Highly flame retardant, strength, and tough epoxy resins and CFRPs via introducing a self-assembly novel ionic bond, rigid-flexible structure PPI

Carbon fiber-reinforced epoxy resin (EP) composites (CFRPs), characterized by their lightweight and superior strength, are frequently employed as structural materials in the automotive and aerospace sectors. Nonetheless, the intrinsic flammability and brittleness of EP considerably constrain their use in advanced manufacturing. In this work, a facile self-assembly approach in an aqueous medium between phosphorus-modified polyhedral oligomeric silsesquioxane (P-POSS) and polyethyleneimine formed a rigid-flexible structure PPI with novel ionic bonds. The synergistic flame retardancy effect of P, N, and Si in PPI on EP curing systems and their CFRPs were achieved. The heat release rate, CO production, and total smoke production of EP/7-PPI were reduced by 38.4 %, 44.8 %, and 25.1 %, respectively, and reached UL 94 V-0 grade, illustrating outstanding fire safety performance. Additionally, the rigid-flexible structure of PPI and the presence of ionic bonds facilitated a remarkable improvement in EP fracture toughness, with an increase of 125.1 % in the unnotched impact strength and 50.5 % in the flexural strength of EP/5-PPI. Moreover, relative to CF/EP, CF/EP/5-PPI showed notable advancements in flame retardancy, strength, and toughness characteristics. This study provides an innovative approach for engineering high-performance EP curing systems and their associated CFRPs.