Analysis of Polystyrene Samples in the Liquid Phase by Differential Scanning Calorimetry
Recently(1,2) there were published two separate studies of the specific heats of amorphous (henceforth called atactic) and isotactic polystyrene, as measured by adiabatic calorimeters. Whereas in the main the results of the two groups agreed rather well, discrepancies did exist amounting to as much as 7% at high temperatures in the liquid range. In order to determine whether the observed differences were the result of the different polystyrene samples used or of experimental errors, we decided to make a careful comparison of the two polystyrenes using a Perkin-Elmer differential scanning calorimeter. Rather to our surprise, we found that differences in the specific heat particularly between the atactic polystyrene samples did exist in the liquid range above Tg and that only after rather long annealing at 200°C did the specific heat of the two atactic samples approach each other.
KeywordsAdiabatic Calorimeter Broad Molecular Weight Distribution Liquid Range Polystyrene Sample Control Cabinet
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