Cyclotriphosphazene hyperbranched P/N/Si prepared flame retardants improve mechanical properties and flame retardancy of epoxy resins

In this study, a cyclotriphosphazene hyperbranched P/N/Si prepared flame retardant (HBPPSi) was synthesized, and the effects of different loadings of HBPPSi on the mechanical properties, thermal stability and flame retardancy of epoxy resin were investigated. The mechanical property studies showed that the addition of HBPPSi could effectively improve the strength and toughness of epoxy resin, in which the strength and toughness of 5% HBPPSi/EP composites were improved by 43% and 59%, respectively. Meanwhile, thermogravimetric analysis and combustion performance test analysis indicated that the loading of HBPPSi could significantly improve the carbon formation rate, flame retardancy, and smoke suppression performance of EP composites. 5% HBPPSi/EP composites achieved a V-1 grade in the UL-94 test, and the LOI value increased to 28.3%. Compared with the pure EP material, the maximum heat release rate (PHRR) and total smoke release (TSP) of the 5% HBPPSi/EP composite were reduced by 47% and 32%, respectively. In addition, the release of toxic smoke CO was also significantly reduced. More importantly, the mode of action of the effect of HBPPSi on the mechanical properties, flame retardant properties, and smoke suppression properties of EP materials was investigated.