Crosslinking starch/oat hull mixtures for use in composites with PLA

Abstract Modification of composite components has been proposed as a tool to improve their functional properties. The present work studied crosslinking of a starch/oat hull mixture by reactive extrusion with sodium trimetaphosphate (STMP), for application in composites with polylactic acid (PLA). The treated mixture was characterized regarding degree of substitution, FT-IR, and thermal properties. The native and modified mixtures were processed by injection molding, together with PLA and glycerol. The microstructure, mechanical properties, shrinkage, density, and thermal properties of the composites were determined. The FT-IR results, increase in phosphorus content and thermal stability after starch/fiber mixture treatment with STMP suggested the occurrence of crosslinking. Better interfacial adhesion between oat hulls and the polymeric matrix was observed in electron micrographs of the composites containing the modified components. Slight decreases in tensile strength and modulus were observed in the modified composites, suggesting that extrusion and subsequent milling may have broken some structures/linkages.

摘要 复合组分改性已被提出作为改善其功能性能的有效手段。本研究采用反应挤出法结合偏三聚磷酸钠（sodium trimetaphosphate, STMP）对淀粉/燕麦壳混合物进行交联改性，以期将其应用于聚乳酸（polylactic acid, PLA）基复合材料。对经改性处理的混合物开展了取代度、傅里叶变换红外光谱（Fourier Transform Infrared Spectroscopy, FT-IR）及热性能表征。将未改性与改性后的混合物分别与聚乳酸及甘油共混，通过注塑成型制备复合材料。对所得复合材料的微观结构、力学性能、收缩率、密度及热性能进行了测试表征。经偏三聚磷酸钠改性的淀粉/纤维混合物的傅里叶变换红外光谱结果、磷元素含量提升以及热稳定性增强，均表明交联反应成功发生。含改性组分的复合材料的电子显微照片显示，燕麦壳与聚合物基体间的界面黏合性能得到改善。改性复合材料的拉伸强度与拉伸模量出现小幅下降，这表明挤出及后续粉碎过程可能破坏了部分结构或化学键。