Effect of Vinyl Chloride Injection on the Morphology of Suspension-Polymerized PVC

The mechanism of growth of PVC granules was investigated by injecting additional vinyl chloride monomer into a conventional suspension polymerization process at two different conversions. Polymerization was sustained for long periods in both cases, with the injection before pressure drop producing a more rapid decrease in properties such as porosity and surface area. With injection after pressure drop, additional polymer growth produced a structure with noticeably inferior plasticizer absorption and gelation properties, even though porosity and surface area values were higher. A discussion of the growth mechanism of PVC granules under the two injection systems is presented and related to the conventional suspension process.