Pressure dependence of dielectric properties of chlorinated polyethylene vulcanizate. I. α relaxation and shift factors

The complex dielectric constant was measured under elevated pressure for the α relaxation of vulcanized chlorinated polyethylene. Both temperature and pressure effects on the static dielectric constants, the activation enthalpy, and volume, and the pressure dependence of the glass‐transition temperature were obtained. The dependence of shift factors on temperature was expressed by the Vogel–Fulcher–Tamman–Hesse (VFTH) equation: −log aT = A − B/(T − T0). The parameters A, B, and T0 for each pressure applied were calculated by minimizing the standard deviation between log aT and experiments. The values of the parameters in the Williams–Landel–Ferry (WLF) equation: −log aT = C1(T − Tg)/[C2 + (T − Tg)], were also estimated from the resulting values of the VFTH parameters. All these parameters depended on pressure. The activation volume plotted against T − Tg decreased with increasing pressure.