This work deals with thermal aspect of the microwaves processing by applying the dielectric effect of attenuation inversion of electromagnetic wave as a solution for uniform treatment. Interest is devoted to the description of electromagnetic and chemical thermal contributions present during microwave heating of a thermosat material. An analytic methods was complemented with experimental data obtained by DSC. The chemical heat contribution is modeled by two methods: analytical and an experimental. The composite was characterized in terms of the reaction progress. The coupled electromagnetic, chemical and thermal model show results that can be evaluated from the temperature evolution. There is an strong rise in the temperature in one point, which is due to the non uniformity of the heat-storage capacity along the composite to be treated. The region of validation of the model is also shown.