Effect of aluminum phosphinate on the flame-retardant properties of epoxy syntactic foams

In this study, the flame-resistant epoxy syntactic foams with different content of hollow glass microspheres (HGM) were prepared by using aluminum diisobutylphosphinate (AlPBu) as flame retardant. Scanning electron microscope (SEM) images of the fracture surface of different epoxy syntactic foams showed that AlPBu particles had good compatibility with the matrix due to their similar polarities. And the limiting oxygen index, UL 94 test, cone calorimeter and thermogravimetric analysis were applied to characterize the flame retardation and thermal behavior of the foams. These results showed that AlPBu improved the flame retardancy of epoxy syntactic foams, while the HGM exhibit a complicated influence on the flame retardation, although both AlPBu and HGM enhanced the char residues and decreased the peak heat release rate as well as the total heat release of composites. In addition, swollen char layers mainly containing the HGM were generated after adding AlPBu. Then, the char residues of the foams after combustion were observed by SEM, and the results were applied to reveal the different fire behaviors of foams with different densities.