Mechanical relaxation in polychlorotrifluoroethylene

Measurements of the viscoelastic functions Δ, G' , G ″, J ′, and J ″ as functions of temperature from −180 to +180°C. have been obtained, using a torsion pendulum apparatus, for several samples of polychlorotrifluoroethylene having widely different crystallinities as determined by density. The low crystallinity samples show two relaxations: a very broad one (γ) centered at about −35°C. which appears to be split into two processes, and one (β) at 84°C. In the higher crystallinity samples, a third process (α) appears at about 137°C., and the high temperature side of the γ relaxation peak is lower in magnitude as compared to the lower crystallinity specimens. For the β peak, which is assumed to be associated with the glass transition, the peak value for G ″ is essentially independent of crystallinity, while both Δ and J ″ show decreases in magnitude with increasing crystallinity. The relationship between the magnitude of the relaxation peak and crystallinity, and dependence of this relationship upon the viscoelastic function chosen to characterize the relaxation are discussed.