Functionalized magnesium hydroxide with zinc borate and 3-aminopropyltriethoxysilane for enhanced flame retardant and smoke suppressant properties of epoxy resins

To improve the fire safety of epoxy resins (EP), a composite with magnesium hydroxide loaded zinc borate (MH@ZBO) was obtained using a heterogeneous deposition method, and then 3-aminopropyltriethoxysilane (APES) was grafted onto the surface of MH@ZBO to produce an organic-inorganic hybrid (MH@ZBO-APES). Subsequently, the EP composite with added MH@ZBO-APES was prepared and its thermal properties and fire safety were evaluated. The results showed that the glass transition temperatures of the EP/MH@30ZBO-10APES composite are improved, and the maximum thermal decomposition rate decreased, and the samples exhibited favorable thermal stability and flame-retarding performance (flame retardancy index: 2.40; LOI: 33%). The enhanced fire safety was a result of two factors. On one hand, the endothermic decomposition of MH and ZBO and the physical barrier of their decomposition products, the catalytic carbonization function of ZBO, the synergistic flame retardation of APES, and its improvement in dispersion to form a denser carbon layer, which plays a role in fire retardation and smoke suppression in the condensed phase. On the other hand, water vapor produced by the decomposition of MH and ZBO, as well as incombustible gas produced by the degradation of APES, are vital in the gas phase.