An Innovative Wood Fire-Retardant Coating Based on Biocompatible Nanocellulose Surfactant and Expandable Graphite

Nanocellulose (CNC) seems to be a promising surfactant, which, together with expandable graphite (EG), forms the essence of an effective natural-based fire-retardant wood coating. In our research, the most suitable composition of the mixture was tested concerning good solubility, dispersion, and consistency. Favorable results were achieved with the formulation composed of a 4% CNC alkaline solution with 80 wt.% of the selected EG. Subsequently, six different types of EG were used to prepare these wood fire-retardant coatings. The effectiveness of treatments was verified using a test with a radiant heat source, where the test samples' relative weight loss, relative burning rate, and surface temperature during 600 s were evaluated. All prepared formulations can be characterized as more or less equally effective. However, the best results were obtained with the EG of GG 200-100 N, where the mass loss of the sample was 8.10 +/- 1.24%. Very good results were also achieved by graphite 25 E + 180 HPH (8.70 +/- 0.89%), which is similar to the previous one, even according to the microscopic assessment of the coating as well as the expanded layer. The graphite type 25 K + 180 (8.86 +/- 0.65%) shows the expanded layer's best adhesion, coating uniformity, and ease of application. The results of this work confirmed that the CNC coating itself has significant retardation effects.