Vitrimerization: A Novel Concept to Reprocess and Recycle Thermoset Waste via Dynamic Chemistry

Abstract

A new approach for reprocessing of existing thermoset waste is presented. This work demonstrates that unrecyclable thermoset materials can be reprocessed using the concept of associative dynamic bonding, vitrimers. The developed recycling methodology relies on swelling the thermoset network into a solution of a catalyst, which enables transesterification reactions allowing dynamic bond exchange between ester and hydroxyl groups within the thermoset network. Thermal and mechanical properties for recycled polyurethane and epoxy networks are studied and a strategy to maintain the properties of recycled materials is discussed. The developed methodology promises recycling and even upcycling and reprocessing of previously thought intractable materials. Moreover, processability of vitrimerized thermosets with common thermoplastic manufacturing methods opens up the possibility of tuning recycled networks by adding nanoparticles. This flexibility keeps the application window of recycled thermosets very broad.

Toward Stimuli‐Responsive Dynamic Thermosets through Continuous Development and Improvements in Covalent Adaptable Networks (CANs)

“…Recently, even the existing waste of epoxy‐polyester and polyurethane thermosets was demonstrated to be recyclable through “vitrimerization,” i.e., the swelling in of significant amounts of an exchange catalyst (tin(II) 2‐ethylhexanoate, 10 wt% in a solvent of choice) 116. Because of such catalyst treatment, at elevated temperatures the solvent swollen and now catalyst‐rich networks were rendered transesterification‐capable and in consequence recyclable.…”

Intrinsic Self-Healing Epoxies in Polymer Matrix Composites (PMCs) for Aerospace Applications

“…A huge stride forward in the design of self-healing epoxy networks has been taken with vitrimers, a remarkable example of associative CANs that have been widely investigated for the last few years. Vitrimers consist of a covalent organic network that can rearrange its topology via reversible exchange reactions that preserve the total number of network bonds (i.e., crosslinking density) and the average functionality of the nodes [ 114 ].…”

Polymer‐assisted fully recyclable flexible sensors

“…Vitrimers, based on transesterification or some other exchangeable covalent bonds, are a newly developed type of reprocessible thermoset polymers that can be directly remolded or reshaped, which can serve as efficiently reprocessible matrix for fully recyclable electronic sensors. 38 A pioneered work led by Manas-Zloczower et al put forward a new concept of vitrimerization for recycling epoxy resin via the addition of transesterification catalyst. 39 As shown in Figure 4A, the pulverized epoxy powders were immerged into a solution contained Tin (II) 2-ethylhexanoate (Sn[Oct] 2 ) and then poured into a mold for hot pressing.…”

“…To improve the recycling efficiency of the whole electronic sensor, numerous attempts have been focused on other dynamically crosslinked thermoset polymers without loss of conductive nanofillers. Vitrimers, based on transesterification or some other exchangeable covalent bonds, are a newly developed type of reprocessible thermoset polymers that can be directly remolded or reshaped, which can serve as efficiently reprocessible matrix for fully recyclable electronic sensors 38 . A pioneered work led by Manas‐Zloczower et al put forward a new concept of vitrimerization for recycling epoxy resin via the addition of transesterification catalyst 39 .…”