The mineral – phosphorus PIN flame retardant, aluminium hypophosphite (AHP) was surface-reacted with melamine to generate a reactive PIN flame retardant (MCAHP) for application in polyurethane.
Analysis (FTIR, SEM) showed that the AHP was effectively coated with a melamine derivative, with external active NH2 groups. The MCAHP showed good compatibility with polyurethane foam, with smooth foam cells. DSC characterisation showed that the active groups contributed to cross-linking during the polyurethane foaming reaction, and so an increased glass transition temperature of the polyurethane foam. A 16.5% MCAHP loading in polyurethane foam enabled to achieve UL94-V0. The flame retardancy effect is considered to be the result of a well-structured char formation, generated by phosphoric acid released from AHP, water release from AHP and sublimination of melamine at c. 320°C consuming heat energy and releasing non-flammable gases which dilute fire gases.
FTIR = Fourrier transform infrared analysis. SEM = scanning electron microscopy. DSC = differential scanning calorimeter.
“Surface modification of aluminum hypophosphite and its application for polyurethane foam composites”, F. Luo et al., J. Therm Anal Calorim, 2016 http://dx.doi.org/10.1007/s10973-016-5908-6 Reducing fire risks from wood in buildings and furniture