Tannic acid-mediated assembly of ultrafine Fe(OH)3 on the surface of phytic acid intercalated LDH to reduce fire hazard and improve mechanical properties of epoxy resin

The preparation of high-performance epoxy resins (EP) with enhanced mechanical properties and flame retardancy for building materials has long been a significant challenge. In this study, bio-based phytic acid (PA) was intercalated into the layers of layered double hydroxides (LDH) via coprecipitation. Subsequently, ultrafine Fe(OH) 3 was in situ grown on PA-intercalated LDH through tannin-mediated assembly, resulting in the synthesis of the LDH-PA@TA-Fe(OH) 3 hierarchical hybrid flame retardant. Comprehensive characterization of its microstructure, morphology, and chemical composition was performed. The EP composite demonstrated a LOI of 31.3 % and a UL-94 V-1 rating when the additive of 7.5 wt% LDH-PA@TA-Fe(OH) 3 was utilized. Additionally, the EP/LDH-PA@TA-Fe(OH) 3 composite demonstrated a substantial reduction in peak heat release rate (pHRR) and peak smoke production rate (pSPR) with reductions of 48.1 % and 52.7 %, respectively, along with a 62.5 % decrease in peak CO production rate (pCOP), compared to neat EP. These improvements in fire safety are primarily ascribed to the synergistic flame retardancy of LDH and Fe(OH) 3 in condensed and gas phases, along with the efficient catalytic charring performance of PA and Fe 3+ . Furthermore, the incorporation of LDH-PA@TA-Fe(OH) 3 enhanced the mechanical properties of EP, which could be ascribed to the improved dispersibility of the modified LDH and the strengthened interfacial interaction. This study introduces a novel approach for the development of highly effective LDH-based hybrid flame retardant materials, enabling the fabrication of EP composites with superior mechanical performance and fire safety.