THE GLASS TEMPERATURE OF POLYMER BLENDS - COMPARISON OF BOTH THE FREE-VOLUME AND THE ENTROPY PREDICTIONS WITH DATA

Experimental glass temperatures for 30 compatible blends have been compared with an equation derived from the hypothesis that the glass temperature is determined by conformational entropy changes and with the well known glass transition temperature (T(g)) versus composition equation of Fox based on volume additivity. Since these equations neglect interactions, it is not surprising that they fail in predicting at least half the experimental T(g) data. Nevertheless the approximate equivalence of the predictions of these two equations suggests that the glass temperature of an infinite molecular weight polymer is proportional to the mass divided by the number of flexible bonds of the monomer unit. As the interactions are disregarded, the two equations are zero-order treatments and thus they can both be improved.