Upgrading mixed plastic wastes to prepare wood plastic composites via solid mechanochemical method

Abstract

Abstract Plastic wastes are integrated with renewable wood fiber (WF) into wood-plastic composites (WPC), which is an economically sustainable way to solve global plastic pollution. However, the current processing strategies are applied mainly to single-polymer wastes, but are ineffective for mixed-waste streams. Herein, we proposed a simple and effective strategy to upcycle mixed plastic wastes to prepare WPC via solid-state shear milling (S3M). Specially, the mixed plastic waste, WF and maleic anhydride grafted polyethylene were co-milled in solid-state. During the mechanical treatment, the bevel ridges on the upper and lower pans in the S3M equipment created many mixing units to continuously exert strong squeezing and shearing forces on the milling composites, enabling mechanically-induced pulverization, dispersion and esterification of the multi-component materials at room temperature. As a result, the mixed plastic wastes with WF were pulverized and mixed simultaneously while hydrophilic WF was transformed to the hydrophobic one, endowing the obtained WPC with exhibited excellent processability and strong interfacial interaction. The flexural strength and modulus reached 39.5 MPa and 4257 MPa, with 72% and 101% enhancement compared to the WPC sample with the same formulation prepared by direct melt-process. This mechanochemistry technology can successfully achieve the upgrading and reuse of mixed plastic wastes and solve the challenges associated with the WF preparation, which plays a crucial role in mitigating plastic pollution.