HIGH-PRESSURE DTA APPARATUS BASED ON AN INSTRON CAPILLARY RHEOMETER.

In recent years, there has been a growing interest in studying the pressure-volume-temperature (P-V-T) relations and the high pressure calorimetric data of polymers for practical industrial needs or academic purposes. This paper describes a straightforward, multifunctional, high-pressure apparatus, and demonstrates its ability as a thermal analytical tool. Differential thermal analysis consists of a measurement of the temperature differential between two objects heated at the same average rate. If one object goes through a first order transition, its temperature will lag behind the other. The physical property of importance in DTA is the thermal diffusivity. The thermal diffusivity, alpha , is defined as alpha equals K/ rho C//P where K is the thermal conductivity, rho is the density and C//P is the heat capacity. The thermal diffusivity can be calculated from the temperature difference between sample temperature and heater temperature, heating rate and vessel dimensions.