Valorizing urban pruning wastes and recycled polyethylene towards sustainable natural fiber-reinforced polymer composites

The current research presents the elaboration of lignocellulosic reinforced polymer composites based on urban pruning wastes (UPW), recycled high-density polyethylene (rHDPE) and water-based acrylic resin. In doing so, UPW fibers were placed in acrylic resin bath. The “embedded” UPW fibers were called EUPW and used as reinforcement. Then, composites were formulated through a 3x2x2 experimental design: EUPW content (5, 10, and 15 wt%), natural fiber size (425 and 1000 µm) and coupling agent presence (none and polyethylene-graft-maleic anhydride). After extrusion and compression molding manufacturing, composites were characterized in terms of FTIR, TGA, and tensile behavior. The FTIR results showed a band at 1700 cm⁻¹ of the composites, representing the acrylate group of acrylic polymer (AP) in EUPW. Additionally, TGA determined that AP provided thermal protection to UPW. Furthermore, it was found that elastic modulus of the composites was increased compared to the neat polymer matrix; however, modulus of elasticity decreased with EUPW addition. According to the statistical analysis, coupling agent effect was the most significant factor on elastic modulus and tensile strength. Finally, the results revealed that combining UPW, acrylic polymer resin, rHDPE and polyethylene-graft-maleic anhydride, composites with relatively positive balanced properties were obtained.