Preparation and properties of bio‐based flame‐retardant rigid polyurethane foams with soybean oil polyols containing phosphorus

Abstract Two types of bio‐based RPUFs (RPUF‐P and RPUF‐PPOA) were prepared that contained ethanol‐modified polyols (Polyol‐E) and one contained an epoxidized polyol modified with phosphoric acid (Polyol‐P), and the other contained epoxidized polyol modified with phenylphosphonic acid (Polyol‐PPOA). The cell morphologies, thermal and mechanical properties, and flame retardancy characteristics of the RPUF, RPUF‐P, and RPUF‐PPOA were studied by scanning electron microscopy (SEM), thermogravimetric analysis(TGA), compression tests, limiting oxygen index (LOI), and cone calorimetry test (CCT). The porous structures revealed that the cell sizes of both RPUF‐P and RPUF‐PPOA increased first and then decreased, and the number of pores decreased first and then increased. Furthermore, the apparent density showed a similar trend of increasing before decreasing. The compressive strengths of the RPUF‐P and RPUF‐PPOA were higher than that of the RPUF, and the compressive strength of the RPUF‐P was better than that of the RPUF‐PPOA, because the hydroxyl value of the Polyol‐P was much higher than that of the Polyol‐PPOA. The crosslinking density of the RPUF‐P prepared by the PM‐200 reaction was much higher than that of the RPUF‐PPOA. The LOI values of the RPUF‐P4 and RPUF‐PPOA4 were 21.68 and 23.10, respectively. Furthermore, the value of the peak of the heat release rate (HRR) was reduced by 40.3% compared with that of pure RPUF. The total heat release (THR), smoke produce rate (SPR), and total smoke release (TSR) decreased with increased Polyol‐P and Polyol‐PPOA addition. The flame‐retardancy residues micrographs showed that the carbon layers generated from the combustion of the RPUF‐P4 and the RPUF‐PPOA4 lacked perforated structures and exhibited better densification than the pure RPUF. Based on the analysis and discussion, the flame retardancy of RPUF‐P and RPUF‐PPOA were improved mainly through a condensed and gas phases mechanism.