Abstract: Polyurethaneimide（PUI）was filled with expandable graphite (EG) and dimethyl methylphosphonate (DMMP) forming flame retarded plastics, whose flame retardant properties, morphology of surface carbon layer, and mechanical properties were studied. Compared with systems containing EG alone, the introduction of DMMP generated more continuous and dense carbon layer after burning, and thus increased the limiting oxygen index from 18.6 % to 33.4 %. The combination of EG and DMMP had less effect on the compressive property of PUI than that when EG was used alone.

Key words: polyurethane-imide, foam, flame retardant, expandable graphite, dimethyl methylphosphonate