荷叶/明胶复合材料性能研究

Study on properties of lotus leaf/gelatin composites

[目的]本文旨在探究利用荷叶和明胶制备全降解复合材料用于食品包装的可能性。[方法]对荷叶进行热水处理后与明胶复合制备全降解复合材料。分析荷叶和明胶的红外光谱,对荷叶/明胶复合材料的力学性能、吸湿性能和导热性能进行测试,并分析复合材料截面的微观形貌。[结果]热水处理能去除荷叶部分木质素、蜡质、果胶等小分子物质,使荷叶表面变粗糙,利于其与明胶的结合;明胶中含有—OH、—NH_(2)、—COO^(-)等基团,能够与荷叶中的—OH形成氢键。荷叶/明胶复合材料的力学性能随明胶含量增加整体呈上升趋势,当明胶含量(以叶片干重计)为25%时,复合材料的弯曲强度和冲击强度最大,分别为14.06 MPa和5.36 kJ·m^(-2)。荷叶/明胶复合材料的平衡吸湿率随明胶含量的增加呈先上升后下降再上升的趋势。当明胶含量为25%时,平衡吸湿率最小,为5.19%,继续增加明胶含量时,复合材料的平衡吸湿率变大。荷叶/明胶复合材料的导热系数随明胶含量的增加而变大,当明胶含量为10%时,导热系数最小,为0.042 W·m^(-1)·k^(-1)。明胶含量的增加能改善荷叶/明胶复合材料层间结合,减少内部空隙,明胶含量为30%时,复合材料截面层间分界模糊,两相结合情况最好。[结论]合适的明胶含量能够改善荷叶/明胶复合材料的层间结合,同时荷叶/明胶复合材料为隔热材料,这些特性使其具有应用于食品包装的可能性。

[Objectives]This study aimed to explore the possibility of the application of green biodegradable biomass composites in the field of food packaging.[Methods]Lotus leaves were treated with hot water and combined with gelatin to prepare full-degradable composites.The infrared spectra of lotus leaf and gelatin were analyzed.The mechanical properties,moisture absorption and thermal conductivity of the composites were tested.The micro-morphology of the cross-section of the composites was analyzed.[Results]Hot water treatment could remove some small molecules such as lignin,wax and pectin from lotus leaf which could lead to a rough surface that could improve the combination with gelatin.Gelatin containes—OH,—NH_(2),—COO^(-)groups,which could form hydrogen bonds with—OH in lotus leaves.The mechanical properties of lotus leaf/gelatin composites increased with the increasement of gelatin content.When the gelatin content was 25%,the flexural strength and impact strength of the composites were the maximum,which were 14.06 MPa and 5.36 kJ·m^(-2),respectively.With the increasement of gelatin content,the equilibrium moisture absorption rate of the composites firstly increased,then decreased and then increased.When the gelatin content was 25%,the equilibrium moisture absorption rate was the minimum,which was 5.19%.If the gelatin content continued to increase,the equilibrium moisture absorption rate of the composites increased.The thermal conductivity of the composites increased with the increasement of gelatin content.When the gelatin content was 10%,the thermal conductivity was the smallest,which was 0.042 W·m^(-1)·k^(-1).When the content of gelatin was 30%,the boundary between layers was blurred,and the bonding between two phases was the best.[Conclusions]Appropriate gelatin content can improve the interlayer bonding of lotus leaf/gelatin composite.At the same time,lotus leaf/gelatin composite is a thermal insulation material,which makes it possible to be used in food packaging.