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 investig ated as a function of frequency and temperature. Attention was focused on the low frequency dielectric properties. Samples with different mo lar masses were studied. Two dipolar retardation processes were observ ed, 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 f ound at high temperatures. The effect was most pronounced at the highe st molar masses. The space-charge mechanism was absent in samples of w ell-kneaded material. This macroscopic polarization process in compres sion molded samples is probably due to discontinuities in the poorly g elified material because of a residual grain particle structure. The d etected 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 i n destroying the grain structure. (C) 1994 John Wiley & Sons, Inc.