Investigation of magnesium hydroxide functionalized by polydopamine/transition metal ions on flame retardancy of epoxy resin

Aiming to impart epoxy resin (EP) with flame retardancy, magnesium hydroxide (MDH) was sequentially functionalized with four transition metals and polydopamine (PDA) to prepare MDH@M-PDA (M includes Fe3+, Co2+, Cu2+, Ni2+). Compared with MDH, MDH@M-PDA presented better dispersion in EP matrix. The results illustrated that a 30 mass% of MDH@Fe-PDA imparted the EP matrix with best fire retardancy and thermal stability. Specifically, the resultant EP/MDH/MDH@Fe-PDA composites remarkably reduced flammability, which is reflected by high LOI value of 29.3% and UL-94 V-0 ratings. The peak heat release rate (PHRR) and total smoke production (TSP) were reduced by 52% and 21%, respectively. Moreover, the impact and tensile strength of EP/MDH/MDH@M-PDA composites are improved compared with EP/MDH due to the better chemical compatibility of PDA in the EP matrix. Notably, this work provided a feasible design for organo-modified MDH and enriched its practical applications of MDH as functional fillers to polymers.