Water-resistant, transparent, and highly efficient flame-retardant wood coating

Wood is widely used in home, construction and other fields, but the problems of easy corrosion of wood, poor flame retardant, low hardness limit the scope of use of wood. Therefore, in this study, we prepared the coating by a simple one-pot sol-gel method, modified silicate (water glass) by introducing green non-toxic organic polymer with sodium silicate solution (water glass) as the base material, and used polyvinyl alcohol (PVA) and aminopropyl double-ended polydimethylsiloxane (2NH₂-PDMS) as the modifier. Triton X-100 as dispersant and ethyl acetate as curing agent were used to prepare three-dimensional crosslinked network structure (C-O-Si-OH-NH₂) sodium silicate composite coating. When exposed to flame, the non-combustible carbon layer formed by the three-dimensional network crosslinked structural coating can act as a strong fire barrier for the substrate, and the flame-retardant performance is far better than other coatings. The resulting coating LOI value exceeds 95 %, and cone calorimetry results show that, compared to uncoated wood, sodium silicate composite coating, the peak heat release rate (PHRR), total heat release rate (THR), smoke emission rate (SPR), total smoke emission rate (TSR) and CO₂ production rate were decreased by 96.6 %, 46.7 %, 96.2 %, 47.1 % and 91.7 %, respectively, and TTI was extended by 252 seconds. In addition, the gel rate (water resistance) of the silicate composite coating increased from 0 % to 61 %, flexibility changes from the curvature radius R>7.5 mm to R=5 mm, the hardness reached 5 H, and the brightness (L*) of the wood coating reached 75. From the above results, by overcoming the shortcomings of traditional sodium silicate coating in water resistance and poor flexibility, this paper innovates a water-resistant, flexible and expandable flame-retardant coating, which provides a new idea for further research on the design and manufacture of a new type of highly efficient, environmentally friendly, transparent and colorless water-resistant flexible and expandable flame-retardant sodium silicate coating.