Fabrication of fire safe rigid polyurethane foam with reduced release of CO and NOx and excellent physical properties by combining phosphine oxide-containing hyperbranched polyol and expandable graphite

In this work, a novel phosphine oxide-containing hyperbranched polyol (POCHP) was synthesized. Then POCHP and/or expandable graphite (EG) were incorporated into rigid polyurethane foam (RPUF). EG increases foam density and deteriorates compressive strength and thermal conductivity, but POCHP has opposite effects. A 12.8% improvement of compressive strength and slightly decreased density and thermal conductivity are achieved by ERPUF50 containing POCHP and EG. And it reaches a limited oxygen index of 30.0% and UL-94 V-0 rating with immediate self-extinguishing behavior after removing flame. The peak heat release rate, total heat release and total smoke production of ERPUF50 are reduced by 71.1%, 52.2% and 71.1% respectively via bi-phase flame retardant mechanisms. Interesting phenomena were observed that POCHP promotes the intumescence of EG after combustion. The results of combustion gas analysis reveal that single POCHP or EG reduces the production of CO but increases the generation of NOx. ERPUF50 exhibits a 52% decrement of CO and an unexpected 40% diminishment of NOx. ERPUF50 with excellent comprehensive properties can not only be used as fire safe thermal insulation material with high physical performances, but also significantly reduce the release of contaminative smoke, CO and NOx in fires and waste RPUF disposal by combustion.