Flame-retardant polyurethane elastomer based on aluminum salt of monomethylphosphinate

Abstract

The flame retardancy of polyurethane (PU) elastomer based on aluminum monomethylphosphinate (MeP-Al) was investigated. Thermal analysis, evolved gas analysis (TG-FTIR), flammability tests (LOI, UL 94), heat release rate (HRR) (microcombustion calorimeter), and chemical analysis of residues (SEM–EDX and FTIR) were used to investigate the flame-retardant performance and mechanism of the PU/MeP-Al. Results show that adding MeP-Al endows PU desired flame retardancy and anti-dripping property. The sample containing 20 mass% of MeP-Al passes the UL 94 V0 rating with LOI value of 29.6% and no dripping during combustion. Moreover, the heat release during combustion and the amount of organic volatile from PU decomposition are significantly reduced. The good flame retardancy, anti-dripping property, dramatically a reduction in release of heat and organic compounds are attributed to the efficient action of the MeP-Al in both the gas and condensed phase. In the gas phase, the MeP-Al decomposes into monomethylphosphinic acid to inhibit flame and reduces the heat release. In the condensed phase, MeP-Al turns into the tough aluminum pyrophosphonate and promotes PU to form stable carbonaceous char by interacting with PU.