Novel nanocomposites based on epoxy resin and modified magnesium hydroxide: Focus on flame retardancy and mechanical properties

In this work, a novel multifunctional organic-inorganic hybrid flame agent (AM-MEL) was prepared from magnesium hydroxide nanosheets decorated by nitrilotrimethylene triphosphonic acid and melamine. Then, an intrinsic flame-retardant epoxy resin (EP) was prepared by covalently incorporating AM-MEL nanoparticles. Meanwhile, ammonium polyphosphate (APP) was added into EP to form an intumescent flame retardant system with AM-MEL. The chemical structure of AM-MEL was characterized by Fourier transform infrared spectra, X-ray photoelectron spectroscopy, and scanning electron microscopy. With the incorporation of 5 wt% AM-MEL and 15 wt% APP, EP/AM-MEL/APP could reach a limiting oxygen index value of 32.0% and achieve UL-94 V-0 rating, along with 88.0%, 70.0%, 81.5%, and 87.3% decrease in the peak heat release rate, total heat release, total smoke production, and the peak CO production rate, respectively, with respect to that of pure EP. The mechanisms of its flame retardant and smoke suppression were investigated.