A double-step compression molding to improve the dielectric properties of PVDF and PVDF-based composites

In the present work, an alternative method to induce the formation of PVDF ? phase was proposed, exploiting a well-known technique widely used for the polymer processing: the compression molding. In particular, it was used a double step process (P2), which consists in preparing a plate of material (i.e. neat PVDF or composite) and then repressing it at high pressure and at a temperature lower than the PVDF melting temperature. As concerns the neat PVDF, the molding conditions were modified to investigate their influence on the final amount of electroactive phase(s) obtained. The impact of processing on dielectric and dynamic-mechanical properties of the PVDF films was also studied on a selected series of samples. PVDF-based composites containing different amount of ceramic particles (such as BaTiO3 and PZT), widely used in the field of energy harvesting, were then prepared by solvent casting or melt blending. Besides a single-step (P1) molding carried out on samples with completely molten PVDF, also the P2 process was applied to the composites in order to investigate its effect on their final properties. The ensuing samples were characterized from morphological, spectroscopic, dynamic-mechanical and dielectric point of views.