In Situ Mineralization of Chitosan‐Modified Calcium Hydroxystannate for Flame‐Retardant and Eco‐Friendly Bamboo Materials

Abstract The global plastic pollution crisis has heightened interest in sustainable alternatives such as bamboo, with the “bamboo‐for‐plastics” initiative providing a low‐carbon strategy. While bamboo‐derived products (e.g., furniture, textiles) may potentially reduce plastic dependency, achieving simultaneous flame retardancy and mechanical robustness in engineered bamboo presents a significant challenge. Herein, a green approach is reported that utilizes in situ synthesis to prepare non‐toxic, halogen‐free calcium hydroxystannate (CSH), which is further modified by partial Ca 2+ substitution with chitosan (CS) cations. Bamboo treated with CSH demonstrated exceptional flame retardancy, with reductions of 37.14% in peak heat release rate (PHRR), 27.28% in total heat release (THR), and 48.06% in total smoke release (TSR) compared to untreated controls. The incorporation of CS simultaneously improved mechanical performance without compromising flame resistance, with the NB‐3Ca‐2Cs‐Sn composite achieving optimal compressive strength, representing a 17.5% increase, alongside a minimal weight gain of 4.56%. This synergistic CSH‐CS mineralisation strategy combines straightforward preparation, effective flame suppression, and mechanical reinforcement, enhancing bamboo's viability for scalable applications in fireproof construction materials.