Conductivity piezoelectric PVDF

A series of pol)rvinylidene fluoride (PVDF) piezoelectric transducers were fabricated. Thick and thin PVDF materials have been Investigated for transducer production. Thinner films were superior because they conform better to the surface of the samples. After initial evaluation, the PVDF transducers will be used to conduct drying studies. 

We have for a number of years developed polymer-based piezoelectric textile filaments and yarns [44]. Filaments are melt spun and bicomponents core-and-sheath type based on a blend of a normal bulk polymer like high-density polyethylene and the piezoelectric material (PVDF), surrounding a core of a conductive polyethylene-carbon black mixture (see Fig. 28.25). The core is electrically conductive and will act like an electrode. 

Another strategy has to be chosen. This is to let the piezofiber (ie, the conductive core with high-density polyethylene (Aspun 6835A, Dow, USA) and carbon black (Ketjenblack EC-600JD Akzo Nobel, the Netherlands) and the piezoelectric sheath with PVDE (Solef 1006, Solvay Solexis, Italy)) mecharucaUy come into close proximity with a conductive thread. Here we take a thread from Class El above, Shieldex (Statex, Germany, silver-coated polyamide). By this we form a textile variant of the triad with the conductive carbon black core as the inner electrode, PVDF sheath as the active layer, and the Shieldex as the outer electrode. 

Among the electroactive polymers, electronically conducting polymers such as polypyrrole and polythiophene and piezoelectric polymers such as polyvinylidine fluoride (PVDF) are the most promising with regard to tissue engineering applications. 

GlauB et al. (2013) have reported the development of a PVDF fibre with a conductive core. The melt-spun bi-component fibre consists of a conductive polypropylene core (containing a 10 wt % carbon nanotubes and 2 wt% sodium stearate (NaSt)) covered with a PVDF sheath. The piezoelectric effects are achieved by draw winding, which favours the all-trans p phase formation. 

Magniez et al. (2013) have demonstrated a method to produce piezoelectric woven fabrics from melt-spun PVDF fibres, which were spun using a Busschaert bi-component extmder. The PVDF fibres were assembled with conductive fibres and were integrated into various woven stmctures, such as plain weave and 2x2 twill weave. A non-conducting nylon yam was used as insulation between two electrodes to prevent short-circuiting. The warp yams were PVDF, and the weft yams were silver-coated nylon. The fabrics were tested for electrical output using a 70 N impact force at a 1 Hz frequency, and a maximum output of 6 V was produced. 

A typical example for the frequency- and temperature-dependent dielectric properties of a piezoelectric polymer is given in Fig. 7 that displays the a-relaxation, related the dynamic glass transition, of a polyvinylidene fluoride (PVDF) film along with an upswing of the dielectric loss at low frequencies due to electrical conduction. 

Bauer and oo-workers (64,117] have conducted extensive studies ot the piezoelectric behavior of PVDF films in shock enviroomenls up to 200 kbar and have shown that they can make excellent transducers for shock-wave phenomena. 

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