Facile Synthesize of an Inorganic–Organic Hybrid for a Simultaneous Improvement of Fire Safety and Mechanical Properties of Epoxy Resins

The traditional inorganic flame-retardant magnesium hydroxide (MH) has since many years been dominating in flame-retardant applications. However, due to its poor compatibility with the epoxy resin matrix, it seriously affects the mechanical properties of the matrix. In the present study, MH has been organically modified to investigate the potential of a novel organic–inorganic hybrid as a flame-retardant curing agent (CEPPM-MH) for flame retardancy of epoxy resins. CEPPM-MH and ammonium polyphosphate (APP) were synergistically introduced into the epoxy thermosets to improve the fire resistance of the composites. For the S7 composite samples that contained 10% of APP and 10% of CEPPM-MH, the LOI was increased to 30.1. Also, the UL-94 test rating was increased to V-0, and the peak heat release rate (pHRR), total heat release (THR), total smoke production (TSP), and peak CO production rate(pCOPR)were reduced by 86%, 53%, 69%, and 79%, respectively, as compared with the pure sample S1. In addition, the flexural strength and flexural modulus were found to be improved by 76.8% and 45.1%, respectively, in the flexural performance test. Furthermore, the organic–inorganic hybrid curing agent, which was prepared by modifying the magnesium hydroxide with water as the only solvent, could be introduced into epoxy resins as both curing agent and flame retardant, which not only effectively reduced the fire risk but also improved the comprehensive performance of the materials. This provides a new idea for the preparation of intrinsically flame-retardant epoxy resins.