Combining layered double hydroxides and carbon nanotubes to synergistically enhance the flame retardant properties of composite coatings

In this study, the flexibility of carbon nanotubes (CNTs) and the excellent flame barrier property and catalytic carbon formation effect of layered double hydroxide (LDH) were fully combined to obtain a high performance composite flame retardant coating. Specifically, polydopamine (PDA) with superior adhesion properties was encapsulated on the surface of CNTs to enhance their dispersion in water. More importantly, the introduction of PDA provided abundant active sites for the adsorption of precursor cations of LDH, which facilitates the uniform loading of LDH on the surface of CNTs to obtain well-structured CNTs@PDA@LDH (CPL) hybrids. The synergistic effect of CNTs and LDH on the flame retardant properties of epoxy resin matrix was investigated. The CPL 2% /EP sample showed the lowest backside temperature (170.78 °C), maximum expansion height (21.60 mm) and expansion rate (17.70), proving its highest thermal insulation effect. In addition, the thermal weight loss test illustrated that CPL 2% /EP exhibited a higher thermal degradation temperature and char residue under both air and nitrogen, confirming its excellent thermal stability. Through the morphological analysis and characterization of the residual char, a reasonable flame retardant mechanism for the CPL hybrid material was proposed.