Mechanical characterizations, recyclability of thermoplastics through melt grafting a dynamic covalent network onto polyethylene

Polyethylene (PE) is the most heavily used polymer worldwide. Theoretically, PE can be further enhanced by methods such as increasing the molecular weight or moderate cross-linking, however these changes lead to increased viscosity and difficulty for processing PE in the molten state, bringing problems such as decreased production efficiency and greater difficulty in recycling. An important research direction has focused on combining the easy processing and mechanical strength of PE. In this study, long-branched polyethylene containing reversible boronic esters bonds (B–O bonds) was prepared by graft copolymerization, and then PE vitrimers were prepared by a complex decomposition reaction with bis(dioxaborolane) crosslinker. This method can directly convert non-functional conventional plastics into dynamic covalent polymers through reactive processing imparting higher tensile strength, Young's modulus, and better heat resistance to PE. The PE vitrimers is demonstrated to have good melt processability based on dynamic B–O bond exchange, uniting strong mechanical and thermomechanical properties with excellent reproducible processability. This work introduces a new way of recycling and reusing traditional plastic and rubber products.