Conversion distribution in diffusion‐governed chlorination of poly(vinyl chloride)

Conversion distribution in particles of chlorinated poly(vinyl chloride) (CPVC) is conceptually described based on balance equations involving mass transfer and chemical reaction. In the physical sorption of chlorine in poly(vinyl chloride) (PVC) as measured by the constant volume cell method, equilibrium concentration and diffusion rate obeyed Henry's law and Fick's law. The rate process of photo chlorination of PVC, which was investigated by the gravimetric method, could be well predicted by theoretical calculation of chlorine diffusion in PVC accompanying the infinitely fast chemical reaction. In a free grain of PVC synthesized by suspension polymerization, the chlorination rate was governed by the polymer‐phase diffusion within agglomerates of coalesced primary particles. To produce homogeneously chlorinated PVC, a periodic photo‐irradiation method was theoretically proposed and experimentally demonstrated. The effect of the periodic operation on the thermal property of CPVC was evaluated by DSC.