Experimental investigation of vinyl chloride polymerization at high conversion: effect of polymerization conditions on polymer properties

A series of poly(vinyl chloride) (PVC) samples was synthesized under various polymerization conditions. It was found that the thermal stability of PVC as measured by dehydrochlorination rate is independent of monomer conversion when the conversion is less than Xf (the conversion at the pressure drop). However, the dehydrochlorination rate increases significantly with conversion for conversions greater than Xf. The thermal stability of PVC decreases with increase in polymerization temperature. These phenomena can be satisfactorily explained by accepted reaction mechanisms and diffusion-controlled kinetics. The reactions forming defect structures are favoured at low monomer concentrations. Therefore, the most effective way to minimize the formation of defect structures is to maintain monomer concentration as high as possible during polymerization after the pressure drop.