Fire Retardancy Properties of Ceramifiable Polydimethylsiloxane/Hydroxyapatite Composites

ABSTRACT To address the urgent demand for advanced flame‐retardant materials capable of preventing devastating fire‐related damages, casualties, and environmental harm, a novel ceramifiable composite has been developed. This composite is based on hydroxyapatite nanofibers (HAP) prepared via a hydrothermal process and combines HAP with zinc borate (ZB), aluminum hydroxide (ATH) and glass powder (GP) dispersed within a polydimethylsiloxane (PDMS) matrix. The optimized formulation (15 phr HAP, 55 phr ZB, 35 phr ATH, and 10 phr GP) demonstrated outstanding fire resistance, achieving a 41.9% reduction in peak heat release rate and extending the ignition time to 104 s, while also meeting UL‐94 V‐0 standards and reaching a high limiting oxygen index of 41.5%. Post‐sintering, the material transformed into a lightweight (0.47 g cm −3 ) porous ceramic. The enhanced flame retardancy and ceramifiable characteristics are attributed to HAP's dual role: it accelerates the formation of a ceramic barrier that effectively impedes heat and mass transfer, and it aids in capturing the gas phase via the liquid phase, resulting in the development of a porous, low‐density ceramic structure.