Dielectric properties of the system polyvinyl chloride-dimethylthianthrene

Abstract

A method is described for determining the dielectric behavior of liquids, gels, and solids at frequencies from 15 to 15,000 cycles/sec., and over a temperature range from −100 to +150°C. Included in the range of sample types are those of a gelatinous nature obtained by dissolving small amounts of polymer in plasticizer. The variation of complex dielectric constant with frequency and temperature for polyvinyl chloride (PVC) combined with dimethylthianthrene (DMT) is given for 0, 10, 20, 40, 60, 80, and 100% PVC by volume, and the apparent activation energy for dipole rotation is determined as a function of the pure plasticizer and low polymer concentrations indicates that a polar plasticized polymer. In view of the data presented here, and that cited for PVC plasticized with di-2-ethylhexylphthalate and tricresyl phosphate, it is concluded that the dielectric dispersion observed in a polar polymer combined with a polar plasticizer is a result of dipole rotation of the plasticizer molecule together with dipole rotation of chain segments of the polymer. The relative importance of each type of rotation will depend on the relative concentrations of polymer and plasticizer and the magnitude of their permanent dipole moments. Dipole-dipole coupling between plasticizer and polymer may also play a part in determining the dielectric dispersion in plasticized polymers.