Preparation of ABD-@MMT Nano-Flame Retardant Toward Fire-Safety and Stable Mechanical Properties for Aramid-Reinforced Epoxy Resin Composites

The mismatch of flame retardancy and mechanical properties is still a challenge for developing high-performance epoxy resin (EP) and its aramid fiber (AF) composite. In this study, bi-DOPO compound (ABD) was prepared by reacting DOPO with acrolein, Na-MMT was modified by octadecyltrimethylammonium chloride to prepare organic MMT(@MMT), and finally, ABD-@MMT nano-flame retardant was prepared by using ABD to intercalate @MMT to solve this problem. After introducing ABD-@MMT into AF/EP composites, it exhibited good thermal stability, excellent flame retardancy, and enhanced mechanical properties. The intercalation and exfoliation of the @MMT layer within the ABD and EP matrix indicated a uniform dispersion of the flame retardant. Especially for the sample of 3%ABD-@MMT/AF/EP composites, the limiting oxygen index (LOI) value increased from 23.8% to 34.7% accompanied by the V-0 rating in the UL-94 test. Scanning electron microscopy (SEM) analysis of residual carbon postcone calorimetry test and the degree of graphitization after muffle calcination supported the superior flame retardant properties of ABD-@MMT nanocompounds. Furthermore, the tensile strength of 3%ABD-@MMT/AF/EP composites measured at 38.3 MPa, representing an 8.5% increase compared to 3%ABD/AF/EP, only decreased by 7% compared to pure AF/EP composites. The incorporation of ABD-@MMT improved both the burning behavior and mechanical properties of the composite, reflecting reduced burning intensity, increased tensile strength, and impact strength. This study presents a novel approach for developing AF/EP composites with enhanced mechanical strength and flame retardancy.