Flame-retarded rigid polyurethane foam <i>in-situ</i> conferred by a bio-based soybean oil polyol containing phosphorus compounds

To reduce the dependency of human life and industrial materials on petroleum, developing renewable and environmentally friendly materials has become one of the research hotspots. In this paper, Soy-DGP was synthesized through a ring-opening reaction between epoxy soybean oil (ESO) and diethylene glycol (DG), followed by a reaction with phenylphosphonyl dichloride(PPDC). Flame-retardant polyurethane foam (RPUF-DGP) was then produced by reacting various amounts of Soy-DGP with isocyanate (p-MDI). It was observed that the addition of Soy-DGP led to a reduction in the mechanical properties due to a decrease in the apparent density of RPUF-DGP. Microscopically, as Soy-DGP was added, the bubble pore size did not change significantly, but the uniformity of the aperture size was decreased. Additionally, the limiting oxygen index (LOI) of RPUF-DGP improved from 19.2% to 22.6% upon adding 80 wt% Soy-DGP. Both the time to ignition (TTI) and time to peak heat release rate (TTP) for RPUF-DGP decreased with increasing Soy-DGP content, shortening the continuous burning time of samples. Examination of the residual carbon structure showed that higher quantities of Soy-DGP resulted in thicker carbon layers on the surface of RPUF-DGP, along with bead-like phosphoric acid formation within the system, which delayed degradation.