Effect of Expandable Graphite Flakes on the Flame Resistance of Oak Wood

One of the strategies to improve the fire resistance of wood is to use flame retardants. It would be best to find an ecological, nonhalogenated flame retardant to improve the fire protection properties. In this work, oak wood (Quercus robur L.) samples were treated with an aqueous solution of sodium silicate and expandable graphite flakes, which were applied to different parts of the samples: only on the top, on the sides and together on the top and sides of samples. The fire characteristics of samples were studied by a non-standard test method—a radiant heat source test which is used to determine the mass loss and ignition time of the tested samples (50 mm × 40 mm × 10 mm), and the measurement was carried out using a visual recording of a thermal camera. The results of the laboratory test method showed a significant positive effect of the application of the retardant treated only on the top and together on the top and the sides of the samples in terms of decreasing the mass loss and the course of temperature. When we treated only the sides of the sample, the results were closer to the untreated samples, so there was more than 80% weight loss and a significant temperature increase. The results demonstrated that the appropriate modification of the wood using sodium silicate and expandable graphite flakes has the potential to reduce the loss of mass by 79% and reduce the rise in temperature on the surface of the sample.