Activation energy dependencies obtained from model-free analysis demonstrated that the activation energy of thermal decomposition of GAP/TEX mixture is lower than that of the pure GAP and TEX components. In the absence of any chemical interaction between the components of the GAP/TEX mixture, the predominance of mass-transfer controlled gas diffusion mechanism over the kinetically controlled nuclei growth in the mixture was anticipated. The early stages of degradation of mixture are determined by the thermal decomposition of polymer (α > 0.25), whereas the later stages (0.25 ≤ α ≤ 1) are determined by that of TEX