Effect of Boric Acid and Melamine on the Intumescent Fire-Retardant Coating Composition for the Fire Protection of Structural Steel Substrates

Intumescent coating is an insulating material designed to decrease heat transfer to a substrate structure. The coating presented
in this research article was based on expandable graphite, ammonium polyphosphate, melamine, and boric acid. Bisphenol A
epoxy resin BE-188 was used as a binder with ACR hardener H-2310 polyamide amine. Different formulations were developed to
study the effect of expansion and heat shielding after fire testing. The coating was tested at 950�C for 1 h. The results show that the
coating was stable and well bonded with the substrate. The coating was characterized with thermogravimetric analysis (TGA, Parkin
Elmer, Norwalk, CT, 06859, USA), Fourier transform infrared (FTIR, Nicolet 400 D Shimadzu spectrometer) spectroscopy, X-ray diffraction
(XRD, Bruker D8 advance Diffracto meter, Bruker Germany), and scanning electron microscopy (SEM, Carl Zeiss Leo
1430VP, UK). The morphology of char was studied by SEM on the coating after fire testing. XRD and FTIR spectroscopy showed the
presence of graphite, boron phosphate, boron oxide, and sassolite in the residual char. TGA (Pyris 1, manufactured by Parkin Elmer,
Norwalk, CT, 06859, USA) and differential thermal gravimetric analysis (DTGA) showed that boric acid enhanced the residual weight
of the intumescent fire-retardant coating.