Organic copper phosphate-decorated layered double hydroxide to enhance the flame retardancy and smoke suppression of epoxy resin

It is essential to endow epoxy resin (EP) with high fire safety and mechanical properties due to its extensive application. In light of the flame-retardant efficiency and facile agglomeration of layered double hydroxide within polymers, surfactant-intercalated LDH decorated with organic copper phosphate (LDH@ATMP-Cu) was developed via electrostatic assembly. The EP composites containing 3 wt% resultant LDH@ATMP-Cu exhibited comparable tensile strength and slightly enhanced glass transition temperature compared to EP. Moreover, EP/LDH@ATMP-Cu achieved a V-0 rating in UL-94 test, an LOI value of 27.5 %, and sharply reduction of peak heat release rate by 57 % and total smoke production by 31 % in cone calorimeter test. Additionally, the flame-retardant mechanism was investigated by analyzing the char residue and pyrolysis gases. The high-efficiency flame retardancy was involved in the flame inhibition of gaseous water release, as well as the barrier effect of the refractory metal oxide from LDH and the high-quality char residue resulting from the catalytic charring effect of ATMP-Cu in condensed phase. Therefore, simultaneously enlarging the interlayer spacing and enhancing surface functionalization is a highly effective approach to improve the flame-retardant efficiency of LDH for polymers.