【作者】 梅小峰；

【导师】 吴大诚；

【作者基本信息】 四川大学 ， 材料学， 2005， 硕士

【摘要】 在淀粉上接枝丙烯酸酯支链,使其兼有天然高分子和合成高分子的优点,并可被生物降解,属于第三代变性淀粉。通过接枝单体的选择和不同配比可以生产出适合多种工业用途的产品,特别是作为经纱浆料,接枝淀粉适用于所有纤维品种,已经成为最具发展潜力的主体浆料。淀粉的接枝改性也因此引起了纺织科学与工程界的广泛关注。淀粉用乙烯基单体的接枝共聚属于自由基聚合机理,目前主要有湿法、干法和淀粉糊化状态接枝法,每种方法都有各自的特点。本文研究了淀粉糊化对淀粉接枝共聚反应的影响,比较了几种引发剂的引发效果,比较了糊化淀粉与丙烯酸丁酯、丙烯酸乙酯、丙烯酸甲酯、甲基丙烯酸几种单体的接枝效果,以及接枝产物的性能;以过硫酸钾为引发剂,探讨了接枝共聚反应规律,得到了最佳工艺条件;最后以接枝淀粉为增容剂,考察了其对淀粉与PVA共混的影响。 淀粉与丙烯酸丁酯以硝酸铈铵引发时,红外光谱证明确实发生了接枝共聚反应。与未糊化相比,糊化后淀粉接枝产物接枝率、接枝效率、单体转化率、接枝频率和支链分子量都降低,但是由于均匀接枝,产物的水溶性好。随着单体浓度的增加,接枝支链分子量增大,接枝频率则是先减小,在[BA]=0.2166mmol/L时达到最小值,随后继续增大单体浓度,接枝频率反而增大。加入适当浓度(4mmol/L)的尿素将有利于糊化淀粉的接枝共聚。接枝产物在接枝率(G%)低于10%时能溶于水,高于10%后开始出现沉淀,在44%左右时,产物完全不能溶解。 淀粉糊化后与丙烯酸丁酯接枝时,比较了硝酸铈铵、高锰酸钾—硫酸、过硫酸铵及过硫酸钾四种引发剂的引发效果,结果表明过硫酸钾为此反应体系的更多还原

【Abstract】 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.更多还原