Full substitution of petroleum-based polyols by phosphorus-containing soy-based polyols for fabricating highly flame-retardant polyisocyanurate foams

To obtain a substitute for petroleum-based polyols and simultaneously solve the flammability problem of polyisocyanurate (PIR) foams, a novel phosphorus-containing soy-based polyol (PCSO) was firstly synthesized. Then, PCSO was used to fabricate biomass flame-retardant PIR foam (P-PIR) by fully replacing petroleum-based polyol. The morphology, compressive strength, thermal conductivity, thermal stability, flammability, and flame-retardant mechanism were studied for the developed PIR. The incorporation of PCSO results in a slight decrease in the compressive strength and an increase in the flame retardancy of PIR foam. To further improve the flame retardancy, a commercial phosphorus-containing polyol (BY30) and an expandable graphite (EG) were added in the P-PIR system. The test results show that the decompositon of PIR was hindered after 330 °C and the char residue was significantly improved. In addtion, the limiting oxygen index of PIR was significantly increased to 35%, and the peak of heat release rate and total heat release were dramatically decreased by 65% and 87%, respectively. A synergistic flame-retardant effect was achieved by combining the gas phase action of PCSO and BY30 with the condensed phase action of EG.