Effects of Fiber Content and Size on the Mechanical Properties of Wheat Straw/Recycled Polyethylene Composites

Wheat straw/recycled polyethylene composites (WRPCs) were manufactured with wheat straw fibers (WS) and recycled polyethylene (rPE) using extrusion followed by hot pressing moulding. The chemical structure and the fiber morphology of WS were analyzed by FTIR and L&W fiber tester. The influence of WS size and content on the mechanical properties, thermal stability and moisture absorption of WRPCs were investigated. The results showed that the performance of rPE based composites was certainly enhanced with the addition of WS. The WRPCs filled with long particle size and high length-to-diameter (L/D) ratio WS could obtain the optimal tensile and flexural performances. With increasing WS contents, the tensile and flexural strength of composites exhibited an increasing trend and the elongation at break decreased gradually. The strength properties of WRPCs decreased when the fiber content was over 50%. The length and content of WS had a significant influence on the moisture absorption of WRPCs. Thermogravimetric (TG) analysis found that WS size had no remarkable impact on the thermal stability of WRPCs. The scanning electron microscopy (SEM) indicated the dispersity of WS in composites increased with the decreasing of WS size, while the interfacial adhesion of WRPCs decreased gradually with the increasing of WS content.