An adiabatic calorimeter for heat capacity measurements of polyurethane foam with blowing agent of HFC245fa in the temperature range 60–290 K

In order to meet the urgent need of heat insulating materials used under low temperature in the area of aerospace, a new PU foam with HFC245fa as blowing agent was developed. In this paper, the heat capacity in the temperature range of 60–290 K of the new material was measured through an automated adiabatic calorimeter, which was composed of a heat insulation system, a power measuring system, a vacuum pumping system and a cooling system. The sample cell of the calorimeter was equipped with a miniature platinum thermometer surrounded by two adiabatic shields and housed in a high vacuum can. The temperature differences among the sample cell and the inner and outer adiabatic shields could be adjusted automatically to less than 0.05 K, all which ensure there was no heat exchange between the sample and surroundings. Under these conditions, the mathematical formulation of the sample with the physical model was given. Through measuring the heat capacity of α-Al2O3, which is a standard reference material, a relatively high reliability with a deviation of ±2.5% of this adiabatic calorimeter was shown compared with the standard data. The results indicate that the newly developed PU foam has a higher heat capacity compared with other heat insulating materials, and there is no obvious sign of any phase transition or thermal anomaly in the entire temperature range. That is to say, the material is thermodynamically stable when used in the low temperature range.