CONSIDERATIONS CONCERNING THE GLASS TEMPERATURE OF BLENDS OF MISCIBLEPOLYMERS

It is shown that experimental Tg vs. composition data of miscible poly mer blends can be adapted by a third order Tg vs. composition equation characterized by two parameters, K-1 and K-2, which result in the sup position that besides the thermodynamically claimed favourable energet ic hetero-interaction, contributions of conformational mixing entropy are responsible for miscibility. K-1 comprises mainly energetic intera ction effects, whereas K-2 is due to effects of the conformational mix ing entropy. It further results surprisingly that K-1 is roughly corre lated with the difference of the solubility parameters of the blend co mponents. At the moment no explanation can be offered for this observa tion.