Double Dynamic Covalent Bonds Cross-Linked Epoxy Resins: Synthesis Strategies, Decomposition Mechanisms, and Properties Evaluation

Environmentally friendly epoxy resin materials have attracted considerable attention due to their decomposable and recyclable properties. However, the desirable balance of thermal and mechanical performance remains challenging. This study integrates triethanolamine (TEOA) as a transesterification accelerator along with dynamic disulfide bonds into epoxy/anhydride systems to create a dual-crosslinked vitrimer, which achieves low viscosity while maintaining dual dynamic covalent bonds. Moreover, the curing kinetics and comprehensive insulation performance including electrical properties, thermal stability and decomposable ability of these systems were emphatically discussed. Results indicate that the dual dynamic network epoxy resin requires elevated curing temperatures but exhibits reduced glass transition temperature (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$T_{\mathrm{g}}$</tex>). Incorporation of cycloaliphatic epoxy resin effectively enhanced thermal resistance, achieving <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$T_{\mathrm{g}}$</tex> of 104° C at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$20 \text{wt} \%$</tex> doping level, which represents 24.6 % improvement compared to that of pure E51 systems. Furthermore, both systems can be completely decomposed in low-molecular-weight chemical solvents. This work provides novel perspectives and options for environmental sustainability of insulating materials and recycling of decommissioned equipment.