Surface engineering of magnesium hydroxide via bioinspired iron-loaded polydopamine as green and efficient strategy to epoxy composites with improved flame retardancy and reduced smoke release

Functionalized magnesium hydroxide (MDH@Fe-PDA) by polydopamine (PDA) and iron chloride (FeCl3) were designed by one-pot method, aiming at improving flame retardancy and reducing smoke release of epoxy resin. The structure of MDH@Fe-PDA was confirmed via Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). MDH and MDH@Fe-PDA with different ratio were introduced into epoxy resin (EP) as flame retardant additives. The enhanced flame retardancy and smoke suppression of EP composites were evaluated by limiting oxygen index (LOI), UL-94 test and cone calorimetry. The resultant EP composites exhibited remarkably reduced flammability, reflected by high LOI value of 29.3%, V-0 rating, as well as a 57% reduction of peak heat release rate for 7 wt% MDH@Fe-PDA loading. In addition, EP/MDH/MDH@Fe-PDA composites decreased the evolution of volatiles significantly. The char structure of EP composites revealed that char with a more intact and continuous structure. A probable mechanism was proposed which involved catalytic charring behavior at the interface and intensive protection by char and strong radical scavenging activity. Notably, this work provided an attractive method to organo-modified MDH, and enriched its practical applications of MDH as functional fillers to polymers.