Thermophysical properties of polyurethane foams and their melts

摘要

The thermal conductivity (λ) and the specific heat (c_p) of seven polyurethane foam formulations and their melts are obtained using a transient plane source technique called the Hot Disk experiment. In the experiment, the Hot Disk sensor is sandwiched by the samples and acts as both a heat source and a temperature sensor. The fundamental assumption is that throughout the experiment, the heat from the sensor does not penetrate beyond the boundaries of the sample. The suitable sample dimensions and sensor radius are determined from the preliminary calculations. Through sensitivity analysis, the appropriate measuring time and output power for the experiments are established. For polyurethane foams, λ ranges from 0.048 to 0.050 W/mK, and c_p ranges from 2359 to 2996 J/kg K. For melts, λ ranges from 0.186 to 0.200 W/mK, and c_p ranges from 1958 to 2076 J/kg K. When foam decomposes into melts, the changes in thermophysical properties shows λ increases by approximately 300%, whereas c_p decreases by approximately 20%. On the basis of these changes, the collapse of the foam structure into melt appears to improve the heat transfer through the material.