二氧化硅的氢键与异相成核作用下木薯淀粉回生机理研究

Starch is a green natural renewable and degradable polymer materials. The retrogradation phenomenon of starch would lead to the changes in the structure and properties. Silica has unique advantages in improving mechanical properties, thermal stability and water resistance of starch material, however the effect of silica on starch retrogradation mechanism has been rarely reported. In this project, cassava starch as the research object, the cassava starch/silica composites are prepared via melt blending method by the combination of macro and micro research methods. Based on the hydrogen bonding interaction theory and heterogeneous nucleation theory, the effect of different content, particle size and surface characteristics of silica on the interaction of starch is investigated. The thermodynamic parameters are obtained starch during retrogradation process, and the retrogradation kinetics equation will be established. The effect of silica on retrogradation rate and index of cassava starch are obtained. The changes of hydrogen bond of cassava starch/silica composite during retrogradation process are explored, and the relationship between hydrogen bonding and retrogradation behavior is revealed. The dispersion, migration and interface bonding conditions of silica particle during retrogradation process of the cassava starch are investigated. The effect of silica on aggregation, granules, crystal, layer structure cassava starch is researched, in order to explore the relationship between structures and retrogradation behavior. Through the research would provide the theoretical basis and method for the perfection of retrogradation mechanism and enhancement of properties of starch materials.

淀粉是可再生、可降解的绿色天然高分子材料。淀粉回生现象导致其结构与性能发生变化，二氧化硅在改善淀粉材料的力学、耐热和耐水性能等方面具有独特的优势，而二氧化硅对淀粉回生机理方面的研究鲜有报道。本项目以木薯淀粉为研究对象，采用熔融法制备木薯淀粉/二氧化硅复合材料，将宏观和微观研究手段相结合，基于二氧化硅的氢键作用和异相成核原理，研究不同用量、粒径及表面性质的二氧化硅与淀粉的相互作用机制，获取淀粉回生过程的热力学参数，建立回生动力学方程，获得二氧化硅对木薯淀粉回生速率、回生指数的影响规律；研究木薯淀粉/二氧化硅复合材料回生过程氢键变化规律，揭示氢键与回生行为关系；探讨淀粉回生过程中二氧化硅的分布、迁移、界面黏结机制，获得二氧化硅对木薯淀粉聚集态、颗粒、晶体、层状结构的影响规律，揭示淀粉/二氧化硅复合材料的结构与回生行为关系。通过该研究为淀粉回生机理的完善、淀粉材料性能的提高提供理论基础和方法。

淀粉是可再生、可降解的绿色天然高分子材料。淀粉回生现象导致其结构与性能发生变化，而二氧化硅对淀粉回生机理方面的研究亟待研究。本项目以木薯淀粉为研究对象，甘油为增塑剂，添加不同用量、表面性质、粒径的二氧化硅(SiO2)，采用熔融法制备木薯淀粉（TPS）/二氧化硅(SiO2)复合材料，研究TPS/SiO2复合材料的热力学参数，建立回生动力学方程，获得二氧化硅对木薯淀粉回生速率、回生指数的影响规律；研究TPS/SiO2复合材料回生过程氢键变化规律，揭示氢键与回生行为关系； SiO2的分布、迁移、界面黏结情况，获得SiO2对木薯淀粉聚集态、晶体形态、大小和晶型的影响规律，构建回生结构模型，揭示淀粉/SiO2复合材料的结构与回生行为关系；分析TPS/SiO2复合材料回生后的力学性能、透光性能、亲疏水性和热性能变化规律，揭示TPS/SiO2复合材料的回生与性能的关系；研究拉伸作用下TPS/SiO2复合材料的回生行为，揭示拉伸作用下TPS/SiO2复合材料回生机理。研究结果表明：随回生时间增加，TPS/SiO2复合材料的回生程度增大；5份SiO2用量促进淀粉回生；SiO2粒径为200nm时回生熔融焓最小；TPS/SiO2复合材料形成淀粉分子间氢键作用，晶体数量的增多，晶型发生变化，最终形成稳定的VH型；SiO2用量、表面特性及粒径大小不改变淀粉晶型。SiO2用量为5份且粒径为20nm时拉伸强度最大，疏水改性后的SiO2提高淀粉复合材料的拉伸强度。随着回生时间的增加，TPS/SiO2复合材料的热稳定性降低；随着SiO2用量增加，TPS/SiO2复合材料的热降解温度升高，添加粒径200nm时复合材料的热降解温度最高；SiO2经KH550改性后和粒径为20nm接触角最大。拉伸作用会促进淀粉复合材料的短期回生、抑制长期回生，破坏淀粉球晶结构，增加SiO2与淀粉的相容性。拉伸作用应力后TPS/SiO2复合材料的回生程度随回生时间增加而增大。通过该研究为淀粉回生机理的完善、淀粉材料性能的提高提供理论基础和方法。