electron- or proton-beam, react with styrene to form a co-polymer that is then sulphonated. 

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