The α to β phase transformation of PVDF through the stretching process at different temperatures was investigated. The optimum stretching conditions were studied and characterised by infrared spectroscopy and differential scanning calorimetry. The maximum β−phase content was achieved at 80°C and a stretch ratio of 5. Accompanying the phase transformation, a orientation of the polymer chains and a packing of the crystalline structure is observed. The stretch ratio does not significantly affect the degree of crystallinity.

β-Poly(vinylidene fluoride) (β-PVDF) exhibits ferroelectric properties due to the special arrangement of the chain units in the crystalline phase. The piezoelectric properties of the material can be optimised by poling the original stretched film. The main effect of the poling process is the alignment of the randomly organised dipolar moments against the applied field. In this work, poled and non-poled β-PVDF from the same batch are characterised by dielectric spectroscopy. The origin of the electrical and mechanical response of poled and non-poled β-PVDF were further explored by far IR spectroscopy and discussed on a molecular level. The main effect of the poling process on the dielectric response of the material is a small increase of the dielectric constant due to the preferential alignment of the main dipolar contribution and a slight decrease of the dielectric loss, due to the more organized amorphous structure. The conductivity is strongly increased by poling, especially the high-temperature conductivity, ascribed mainly to hopping conductivity due to free charges induced during poling. FTIR experiments indicate that the origin of these effects and also of the variations in the thermo-mechanical response of the material can be found in the reorientation of the crystalline dipoles along the poling field, together with a partial reduction of the amount of α phase and an increase of the amount of β phase. The α to β transformation, mainly due to the stretching process, seems to be optimized by the poling process.

The a -* , phase transformation of PVDF through the stretching process at different temperatures was investigated. The optimum stretching conditions were studied and characterised by infrared spectroscopy and differential scanning calorimetry. The maximum a-phase content was achieved at 80°C and a stretch ratio of 5. These samples were poled at several electric fields by the corona charge method. The effect of the electric field on the phase transformation was studied by infrared spectroscopy.

The kinetics of the isothermal crystallization of the γ-phase Poly(vinylidene fluoride) has been investigated. Samples were prepared from the melt at different crystallisation temperatures and the variation of the microstructure of the samples was monitored with time by optical microscopy. Raman and Infrared transmission spectroscopies also show the appearance of the γ-phase for higher crystallisation temperatures. Two types of γ-phase spherulites have been identified. These spherulites represents different ways to obtain the γ-phase and show different thermal stability. The correlation between microstructure and kinetic parameters allows the tailoring of the microstructure by choosing the crystallisation conditions of the samples.