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synopsisAn experimental study of thermal polymerization of styrene in the temperature range 100-20O0C and conversion range 0-100% is reported. Conversions, molecular weight averages, and molecular weight distributions were measured. A kinetic model with third-order initiation gives a satisfactory fit of conversion and number-and weightaverage molecular weights over the ranges of temperature and conversion investigated. This model should find use in the design, simulation, and optimization of polystyrene reactors.

An updated review on suspension polymerization is presented. The time period from 1991 to 1995 is stressed, as well as research articles or reports not considered in previous reviews. Our review is aimed at providing a sound basis for the theoretical background required to build an effective model for the particle size distribution (PSD) in suspension polymerization. All major phenomena that affect the PSD are considered, and a proposed approach to develop an accurate, yet simple, model is included. Most of the experimental information in this review is related to the styrene/divinylbenzene copolymerization system, although the ideas and models are not exclusive to this system.

synopsisThis manuscript reports on an experimental investigation of the chemical-initiated (AIBN) bulk polymerization of methyl methacrylate to limiting conversion a t temperatures of 50°, 70") and 90°C. The change in the cumulative differential molecular weight distribution (CDMWD) with respect to conversion was measured by gel permeation chromatography (GPC). These CDMWD's were differentiated to determine the instantaneous differential molecular weight distribution (instantaneous DMWD) over the range of conversions investigated. These experimental instantaneous DMWD's were found to agree with theoretical distributions predicted by classical free-radical kinetics over the entire conversion range and where diffusion control of the termination reactions is dramatic. A correlation of the dimensionless group a (where a = ktdR,/ kP2M2) with free volume is proposed. This correlation appears to adequately account for diffusion control of the termination reaction. A kinetic model for the bulk polymerization of methyl methacrylate has been developed. This model should find use in the design, simulation, and optimization of PMMA reactors. MODEL DEVELOPMENTFurther detail of the material to be discussed here may be found elsewhere.' The reactions which are significant in the bulk polymerization of MMA with a free radical initiator follow. Initiation:I = rate of formation of free radicals of chain length unity, Ri.I n order to keep the model as general as possible at this stage, we shall not consider the detailed mechanism of initiation, but rather will use the net production of radicals Ri in the analysis. Propagation:h i R; + M -R;+1 (isotactic placement) R; + M k,. R;+' (syndiotactic placement)

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