An anti-melt dripping, high char yield and flame-retardant polyether rigid polyurethane foam

Endowing rigid polyurethane foam (PUF) with a good fire-retardancy is essential for improving fire safety. Chemical improvement in fire-retardancy by using reactive-type flame retardants is better because of the disadvantages of traditional additive-type flame retardants. A reactive flame retardant tri-glycidyl phosphate (POG), which was synthesized by using phosphorus oxychloride and glycidol, was bound to the cross-linked network structure of PUF. The effects of POG on the physical-mechanical properties, morphology, thermal stability and fire-retardancy of PUF system were systematically investigated. Research results showed that POG resulted in an improvement in the thermal insulation ability and a slight decrease in the compressive strength of PUF. Furthermore, thermogravimetric analysis certified that the thermal stability and the char yield at 700 °C of PUF were significantly enhanced by incorporating POG. The limiting oxygen index increased to 22.3% with rising loading of POG. Moreover, a 30.2% decline in total heat release was achieved, the time to flameout was significantly shortened. Additionally, the vertical burning test illustrated that POG effectively limited the spread of flame and eliminated melt dripping. Further study confirmed that the fire-retardancy of PUF was significantly improved by inhibiting flame in the gas phase and charring in condensed phase.