Mechanochemical ball milling as an emerging tool in chemical recycling and upcycling of waste polymers

Abstract

Exponential growth of the global plastics production in the past 70 years has unfortunately not been followed by at least comparable recycling rates, ultimately leading to a plastic pollution crisis we are currently facing with. The very same physical and chemical properties of polymeric materials which have been tailored for specific purposes, now pose a challenge in front of researchers who strive to come up with solutions to reverse them and enable full depolymerization back to the monomer level. This approach lies at the core of chemical recycling, a promising technology that has the potential to convert all-present waste plastics into valuable feedstock for the production of virgin-grade polymers and/or upcycling to novel functional materials. While traditional methods rely on thermochemical or thermocatalytic processes under high temperatures and pressures, new opportunities in chemical recycling of plastics have emerged with mechanochemical ball milling. In a short period, this methodology has been proven as highly efficient and selective for depolymerization of commodity plastics, with significant advancements in recycling of even challenging addition polymers. This review article aims to provide readers with a systematic overview of recent contributions in the field, focusing on the application of ball milling as an environmentally-friendly robust and easy-to-implement technique.