Experimental investigation of vinyl chloride polymerization at high conversion: molecular-weight development

A comprehensive model for molecular-weight development during the suspension polymerization of vinyl chloride has been developed. The poly(vinyl chloride) (PVC) was characterized by low-angle laser light scattering (LALLS) and gel permeation chromatography calibrated using the results of LALLS measurements. Kinetic parameters were estimated using accumulated molecular weights measured at different conversions and polymerization temperatures. The present model is in excellent agreement with the experimental accumulated number-, weight- and Z-average molecular weights and distribution data over the entire conversion range. The mechanisms of termination and chain transfer and the effect of conversion, monomer and initiator concentrations and polymerization temperature on molecular-weight development are discussed in some detail. The present model predicts instantaneous molecular weights and distributions in each phase, the total instantaneous and accumulated molecular-weight averages, and instantaneous and accumulated molecular-weight distributions as functions of the reactor operational conditions, and can satisfactorily explain the kinetic features of PVC molecular-weight development.