Combining inherent and additive phosphorus-containing flame retardants for enhancing flame retardancy and smoke suppression effects on polyisocyanurate-polyurethane foam

This study focuses on further improving flame retardancy and reducing the amount of toxic-smoke released of phosphorous-containing flame-retardant polyisocyanurate-polyurethane foams (FPIRs) through the additive effect between reactive flame-retardant diol (BEOPMS) and dimethyl methylphosphonate (DMMP). The surface morphologies, combustion behavior and flame-retardant mechanism of FPIRs were evaluated by scanning electron microscope (SEM), limiting oxygen index (LOI), cone calorimeter (CC) and thermogravimetry-Fourier transform infrared (TG-FTIR) analysis. It was found that the addition of DMMP decreased the thermal-degradation temperature and reduced the compressive strength gradually of FPIRs. More importantly, the PHRR, THR, and TSR of FPIR were observed to be depressed by 72%, 82% and 38%, respectively, in the case of adding only 15 phr DMMP in the FPIR system. The LOI of FPIR could significantly improve from 22.0 vol% to 29.5 vol% after the introduction of BEOPMS and 25 phr DMMP together. Based on CC, TG-FTIR, and SEM/EDS analysis, an additive effect mainly in the gas phase between BEOPMS and DMMP was included to explain the beneficial effect in suppressing heat and smoke release.