Conversion studies in a novel reaction injection molding process for syndiotactic polystyrene

Abstract

Syndiotactic polystyrene (sPS) has successfully been produced using a novel reaction injection molding (RIM) process and a metallocene catalyst. Previous studies have shown that many of the requirements for a RIM process are achievable. However, problems due to incomplete conversion of monomer have hindered the commercial development of this process. 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 fraction, molecular weight, melting point, and stereoregularity of the polymer produced. It was found that this RIM process was not mixing limited. Longer reaction times resulted in an increase in conversion, with no significant change in the polymer properties. Mold wall temperature had the greatest effect on both the conversion and polymer properties. Lower mold wall temperatures resulted in an increase in the conversion. At both of the temperature extremes studied, the polymer properties deteriorated. Infrared spectroscopic analyses of the as-polymerized 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. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2679–2693, 1998