Synthesis of reactive phenylphosphoryl glycol ether oligomer and improved flame retardancy and mechanical property of modified rigid polyurethane foams

Abstract

A novel reactive phenylphosphoryl glycol ether oligomer (PPGE) was synthesized to improve the flame retardancy of rigid polyurethane foam (RPUF). The PPGE segments in RPUF simultaneously enhanced its compressive modulus and flame retardancy. With the incorporation of 2% phosphorous weight content in RPUF, the limiting oxygen index value of 2%PRPUF improved from 20.0% of neat RPUF to 24.5%. The cone calorimeter test results demonstrated that the total heat release and peak heat release rate values of 2%PRPUF decreased, approximately 24% and 18% lower than those of neat RPUF, respectively. The combination of 2%PRPUF with expanded graphite (EG) efficiently reduced the flame spread rate and smoke toxicity of flame retardant RPUF. The flame-retardant mechanism of the 2%PRPUF/EG demonstrated that the synergistic effect of phosphorous-containing radical inhibition and the barrier of expansive char residue consequently led to a highly efficient flame retardancy. The reactive phosphorous-containing oligomer is promising in the development of high-performance flame-retardant thermal insulation RPUFs. Keywords: Rigid polyurethane foam, Reactive phosphorous-containing oligomer, Flame retardancy, Smoke toxicity, Mechanical property