In situ biomineralization of metal phytates in wood for improved bio-durability and flame retardancy

Abstract

This study investigated the in-situ biomineralization of metal phytate in wood to improve the antifungal and flame-retardant properties. Pine and aspen wood were impregnated with phytic acid and metal chlorides (copper, aluminum, and iron) via two treatment pathways. Path-1 involved treating wood with metal chlorides followed by phytic acid, while Path-2 involved the reverse order. Mass gain and accelerated leaching tests were performed to assess the treatment retention, followed by soil-block decay testing against four wood-decaying fungi and fire-related assessments on aspen via thermogravimetric analysis (TGA) and mass loss calorimeter (MLC) test. Path-2 resulted in significantly higher initial mass gain than Path-1, but experienced more substantial mass loss during leaching, indicating weaker fixation of PA-derived components. Before leaching, most treated samples exhibited improved decay resistance, with mass loss values below 10%. However, decay resistance decreased after leaching, indicating the importance of fixation stability for long-term durability. TGA showed that treated samples before leaching exhibited earlier thermal degradation and higher residual char yield than controls, while MLC measurements revealed reduced peak heat release rate, total heat release, and fire growth index, as well as higher char residue. Importantly, these flame-retardant properties were largely retained even after leaching. Overall, these results indicate that in situ metal–phytate formation can provide measurable improvements in fire performance, while fungal protection remains dependent on treatment retention. Further optimization of fixation chemistry is recommended to achieve more durable, bio-based wood protection.