Glass transition phenomena in several polymers were studied by dielectric and dilatometric measurements. The dielectric measurements were made over the frequency range of 10−4 or 10−1 to 106 cycles/sec. and the temperature range of the glass transition. In the dilatometric study, volume relaxation curves and volume vs. temperature curve were obtained. The transition in three amorphous polymers, (polyvinyl acetate, polystyrene, and polymethyl methacrylate), depends upon frequency or rate of cooling and seems to be an apparent transition. In three crystallizable polymers, (vinylidene chloride‐vinyl chloride copolymer, polyethylene terephthalate, and polyacrylonitrile), the magnitude of the dielectric absorption decreases steeply with decreasing temperature in the transition range, and the transition by the volume expansion remains when equilibrium is attained. The transition in the three crystallizable polymers seems to be a real one. Temperature dependences of the activation energies of the dielectric relaxation processes have been described.

SynopsisThe dielectric properties and the d.c. conductivity of poly( vinyl chloride), poly(viny1 acetate), polychlorotrifluoroethylene, and poly(ethy1ene terephthalate) were measured at temperatures above and below the glass transition temperature and a t various pressures up to 3000 atm. The a relaxation associated with the micro-Brownian motion of amorphous chain segments depends strongly upon temperature and pressure, while the B relaxation due to local-mode motion of the frozen main chain shows weak dependence on temperature and pressure. It is found that the free volume concept is valid for description of the temperature and the pressure dependence of the relaxation time for the a process. Activation energy and volume for both relaxation processes are determined from the experimental data. A simple relation between activation energy and volume for the a relaxation and pressure dependence of the glass transition temperature are derived. Temperature and pressure dependence of the d.c. conductivity in the rubbery state are notably different from those in the glassy state. Ionic conduction appears to be dominant in these polymers.

The dielectric properties of three kinds of polymonochlorotrifluoroethylene having various degrees of crystallinity were studied. The measuring instruments by which the dielectric properties can be measured over a wide range of frequency are briefly described. The dielectric measurements for three samples are made over a frequency range 0.1 to 106 cycles/sec. and a temperature range of −50 to 140°C. The main conclusions from the experimental results are as follows. Two dielectric dispersions observed would be due to the polar groups in amorphous regions. At the melting temperature, the positions of the two dispersions would coincide with each other. The energies of activation for the two loss processes are 16.8 and 57.0 kcal., respectively. Interpreting from the variation of the magnitude of the dielectric dispersion with temperature, the glass transition temperature of this polymer extends over the wide range from −80 to 60°C. For the low temperature dispersion, the value of Cole‐Cole's parameter β has constant value of 0.3 below 20°C. and increases with temperature above 20°C.

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The 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.