Synergistic effects and flame-retardant mechanism of aluminum diethyl phosphinate in combination with melamine polyphosphate and aluminum oxide in epoxy resin

In this work, the melamine polyphosphate (MPP) and aluminum oxide (Al2O3) were used to investigate their synergistic effects with aluminum diethyl phosphinate (AlPi) on enhancing the flame retardancy of epoxy resins (EP). The results indicated that low loadings of only 3.2mass% AlPi, 1.6mass% MPP and 0.2mass% Al2O3 can make EP get high LOI value of 33.5% and UL-94V-0 rating. The results also showed that the multi-component system of AlPi, MPP and Al2O3 in appropriate mixing ratio had good smoke suppression effect. The total smoke production of flame-retarded EP was decreased by as much as 64% compared with EP. Joint analysis by multiple techniques of cone calorimeter test, thermogravimetric analysis (TGA), Fourier infrared spectra (FTIR), X-ray photoelectron spectroscopy and TGA coupling FTIR was shown that the flame-retardant mechanisms of the flame-retarded EP by loading of AlPi, MPP and Al2O3 were proposed as synergistic mechanism in gas and condensed phase. The excellent flame retardancy of EP/AlPi/MPP/Al2O3 composite was improved by the formation of protective char layer from the high valence phosphorus compounds in the residual char.