Sustainable, transparent and fire-retardant wood composites

Materials derived from transparent wood (TW) have become a focal point of research due to their exceptional physical, chemical, and optical properties. In this study, a novel approach was undertaken to enhance the fire resistance of wood material by coating wood aerogel with bentonite nanoparticles. This coating process aimed to create flame-retardant wood, thereby increasing its safety and usability in various applications. Following this, the bentonite-coated wood was integrated with waterborne polyurethane (WPU) to develop a new form of transparent wood, which combines the beneficial attributes of both materials. The results obtained from the experiments showed that the bentonite-coated wood aerogel exhibited remarkable fire resistance. During combustion tests, it demonstrated the ability to self-extinguish, highlighting its effective flame-retardant properties. Notably, the treated wood aerogel achieved significant reductions of 48 % in the peak heat release rate (PHRR) and 39 % in total heat release (THR) when compared to standard wood aerogel samples. This underscores the effectiveness of the bentonite coating in enhancing the fire safety profile of the wood material. Furthermore, the study involved a comprehensive evaluation of the optical properties, thermal stability, flame retardancy, and mechanical strength of the WPU/wood composites. The transmittance measurements for the composites, including WPU/wood, WPU/wood-B1, and WPU/wood-B2, were found to be below 60 %, which is notably lower than the 70 % transmittance observed in pure WPU samples. This reduction in transmittance suggests a trade-off between transparency and enhanced material safety. Additionally, the introduction of bentonite resulted in the composite WPU/wood-B2 achieving substantial reductions in fire-related metrics, with 32 % and 30 % decreases in PHRR and THR, respectively, compared to pure WPU. This finding points to the potential of bentonite integration in improving both the flame retardancy and overall safety of polymer-wood composites.