Thermal Degradation of Fluorocarbon Elastomers

Perfluoroelastomers (ASTM designation FFKM) such as copolymers of tetrafluoro-ethylene (TEE) and perfluoromethylvinyl ether (PMVE) can maintain their thermal stability to temperatures as high as 300°C (572°F) or even higher, with a maximum continuous service temperature of 315°C (599°F). Moreover, instead of hardening, the elastomer becomes more elastic with aging [13]. 

Fluoroelastomers (ASTM designation FKM) such as copolymers of VDF and HEP typically have a maximum continuous service temperature of 215°C (419°F). Some metal oxides may cause dehydrofluorination at a temperature of 150°C (302°F) or even lower [16]. Copolymers of VDF and CTFE (e.g., Kel-F) have a maximum longterm service temperature of 200°C (392°F). Fluorocarbon elastomers based on copolymers of VDF/HPFP (hydropentafluoropropylene) and on terpolymers of VDF/ HPFP/TFE have lower thermal stability than copolymers of VDF/HFP because they have a lower fluorine content than the latter [17]. A detailed study of thermal stability of fluoroelastomers was performed by Cox, Wright, and Wright [18]. 

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