Construction of TPP@MCA hybrid for enhancing fire safety and mechanical properties of epoxy resin

Enhancing the fire safety and mechanical properties of widely used epoxy resin (EP) composites is essential for safeguarding critical infrastructure and protecting public safety. By recrystallising triphenylphosphine (TPP) on the melamine cyanurate (MCA) surface, a TPP-decorated MCA hybrid (TPP@MCA) was constructed via a safe room-temperature recrystallization method and applied to prepare a series of EP/TPP@MCA composites with different compositions. EP/10TPP@MCA demonstrated a high limiting oxygen index (LOI) of 38.2% and fast self-extinction in vertical combustion rating (UL-94), an inherent property that forms the basis for intrinsic fire safety. The peak heat release rate and total heat release of EP/10TPP@MCA only 579.6 kW/m 2 and 48.1 MJ/m 2 , which was reduced by 44.3% and 44.2%, respectively, compared with those of pure EP. Char residue analysis indicated that the dense phosphate-containing structure and the nitrogen-rich carbon layer acted as synergistic, dual flame-retardant mechanisms in the condensed phase. Specifically, they served as both a flame retardant and a heat insulator to protect the EP matrix. A notable increase in the flexural strength of EP/5TPP@MCA with enhancements observed by 17.0%. Thus, the TPP@MCA hybrid offers an intrinsic safety solution by integrating multi-mode flame retardant mechanisms directly into the EP matrix, effectively suppressing the original fire hazards.