Study On Graft Copolymer Of Cationic Starch And Styrene-Acrylic Emulsion

In recent years, more and more studies on the synthesis of starch graft copolymers were carried out over the world, which include the graft copolymerization reaction of starch with monomers such as acrylamide, acrylic acid, styrene, vinyl acetate, methyl methacrylate. Styrene/butyl acrylate polymer was widely used and became the fastest growing synthetic polymer surface sizing agent because of its low viscosity of product, its simple synthesis process, and its ease of use. But the styrene-acrylic emulsion was relatively expensive; Starch was inexpensive, while its water resistance was poor, and it was easy to fracture. These disadvantage could be improved by the graft copolymerization with starch and styrene acrylic emulsion.In the first part of this thesis, the preparation of cationic starch separately by wet process was studied. The effects of some factors were investigated such as the dosage of cationic etherifying agent and NaOH, reaction temperature and reaction time. The optimum preparation conditions were explored by single factor experiment:the dosage of CHPTMA and NaOH was35%and10%respectively, the reaction time was3h and the reaction temperature was75℃. Under the optimum conditions, the cationic starch that prepared with DS at0.02could be dissolved in cold water to form transparent solution.In the second part, graft copolymerization of cationic starch with styrene (St) and butyl acrylate (BA) was carried out via soap-free emulsion polymerization with ammonium persulfate-sodium bisulfate as initiator. The important factors of graft polymerization were investigated. The optimal conditions were as follows:the dosage of initiator was6.0%in the reaction system, m(starch):m(monomers)=1:4, m(St):m(BA)=1:1, and reaction temperature was50℃. Infrared spectroscopy showed that both styrene (St) and butyl acrylate (BA) had participated in the grafting reaction.In the end, the thesis studied the performance of graft copolymerization of cationic starch with styrene and butyl acrylate emulsion and provided a theoretical basis for emulsion performance by studying the influence of different reaction factors on the emulsion properties.