【作者】 林华；

【导师】 符新；

【作者基本信息】 华南热带农业大学 ， 材料学， 2007， 硕士

【摘要】 本文以木薯淀粉为接枝骨架，醋酸乙烯酯为接枝单体，通过引发体系的选择、制备工艺条件的筛选，制备接枝淀粉共聚物。再添加PVA增塑和交联反应处理，考察了PVA用量、交联剂种类及用量、交联时间及交联温度对接枝淀粉共聚物力学性能的影响，并研究了接枝共聚物的降解性能，制备出具有良好力学性能和降解性能的接枝淀粉材料。采用红外光谱（FTIR）、热重分析（TG／DTG）、扫描电镜（SEM）、差热扫描量热（DSC）、X射线衍射（XRD）及动态力学分析（DMA）等对接枝淀粉材料的结构、性能进行了表征。研究结果表明：引发体系对木薯淀粉——醋酸乙烯酯接枝共聚物反应有较大的影响。在研究的引发体系中，过硫酸铵的引发效率最好，Fe²⁺—H₂O₂次之，硝酸铈铵最差。以过硫酸铵为引发体系，可以获得较高的单体转化率、接枝率和接枝效率，从而得到最适宜的制备工艺条件：淀粉浓度为5％，单体与淀粉的质量配比为2.0，引发剂浓度18.0mmol／L，反应温度60℃，反应时间3h。采用此工艺制备的产物为木薯淀粉与醋酸乙烯酯接枝共聚物，共聚物为无定形结构。木薯淀粉的热降解历程为一步历程，而共聚物的热降解为三步历程，较为复杂，共聚物具有较好的热稳定性。通过加入PVA和交联剂处理，改善了木薯淀粉与醋酸乙烯酯接枝共聚物的力学性能。PVA、交联剂种类和用量及交联处理对共聚物的力学性能有较大的影响，在采用的交联剂中，环氧氯丙烷的效果较好，甲醛次之，六偏磷酸钠较差。当PVA用量为1％，环氧氯丙烷用量为1％，交联反应温度为60℃，交联反应时间为30 min时，可制备出具有良好力学性能的接枝淀粉材料。接枝单体的用量对接枝淀粉材料的力学性能有一定的影响，单体用量越大，共聚物的拉伸强度越低，扯断伸长率越大，共聚物的吸水率越小，湿强度及扯断伸长率先增加后减少。VAc与淀粉的质量配比对接枝淀粉材料动态力学性能有一定的影响。三种配比的共聚物的DMA研究表明：在小于-50℃范围内，单体用量大的共聚物的E′较大，并在-50℃～50℃范围内，单体用量大的共聚物E′较小，当温度大于120℃后，三种配比的共聚物的E′相同。单体与淀粉配比为1：1的共聚物出现两个内耗峰，配比为2：1和3：1的共聚物，出现三个内耗峰。单体用量越大，内耗峰面积越大。木薯淀粉与醋酸乙烯酯接枝共聚物（接枝淀粉材料）具有良好的的生物降解性能：α-淀粉酶、枯草杆菌对此接枝共聚物具有良好的降解作用，在5天内，此共聚物的生物降解速度最快。土埋也能快速地促进接枝共聚物的降解，在60天内，共聚物具有较快的降解速度，淀粉含量较大的共聚物，降解失重较大，共聚物越易于降解。在实验的时间范围内，共聚物除了淀粉部分发生生物降解外，共聚物的支链结构部分也发生了生物降解，共聚物具有完全生物降解性。更多还原

【Abstract】 In this paper, with cassava starch as graft framework, VAc as graft monomer, grafted starch was prepared through the choices of initiating system and preparing conditions. The effects of PVA content, kinds and content of cross-linking agent, cross-linking time and cross-linking temperature on mechanical properties and degradation property of grafted starch materials were investigated, and the grafted starch materials with good mechanical and degrading properties were prepared. The structure and properties of grafted starch copolymer were determined with FTIR、TG/DTG、SEM、DSC、XRD and DMA.The results show that initiating system has an effect on grafting copolymerization ofcassava starch and VAc monomer. In the initiating systems studied, （NH₄）₂S₂O₈ has the best initiating efficiency , and Fe²⁺-H₂O₂ second; （NH₄）₂Ce（NO₃）₆ last.Higher monomer conversion, grafted ratio and efficiency could be obtained with initiating system of （NH₄）₂S₂O₈.The optimum preparing condition is concentration of starch 5%, mass ratio of monomer and starch 2.0, concentration of initiator 18.0 mmol/L, reaction temperature 60℃and reaction time 3h. The product with above preparing technology is grafted copolymer of Cassava Starch and Vinyl Acetate. The copolymer is amorphous structure. The degrading course of cassava starch by heat is one step, whereas the degrading course of copolymer three and provided with better heating stability.Mechanical properties of cassava starch-VAc grafted copolymer is improved with PVA and cross-linking agent added. PVA content, Kinds and content of cross-linking agent and cross-linking treatment have relatively big influence on mechanical properties of copolymer. As for cross-linking agent, epoxypropane has the best effect , formaldehyde second, and hexametaphosphate third.The excellent mechanical properties of cassava starch-VAc grafted copolymer could be prepared with PVA content 1%, dosage of epoxypropane 1%, cross-linking temperature 60℃and cross-linking time 30min.Content of graft monomer has an effect on mechanical properties of copolymers. With content of monomer increasing, ultimate tensile strength of copolymer decreases, elongation at break increases, water absorpton ratio of copolymer decreases at first then decreased.Mass ratio of VAc and starch has an effect on dynamic mechanical properties of grafted starch.DMA study shows that E ’ of copolymer increases with increasing monomer content as temperature less than -50℃, decreases in -50℃to 50℃,and remains the same value more than 120℃. There appear two peaks of internal friction as the ratio of monomer and starch is 1:1,and three peaks 2:1 and 3:1. The peak area of internal friction increases with increasing content of monomer.The grafted copolymers show a good biological degrading property. Bacillus andα-amylase have excellent degrading effect on grafted copolymer, the biological degrading rate of copolymers is the fastest in 5 days. Burying with clay also speeds up the degradation of copolymer. Degrading rate increases with increasing starch content of copolymer. The branch structure of copolymer appears biological degradation besides starch.更多还原