Desenvolvimento e caracterização morfológica e cristalina de nanomembranas piezoelétricas de poli(fluoreto de vinilideno) HFP e TRFE dopadas com nanotubo de carbono

Abstract

Piezoelectric materials are investigated by several authors due to the wide application in the energy scenario and as sensor / actuators. Although the use of ceramic materials is very important, the class of piezoelectric materials known as piezopolymers has gained prominence due to the low toxicity, better stability and processing of these materials, especially polyvinylidene fluoride (PVdF) and its copolymers. The main focus of this work was to investigate the crystallinity of poly(vinylidene fluoride-co-hexafluoropropylene) - PVDF HFP and poly(vinylidene fluoride- trifluoroethylene) - PVDF TrFE nanomembranes produced from a polymer solution containing a ratio of 88/12 mass of solvent / solute and solvent as DMF and acetone in a volumetric ratio of 60 / 40. The synthesis of nanomembranes was done using the electrospinning technique, to induce a beta phase formation, which is responsible to the piezoelectric behavior. Carbon Nanotubes (CNT) were added in the following concentration: 0.15%, 0.30% and 0.60% (w / w) during the synthesis of the nanofibers, and the effect generated on the polymorphism of PVDF by nanostructures was evaluated. To ensure a better dispersion of CNT in the polymer solution, a surfactant Sodium Dodecylbenzene Sulfonate (SDBS) was used in the proportion of 0.01% of carbon nanotube and 200ppm SDBS. The morphological analyzes were performed by Scanning Electron Microscopy (SEM), as well as the analysis of the crystalline phases using Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR) and X Ray Diffraction (XRD). Surface wettability of the nanowires was evaluated by the contact angle between the perimeter of a water drop and the surface. The hydrophobicity tests show a hydrophobic character for most nanomembranes, except for fibers doped with 0.60% CNT functionalized, in wich case the result was a contact angle well below 90 °. The results of the XRD and FTIR analyzes indicated that the nanomembranes with a lower concentration of functionalized nanostructure had an increase in crystallinity as a whole and especially in the beta phase. From the morphological failure-from-spring analysis to the nanometric carbon-fiber and standard-pattern values, similar to a sample of a carbon nanotube in the fibers and standard-pattern values processing from the electrospinning technique. The DSC results indicate an increase in the crystallization temperature for CNT polymer solutions and that this technique can be used in a complementary manner to the FTIR and XRD.