A phosphorus/nitrogen/boron co-curing agent for enhancing flame retardancy, mechanical properties transparency of epoxy resin

The development of flame retardant co-curing agents that simultaneously impart flame retardancy, mechanical properties and transparency to epoxy resin (EP) poses a novel challenge in meeting the demands of new quality productive forces. In this work, a flame retardant co-curing agent, FPDB, derived from 9,10-dihydro-9-oxa-10-phospha-phenanthrene-10-oxide (DOPO) and incorporating P, N and B is successfully synthesizes. The flame retardant co-curing agent FPDB can act on both the gas and the condensed phase simultaneously, improving the flame retardancy of EP. EP/FPDB5 achieves a V-0 rating in vertical combustion (UL-94) with a limiting oxygen index (LOI) of 31.8 %. The cone calorimeter tests (CCT) reveal that EP/FPDB5 reduces the peak heat release rate (pHRR) and total heat release rate (THR) by 41.6 % and 32.3 %, respectively, compared with those of EP. Moreover, the tensile strengths of EP/FPDB1, EP/FPDB3 and EP/FPDB5 are 71.15, 66.84 and 58.21 MPa, respectively, which are higher than those of pure EP (56.77 MPa). Additionally, the incorporation of FPDB maintains the transparency of EP, with EP/FPDB1 exhibiting a transmittance of 89.8 %. In summary, this work provides a feasible strategy for the preparation of high-performance multifunctional EP.