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

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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.