Graphene Oxide Nanosheets Decorated with MgAlCr-Layered Double Hydroxide Nanosheets as Flame Retardant Coatings for Steel

Epoxy (EP)-based intumescent flame retardant (IFR) coatings were widely applied for protection of steel substrates during fire. Nevertheless, the intumescent coating required some optimization due to inferior compactness and poor antioxidation of its carbon residue. In this work, novel inorganic nano-GO/MgAlCr-LDHs were synthesized and employed for enhancing the flame retardation of traditional intumescent coatings containing ammonium polyphosphate (APP), pentaerythritol (PER), and melamine (MEL). The X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy analysis results showed that nano-GO/MgAlCr-LDHs were successfully synthesized, and the X-ray power spectroscopy (XPS) spectra further indicated that there were some interactions between GO nanosheets and MgAlCr-LDH nanosheets in GO/MgAlCr-LDHs. The thermogravimetric analysis (TGA) results indicated that nano-GO/MgAlCr-LDHs could effectively perfect the thermal stability and char formation of IFR coatings with a maximum pyrolysis temperature (Tmax) of 385.9 °C and the highest char residue of 34.6 wt % in air. The microscale combustion calorimeter (MCC) data revealed a 51.7% decline in the peak heat release rate (pHRR) and a 29.7% reduction in the total heat release (THR) compared with those of neat EP coatings when introducing nano-GO/MgAlCr-LDHs into the coatings. Finally, the analysis of char confirmed that the flame retardant mechanism was divided into condensed phase and gas phase mechanisms.