The physicomechanical behavior and flammability properties of waste polyethylene and recycled waste rubber powder blend (WPE/RWRP/MA) filled with antimony trioxide (Sb2O3), at different contents 5, 10, 15, and 20 wt %, and irradiated with different gamma radiation doses, namely 50, 75, 100, and 150 kGy, were investigated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and limiting oxygen index (LOI) measurements. Tensile strength, elongation at break, elastic modulus, hardness, swelling properties, and electric conductivity behaviors were also investigated. Experimental results emphasized that Sb2O3 particles retard degradation and flammability of the composite. The LOI increases from 16 to 20.9 with 20 wt % Sb2O3 specimen irradiated with 150 kGy. Improvement in thermal stability at conditions of 15 wt % Sb2O3 and a dose of 75 kGy was demonstrated by TGA.DSC measurements showed that Tm significantly increased in the presence of the filler. Mechanical characterization tests showed a significant increase in tensile strength within the range 510 wt % Sb2O3. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012