DSC analysis indicated that the Tg of f-MWNTs/Elvaloy4170 MMM was higher than that of polymer membrane and increased as the nanotubes content increased in the polymer matrix. The increase in the Tg of f-MWNTs/Elvaloy4170 MMM is attributed to the restrictions of the polymer chains movement caused by a favorable interfacial interaction between f-MWNTs and Elvaloy4170 matrix. In other words, the incorporation of the nanotubes into the polymer matrix restricts the rotation of polymer chains and causes an increase in chain rigidity of the polymer, which in turn affects the characteristics of the continuous phase. These results are in accordance with former studies describing that dispersion of CNTs inside the polymer matrix increases the Tg of the resulting MMM [46] and [61].