Molding of syndiotactic polystyrene under its melting temperature

Syndiotactic polystyrene (SPS), a thermoplastic polymer that exhibits a hig h T-m in some crystalline forms, can be conveniently processed by a cold-co mpaction technique. Processing temperatures in the range of 150-210 degrees C, well below the T-m, gives rise to physicomechanical properties comparabl e and even better than those obtained by thermal compression or injection m olding. The optimum treatment temperature seems to fall around 175 degreesC . X-ray diffraction analysis, thermal analysis, and density measurements su ggest that such behavior is connected to phase transitions of SPS and favor ed by the presence of styrene included in the crystalline fraction. (C)\ 20 01 John Wiley & Sons, Inc.