Upcycling Waste Low-Density Polyethylene into Highly Crystalline Graphite

Abstract

Only a small fraction of the global plastic waste is recycled, and the recycled materials are often of lower quality. For example, only 14% of the world's total plastic is recycled, with low-density polyethylene (LDPE) accounting for only 4% of it. This study presents a novel approach to transforming waste LDPE into electrically conductive artificial graphite with high crystallinity using stabilization and graphitization processes. This method achieves a carbon yield of 89.4%, surpassing yields from conventional polymer precursors, such as polyacrylonitrile and polyamide. The resulting LDPE-derived graphite (LGP) exhibits a high crystallinity and electrical conductivity, twice those of natural graphite and comparable to those of artificial graphite, which typically requires extensive heat treatment to prepare. LGP can be used in pastes and inks for advanced applications, such as 3D printing, flexible electrodes, heaters, and photothermal devices. Additionally, the high crystallinity of LGP enables the formation of larger graphene oxide (GO) with an average size of 4.1 ± 2.4 µm, because the larger crystalline domains in LGP facilitate the exfoliation process. The approach developed in this study contributes significantly to LDPE waste management and provides a pathway for the fabrication of valuable carbon materials for broad industrial applications.