Enhanced thermal properties of silica nanoparticles and chitosan bio-based intumescent flame retardant Polyurethane coatings

Abstract Novel bio-based flame retardant coatings were synthesized through the process of grinding, mixing and curing process. The flame retardant coatings reinforced with silica nanoparticles (SiO2 NPs) have been prepared at five different formulation levels having F0 (Without adding SiO2 NPs), F1(2% w/w SiO2 NPs) and F2(4% w/w SiO2 NPs) combination with urethane resin, ammonium polyphosphate and chitosan. After the preparing of these formulated coatings were characterized by Flammability tests, combustion tests, and thermal stability tests. The peak heat release rate (PHRR) peak of the urethane filled with functionalized SiO2 NPs is observed to decrease dramatically with increasing functionalized SiO2 NPs loadings. An increase in the LOI value was observed with the increase in wt% of SiO2 NPs. From the UL-94 V data, it was confirmed that the F1, and F2 formulations have passed the flame test and were rated as V-0. The TGA result revealed that addition of SiO2 NPs could improve the thermal stability of the composite at 800 °C by forming high residual char. All the findings achieved suggest that the presence of SiO2 NPs in the formulation of urethane resin has shown the excellent impact as flame retardant coatings.