Abstract: Epoxy resin （EP） is widely used as structural material on aircrafts. Exploring and designing high-performance flame retardants for EP is critical to the fire safety of civil aviation. In this study, nanosheets of MgAl layered double hydroxide （MgAl-LDH） were grown on the skeleton of interlaced functionalized CNTs （F-CNTs） to construct an in-situ composite structure of MgAl-LDH/F-CNTs. Then the MgAl-LDH/F-CNTs composite structure was used as a mechanical support to further accommodate CuMoO4 nanoparticles to obtain the synergistic flame retardant of MgAl-LDH/F-CNTs-CuMoO4. The built MgAl-LDH/F-CNTs in-situ composite structure can realize the uniform distribution of the flame retarding components （LDH nanosheets, functionalized carbon nanotubes and CuMoO4 nanoparticles） in the polymer substrate. Compared with pure epoxy resin without flame retarding treatment, the peak heat release rate of EP@MgAl-LDH/F-CNTs-CuMoO4 in the combustion test can be reduced by 40.5%, the total heat release can be lowered by 7.49%, the CO production and total smoke release can be respectively decreased by 43.0% and 26.3%, and the limiting oxygen index can be increased by 38.2%. It can be seen that the flame retarding performance of EP composite with flame retardant treatment is significantly improved. In addition, the tensile and bending strengths are decreased by only 7.1% and 22.4%, indicating that the addition of F-CNTs and the construction of MgAl-LDH/F-CNTs composite structure can effectively compensate for the deteriorating effect of inorganic flame retardants on the mechanical strength of EP.

Key words: layered double hydroxide, carbon nanotube, in-situ composite structure, flame retardant, epoxy resin