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Casein-based rigid polyurethane foam (RPUF) with different ratios of starch and sepiolite were prepared by a one-step process. Thermogravimetric analysis, CONE analysis, scanning electron microscopy analysis, limiting oxygen index (LOI) analysis, vertical combustion analysis, and mechanical property analysis were used to explore the thermal stability, flame retardancy, and compressive properties of the modified RPUFs, respectively. The results showed that the initial decomposition temperature and activation energy (E) of RPUF-C5ST2SE3 (5 g casein, 2 g starch, and 3 g sepiolite) were the highest. Under the condition of radiant flux of 50 kW/m2, the peak heat release rate (PHRR), total heat release (THR), peak smoke production rate (PSPR), and total smoke release (TSR) were reduced by 35.92%, 10.83%, 36.67%, and 18.20%, respectively, compared with the RPUF without flame retardant. By analyzing the carbon residue, it was found that RPUF-C5ST2SE3 had the highest carbon residue and its carbon residue morphology was relatively intact. In addition, the RPUF-C5ST2SE3 had the highest LOI and a UL-94 rating of V-0. At the same time, it also had the best mechanical property. The present experimental results can provide a useful reference for future RPUF flame retardant studies.
Zhang et al. (Tue,) studied this question.