The role of multi-wall carbon nanotubes in char strength of epoxy based intumescent fire retardant coating

•IF4-MWCNTs showed the back side substrate temperature 273 °C after the 60 min fire test.•TGA results showed that 0.5 wt% MWCNTs enhanced the residual weight of char up to 29.35 wt%.•An increase in MWCNTs quantity up to 0.5 wt% enhanced the carbon content up to 52 wt%.•Pyrolysis GC-MS confirmed that formulations IF4-MWCNTs released less gaseous product compared to IF1-Control.•0.5 wt% of MWCNTs sustained its reliability up to 90 days in accelerated weathering chamber.

Fire resistance of coatings mostly depends on the formation of char. In this work Multi-wall carbon nanotubes (MWCNTs) were used to improve fire retardant and char properties of the intumescent coating. Different coating formulations were prepared and their heat shielding performance was tested at 950 °C according to ASTM E-119. Char expansion was studied using fire furnace test. Field emission scanning electron microscope was used for char morphology. By means of X-ray Diffraction and Fourier transform infrared spectroscopy the presence of carbon, borophosphate; boron oxide and sassolite in the char was identified. Thermogravimetric analysis results showed that 0.5 wt%MWCNTs enhanced the residual weight of char up to 29.35 wt%. X-ray photoelectron spectroscopy (XPS) confirmed that 0.5 wt% MWCNTs enhanced the carbon content up to 51.90 wt%, lowering oxygen content to approximately 25 wt% in the char that improved the fire resistance performance of the coating. Pyrolysis analysis confirmed that 0.5 wt% MWCNTs formulation released less gaseous products and reduced the decomposition of gaseous products. An accelerated weathering test ASTM D 6695-03 also revealed that 0.5 wt% of MWCNTs sustained its reliability up to 90 days in accelerated weathering chamber.