| Abstract: | A tracer dye technique was used to investigate the effect of turbulence intensity, stirring time, and the type and concentration of the suspending agent, partially hydrolyzed poly(vinyl acetate) (PVA), on the coalescence rate of vinyl chloride monomer (VCM) droplets in an agitated liquid–liquid dispersion. It was found that the extent of coalescence rises slowly with mixing time, is roughly proportional to the agitation speed, and decreases sharply when the concentration of stabilizer is increased. Coalescence rate depended on the degree of hydrolysis of the stabilizer. The method of addition of initiator during VC suspension polymerization was also studied and its effects on the polymerization conversion and final PVC particles' properties were determined. It was found that the polymerization reaction occurs more uniformly in all the VCM droplets when the initiator was predissolved in the VCM prior to reaction compared with the case when the initiator was predispersed in the continuous water phase. Also, for the same reaction time, the conversion was higher in the former case. During polymerization, the concentration of PVA in the aqueous phase decreased substantially and the porosity of the polymer particles was reduced. © 1996 John Wiley & Sons, Inc. |
