Synthesis of Chlorinated Poly(vinyl chloride) with Uniform Distribution of Chlorine Assisted by Supercritical Carbon Dioxide and a Cosolvent

For the first time, a preliminary foaming treatment for poly(vinyl chloride) (PVC) was adopted to facilitate the chlorination of PVC with the assistance of supercritical carbon dioxide and acetone. The chlorine content of chlorinated poly(vinyl chloride) (CPVC) obtained from pretreated PVC had exceeded 0.66 g g–1, while that of CPVC using nonpretreated PVC only reached about 0.60 g g–1. Analysis of the particle diameter and morphology of pretreated PVC showed that the preliminary treatment had enlarged the particle diameter and inner pore structure. Gel permeation chromatography, differential scanning calorimetry, and 13C NMR analysis showed that the obtained CPVC had a narrow molecular weight distribution, excellent thermal properties, and uniform chlorine distribution. Furthermore, an improved kinetics model was proposed to indicate the crucial step of chlorination. The frequency factor was expressed as the ratio of the particle volume of the foamed PVC to that of the original PVC. Consequently, the model values of the chlorine content agreed well with the experimental values.