Effects and Mechanisms of Ultralow Concentrations of Different Types of Graphene Oxide Flakes on Fire Resistance of Water-Based Intumescent Coatings

This study examined the effect of ultralow concentrations of three types of graphene oxide (GO) flakes on the fire resistance of water-based intumescent coatings, which are used widely as fire protectants for steel structures. The fire resistance of the coatings was assessed using a small-scale fireproof testing furnace, and their elemental compositions, oxidation states, and char-layer microstructures were analysed using Thermal Gravimetric analyzer (TG), X-ray Diffraction (XRD), Scanning Electron Microscope (SEM)SEM, and X-Ray Photoelectron Spectroscopy (XPS)XPS, and the reaction mechanisms were revealed. The results show that three types of GO with different sizes and thicknesses all have the ability to enhance the fire-resistance performance of intumescent coatings at different extremely low dosages (0.001%–0.002%), with a maximum increase of 20% compared to that of the blank. Compared with small GO flakes, large GO flakes more effectively enhanced the fire resistance of coatings. The mechanism of enhancement of GO is attributed to two factors. On the one hand, although the presence of GO did not affect the type of final product of intumescent coatings, it affected the proportion of products. After adding GO, the production of titanium pyrophosphate increased, leading to an increase in the strength of the char layer. On the other hand, the microstructure of the char layer of the intumescent coating added with GO has been improved, leading to a significant improvement in the fire-resistance performance. When the dosage was greater than 0.002%, GO tended to agglomerate, which diminished its ability to enhance the fire resistance of coatings. Agglomerated GO can also leaded to a deterioration in the crystal structure of titanium pyrophosphate, thereby affecting the strength of the char layer.