Enhanced flame-retardant and mechanical properties of epoxy resin by combination with layered double hydroxide, Mg2B2O5 whisker, and dodecyl dihydrogen phosphate

A composite particle with layered double hydroxide (LDH) was deposited onto the surface of the Mg2B2O5 whisker (MBW) using a co-precipitation method. Subsequently, dodecyl dihydrogen phosphate (DDP) was grafted onto the surface of the LDH-coated MBW to synthesize an inorganic–organic hybrid ([email protected]–DDP). The [email protected]–DDP was incorporated into epoxy resin (EP) to fabricate a composite, and its curing behavior, fire properties, and mechanical properties were assessed. The results revealed that the cure index value of the EP/[email protected]–DDP composite was between ΔT* and ΔH*, indicating an excellent cured state. Moreover, it exhibited good flame-retarding performance (LOI: 32.5%; UL94: V-1 rating; flame retardancy index: 1.57). The improved fire safety was attributed to the barrier function of MBW, the presence of metallic oxides generated from LDH, and the catalytic dehydration of phosphorus oxoacids produced during the decomposition of DDP. The PO radicals generated from DDP were capable of capturing HO and H radicals in the gaseous phase. Furthermore, the incorporation of [email protected]–DDP improved the mechanical properties of the EP. The results presented herein can be applied to developing a novel strategy for designing multifunctional flame retardants that can be used to decrease the fire risk of EP.