In order to improve the special working environment of underground coal mines and the safety of polyurethane(PU)grouting materials in application,the expandable graphite(EG)and dimethyl methyl phosphonate(DMMP)were se-lected to be added in PU slurry to explore the optimal process formulation,and EG/DMMP modified polyurethane grouting materials were produced.Meanwhile,the influence of EG and DMMP on the maximum reaction temperature,curing time,ther-mal conductivity,mechanical properties and flame-retardant properties of the slurry was investigated by infrared thermometer,thermal conductivity meter,electronic universal testing machine and cone calorimeter.The results show that when 1％EG and 1％DMMP are compounded and introduced into the system,it not only reduces the maximum reaction temperature of the slur-ry,but also gives the slurry excellent flame retardant,smoke suppression and toxicity reduction performance.The peak heat re-lease rate,the total heat release,and the peak rate of carbon monoxide generation of the PU grouting composites are reduced by 43.5％,32.2％,and 30.3％respectively compared with those of pure PU,and the compression strength and tensile strengths are 55.7 MPa and 51.0 MPa,respectively,which fulfils the double demand of EG/DMMP modified polyurethane grouting material basically solves the hidden danger of"thermal runaway"of the grouting material while considering its me-chanical properties.The research results can provide a certain guarantee for the safe application of PU grouting materials in underground coal mines.
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