Bio-based phytic acid-amino acid/OMMT synergistic system for fire safety and performance-enhanced ramie fiber-reinforced epoxy composites

A novel biomass-based synergistic flame retardant PALAOMMT was prepared via a simple process for EP/RF composites. • PALAOMMT 3 (3% OMMT) enabled EP/RF to achieve LOI 34.6%, UL-94 V-0. • 3% OMMT mitigated the negative impact of PALA on mechanical properties through enhanced interfacial interactions. • This work provides a green halogen-free strategy for natural fiber-reinforced polymer flame retardancy. Despite their advantages, such as low cost and lightweight, the inherent flammability of ramie fiber-reinforced epoxy composites (EP/RF) significantly restricts their practical applications. To address this limitation, a high-performance flame retardant, designated as PALAOMMT, was synthesized, and the resultant flame retardant was employed to modify the surface of ramie fabrics, which were subsequently used to fabricate the corresponding EP/RF composites. The flame retardant containing 3% OMMT relative to PALA (referred to as PALAOMMT 3 ) exhibited the most outstanding flame-retardant performance. With a 20% weight gain of PALAOMMT 3 on the ramie fiber surface, EP/RF-PALAOMMT 3 achieved a limiting oxygen index of 34.6% and a UL-94 V-0 rating, with its peak heat release rates reduction of 27.2% and 44.3%, while the total heat release decreased by 36.8%. The incorporation of OMMT promoted the formation of a denser and more stable char layer, which provided an effective physical barrier in the condensed phase. This char layer markedly hindered heat conduction and suppressed the release of combustible volatile products. Thus, this work not only presents a novel and effective strategy for improving the fire safety of EP/RF composites but also identifies key directions for the synergistic optimization of flame retardancy and mechanical properties in future research. Download: Download high-res image (523KB) Download: Download full-size image