Enhancing recyclability of epoxy resins through mechanochemical functionalization

Attention to the environmental effect of all human activities, particularly sustainability, is central to political agendas, company strategies, and contemporary scientific study. In fact, in 2020, the European Commission released an action plan for a novel circular economy, including guidelines for designing more sustainable goods and reducing waste [1]. The circular economy is a production and consumption paradigm promoting the reuse, repair, restoration, and recycling of existing resources and items for as long as possible, hence extending product life cycles. Thermosetting materials, like epoxy resins, fail to fit into the framework of a circular economy since they do not melt and have excellent mechanical and chemical durability due to their covalently crosslinked structure. However, the scientific community identified a solution to this problem through the development of so-called Covalent Adaptable Networks (CANs): materials having a three-dimensional network consisting of dynamic covalent bonds that can be broken and restored in response to a specific stimulus [2]. In this approach, certain well-designed thermosets may be remolded, repaired, and reused in accordance with circular economy requirements. Another issue that remains unresolved is the massive volume of epoxy resins that were previously made and dispersed globally. Fortunately, this issue may be remedied through the use of CANs. The addition of appropriate compounds (e.g., catalysts) to unrecyclable epoxy resins by different methods, such as reactive blending, mechano-chemical functionalization, or infusion, might guarantee the reprocessability of a significant number of materials that currently exist [3]. Among these techniques, mechanochemical functionalization allows the incorporation of the appropriate additives without the need for a solvent, transforming standard epoxy resins into ones that can then be processed again.