The best formula green polyester flame retardant PU is: 100 parts of a polyester polyol polyurethane wear plate, 0.18 parts of an organic tin supply polyurethane wear plate, the isocyanate index of 1.05. Phosphorus flame retardants 2.5% of the total mass of material rigid polyurethane sheet, the temperature was 25 degrees Celsius, 18 parts of blowing agent. Average burning time green polyester flame retardant PU greatly shortened 8S reached the standard B1 class flame retardant materials. Decomposition products at high temperatures in the polymer surface forms a protective film, from the PU to prevent burning effect. Polyurethane sandwich panels are widely used in large industrial plants, cold storage, garage, mobile homes, exhibition halls, stadiums, shopping centers, airports, power plants, villas, hospitals, and high-rise office buildings and other areas of the formation, due to the excellent insulating properties Main application industrial and civil buildings roof and wall.