To the purpose of studying the effect of composition on the glass transition temperature (Tg) of a series of polymer electrolytes based on blends of polyethylene oxide (PEG), poly (octafluoropentoxytrifluoroethoxy)phosphazene (PPz) and poly(epichlorhydrine), a mathematical model was applied to results obtained through DSC determination using seven ternary blends selected by an experimental design. The parameters of the model were chosen by means of stepwise linear regression method. The final model proved to be appropriate (R(2)=0.997; s=0.99 K) to predict the Tg values. From a structural point of view it was found that the lowest Tg values were obtained for the blends containing the smallest PECH portion.