Vinylidene fluoride properties

Properties ethylene-propylene resin Poly(vinylidene fluoride) Unfilled Glass-fiber- reinforced ethylene copolymer Cellulose- filled Glass-fiber- reinforced... 

Table 3. Electrical Properties of Poly(vinylidene fluoride)...

The most chemical-resistant plastic commercially available today is tetrafluoroethylene or TFE (Teflon). This thermoplastic is practically unaffected by all alkahes and acids except fluorine and chlorine gas at elevated temperatures and molten metals. It retains its properties up to 260°C (500°F). Chlorotrifluoroethylene or CTFE (Kel-F, Plaskon) also possesses excellent corrosion resistance to almost all acids and alkalies up to 180°C (350°F). A Teflon derivative has been developed from the copolymerization of tetrafluoroethylene and hexafluoropropylene. This resin, FEP, has similar properties to TFE except that it is not recommended for continuous exposures at temperatures above 200°C (400°F). Also, FEP can be extruded on conventional extrusion equipment, while TFE parts must be made by comphcated powder-metallurgy techniques. Another version is poly-vinylidene fluoride, or PVF2 (Kynar), which has excellent resistance to alkahes and acids to 150°C (300°F). It can be extruded. A more recent development is a copolymer of CTFE and ethylene (Halar). This material has excellent resistance to strong inorganic acids, bases, and salts up to 150°C. It also can be extruded. 

The inability to process PTFE by conventional thermoplastics techniques has nevertheless led to an extensive search for a melt-processable polymer but with similar chemical, electrical, non-stick and low-friction properties. This has resulted in several useful materials being marketed, including tetrafluoro-ethylene-hexafluoropropylene copolymer, poly(vinylidene fluoride) (Figure 13.1(d)), and, most promisingly, the copolymer of tetrafluoroethylene and perfluoropropyl vinyl ether. Other fluorine-containing plastics include poly(vinyl fluoride) and polymers and copolymers based on CTFE. 

A 50 50 mol/mol copolymer of hexafluoroisobutylene (CH2 = C(CF3)2) and vinylidene fluoride was made available by Allied Chemical in the mid-1970s as CM-1 Fluoropolymer. The polymer has the same crystalline melting point as PTFE (327°C) but a mueh lower density (1.88g/cm ). It has excellent chemical resistance, electrical insulation properties and non-stiek characteristics and, unlike PTFE, may be injeetion moulded (at 380°C). It is less tough than PTFE. 

Fluorinated rubbers, copolymers of hexafluoropropylene and vinylidene-fluorides, have excellent resistance to oils, fuels and lubricants at temperatures up to 200°C. They have better resistance to aliphatic, aromatic and chlorinated hydrocarbons and most mineral acids than other rubbers, but their high cost restricts their engineering applications. Cheremisinoff et al. [54] provide extensive physical and mechanical properties data on engineering plastics. A glossary of terms concerned with fabrication and properties of plastics is given in the last section of this chapter. 

Flame resistance The underwriters ruling on the use of self-extinguishing plastics for contact-carrying members and many other components introduces critical material selection problems. All TSs are basically self-extinguishing. Nylon, polyphenylene oxide, polysulfone, polycarbonate, vinyl, chlorinated polyether, chlorotrifluoroethy-lene, vinylidene fluoride, and fluorocarbon are examples of TPs that may be suitable for applications requiring self-extinguishing properties. Cellulose acetate and ABS are also available with these properties. Glass reinforcement improves these materials considerably. 

Mascia, L., Pak, S.H., and Caporiccio, G. Properties Enhancement of Fluorosilicone Elastomers with Compatibilized Crystalline Vinylidene Fluoride Polymers, Eur. Polym. J. 31(5), 459 65, 1995. 

Baltd-Calleja, F. J., Gonzalez Arche, A., Ezquerra, T. A., Santa Cruz, C., Batallon, F., Frick, B. and Lopez Cabarcos, E. Structure and Properties of Ferroelectric Copolymers of Poly(vinylidene) Fluoride. Vol. 108, pp. 1-48. 

Hietala, S., Skou, E. and Sundhokn, F. 1999. Gas permeation properties of radiation-grafted and sulfonated poly-(vinylidene fluoride) membranes. Polymer 40 5567-5573. 

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