Leveraging mechanochemistry for sustainable polymer degradation

Abstract

Over 8 billion tons of plastic have been produced to date, and a 100% reclamation recycling strategy is not foreseeable. This review summarizes how the mechanochemistry of polymers may contribute to a sustainable polymer future by controlling the degradation not only of de novo developed designer polymers but also of plastics in existing waste streams. The historical development of polymer mechanochemistry is presented while highlighting current examples of mechanochemically induced polymer degradation. Additionally, theoretical and computational frameworks are discussed that may lead to the discovery and better understanding of new mechanochemical reactions in the future. This review takes into account technical and engineering perspectives converging the fields of trituration and polymer mechanochemistry with a particular focus on the fate of commodity polymers and potential technologies to monitor mechanochemical reactions while they occur. Therefore, a unique perspective of multiple communities is presented, highlighting the need for future transdisciplinary research to tackle the high-leverage parameters governing an eventually successful mechanochemical degradation approach for a circular economy.

Liquid-Assisted Grinding Enables a Direct Mechanochemical Functionalization of Polystyrene Waste

“…The kinetics of prolonged functionalization reactions under BMG conditions are likely to be competitive with those of chain scission, resulting in excessive backbone degradation and loss of desired bulk properties. 50 This degradation via BMG can be leveraged for polymer depolymerization, 26,51,52 chain-end functionalization, 53,54 or radical functionalization. 55 For PS, while chain scission under BMG is well documented above a limiting molar mass, Mlim (ca.…”

Modeling Mechanochemical Depolymerization of PET in Ball-Mill Reactors Using DEM Simulations

“…One promising alternative is the depolymerization of polymers in the solid state via mechanically-induced reactions. − Mechanochemical reactions are typically performed in ball mills, in which contacts and collisions between grinding surfaces (balls and reactor wall) supply the energy required to chemically transform the (usually particulate) solid reactants caught between these surfaces. ,− Mechanochemistry has been successfully demonstrated on a laboratory scale for the production of lignocellulosic biomass, , cellulose, − ammonia − and lignin. − Particularly for poly­(ethylene terephthalate) (PET), Štrukil and Tricker et al recently demonstrated its complete depolymerization to monomers inside ball mills. Moreover, mechanochemical routes have recently been explored for the depolymerization of various polymers such as polystyrene (PS), , polyethylene (PE), and poly­(α-methylstyrene) (PMS) and in the dechlorination of polyvinyl chloride (PVC). , In addition to the ability to efficiently process solid reactants, ball milling is a highly scalable industrial process being utilized in a wide variety of grinding applications, from minerals and cement, to chemicals and pharmaceuticals. − Despite these advantages, mechanochemical reactions are often seen and modeled as “black-boxes”, which hinders the fundamental understanding of mechanically induced reactions .…”

“…One promising alternative is the depolymerization of polymers in the solid state via mechanically-induced reactions. 14 − 16 Mechanochemical reactions are typically performed in ball mills, in which contacts and collisions between grinding surfaces (balls and reactor wall) supply the energy required to chemically transform the (usually particulate) solid reactants caught between these surfaces. 15 , 17 − 20 Mechanochemistry has been successfully demonstrated on a laboratory scale for the production of lignocellulosic biomass, 21 , 22 cellulose, 23 − 25 ammonia 26 − 29 and lignin.…”

Liquid-assisted grinding enables a direct mechanochemical functionalization of polystyrene waste

“…The kinetics of prolonged functionalization reactions under BMG conditions are likely to be competitive with those of chain scission, resulting in excessive backbone degradation and loss of desired bulk properties. 50 This degradation via BMG can be leveraged for polymer depolymerization, 26,51,52 chain-end functionalization, 53,54 or radical functionalization. 55 For PS , while chain scission under BMG is well documented above a limiting molar mass, M lim ( ca.…”