Enhancing strength, toughness, and flame retardancy of epoxy resins through in-situ interpenetrating network modification

The toughening of epoxy resin, crucial for advanced materials, typically requires balancing between enhancing specific properties and potential compromises elsewhere. This study presents a breakthrough in epoxy resin toughening using a novel approach: incorporating isophorone diisocyanate (IPDI) modified naringenin (IPNA) to create an in-situ interpenetrating network (IPN) with a one-pot method alongside DDM. This method fosters a cohesive IPN structure without phase separation, markedly boosting both strength and toughness. Specifically, with 15 wt% IPNA, tensile strength surged by 61.9%, and elongation at break by 240.2%. Additionally, IPNA's robust carbonization at high temperatures significantly enhances flame retardancy. Tests revealed a 62.9% reduction in peak heat release rate (PHRR) compared to unmodified epoxy, achieving an oxygen index (LOI) of 33% and a UL-94 V-1 rating. This research not only advances the toughening of epoxy resins but also opens new pathways for utilizing bio-based materials to simultaneously improve mechanical properties and flame resistance.