Mechanical Relaxation of Poly (Vinylidene Fluoride) and Copolymer of Vinylidene Fluoride and Tetrafluoroethylene in α and β Relaxation Regions

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Abstract
From torsional stress relaxation measurements on two kinds of poly (vinylidene fluoride) (PVDF) and a copolymer of vinylidene fluoride (VDF) and tetrafluoroethylene (TFE) between -80°C and +90°C, three relaxations are found and named α2, α1 and β in order of descending temperature. The activation energy and relaxation spectrum are determined by the method of reduced variables. It is concluded that the β relaxation is caused by the micro-Brownian motion of amorphous chains, considering the temperature dependence of the relaxation time. The relaxation characteristics of the α1 and α2 relaxations for PVDF, VDF-TFE copolymer and polyethylene are shown to be very similar and to be independent of the difference in chemical structure. The α1 and α2 relaxations in these polymers are thus thought to be caused by the same molecular mechanisms.

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