The invention discloses a
flame retarding
polyurethane foam and a preparation method thereof. The
flame retarding
polyurethane foam comprises the following raw materials of premixed polyether
polyol, diisocyanate and a composite
flame retardant, wherein the weight ratio of the premixed polyether
polyol to the diisocyanate is 1: (1-1.5), the usage amount of the composite flame retardant is 10%-20% of that of the premixed polyether
polyol, the composite flame retardant comprises
graphite and dimethyl
phosphate, and the weight ratio of the
graphite to the
dimethyl phosphonate is (0.8-3):1. According to the flame retarding
polyurethane foam and the preparation method thereof, the used
graphite and the dimethyl methyl
phosphonate are synergetic with each other, the graphite can be rapidly expanded into an efficient heat insulation
oxygen barrier which is capable of preventing polyurethane from flaming, and the dimethyl methyl
phosphonate is used for catalyzing
dehydration and
char formation of polyol to achieve the effect of retarding flame. To improve flame retarding performance of rigid polyurethane foams, compared with rigid polyurethane foam
oxygen index generated during the usage of the graphite or the dimethyl methyl
phosphonate, the rigid polyurethane foam
oxygen index generated during the simultaneous usage of the graphite and the dimethyl methyl phosphonate can be increased by 5.