Graft Copolymerization Of Gelatinized Starch And Its Applications

The grafted starch with polyacrylate branches has advantages of both natural and synthetic polymers. This product is biodegradable, and called "the third generation of modified starches". Through selecting different kinds of grafted monomers and the mixed proportion, we could obtain products, which are suitable for multiplicative industrial applications. For the warp sizing agent, the grafted starch can be used in all kinds of fiber and has been the most potential main sizing agent. So in textile science and engineering, the grafted starch has been paid much attention in recent years. Graft copolymerization of vinyl monomer onto starch follows the free radical polymerization mechanism. The graft copolymerization is currently in the state of wet, dry, or gelatinized starch, and each one has different characteristics. In the paper, the investigation was focused on the influence of starch gelatinization on the graft copolymerization. In this way, several reaction parameters were discussed, such as initiators, monomers, and grafting polymerization conditions. The used monomers included butyl acrylate, ethyl acrylate, methyl acrylate and methacrylic acid. The properties of grafted products were also determinate. For a certain graft copolymerization using potassium persulate as initiator, the reaction rule was investigated. Meanwhile, taking the grafted starch as a compatibilizer into blends of starch and PVA, its influence to the blends system was inspected.For a product of poly(butyl acrylate)-g- starch initiating with ceric ammoniumnitrate, infrared spectrum showed that graft copolymerization has taken place. The grafting percent, grafting efficiency, grafting frequency, total conversion of monomer, and average molecular weight of the grafted side chain were decreasing for the gelatinized starch in comparison with that for granular starch. However, for the former, the product has better solubility for its homogeneity of grafting. Molecular weight of the grafted side chain increased with increasing the monomer concentration. As the enhancement of monomer concentration, the grafting frequency first decreased, until the minimum with corresponding concentration 0.2166 mmol/L, and then increased. "Adding appropriate amount (4mmol/L) of carbamide as an additive into the starch paste system could be in favor of the graft polymerization. The grafting products had good solubility when the grating percent (G %) was less than 10%. Precipitation would be appeared if the G% was higher than 10%. When the G% is about 44%, the products would be no longer soluble in water.Four initiation systems, eerie ammonium nitrate, potassium permanganate -sulfate acid, ammonium persulfate and potassium persulfate, were used to initiate the graft polymerization of butyl acrylate onto gelatinized starch. The initiating effects were investigated, and the results showed that the potassium persulfate was the best initiator for this reaction. Initiating with potassium persulfate, the influences of monomer concentration, initiator concentration, reaction temperature and reaction time on the grafted parameters were studied. Such a condition was optimized, as monomer concentration 0.1404mmol/L, initiator concentration 6mmol/L, reaction temperature 60 °C and the time 3h, for butyl acrylate grafted onto starch. Under the condition, graft polymerizations of ethyl acrylate and methyl acrylate with gelatinized starch were done. The grafting effect was the best for BA and the worst for MA.Starch was also grafted with methacrylic acid according to the infrared spectrum. The graft copolymerization was initiated by potassium persulfate-sodium thiosulfate. The product could be used as a compatibilizer, which stabilize starch-PVA blend pastes. It was shown by experimental data that the stability of blend pastes enhances with increasing the hydrolysis degree of PVA, and that the blend pastes will be morestable if increasing the graft percentage and amount of the grafted starch. The use of grafted starch as a basic material in the blended pastes was investigated. Comparing with starch, the initial demixing time of the grafted starch-PVA blend paste increased and the subsidence ratios decreased. When the graft percentage of the grafted starch was 16.67%, phase separation did not occur within 24h. The SEM photographs of chorion did not show any phase-separated image for the film of the starch and PVA with the addition of grafted starch. Through grafted modification, the elastic recovery capability of the modified starch increased from 64.58% for starch to 79.16% for PMAA-g-starch with the graft percentage 16.67%. Adding the grafted starch into the blend pastes, the mechanical properties of the chrion of blend pastes would.be enhanced.