Formulation of environmentally robust flame-retardant and superhydrophobic coatings for wood materials

Developing flame-retardant wood with integrated anti-wetting property, self-cleaning and good weatherability, has received intensive attention, which is vital to the rapid advancements in construction and building materials. Here, a superhydrophobic and flame-retardant coating is constructed based on a trinity monocomponent intumescent flame retardant, polydimethylsiloxane resin and modified SiO2 nanoparticles. Such a coating can endow wood materials with high flame retardancy and self-cleaning performances. In comparison to pristine woods, the surface-treated wood shows a self-extinguish behavior in the vertical burning test with an obviously increased limiting oxygen index of 31.0% and UL 94 rating of V0. The peak heat release rate is reduced by 24.4% and the total heat release after surface treatment is decreased to 24.5 MJ/m2. The water-repellency of sample is greatly improved with water contact angle over 154° and slide angle below 5°, exhibiting appreciable resistance to dust contamination. Due to the significant anti-wetting property, the coating can effectively protect the inner flame-retardant layer from water penetration, thereby the treated wood can preserve high flame-retardant performances even after being immersed in water for 24 h. More importantly, the modified wood material can endure different harsh environmental conditions, including high temperatures, UV light irradiation, hydrothermal environment and mechanical impact, without losing the superhydrophobicity or flame retardancy, presenting high weatherability and mechanical robustness. The findings provide an effective approach to prepare high-weatherability fire-safety wood materials that have application potential in outdoor environments.