Dynamic mechanical analysis and creep behaviour of β-PVDF films

In this work, tensile dynamic mechanical analysis (DMA) was used to characterise the solid-state rheological properties of a commercial β-polyvinylidene fluoride (PVDF) film in the two main directions (longitudinal and transversal to the stretch direction). The β-relaxation, assigned to the segmental motions within the amorphous phase, is observed at ∼−25 °C. The αc-relaxation is observed above room temperature. This relaxation is the main responsible for the anelastic properties of the material and to the short-term creep behaviour. Longer-term creep tests along the longitudinal direction were also performed and the Eyring model was applied, in order to characterize the flow-process within the polymeric structure. The results suggest that long-term creep is mostly controlled by the deformation of amorphous tie-chains that connect adjacent crystalline lamellae.