Electrical β‐relaxation of die‐drawn isotactic polypropylene

Measurements of a.c. impedance were carried out in the frequency range 1 Hz to 10 6 Hz at room temperature on isotropic and die-drawn isotactic polypropylene. It was found that the a.c. impedance decreases with increasing draw ratio in the frequency range 1 Hz to 10 4 Hz and then becomes independent of draw ratio with increasing frequency. A dramatic drop in the a.c. impedance was observed in the frequency range 10 4 to 10 6 Hz, which is associated with a β-relaxation process. The intensity of the β-relaxation peak decreases with increasing draw ratio and nearly disappears for a draw ratio of 16.8. The Cole-Cole plots show good semicircles for isotropic and die-drawn samples indicating that a certain polarization mechanism is dominant in polypropylene.