Effects Of The Monomer's Water Solubility On The Kinetics Of The Suspension Polymerization And Polymer Properties

Effects of monomer's water solubility on the kinetics of polymerization, molecular weight and copolymer of (co)polymer were studied. On the basis of the kinetic model for bulk polymerization, that of suspension polymerization was presented.A small amount of oil-soluble initiator, BPO, was dissolved in the aqueous phase and some monomer was polymerized for the water soluble of monomer, when acrylonitrile (AN) suspension polymerization was taken. But comparing with the total conversion, the polymerization in the water phase could be neglected. In addition, the water-to-monomer ratio affected the kinetic curves of AN suspension polymerization. As the water-to-monomer ratio increased, the limit conversion decreased. It indicated that the monomer dissolved into the aqueous phase and would not return into the oil phase all. Furthermore, polymerization conversion in high conversion is larger than the conversion in the aqueous phase. It indicated that a part of monomer dissolved in the aqueous phase could return into the oil phase.The aqueous suspension homopolymerization of methyl methacrylate (MMA) at large water-to-monomer ratio was investigated. Comparing with the bulk polymerization of MMA, there were large differences between the kinetic curves of suspension and bulk polymerization, and the water-to-monomer ratio affected the kinetic curves of MMA suspension polymerization. In order to study the affecting reasons of monomer's water solubility on the kinetics of its suspension polymerization in detail, a modified kinetic model for the MMA suspension polymerization is presented on the basis of its bulk polymerization kinetic model and three assumptions. The three assumptions were: the amount of the monomer which solvents in the water should be deducted, the propagation and termination rate constants should be decreased, and small amount of oil-soluble initiator had been introduced into the aqueous phase. Using the modified kinetic model, the effects of water-to-monomer ratio, polymerization temperature and initiator concentration were predicted. The simulated kinetic curves were in agreement with the experimental data. The affecting factors on molecular weight were opposite to that of kinetics. It could prove three assumptions were reasonable.AN's water solubility was large, it distributed itself between the oil and the aqueous phases when it was copolymerizated with styrene (St). It indicated the partition coefficient was a function of temperature and AN's concentration in oil phase. Effects of AN's solubility on the kinetic curves of AN-St copolymerization were investigated. As the water-to-monomer ratiodecreased, AN and St ratio increased, polymerization temperature enhanced and initiator concentration increased, the conversion would increase.Effects of AN's solubility on the molecular weight of AN/St suspension copolymer. .were investigated. As the water-to-monomer ratio increased, AN and St ratio decreased, polymerization temperature decreased and initiator concentration decreased, the number and weight average molecular weight would increase.Effects of AN's solubility on the copolymer composition of AN/St copolymer were investigated. In order to study the affecting reasons of monomer's water solubility on the suspension copolymer composition in detail, a modified model was presented on the basis of its bulk copolymerization model and two assumptions. The two assumptions were: the amount of the monomer dissolved in the water should be deducted, and apparent reactivity ratio should be changed. Using the modified model, the effects of water-to-monomer ratio and monomer ratio were predicted. The simulated copolymer composition curves were in agreement with the experimental data. The copolymer composition distributing was even at low conversion, while it was not even at high conversion.