Characteristics of wheat straw fiber/polylactic acid composites: Effect of different fiber morphologies and modification methods

Generally, the morphological parameters of plant fibers significantly impact the properties of plant fiber-reinforced resin-based composites. In this study, the physicochemical properties of straw fibers with varying morphological characteristics were systematically analyzed. The performance variations of polylactic acid (PLA)-based composites reinforced with straw fibers of different aspect ratios were investigated. The result provided a theoretical basis for optimizing the interfacial adhesion and overall performance of straw fiber/PLA composites. Furthermore, the reinforcement effect of high-aspect-ratio straw fiber (HSF)/PLA composites modified with PLA-g-MAH, titanate, and sodium silicate on interfacial compatibility was systematically investigated. The results showed that HSF, with the highest aspect ratio (11.84), exhibited the most significant reinforcement effect on the PLA matrix, followed by the 60-mesh wheat straw powder. At a fiber loading of 20 wt%, HSF/PLA composites exhibited the highest impact strength (21.1 kJ/m 2 ). The tensile strength, elongation at break, flexural strength, flexural modulus, and impact strength of sodium silicate-modified composites improved by 18.3, 12.7, 19.3, 15.3, and 10.1 %, respectively. Compared with unmodified composites, titanate-modified composites exhibited increased crystallinity (37.6 %) and reduced water absorption (1.18 %). All 20 wt% HSF/PLA composites, regardless of the modification, met the industrial standards for wood–plastic decorative boards. These findings provide insight into the development of lightweight, high–strength, and cost-effective bio-based composites. • The overall properties of PLA matrix composites were explored using SF of different morphologies as reinforcement materials. • The morphology of straw fibers significantly affects the mechanical properties and interface strength of the composite. • The addition of high aspect fibers can effectively enhances the overall mechanical properties of the composite. • Sodium silicate and cellulose work together to create a uniform and dense protective layer on the fiber surface. • Titanate interacts with both the fiber and PLA, significantly enhancing crystallization and water resistance.