Today structural polymeric materials including epoxy-based, are widely used in many branches of industries, to reduce the metal consumption. At the same time, the use of such materials reduces greatly fire safety. It is therefore important to take into account and pay special attention to it while developing polymer composite materials, in the study of their thermal properties, as well as their destruction under the thermal field. The paper considers a number of issues associated with reducing the flammability of polymeric composite materials by applying of fine-grained refractory fillers. Studied composites were based on bisphenol epoxy resin brand ED-20; for crosslinking it, the polyethylenepolyamine of low molecular weight as hardener was used. Tris(2-chloroethyl) phosphate was applied as plasticizer. Refractory fine-grained additives of different physical nature (grain size of 5…10 micron) were used as fillers (sovelite powder, calcium carbonate, sodium dichloroisocyanurate). Thermal properties of epoxy composites in the temperature range Δ Т =303…873К were studied. Tris(2-chloroethyl) phosphate was applied as plasticizer. Refractory fine-grained additives of different physical nature (grain size of 5…10 micron) were used as fillers (sovelite powder, calcium carbonate, sodium dichloroisocyanurate). Thermal properties of epoxy composites in the temperature range Δ Т =303…873К were studied. The values of Martens heat resistance, thermal linear expansion coefficient, glass-transition temperature, relative shrinkage of the composites developed were also set during investigation. According to the research, it is recommended to input the calcium carbonate particles in amount of q = 60 wt % in plasticized epoxy binder for the formation of composites with improved thermal properties. It is also found that the input of sovelite powder particles in amount of q = 20 wt % is economically feasible due to increase of the Martens heat resistance, both thermal linear expansion coefficient and shrinkage reduction, as well as increase of glass-transition temperature observed with such filling.