Fluoroelastomers and the Three Basic Polymer Families

The Fluorocarbon elastomers consist of three basic polymer families. The first is a copolymer of vinylidene fluoride and hexafluoropropylene, commonly referred to as Type A. This family has a fluorine content of approximately 66%. The second family is a terpolymer of vinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene, with a fluorine content of approximately 68% and is referred to as Type B polymer. The third type is the tetrapolymer family or Type GF, consisting of vinylidene fluoride, hexafluoropropylene, tetrafluoroethylene and a proprietary cure site monomer that allows the material to be vulcanized with peroxides. This family has a fluorine content of approximately 70%. Fluorine content is an important consideration in choosing a material to use as a gasket seal, because the higher percentage fluorine polymers have greater resistance to swell and degradation from most fluid exposures. Methyl alcohol (methanol) can be used to illustrate this effect.

Polymer Type	Percentage Fluorine	Volume Swell in Methanol
A Type	65% to 66%	90% (168 hrs @ 73°F)
B Type	67% to 68%	40% (168 hrs @ 73°F)
GF Type	69% to 70%	5% (168 hrs @ 73°F)