Characterization and fire protection properties of rubberwood biomass ash formulated intumescent coatings for steel

Rubberwood biomass ash (RWA), which was derived from the combustion of rubberwood biomass in a fuel factory, was obtained for reuse as a natural mineral filler substitute in water-based intumescent coatings. The specific surface area of the RWA was 3.10 m2/g, with the particle's surface areas predominant composed of mesopores, which was justified using the Brunauer–Emmett–Teller Test (BET). Rubberwood ash coatings (RWAC) formulated with 3.0 wt% RWA exerted the most homogenous and durable surface matrix in the Accelerating Weathering Test (AWT). Fire-resistant test (FRT) and thermogravimetric analysis (TGA) demonstrated the incorporation of the RWA with the intumescent flame-retardant formulation, generated positive effects in equilibrium end temperature, thermal decomposition, and weight loss reductions. These effects are most prominent in the RWAC-3, which was comprised of 3 wt% RWA, and 50/40/7 wt% vinyl acetate (VA)/intumescent flame retardant additive (IFRA)/pigment. The RWAC-3 showed the lowest equilibrium end temperature at 131.4 °C, the lowest thermal degradation at 71 wt%, and the highest carbonaceous char formation at 12.8 mm. The Surface Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDX) results exhibited a dense, compact, and coherent char formation for the RWAC-3 sample. The abundant O and P crosslinking structures in the RWAC-3 contributed to the quality of the char barrier. These results are supported by the evidence from Fourier-Transform Infrared Spectroscopy (FTIR), and X-Ray Diffractometer (XRD), which revealed the stretching of the O–H, P–O–C, and PO molecular functional groups, and the presence of thermally stable phosphate compounds in the RWAC-3