The Role of Isocyanate Index and Flame Retardant in Reducing CO (g) and Smoke Emissions of Soy‐Based Rigid Polyisocyanurate Foams

Abstract

Enhancing the flame retardancy of bio- based rigid polyurethane foams (RPUFs) is a crucial step toward improving the sustainability of the polyurethane industry. In this work, we systematically analyzed the effect of increasing the isocyanate index (NCOindex) and the flame retardant (FR) content using a polyol with high renewable content (> 97 wt.%). We found outstanding results regarding the CO(g)/CO2(g) index, the most important safety parameter in terms of human safety, whereas a significant reduction of 78% and 69.6% was observed as a function of increasing the NCOindex and FR content, respectively. In addition, the FR did not cause an increase in the total smoke production (TSP); on the contrary, it decreased up to 31.4% after increasing the FR concentration. The MAHRE parameter was also substantially improved, up to 40.6%, indicating the formation of a thicker char layer that protected the foam during burning. This was achieved simultaneously with outstanding improvements in the specific compressive strength of up to +155%. The studies were substantiated by a comprehensive physicochemical characterization using TGA analysis, water absorption, initial thermal conductivity, FTIR analysis, and cell geometry using SEM. These results are of paramount importance to promote the use of bio- based RPUFs with enhanced fire retardancy.