CONVERSION STUDIES IN A NOVEL REACTION INJECTION-MOLDING PROCESS FOR SYNDIOTACTIC POLYSTYRENE

Syndiotactic polystyrene (sPS) has successfully been produced using a novel reaction injection molding (RIM) process and a metallocene catal yst. Previous studies have shown that many of the requirements for a R IM process are achievable. However, problems due to incomplete convers ion of monomer have hindered the commercial development of this proces s. In attempts to overcome this conversion limitation and gain insight into its nature, the effects of the extent of mixing, reaction time, and mold wall temperature were investigated on the monomer conversion and polymer properties. The properties of interest included the sPS fr action, molecular weight, melting point, and stereoregularity of the p olymer produced. It was found that this RIM process was not mixing lim ited. Longer reaction times resulted in an increase in conversion, wit h no significant change in the polymer properties. Mold wall temperatu re had the greatest effect on both the conversion and polymer properti es. Lower mold wall temperatures resulted in an increase in the conver sion. At both of the temperature extremes studied, the polymer propert ies deteriorated. Infrared spectroscopic analyses of the as-polymerize d samples indicated that sPS helical conformations were present. This suggested that the styrene monomer may be entrapped within the helical crystalline structures of sPS, preventing complete monomer conversion during this sPS RIM process. (C) 1998 John Wiley & Sons, Inc.