Recycling Epoxy by Vitrimerization: Influence of an Initial Thermoset Chemical Structure

Abstract

Epoxy/anhydride-cured thermosets are widely used in aerospace and wind energy structures. Recycling the enormous amounts of epoxy thermoset waste remains a global challenge. Vitrimerization, a practical, low-cost, eco-friendly, and scalable method, was developed for closed-loop recycling of the cross-linked epoxy by converting the permanent network into a vitrimer-type dynamic network. Here, we study the effect of virgin epoxy network properties on network reforming efficiency and the activation energy of the dynamic network by varying the epoxy/anhydride ratio. The results point out that the permanent network cross-link density and glass transition temperature have a more pronounced effect on vitrimerization efficiency in comparison with the concentration of free hydroxyl groups in the system. The result can be potentially used to better control vitrimerization efficiency in recycling epoxy thermoset polymers and tailor the vitrimerized product properties.

Vitrimerization of Crosslinked Unsaturated Polyester Resins: A Mechanochemical Approach to Recycle and Reprocess Thermosets

“…The concept of vitrimerization has been recently developed in our group to obtain vitrimer‐type dynamic networks from permanently cross‐linked thermosets through a simple one‐step process. [ 20 , 21 , 22 , 23 , 24 ] In this method, the exchangeable metal−ligand sites form via ball milling the thermoset network with a proper catalyst. [ 20 , 21 ] The properties of the initial thermosets are mostly recovered in the vitrimerized systems.…”

Novel Application of Mechanochemistry in Waste Epoxy Recycling via Solid-State Shear Milling

“…Carbon neutrality means energy saving and emission reduction, and the utilization of renewable energy becomes an important method. − As the saying goes, garbage is a misplaced resource. To save energy and reduce emissions, we must not only cherish and make better use of existing resources but also recycle and reutilize the waste. , Attributed to the excellent mechanical properties, adhesion, insulation, corrosion resistance, and flexible processing technology, epoxy (EP) resin had been widely used in various fields such as composite materials, coatings, adhesives, plastic sealants, etc. − However, with the end of life for epoxy products, the volume of waste epoxy increased rapidly. For example, the life of wind turbine blades is generally 20 years, it is predicted that the waste generated by the world’s wind power industry will exceed 480 000 tons in 2050. − In addition, in the manufacturing process of epoxy products, a large number of scraps and leftovers are produced inevitably.…”

Regulating Lignin-Based Epoxy Vitrimer Performance by Fine-Tuning the Lignin Structure

“…The introduction of dynamic covalent bonds into epoxy resins can not only yield good mechanical properties but also induce the rearrangement of the polymer network via thermally induced chemical bond-exchange reactions, endowing the resultant polymers with excellent self-repair ability and reprocessability . Among various dynamic covalent bonds, transesterification reactions have received the most attention since such reactions can be readily applied to epoxy/acid and epoxy/anhydride systems to obtain epoxy materials with excellent self-repair ability and reprocessability. , However, most epoxy vitrimers with dynamic covalent bonds are currently derived from petrochemical feedstocks. It remains a challenge to develop green and sustainable epoxy resins with dynamic bonds from renewable resources. − …”