Chemical copolymers Vinylidene fluoride-hexafluoropropylene elastomers

Trifluoronitrosomethane-tetrafluoroethylene copolymer vulcanizates have outstanding resistance to chemicals, being generally superior to vinylidene fluoride-hexafluoropropylene elastomers. Some fluorinated solvents cause appreciable swelling. 

Perfluoroelastomer (tetrafluoro-perfluoromethyl vinyl ether copolymer) Introduced by DuPont in 1977 as Kalrez , this elastomer combines the properties of a conventional fluoroelastomer, such as vinylidene fluoride-hexafluoropropylene copolymer, with those of a fluorocarbon resin such as polytetrafluoroethylene. It has found application for O-rings and seals that must withstand strong chemicals and solvents at high temperatures. 

After vulcanization with BPO in the presence of ZnO, amines, or diisocyanates, copolymers of vinylidene fluoride with hexafluoropropylene (70 30) or trifluorochloroethylene (70 30 and 50 50) give oil-resistant, chemically inert elastomers which can be used at temperatures up to 150-200°C. However, these elastomers can be used down to temperatures of only — 10 to — 50°C. 

The vinylidene fluoride(VDF)-hexafluoropropylene(HFP) copolymers are well-known fluorocarbon elastomers which have excellent thermal, oil and chemical stability. Due to their inert structure, curing is more difficult compared with the hydrocarbon elastomers such as styrene-butadiene copolymer, acrylonitrile-butadiene copolymer etc. It is known that two curing recipes described below are practically usable for these fluorocarbon elastomers. 

Most of the other fluorine-containing monomers such as trifluoroethylene, hexafluoropropylene, and pentafluoropropylene are used only for copolymerization with vinyl fluoride, vinylidene fluoride, and tetrafluoroethylene [506,521,535,559-562]. Those copolymers, after a convenient vulcanization procedure using peroxides, diisocyanates, or amines, can be applied as fluorocarbon elastomers [564]. Due to the fluorine content, they have high chemical resistance and often a broad temperature range for application [612]. Polymers of interest are the vinylidenefluoride/hexafluoropropylene copolymer and the... 

Some fluorinated polymers which show exceptional thermal stability and chemical inertness are Kel-F elastomers, made of a copolymer of chlorotrifluoroethylene-vinylidene fluoride C1CF=CF2/ CH2=CF2, and Viton, a copolymer of hexafluoropropylene and vinylidene fluoride CF2=CF—CF3/ CH2=CF2. 

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