Glass transition temperatures of copolymer and terpolymer fluoroelastomers

The Fox, Gordon-Taylor-Wood, Johnston and Barton equations have been applied to predict the glass transition temperatures, Tg of vinylidene fluoride-hexafluoropropene (VDF-HFP) copolymers and VDF-HFP-tetrafluoroethene (TFE) terpolymers. The Fox equation fails to describe the co- and terpolymer systems. The experimental data for VDF-HFP copolymers are well interpreted by the Gordon-Taylor-Wood equation. The Johnston and Barton equations, based on sequence distribution, yield good results for VDF-HFP and VDF-HFP-TFE. The assumptions made about kinetic constants of propagation and the Tg contributions of alternating monomer dyads and polyTFE are also discussed.