New Sustainable Intumescent Coating Based on Polyphenols Obtained from Wood Industry Waste

The global proliferation of Pinus radiata, known for its rapid growth and wood density, has led to an environmental challenge-significant waste production, especially bark, without a clear valorization route. This waste poses ecological concerns, and despite the crucial role of forest resources in structural applications, their limited fire resistance requires the use of coatings. However, traditional coatings lack an eco-friendly footprint. Addressing this challenge, this study aims to develop an intumescent coating with tannins extracted from waste bark, offering a sustainable alternative. This not only repurposes waste on a global scale but also aligns with the imperative for environmentally friendly materials, contributing to sustainable practices in the construction and wood treatment industry. This study achieved an eco-friendly FRR15 (fire resistance ratio 15) fire resistance classification with a 15% equivalence of low-molecular-weight tannins, presenting a sustainable alternative to commercial products. Characterization showed low-molecular-weight tannins comparable to conventional charring agents, with high hydroxyl content and oil absorption, while high-molecular-weight tannins exhibited lower viability. A reference coating achieved FRR30 fire resistance, aligning with commercial strength. The mechanical properties of tannin-based coatings matched commercial standards, with increased abrasion resistance and adhesion and decreased flexibility. Intumescent coatings with higher tannin content significantly reduced wood substrate charring and mass loss in flame response assessments.