Preparation Of Heat Resistant Agent With N-Phenylmaleimide By Emulsion Copolymerization

The copolymers of vinyl monomer/N-substituted maleimide were synthesized to be used as the heat-resistant agent (HRA) of ABS and PVC. According to the review and research thinking, N-phenylmaleimide(PMI), styrene(St), acrylonitrile or methyl methacrylate(MMA), α-methylstyrene(α-MeSt) were selected to be copolymerized. PMI was used to enhance the heat resistance of HRA, styrene to improve the melt flowability of HRA, the polar monomers AN and MMA to adjust the solubility parameter of HRA, and a-methylstyrene to cut down the cost of HRA.On the basis of above design idea, PMI-AN-St-α-MeSt and PMI-MMA-St-α-MeSt tetra-copolymers were synthesized and their properties such as glass transition temperature (Tg), solubility parameter, mechanical properties and processing properties were characterized. The results showed that both of them were suitable as the HRA of ABS and PVC in a reasonable range of monomer ratio, and the PMI-AN-St-α-MeSt tetra-copolymer was more suitable in a deep consideration of cost and copolymerization process.The kinetics of the PMI/St/AN/α-MeSt copolymerization was studied. It showed that the high conversion could be reached when the mole ratio of PMI+AN was no more than St+a-MeSt. The total active energy of the copolymerization was E_a=84.14kJ/mol and the reaction rate was Rp∝c[KPS]^0.46[SDS]^0.57. The effects of emulsion copolymerization conditions on the molecular weight and the Tg of the copolymer were also investigated. It indicated that the molecular weight of the copolymer decreased when the temperature, applied quantity of initiator and emulsifier in copolymerization were increased, but the Tg was not influenced. When the chain transfer agent was added, the molecular weight of the copolymer was sharply decreased.Feeding method and particle size control were further investigated in details. It showed that the maximum Tg of the copolymer with same monomer ratio could be obtained by dropping the St solution of PMI into AN/a-MeSt reaction system. Particle size of the copolymer was influenced by the quantity and feeding method of the emulsifier. Coagulation could enlarge the particle size of the copolymer. Comparing with different flocculant,3 was prefer to be used. The size of the coagulation particle was influenced by the applied quantity of flocculant, agitation, and specially the coagulation temperature. The diameters of the coagulation particles all above 200um could be obtained when the coagulation temperature was higher than the Tg of the copolymer. These particles could be also obtained by adding fluccolant during the copolymerization. However, the adding time of the fluccolant should be precisely held. Emulsion-suspension polymerization was another way to enlarge the particle size of the copolymer.The properties of ABS/HRA. PVC/HRA were investigated. It showed that the heat resistance and tensile strength of each blend were improved obviously, while the impact strength and processing property decrease slightly with the increasing of HRA content. The processing property of the blend could be improved by decreasing the molecular weight of the HRA.