A thermal degradation study of polyesterurethane based on 4,4’-diphenylmethane di-isocyanate interacted with "d"-block cations is presented. Studies were made of the influence of both the atomic number Z in the 3d series (Cr3+, Fe3+, Co2+ and Cu2+) and of the principal quantum number n = 3, 4 and 5 (Cu2+, Ag+, Au3+). For the relationship between the activation energy and the reacted fraction, an analytical equation that we proposed in a previous publication was verified. The physical parameter z*/r, calculated using Slatter’s rules, gives semi-quantitative information on the thermal behavior of these compounds.