Studies On Grafting Copolymerization Of Styrene And Maleic Anhydride Onto Rubber

In view of the multi-phase multi-component bulk polymerization, kinetics, phase inversion, control and optimum of composition and structure of grafting copolymerization of styrene-maleic anhydride onto rubber have been studied. Good heat resistant and impact resistant rubber modified random copolymer of styrene and maleic anhydride (R-SMA) resin is prepared by semi-batch and continuous processes.The mechanisms of grafting reaction of styrene onto low-cis and high-cis polybutadiene by thermal and chemical initiations are investigated by analysis of the micro-structures of rubber and their grafting copolymer. And the effect of rubber phase on grafting reaction is studied by examining the evolution of the true and the apparent grafting ratios in polymerization process.The effects of polymerization conditions, such as rubber content and varieties, reaction temperature, ratios of monomer/co-monomer/initiator/solvent, inflow rate of co-monomer and agitation conditions etc., on the phase behavior have been discussed in detail. It is concluded that phase separation is determined by the thermodynamic equilibrium, and related with temperature and compositions, while the phase inversion is operated by the thermodynamic and the dynamic behaviors, determined not only by temperature and compositions, but also by viscosity and agitation.On the basis of analysis of experimental results, two Monte-Carlo models, steady model and dynamic model, have been presented to simulate the phase inversion process. The steady model is able to predict the start and the end points of the phase inversion, although the model parameters have no distinct physical meanings. The factors, such as agitation strength, density, viscosity, interfacial surface tension, grafting efficiency and volume fraction etc., have been considered in the dynamic model, which can predict the start point of phase inversion successfully.A new heterogeneous model has been developed to simulate the kinetics of bulk graft copolymerization of styrene onto rubber. Experimental data and simulation results showed that cage effect of initiator and low reactivity of rubber radical are keyfactors of reduction of polymerization rate in presence of rubber. The polymerization rate is also affected by gel effect when the higher viscosity rubber is used. Different effects on polymerization rate are given by different rubbers because of their disparity of structure and viscosity.The copolymerization kinetics and copolymer composition for semi-batch graft copolymerization of styrene and maleic anhydride onto rubber under various conditions have been investigated. It is concluded that the inflow rate of comonomer is the key factor of polymerization rate and maleic anhydride content. The factors, which lead to reduction of charge transfer complex (CTC), are contributed to decreases of polymerization rate and MAH content. The heterogeneous model has been used in simulation of semi-batch graft copolymerization of styrene and maleic anhydride onto rubber. It is found that simulation results are good agreed with experimental data when it is difficult for CTC to exist.The relationship between microstructure of rubber with impact strength of resin is investigated. The toughness increases with the true grafting ratio (TGR) in lower TGR. And it mainly depends on the size and size distribution of rubber phase when TGR is more than 120. The more the MAH content in matrix resins, the bigger rubber particle is required.The influences of operation methods, start-up policies, agitation condition and residence time on performance of the continuous graft copolymerization of styrene and maleic anhydride onto rubber and the difference in the morphology of rubber phase between semi-batch and continuous polymerization processes have been investigated also. A proper continuous technology has been select to prepare the high performance impact R-SMA.