Dielectric behavior of copolymers of vinylidene chloride and vinyl chloride

Abstract

AbstractThe dielectric properties of copolymers of vinylidene chloride and vinyl chloride with various compositions are studies. The dielectric measurements are made over the frequency range 0.1 to 106 cycles/sec. and the temperature range ‐23 to 84°C. Glass transition temperatures of the copolymers are determined by a dielectric method which is based on the temperature desendence of the magnitude of the dielectric dispersion. The larger the content of vinylidene chloride, the lower is the glass transition temperature. Effect of cooling speed on the magnitude of the dispersion is investigated. From the dielectric point of view, as a concequence, the glass transition seems to imply any essential transition in addition to an apparent relaxation phenomena. Energyof activation for the relaxation prosess depends upon the temperature and becomes maximum at a little higher temperature than the glass transition temperature. The temperature where the energy of activation becoms maximum is lowered when the sample is cooled more slowly. Cole‐Cole's prameter relating the distribution of relaxation times is constant below the glass transition temperature and increases linearly with temperature above the glass transition temperature and seems to become unity at the melting temperature. This result coincides with that for the parameter of polychlorotrifluoroethylene.