Polymerization Kinetics Of Styrene In Isotactic Polypropylene Pellets And Evolution Of Phase Morphology During Polymerization

Polymerization kinetics of styrene (St) in commercially available isotactic polypropylene (iPP) pellets and the phase morphology evolution during polymerization are investigated. The polymerization rate of St in iPP pellets is slightly faster than in the corresponding bulk and suspension polymerizations carried out under similar reaction conditions due to the existence of two reaction sites: amorphous PP and polystyrene (PS), which are formed by polymerization-induced phase separation. Two mechanisms are proposed for the phase morphology evolution: nucleation and growth, and St-assisted coarsening of phase structure. During polymerization, the size of the dispersed PS particles increases with polymerization time no matter at which position of the pellet, but the increasing amplitude is much bigger at 200 m distance to the edge than at the center due to much more significant occurrence of St-assisted coarsening of phase structure which is attributed to both high values of PS/PP and St/PP resulted from polymerization-induced diffusion of St. (c) 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43934.