A Compatible Interface of Wheat Straw/Polylactic Acid Composites Collaborative Constructed Using KH570–Nano TiO2

Poor interfacial compatibility between wheat straw and polylactic acid (PLA) remains a problem that directly affects the overall performance of wheat straw/PLA composites, thereby reducing the scope of application of these types of composites. To address this concern in this study, a silane coupling agent, KH570, and nano TiO2 were used to synergistically construct wheat straw/PLA composites with compatible interfaces. Scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry were conducted to investigate the underlying mechanism of synergistic modification. Analysis of the mechanical and water resistance properties indicates that the agglomeration of nano TiO2 in the synergistically modified composites is reduced, leading to the improved interfacial compatibility of the composites, tightened two-phase combination, and weakened stress concentration. Consequently, the mechanical strength and water resistance of the composites are effectively enhanced. Compared with unmodified composites, the blending and tensile strength of the synergistically modified composites increased by 25.4% and 44.7%, respectively, and its 96 h water absorption rate decreased by 17.4%. Analysis of the thermal stability and crystalline structure showed that the crystallinity of the synergistically modified composites was significantly enhanced, and the thermal stability was improved. Analyses of the rheological properties showed that the storage modulus (G′) of the synergistically modified composites was significantly improved under strain sweep, indicating that the two phases of the synergistically modified composites possessed enhanced bonding strength and internal structural stability. Frequency scanning showed that the complex viscosity (η*) of the synergistically modified composites exhibited the greatest improvement, indicating that a compatible composite interface was constructed by synergistic modification; moreover, the strong physical crosslinking effect and the nano TiO2 interparticle interaction friction hindered the flow of the composites. In this paper, for the first time, a silane coupling agent, KH570, was used to construct wheat straw/PLA composites with a compatible interface utilizing nano TiO2 to enhance the overall properties of the composite, which provides favorable properties for applications of wheat straw/PLA composites.Graphical Abstract