News Coatings Technologies
Sustainable biochar coating improves fire protection of wood
Researchers have developed a halogen-free flame-retardant composite coating for wood that combines polyvinyl acetate with biochar, kaolin and trimethylsilyl polyphosphate. The system significantly reduces heat release and smoke generation, offering a sustainable route to improved fire safety in construction and interior applications.
Wood is widely valued as a renewable and sustainable construction material, yet its inherent flammability continues to limit its safe application in many building contexts. To address this challenge, researchers have developed a novel halogen-free composite coating designed to enhance the fire resistance of wood while maintaining a sustainable material profile.
The coating formulation combines polyvinyl acetate (15 wt%) as the binder with biochar (0.5 wt%), kaolin (2 wt%) and trimethylsilyl polyphosphate (3 wt%) dispersed in methanol. The composite was prepared by solution blending and applied via single-layer drop-casting at a thickness of approximately 0.6 mm onto the wood surface.
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Char yield and thermal stability significantly improved
A comprehensive characterisation programme employing ATR-FTIR, Raman spectroscopy, TEM, TGA/DTG/DSC, cone calorimetry and optical/3D surface analysis confirmed uniform filler dispersion, strong chemical interactions and enhanced thermal stability. The coated samples achieved a char yield of approximately 26 % at 800 °C, indicating the formation of a compact and protective char layer.
Lower heat release and smoke generation
Cone calorimeter testing demonstrated substantial improvements in fire performance. Total heat release decreased to 48.77 MJ/m² compared with 63.56 MJ/m² for uncoated wood, while the average heat release rate dropped to 80.82 kW/m² from 100.65 kW/m². The mass loss rate was also reduced to 6.558 g/s·m² versus 7.781 g/s·m² for the reference. Additionally, lower smoke volume rates and surface temperatures confirmed improved flame retardancy and smoke suppression. The findings demonstrate that this bio-based, halogen-free composite coating offers a promising and sustainable solution for enhancing the fire safety of wood in construction and interior applications.
Source: Kolya, H. et al., Sustainable flame-retardant composite coating for wood using biochar, kaolin, polyvinyl acetate, and trimethylsilyl polyphosphate. Progress in Organic Coatings, 110124 (2026).
