Synthesis of rigid polyurethane foams with castor oil-based flame retardant polyols

• We report a new castor oil-based flame retardant polyols used in polyurethane foam.
• The castor oil-based flame retardant polyols is one kind of polyols with diethyl phosphate in the molecular chain.
• Polyols show superior reaction activity with isocyanate.
• The fire retardant incorporated in the molecule chain increased LOI and thermal stability of polyurethane foam.
• Although the content of P element is only 3%, LOI value can reach to 24.3% without any other flame retardant.

A new method of introducing castor oil based flame-retardant polyols (COFPL) into polyurethane foams was explored in this paper. Castor oil was alcoholyzed with glycerol. And epoxidation of glycerolysis castor oil was carried out by formic acid and hydrogen peroxide (H2O2). The flame-retardant polyols were gotten though ring-opening reaction with diethyl phosphate. A novel castor oil-based polyurethane foam has been prepared by a one-shot process with and without COFPL. The structure of COFPL was characterized by FT-IR and 1HNMR and the two studies exhibited characteristic peaks for COFPL. The thermal degradation and fire behaviour of polyurethane foams were investigated by limiting oxygen index (LOI), cone calorimetry test and thermogravimetry analysis. It has been shown that although the content of P element is only about 3%, the fire retardant incorporated in the castor oil molecule chain increased thermal stability and LOI value of polyurethane foam can reach to 24.3% without any other flame retardant. The compression strength of polyurethane foam was also improved with the increase of flame-retardant polyols. Morphology of polyurethane foams was examined by scanning electron microscope (SEM) and found to be displayed the regular size and high percentage of close area of the cell. Therefore, rigid foams from castor oil-based flame retardant polyols appear suitable for a wide range of applications.

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