A broad‐band dielectric study of poly(vinyl chloride): Effect of molar mass and processing conditions on space‐charge mechanisms

The dielectric properties of poly(vinyl‐chloride) (PVC) were investigated as a function of frequency and temperature. Attention was focused on the low frequency dielectric properties. Samples with different molar masses were studied. Two dipolar retardation processes were observed, one due to a local motion in the polymeric chain and the other at the glass transition. In compression‐molded samples of high molar mass an additional low‐frequency space‐charge polarization mechanism was found at high temperatures. The effect was most pronounced at the highest molar masses. The space‐charge mechanism was absent in samples of well‐kneaded material. This macroscopic polarization process in compression molded samples is probably due to discontinuities in the poorly gelified material because of a residual grain particle structure. The detected effects of air inclusions in a PVC matrix can be described by the Maxwell‐Wagner theory. The magnitude of the space‐charge mechanism is an indication of the effectiveness of the processing method used in destroying the grain structure.