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)|