Development of poly(vinylidene fluoride)/thermoplastic polyurethane/carbon black-polypyrrole composites with enhanced piezoelectric properties

Poly(vinylidene fluoride)/thermoplastic polyurethane (PVDF/TPU) composites filled with carbon-black polypyrrole were prepared via melt compounding followed by compression molding and fused filament fabrication. CB-PPy was added to the blends from 0 up to 15% to possible act as nucleating filler for PVDF β phase in order to increase its piezoelectric response. The influence of blending PVDF and TPU and of the addition of CB-PPy on the overall crystallinity, content of β phase, and piezoelectric response of composites were investigated by differential scanning calorimetry (DSC), Fourier-transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD) and determination of the piezoelectric coefficient (d33). It was found that the addition of TPU to PVDF induced an increase of the crystallinity degree and content of β phase in PVDF. Moreover, although the degree of crystallinity of the composites decreased with the addition of CB-PPy, the percentage of β phase in PVDF was increased. This effect is more significant in samples with filler concentration higher than 6 wt%. As expected, the d33 of the composites increased as the content of the β phase increased. Furthermore, 3D printed samples displayed lower content of β phase and reduced piezoelectric responses when compared to compression molded samples with same composition.