The influence of 0.1, 0.25, and 0.5 wt% of graphite and graphite oxide on the thermal and mechanical behavior of a PP-70 polyester resin was analyzed. According to the infrared spectra, the addition of graphite particles reduce the intensity of the ester groups reflecting a physical interaction between the filler and the polymer. The thermogravimetric analysis revealed a slightly increase in the decomposition temperature from 400 to 415 degrees C when 0.25 wt% of graphite oxide particles were incorporated. Dynamic-mechanical analysis behavior of polymer composites showed low interaction of graphite particles with polyester matrix, which changed the thermo-mechanical stability of composites. The flexural behavior for the two composites, obtained from stress-strain curves, showed that incorporation of 0.5 wt% of graphite and graphite oxide reduces the stiffness from 2700 to 2100 and 2250 MPa; in addition, the strength was also decreased from 98.1 to 68.2 and 63.5MPa; respectively. (C) 2018 Elsevier Ltd. All rights reserved.