Relaxational behaviour of polyvinylidene fluoride

The relaxational behaviour of polyvinylidene fluoride (PVF₂) has been characterized by static and dynamic mechanical measurements, carried out in the temperature region between 90 K and 420 K at frequencies of about 1 Hz and 1 kHz. Combination of these mechanical data with dielectric literature data and our own results on thermally stimulated depolarization current measurements has led to the decomposition of the relaxation spectrum in three main relaxations α, β, γ. The γ-relaxation results from thermally activated (0.5 eV) local molecular oscillations in the amorphous phase. The β-relaxation is due to micro-Brownian motions of the linear-chain segments near the glass transition temperature. The process is not thermally activated but can be described by models related to the free-volume theory. The crystalline viscoelastic α-relaxation region is a conglomerate of thermally activated (1.4 to 2 eV) processes near the crystalline melting point.