Syndiotactic polystyrene (SPS), a thermoplastic polymer that exhibits a high T-m in some crystalline forms, can be conveniently processed by a cold-compaction technique. Processing temperatures in the range of 150-210 degreesC, well below the T-m, gives rise to physicomechanical properties comparable and even better than those obtained by thermal compression or injection molding. The optimum treatment temperature seems to fall around 175 degreesC. X-ray diffraction analysis, thermal analysis, and density measurements suggest that such behavior is connected to phase transitions of SPS and favored by the presence of styrene included in the crystalline fraction. (C)\ 2001 John Wiley & Sons, Inc.