摘要:
以玉米淀粉和马来酸酐(MAH)为原料,通过干法合成MAH酯化淀粉,通过熔融挤出法制备酯化淀粉/聚乳酸(PLA)复合材料.研究了MAH用量对复合材料结晶度和相容性的影响,同时考察了相容性和结晶度的变化对复合材料热性能、熔融流动性能、力学性能、耐水性能和流变性能的影响.FTIR结果证明通过干法成功合成了MAH酯化淀粉.酯化淀粉的取代度随MAH用量增多逐渐增大,反应效率高达90%.XRD和DSC结果表明:随着MAH用量增多,酯化淀粉/PLA复合材料的结晶度逐渐降低,淀粉和PLA的相容性逐渐提高.结晶度的降低和相容性的提高使复合材料的玻璃化转变温度逐渐降低,熔融流动性提高,耐水性提高.在力学性能和流变性能受相容性和结晶度的共同影响下,酯化淀粉中MAH用量从0增加到1.0wt%时,复合材料拉伸强度、弯曲强度、储能模量和复数黏度都逐渐增大,MAH用量超过1.0wt%后,性能逐渐降低.
Abstract:
Maleic anhydride (MAH) esterified starch was synthesized by dry method with corn starch and MAH as raw materials, and esterified starch/polylactic acid (PLA) composites were prepared by melt extrusion. Effects of MAH amounts on the degree of crystallinity and compatibility of composites were studied. At the same time, the influence of compatibility and degree of crystallinity change on thermal property, melt flow property, mechanical property, water resistance and rheology property of composites were investigated. FTIR results show that MAH esterified starches were successfully synthesized by dry method. Degree of substitution of esterified starch gradually increases with the increasing of MAH amounts, and the reaction efficiency is up to 90%. XRD and DSC results show that with the increasing of MAH amounts, the degree of crystallinity of composites decreases, which makes the compatibility between starch and PLA increase gradually. The decrease of degree of crystallinity and the improvement of compatibility cause the decreased glass transition temperature and the increased melt flow and water resistance. The mechanical properties and rheological properties are affected by the combination of the compatibility and degree of crystallinity. The tensile strength, bending strength, storage modulus and complex viscosity increase gradually when MAH amount increases from 0 to 1.0wt%, but these properties decrease gradually when the amount of MAH is more than 1.0wt%.
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