Solid-State Shear Milling for Recycling Aluminum–Plastic Packaging Waste: A Sustainable Solution for Mixed Plastic Waste

Abstract

The application of paper–aluminum–plastic packaging has been widely adopted in various fields such as the food and medical industries, owing to its exceptional preservation and obstruction properties. Nonetheless, the recycling process for paper and aluminum from this packaging type typically involves water pulping and solvent separation. The resulting residual waste, commonly known as multi-plastic waste (PMW), poses significant challenges in terms of separation and recycling. In this research article, we propose a solution for the recycling of PMW using solid-state shear milling (S3M). This process utilizes powerful three-dimensional shear force to achieve pulverization and excellent dispersion of multicomponent polymers, all while maintaining ambient temperature conditions. The thermoplastic processability of milled PMW powder was improved. The results indicate that a significant reduction in the the average particle size of PMW from 700 μm to 226 μm after 10 milling cycles, as evidenced by both a particle size analyzer and SEM. Furthermore, S3M processing leads to a good dispersion of PMW domains, as confirmed by the reduction in domain size from 9.64 μm to 2.65 μm. DSC and DMA reveal excellent compatibility between the components of the composite, resulting in improved mechanical properties such as tensile stress (from 14.03 MPa to 22.02 MPa) and unnotched impact strength (from 3.26 KJ/m2 to 4.82 KJ/m2). The findings suggest that S3M technology could be an effective and sustainable method for recycling PMW without any separation process, with promising industrial application.