Influences of nano bio-filler on the fire-resistive and mechanical properties of water-based intumescent coatings

•Eggshell, a novel nano bio-filler for water-based intumescent coating.•Addition of nano bio-filler enhanced the mechanical properties of coating.•Appropriate combination of flame-retardant ingredients improved the fire protection.•Nano eggshell has a great potential as a renewable bio-filler for coating. In the modern design of commercial buildings, the requirements for fire safety and evacuation must comply with to ensure the protection of human lives and property. The applications of flame-retardant materials in buildings play a vital role in reducing the risks of fire propagation. This study aims to synthesize an eco-friendly intumescent coating by incorporating the novel eggshell (ES) nano bio-filler. The samples were then characterized using Bunsen burner, thermogravimetric analysis (TGA), scanning electron microscope (SEM), Fourier transform infrared (FTIR) and pull-off adhesion tester. The coating D with an appropriate combination of the binder and flame-retardant ingredients had significantly improved the formation of char thickness in protecting the coated steel. This char layer showed a denser and more uniform foam structure surface in the SEM micrograph. Additionally, this formulation had exhibited the highest adhesion strength of 2.13 MPa, which indicated the effectiveness of interface attachment on the substrate. Moreover, the thermal stability of the formulation had also increased in thermal analysis. Therefore, the outcomes of the research revealed that uses of optimal quantity of nano bio-filler leading to better fire protective performance and mechanical properties of the intumescent coating.