| There had a long history that starch was used in industrial production for using as a kind of preferred crude macromolecule compound. There also had a limitation in its application as a result of its character of hydrophilicity, gelatinization, and glutinosity.The graft copolymerization of vinyl monomers onto starch was an important method for the chemical modification of starch. Grafted starch could be synthesized through chemical initiator or high-energy ray activated starch in order that low-grade polymer was grafted onto starch as a branched chain. As grafted starch was copolymer of starch and monomers, it had wide application area.Preferred monomers included vinyl acetate, methyl acrylate, methyl methacrylate, ethyl methacrylate, hydroxyethyl methacrylate, hydroxymethyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, butadiene, styrene and maleic anhydride and mixtures thereof.Starch graft copolymers had extensive application. It could be used in super-absorbent, biodegradable plastics, paper-making industry additive, environment effluent disposal, petroleum industry, medical and pesticide industry, and adhesives industry.The soluble starch was modified by means of graft copolymerization in experiment, in order to prepare grafted copolymer which possessed both favorable qualities of starch and monomers, and to be used as a new kind of binder in printing ink. Based on literatures, a study on graft emulsion copolymerization of styrene/butyl acrylate onto starch was carried out by using ammonium persulfate as initiator and sodium dodecyl sulfate as emulsifier. The influence of initiator concentration, monomer concentration, reaction temperature, and reaction time on grafting parameters of starch graft copolymers was investigated. Finally, the reaction mechanism was also discussed, the possible kinetic model was supposed according the results of experiment. The model agreed well with the experimental results. The main conclusions as below:1 Ammonium persulfate was a quite effective initiator in graft copolymerization of styrene/butyl acrylate with soluble starch. It was found that grafting degree approached 250.5%, grafting efficiency approached 73.8%, and the maximum monomer percentconversion approached 95.8%.2 The pre-gelatinization of starch had important influence on graft copolymerization. Compared grafting efficiency in different gelatinization conditions, the experiment showed that the grafting efficiency was preferable if the starch was gelatinized under 75℃ for 30 minutes.3 If the solid content of polymer emulsion was 30%, the perfect grafting efficiency was obtained when the weight ratio of starch and monomers was 1:4. On the condition of weight ratio between styrene and butyl acrylate was 2:1, grafting efficiency was also perfect.4 The preferred initiator consistency was 6.0×10-3mol/L. The homopolymer in the product was increased if the initiator consistency was over 6.0×10-3mol/L. It was preferable that the emulsifying agent consistency was 0.0208mol/L.5 The optimal reaction temperature was 53℃. The optimal reaction time was 3.5 hours. If the reaction temperature was above 53℃ or the reaction time was above 3.5 hours, the homopolymer content of the product would increase.6 The evidence of graft copolymer had been researched by means of infra-red spectrogram. The graft was occurred on the surface of starch grain through the testing result of SEM photograph.7 The expression of graft polymerization rate at the beginning of reaction was obtained from experiment was expressed as:...
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