Preparation of a novel intrinsic flame retardant epoxy resin based on L-arginine functionalized magnesium hydroxide

In this study, bio-based L-arginine (Arg) and phosphite were selected as raw materials and used to modify magnesium hydroxide, generating an intermediate (APM) that was reacted with melamine (MEL) to produce a curing agent (APM-MEL) with flame retardant properties. A flame retardant epoxy resin (EP) was prepared in a curing reaction by adding APM-MEL and ammonium polyphosphate (APP) to the epoxy prepolymer in varying amounts (wt%). The chemical structure and surface morphology of APM-MEL have been characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The thermal stability, flame retardancy and mechanical properties were evaluated by thermogravimetric analysis (TG), the UL-94 vertical combustion test, use of the limiting oxygen index (LOI), cone calorimetry and bending tests. The results have revealed that the epoxy resin prepared from the addition of 5% APM-MEL and 15% APP achieved a UL-94 V-0 level with a LOI of 30.8%. Compared with pure EP, the peak heat release rate, total heat release, smoke production rate and total smoke production of the samples were reduced by 85.68%, 53.15%, 85.86% and 62.05%, respectively. The flexural strength and flexural modulus were improved by 117.3% and 130.5%, respectively. The bio-based functionalized magnesium hydroxide curing agent prepared in this study exhibits excellent flame retardant and mechanical properties, effectively reducing fire risk and can serve as the basis for the development of multifunctional curing agents.