HEAT CAPACITY MEASUREMENTS ON POLYETHYLENE IN THE TEMPERATURE RANGE OF 2.4 TO 30 K.

Specific heat measurements on three samples of polyethylene, differing only in density, were made in the temperature range of 2.4 to 30 K. A definite density dependence was noted for the specific heat in this temperature interval which allowed extrapolation of the data to completely crystalline and completely amorphous cases. At the lowest temperatures, the amorphous results were observed to display an excess heat capacity which could be accounted for by the occurrence of a single delta function peak in the low frequency part of the vibrational spectrum. This excess did not appear in the completely crystalline extrapolated data, and the specific heat was found to be proportional to the cube of the temperature up to 9 K. An attempt was made to compare the results with two theoretical models Tarasov and Stockmayer-Hecht with only fair agreement in one case, and none in the other. The agreement with previous experimental results is excellent if the density dependence and the excess heat capacity are considered. Author