Correlations between dynamic fragility and dynamic mechanical properties of several amorphous polymers

In the present paper, dynamic mechanical properties were measured for several amorphous polymers ranging from strong to fragile. The results indicate that the storage modulus changes steadily, and the loss modulus peak and the tan delta peak are broader for strong glass-forming polymers. Three variables, the steepness index (S), the transition wideness (W) of storage modulus and the integration area (A) of tan delta, were defined to illustrate the potential correlation between the dynamic fragility index (m) and the dynamic mechanical properties. It is found that W and A can be correlated with m by power law equations, while an exponential relationship between S and m is observed. Moreover, as m decreases, the tan delta peak is more and more apart from the loss modulus peak and the point where the storage modulus begins to drop. These phenomena are interpreted in terms of chain packing efficiency. (C) 2009 Elsevier B.V. All rights reserved.