Rosin‐Based Si/P‐Containing Flame Retardant Toward Enhanced Fire Safety Polyurethane Foam

Environmentally friendly flame retardant such as polysiloxane has long been sought for varied studies in recent years and can be further improved to overcome the challenges of additional applications. Herein, a novel synergistic‐effect flame retardant containing Si and P is synthesized. Si‐P containing flame retardant (DOPO‐MGSO) is then added into a network to fabricate rigid polyurethane foam via a one‐step process. The bio‐renewable resource maleopimaric acid (MPA) impedes conversion of the cyclic siloxane, thereby enhancing the compactness of the silica layer in condensed phase. Furthermore, the DOPO groups quench free radicals in the gas phase. Compared with the unmodified sample, the limiting oxygen index of the modified foam increases from 17.1% to 25.2%. Moreover, CONE tests show that the peak heat release rate decreases from 260.1 to 136.2 kW m⁻¹ (close to 50%) after modification. Importantly, the generation of silica‐rich char significantly reduces the total smoke release (decrease from 1154.4 to 715.9 m² m⁻²). In addition, the improvement of compressive strength benefits from the MPA rigid ring.