The different transitions and reactions involved in the thermal processing of ternary ethylene vinyl acetate (EVA)-polyethylene (PE)-azodicarbonamide (ADC) mixtures with different concentrations of PE and ADC, which was used as a foaming agent, were studied by means of differential scanning calorimetry. The effect of the concentration of PE in the ternary samples was practically linear, which showed an increase in the fusion heat of the PE and the PE domains of the EVA. On the contrary, the mechanism of the thermal decomposition of ADC that the ternary mixtures contained was strongly dependent on its concentration in the sample, which showed clear deviations from linearity. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 3217-3224, 2008