Recovery processes in amorphous polymers

The release of stored energy and the recovery of dimension and volume of cold compressed polystyrene (PS), polymethyl methacrylate (PMMA) and polycarbonate (PC) were studied. The release of stored energy has two peaks, one broad peak at 70 deg C (PS), 55 deg C (PMMA) and 85 deg C (PC) and one sharp peak at 113 deg C (PS, T sub g = 105 deg C), 123 deg C (PMMA, T sub g = 117 deg C) and 157 deg C (PC, T sub g = 152 deg C). The recovery of dimension has only one peak at 114 deg C (PS), 124 deg C (PMMA) and 157 deg C (PC). This peak agrees very well with the second peak in the release of stored energy. The recovery of volume has a broad peak similar to the first peak in stored energy. Thus, there are probably two recovery processes in these polymers: one releases energy and recovers volume below T sub g and the other releases energy and recovers dimension above T sub g . These two processes are consistent with the two-stage formation mechanism of shear bands in amorphous polymers. 48 ref.--AA