Effect of the mechanical stretching on the ferroelectric properties of a (VDF/TrFE) (75/25) copolymer film

Abstract

The transition phase behaviour of a vinylidene fluoride–trifluoroethylene (VDF–TrFE) copolymer film was studied after being subjected to different mechanical stretching levels in both longitudinal (L) and transversal (T) directions relatively to the initial extrusion direction. Both ferroelectric–paraelectric (FE–PE) and melting transitions were detected in the films by differential scanning calorimetry, that were not affected by L stretching. This suggests that sliding mechanism along the c-axis of such films during plastic deformation influences slightly the all-trans chain conformations and the CF2 dipole orientation. On the other hand, the FE–PE peak decreases in area and temperature upon T stretching, indicating a damage of the ferroelectric phase. However, the melting peak maintains unchanged. This fact provides evidence that the mechanical stretching do not change the total degree of crystallinity. The results suggest that the stretching induces a FE–PE phase transformation, without affecting the degree of crystallinity.