Vinylidene fluoride molecular weight

Polymer gels and ionomers. Another class of polymer electrolytes are those in which the ion transport is conditioned by the presence of a low-molecular-weight solvent in the polymer. The most simple case is the so-called gel polymer electrolyte, in which the intrinsically insulating polymer (agar, poly(vinylchloride), poly(vinylidene fluoride), etc.) is swollen with an aqueous or aprotic liquid electrolyte solution. The polymer host acts here only as a passive support of the liquid electrolyte solution, i.e. ions are transported essentially in a liquid medium. Swelling of the polymer by the solvent is described by the volume fraction of the pure polymer in the gel (Fp). The diffusion coefficient of ions in the gel (Dp) is related to that in the pure solvent (D0) according to the equation ... 

Most ultrafiltration membranes are porous, asymmetric, polymeric structures produced by phase inversion, i.e., the gelation or precipitation of a species from a soluble phase. See also Membrane Separations Technology. Membrane structure is a function of the materials used (polymer composition, molecular weight distribution, solvent system, etc) and the mode of preparation (solution viscosity, evaporation time, humidity, etc.). Commonly used polymers include cellulose acetates, polyamides, polysulfoncs, dyncls (vinyl chlondc-acrylonitrile copolymers) and puly(vinylidene fluoride). 

The homopolymers poly(methyl methacrylate) and poly-(ethyl methacrylate) are compatible with poly(vinylidene fluoride) when blended in the melt. True molecular com-patibility is indicated by their transparency and a single, intermediate glass transition temperature for the blends. The Tg results indicate plasticization of the glassy methacrylate polymers by amorphous poly(vinylidene fluoride). The Tg of PVdF is consistent with the variation of Tg with composition in both the PMMA-PVdF and PEMA-PVdF blends when Tg is plotted vs. volume fraction of each component. PEMA/PVdF blends are stable, amorphous systems up to at least 1 PVdF/I PEMA on a weight basis. PMMA/ blends are subject to crystallization of the PVdF component with more than 0.5 PVdF/1 PMMA by weight. This is an unexpected result. 

The inclusion of the relatively large chlorine into the polymeric chain reduces the tendency to crystallize. Commercially available grades include a homopolymer, which is mainly used for special applications, and copolymers with small amounts (less than 5%) of vinylidene fluoride.84 The products are supplied as powder, pellets, pellets containing 15% glass liber, and dispersions. Low-molecular-weight polymer is available as oil or grease. The oil is used to plasticize PCTFE.85... 

Raw-gum fluorocarbon elastomers are transparent to translucent with molecular weights from approximately 5000 (e.g., VITON LM with waxy consistency) to over 200,000. The most common range of molecular weights for commercial products is 100,000 to 200,000. Polymers with molecular weights over 200,000 (e.g., Kel-F products) are very tough and difficult to process. Elastomers prepared with vinylidene fluoride as comonomer are soluble in certain ketones and esters, copolymers of IFF and propylene in halogenated solvents perfluorinated elastomers are practically insoluble.16... 

Effects of additives in the matrix were observed by substituting for methyl methacrylate a poly (methyl methacrylate) homopolymer with a solution molecular weight of 950,000, a vinylidene fluoride copolymer (Pennwalt s Kynar 7201), and a methacrylate-butadiene-styrene impact modifier (Marbon s Blendex BTA IIIN). Concentrations were 2% on the total dispersion volume. The same additives were studied at the same volume concentration in the dispersed phase. Barium sulfate (Whittaker, Clark, and Daniels Barytes No. 91), a commonly used additive for radiopacity, was also studied in the dispersed phase. Responses were observed by the test methods described below. 

Saraf MK (2001) Polymerization of vinylidene fluoride in supercritical carbon dioxide Molecular weight distribution. Masters Thesis, North Carolina State University, Raleigh, NC... 

ERE Erenburg, E.G., Pavlova, L.V., Osipchuk, E.O., Dolgopolskii, I.M., Konshin, A.I., Rabinovich, R.L., and Poddubnyi, l.Ya., Flexibility of molecular chains and molecular-weight distribution of vinylidene fluoride-perfluoro(methyl vittyl ether) copolymers, Vysokomol. Soedin., Ser. A, 20, 382, 1978. 

Vinylidene fluoride (b.p. — 84°C) is free-radically polymerized in suspension or emulsion at 10-300 bar and 10-150°C. Suspension-polymerized material contains less branching and consequently a narrower molecular-weight distribution than the emulsion-polymerized material. For this reason, the suspension-polymerized material has higher crystallinity, greater mechanical strength, and better chemical stability. Materials from both polymerization methods contain a considerable proportion of head-to-head linkages. 

UHMWPE Ultra-high-molecular-weight polyethylene VDF-HFA Copolymer of vinylidene fluoride and hexafluoro acetone VDF-TFE Copolymer of vinylidene fluoride and tetrafluoro ethylene VLDPE Very low-density polyethylene compat. Compatibilization, compatibilized, etc. cone. Concentration... 

Miscibility of polymer blends is relatively rare, and is usually limited to a narrow range of independent variables, such as composition of a copolymer, molecular weight, temperature, pressure, and so on [185]. The miscible blends are mainly of academic interest - the information obtained is useful for designing compatibilizers. Exceptions are blends of poly(vinylidene fluoride) (PVDF) with acrylic or polyimide (e.g., PMMA), which are characterized by outstanding UV stability and are used for... 

Polyvinylidene fluoride) (PVDF) first became commercially available in 1961. It is made by the polymerization of vinylidene fluoride in aqueous medium under pressure but details of the process have not been disclosed. Two grades of polymer are available with differing average molecular weight, namely 300 000 and 600 000. 

Mandelkern, L., Martin, G.M. and Quinn, FA. (1957) Glassy state transitions ofpoly-(chlorotrifluoroethylene), poly-(vinylidene fluoride), and their copolymers. /. Res. Natl. Bur. Stand., 58, 137 Fox, T.G. and Loshaek, S. (1955) Influence of molecular weight and degree of crosslinking on the specific volume and glass temperature of polymers.. 1. Polym. Sci., 15, 371. 

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