Mathematical Modeling Of Methacrylates Bulk Polymerization

Polymethyl methacrylate(PMMA)is widely used as plexiglass and fiber optics for its good transparency.PMMA molding plastic with high performance is usually prepared by solution polymerization under low temperature and bulk polymerization at high temperature which is the priority for producing high quality PMMA.While,gel effect phenomenona is especially remarkable in the methacrylates bulk polymerization.Mathematical modeling could guide the design of polymerization process.The viscosity of solution is related to the concentration,the temperature and the molecular weight distribution as well as the glass transition temperature of polymer.Based on the diffusion theory,the mathematical framework of gel effect model for radical polymerization was developed to describe the kinetics of methyl methacrylate(MMA)homopolymerization and MMA/butyl acrylate(BA),MMA/butyl methacrylate(BMA),MMA/styrene(ST)copolymerization.The parameter in the gel effect model was determined by the experiment data.The applicability of the model in the different bulk polymerization system in the temperature lower than the glass transition temperature(Tg)and higher than that was verified.Finally,the process design for PMMA preparation with narrow molecular weight distribution was proposed.For MMA homopolymerization,the model is suitable for the methyl methacrylate bulk polymerization in the temperature lower than the glass transition temperature and higher than that with initiator and chain transfer agent.The calculated conversions,molecular weight and polymer dispersity index were in good agreement with the data measured from experiments.For MMA/BA copolymerization,model parameter ? is related with copolymer Tg which is changeable during the polymerization at the temperature across and higher than Tg.While,the gel effect model parameter ? in MMA/BMA copolymeirization at high temperature higher than copolymer Tg is fixed.For MMA/ST copolymerization at the temperature below copolymer Tg,the gel effect model parameter ? is related with copolymer composition F.The gel effect models can be applied to the copolymerization system at the temperature below,higher than copolymer Tg and across Tg.The calculated conversion,molecular weight,copolymer composition were in good agreement with experiment data.Based on the methacrylates bulk polymerization model,the gel effect could be weaken by the low convervision controlled and high temperature polymerization,which could guide the preparation of PMMA with narrow molecular weight distribution.