Preparation and characterization of polydopamine/melamine microencapsulated red phosphorus and its flame retardance in epoxy resin

Polydopamine/melamine composite microencapsulated red phosphorus (RP@PDA/MA) was prepared and applied as the flame retardant for epoxy resin (EP) in this work. For comparison, polydopamine (PDA) coated red phosphorus (RP@PDA) was also prepared. The microstructure, chemical composition and thermal decomposition of the as prepared samples were systematically characterized. The results showed that PDA and PDA/MA shell structures were fabricated successfully via convenient water-based processes at room temperature. The flame retardance of red phosphorus (RP), RP@PDA, and RP@PDA/MA on EP was evaluated. The results showed that EP blending with 7 wt% RP@PDA/MA passed V-0 degree in the vertical burning test (UL-94), reached a limited oxygen index (LOI) of 30.9% and decreased the peak heat release rate of EP by 65.1% in the cone calorimeter test. The satisfactory flame retardance can be attributed to the intumescent flame retardant system consisting of RP@PDA/MA. The PDA and PDA/MA shell structures also improved the compatibility between RP and EP, thus RP@PDA and RP@PDA/MA had less significant impact on the tensile-strain properties of EP.