A green and eco-friendly method to enhance Bamboo flame resistance via calcium alginate assisted in-situ mineralization of hydroxyapatite

Developing environmentally friendly methods for modifying bamboo is important. This study proposed a method to enhance the flame retardancy of bamboo through calcium alginate (CaAlg) forming and hydroxyapatite (HAP) mineralization. Scanning electron microscopy and elemental analysis demonstrated that HAP was uniformly deposited within and on the surface of bamboo cells with the assistance of CaAlg. The residue yield of the treated bamboo increased by 49.8% and 40.7% under air and nitrogen atmospheres, respectively. The limiting oxygen index increased from 23.4% to 26.6%. Furthermore, compared to the untreated bamboo, the treated bamboo exhibited reductions of 45.2%, 25.8%, 25.6%, and 30.7% in peak heat release rate, total heat release, peak smoke production, and total smoke release, respectively. The layer of CaAlg and HAP particles cross-link within the bamboo cells, forming a dense protective barrier that prevented the entry of heat, flammable gases, and the release of toxic smoke. The mechanical properties of the bamboo were not reduced by this gentle treatment. The mineralized bamboo fabricated using this method showed potential as a sustainable building material due to its improved flame retardancy and mechanical properties.