Fragility – Density of state and relaxation processes in polymeric materials

The values of different parameters defined in the Random Walk Model (RWM) as: the Density of Possible Metastable States g(E), the metastable state number NE, the apparent activation energy Ea/R and, the Cooperative Rearranging Regions distribution σ, have been calculated at Tg for two polymeric sample families (PVC, EVA70, PVC/EVA70 blend, and Unsaturated Polyester Resin samples). We show that these quantities allow to describe the configurational space, and we verify that the evolutions found for these different parameters versus the fragility are in a good agreement with the Strong-Fragile concept predictions.