Study On Natural Latex Modified By Graft Copolymerization With Microwave Radiation

With the growing up of the microwave radiation heating technology, especially, the successful development of the high power magnetron, it provides the conditions for the application of microwave heating technology. At present microwave heating technology has his space in the rubber industry because of its fast heating speed, high efficiency, energy saving, environment and other advantages. The traditional methods on grafting modifications of natural rubber mainly include chemical method, photopolymerization, irradiation-induced polymerization and mechanical force initiation. In this paper the graft copolymerization reaction took place between monomers and natural rubber latex by this new microwave heating method, for looking for a new method to prepare grafted latex.The reactants were placed in the microwave field in this experiment. Their molecules realigned with the changing high frequency magnetic field, and had to overcome molecular interactions and the original thermal motion, thus produced an effect similar to "friction" and a great deal of heat. Then the microwave heating was implemented. Methyl methacrylate (MMA) and acrylamide (AM) were selected as monomer to react with natural rubber latex, respectively. The influence factors of reaction were studied by orthogonal experiment. Meanwhile the effects of microwave temperature, reaction time and the amount of initiator and monomer on the grafting rate and grafting efficiency were investigated. The grafted copolymers were characterized by FTIR,1HNMR, TG/DTG, and DSC. The solvent resistances of the products were also investigated.The results show that microwave temperature, microwave time, the amount of monomers and the dosage of initiator have an influence on the grafting rate and grafting efficiency of the grafted products; and the optimum reaction conditions are different for different monomers. The optimum reaction condition for the preparation of NR-g-MMA graft copolymer is as follow:the oxidation-reduction initiator system was potassium persulfate and sodium sulfite, the content of initiator0.4%, microwave temperature80℃, reaction time1h-2h and the mass ratio of monomer to latex1:1. The optimum reaction condition for the preparation of NR-g-AM graft copolymer is as follow:the oxidation-reduction initiator system was potassium persulfate and sodium sulfite, the content of initiator0.4%, microwave temperature80℃, reaction time1h-2h and the mass ratio of monomer to latex1:1. FTIR analyses confirmed the existence of NR-g-MMA graft copolymer in the reaction products. TG and DTG showed that the thermostability and thermo-oxidative stability of NR-g-MMA and NR-g-AM graft copolymers improved slightly. The solvent resistance of NR-g-AM improved greatly.