Green and Facile Fabrication of Magnesium-Aluminum Hydrotalcite for Synergistic Flame Retardancy, Smoke Suppression, and Thermal Insulation in Epoxy Resina

A dual-surfactant modification strategy was developed to synergistically enhance the flame retardancy and smoke suppression of epoxy resin (EP) by co-modifying Mg-Al layered double hydroxide (LDH) with sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate (SDBS). This dual-surfactant approach is novel as it integrates two distinct functionalities—linear alkyl chain compatibility provided by SDS and aromatic sulfonate-induced charring contributed by SDBS—resulting in a synergistic improvement in LDH dispersion, interfacial bonding, and catalytic char formation, thereby achieving superior fire safety performance in EP composites. The modified SDS + SDBS-LDH was synthesized via a green ion-exchange route and uniformly dispersed in EP at a loading of 5 wt%. In cone calorimeter tests, total heat release and total smoke production decreased by 33.3% and 22.9%, respectively, while CO and CO 2 release rates dropped by 75.8% and 48.7% compared with pure EP. When applied as a coating, EP/5SDS + SDBS-LDH reduced the back-surface temperature of wood by 76.1%, demonstrating excellent thermal insulation and practical potential. This work provides a scalable and eco-friendly strategy for designing high-performance, flame-retardant epoxy composites through synergistic dual-surfactant modification of LDH.