Study of the α-relaxation of PVC, EVA and 50/50 EVA70/PVC blend

The dipole dynamics and alpha-relaxation behaviour of polyvinyl chloride PVC, poly(ethylene-co-vinyl-acetate) EVA(70) and blend of them EVA(70)/PVC have been investigated by differential scanning calorimetry (DSC) and dielectric relaxation spectroscopy (DRS). The differential scanning calorimetry (DSC) thermograms measured on samples show a single glass transition in the analysed temperature range. These three polymers are wholly amorphous and pure PVC and pure EVA(70) are miscible in the ratio 1:1. The glass transition temperature T-g decreases significantly with presence of EVA(70). Furthermore, the values of apparent activation energies for molecular motions at the alpha-relaxation and the values of fragility index have also been determined for each sample using Moynihan expression for DSC results and Vogel-Fulcher-Tammann-Hesse (VFTH) form for DRS results. It is shown a large dependence of all the values of these parameters with the content of EVA(70). Comparing these three polymers, we found that the more fragile glass forming liquid is the PVC. Fragility decreases drastically with EVA(70) content. EVA(70) and EVA(70)/PVC blend exhibit practically the same behaviour. The effect of inter- and intra-molecular interactions on fragility is discussed to explain these variations. (c) 2004 Published by Elsevier Ltd.