Resumen:
In this work, PVDF-BaTiO3 composites were prepared using cryogenic high-energy ball milling (HEBM) and subsequent hot pressing. PVDF-BaTiO3 mixtures with different weight fractions of submicrometric BaTiO3 particles were subjected to 1h of active milling. By applying pressure at 200 degrees C the resulting powder was molded in the form of thin discs. This processing method allowed us to obtain an extraordinary uniform dispersion of the BaTiO3 particles within the PVDF polymer matrix. A morphological and structural characterization of the materials was done using conventional techniques (DSC, FTIR, XRD, SEM). Piezoelectric characterization of the specimens was also carried out by two different tests for inducing output voltage signals in the materials: i) single impact by ball free fall; and ii) macroscopic tapping. It was found that the output voltage decreases in both cases with the amount of BaTiO3 particles. The origin of this observation does not seem to be due to changes in the crystalline structure or morphology of the PVDF induced by the presence of BaTiO3. Rather, it can be explained taking into account that the constituents of the composites under study, BaTiO3 and PVDF, have opposite piezoelectric effects.
