Magnesium hydroxide (MDH) treated with polydopamine and metal ions showed improved fire performance effect in epoxy. Polydopamine, a bio-inspired polymeric coating material, was polymerised in the presence of the well-recognised mineral PIN flame retardant MDH and of different transition metal ions (iron, cobalt, copper, nickel, at ratio of approx. 1:1:0.12 w/w). This resulted in a coated MDH – metal ion particles. These were cured, mixed into epoxy resin (EP-44), then cured at 30% w/w loading. The PDA coating of the MDH is considered to have improved fire performance effectiveness both because of breakdown of MDH agglomerates during the processing (smaller MDH particles) and better dispersion in the epoxy. Mechanical properties were improved compared to pure epoxy. Non-treated MDH increased the LOI of the epoxy by nearly +30%, and achieved UL 94 V-1 (3 mm), compared to pure epoxy not rated. Inclusion of the metal ions further improved fire performance, in particular with iron which enable +42% LOI (vs. pure epoxy) and UL 94 V-0. Smoke release was very considerably reduced by untreated MDH, and was even further reduced by inclusion of copper ions.
“Investigation of magnesium hydroxide functionalized by polydopamine/transition metal ions on flame retardancy of epoxy resin”, D. Zhu et al., J. Thermal Analysis and Calorimetry 2022 https://doi.org/10.1007/s10973-022-11467-5 Image = dopamine.