Influences of Initiators on Conversions of Vinyl Chloride Micro-Suspension Polymerizations and Particle Size Distributions of Poly(vinyl chloride) Resins
1.State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, China;
2. Hangzhou Electrochemical Group Co, Hangzhou 311228, China
Abstract Vinyl chloride(VC) micro-suspension polymerizations(MSP) were carried out using a water-soluble initiator of ammonia persulfate (APS) and an oil-soluble initiator of 2,2'-azobis-(2,4-dimethylvaleronitrile) (ABVN), respectively, and their performances were compared with those of VC suspension polymerization (SP) initiated by ABVN and VC emulsion polymerization (EP) initiated by APS. Influences of initiator types on the particles size distribution of the resulted PVC latexes and the rheological behavior of plasticized PVC pastes were also investigated. It was found that VC MSP exhibited a higher conversion than SP, and lower conversion than EP after the same polymerization time under the same initiation condition. PVC latex prepared by MSP using APS as the initiator contained a greater number nano scale particles (size smaller than 100 nm), while almost no nano scale PVC particles were observed in PVC latex prepared by MSP using ABVN as the initiator. The above kinetics and size distribution differences were attributed to the different partition of primary free-radicals in water/micelles/monomer (sub) droplets, and the different nucleation modes. The plasticized paste prepared from MSP PVC using APS as the initiator showed pseduoplastic behavior and greater apparent viscosity, while the plasticized paste prepared from MSP PVC using ABVN as the initiator showed dilatant behavior.
