A mechanistic study of the fire performance of the silica and zinc borate nanoparticles-incorporated intumescent coatings based on epoxy resin

An epoxy-based intumescent coating containing the silica and zinc borate nanoparticles was fabricated. The fire performance of the coating with the optimum formulation was investigated in terms of the changes in the physical and chemical structure of the formed char layer during the exposure to a temperature of 1000°C. The state of the chemical structure was analyzed by performing the Fourier-transform infrared spectroscopy, x-ray diffraction, and x-ray photoelectron spectroscopy analysis from the char layer at the three-time intervals of 10, 30, and 60 min of the heating process. The innovative Condorcet method was also employed to examine the changes in the physical structure of the formed char layer. Some instabilities were detected in the physical structure of the char layer in the middle period of heating. Moreover, a gradual formation of silicon carbide crystalline structure was observed on top of the surface, followed by its oxidation to silica over time. In contrast, in the bulk structure, silicon crystalline structures (Coesite) intensified with time. Boron nitride was also increasingly created on the top surface and in the bulk of the coating over the heating time. These findings proved the effective role of the silica and zinc-borate nanoparticles in the fire performance of epoxy-based intumescent coatings.