Propylene based fluoroelastomers

Fluoroelastomers based on TFE and propylene (e.g., AFLAS) (see Section 5.1.1) swell to a high extent in aromatic hydrocarbons because of the relatively low fluorine content (54%). However, because of the absence of VDF in their structure, they exhibit a high resistance to highly polar solvents such as ketones, which swell greatly all fluoroelastomers containing VDF. In addition, elastomers based on copolymers... 

The second period from 50 to mid 70s might be the era of copolymers. Major improvements of processabilities or porperties of homopolymers like PTFE were attained in this period. The copolymers include FEP, ETFE and PFA which is a copolymer of TFE and perfluoropropyl vinyl ether. Another progress in this era is the commercial-ization of fluoroelastomers such the most popular elastomer as Viton, that is the copolymer of vinylidene fluoride and hexafluoropropylene or sometimes with TFE as a ter-monomer, which was followed by tetrafluoroethylene-based elastomers with propylene or perfluoromethyl vinyl ether comonomers. 

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