N-phenylmaleimide(PMI)is used to copolymerize with vinyl chloride (VC) for improving the heat resistance of PVC

but the instantaneous and integral copolymer compostition varies greatly with conversion for vinyl chloride/N-phenylmaleimide copolymerization systems.The recurrence method deduced from Mayo-Lewis equation was applied to investigate quantitatively the variations of copolymer compositions wtih conversion for VC/PMI suspension copolymerization.The copolymer compositions can be controlled andzed by means of selecting a third monomer and its content.For VC/PMI suspension copolymerization

acrylonitrile(AN)was preferably selected to improve copolymer conposition homogeneity in order to improve heat resistance and other properties.The ranges of monomer feed fraction with the copolymer composition error of PMI lower than 0.05 ot 0.1 was gained

which could direct the study on VC/PMI/AN suspension terpolymerization.On the basis of the prediction

controland optimization of the copolymer composition variation with conversion and the features of the polymerization technology

the optimum region of monomer feed fraction for VC/PMI/AN suspension terpolymerization was obtained.