TY - JOUR A1 - Zhang, Xiaoqing A1 - Zhang, Xinwu A1 - You, Qiong A1 - Sessler, Gerhard M. T1 - Low- cost, large- area, stretchable piezoelectric films based on irradiation- crosslinked poly ( propylene) JF - Macromolecular materials and engineering N2 - Low cost, large area, lightweight, stretchable piezoelectric films, based on space-charge electret with a foam structure (i.e., ferroelectrets or piezoelectrets), have been fabricated by using commercially available irradiation cross-linked poly(propylene) (IXPP) foam sheets. Piezoelectric d(33) coefficients are as high as 100pCN(-1). The piezoelectric performance in such IXPP films is well preserved for repeated strains of less than 10%. Piezoelectric d(33) coefficients are frequency independent in the range from 2 to 100Hz. Such new class materials may be applied in sensory skins, smart clothing, bio-inspired systems, microenergy harvesters, and so on. KW - crosslinked poly(propylene) KW - ferroelectret KW - piezoelectricity KW - stretchability Y1 - 2014 U6 - https://doi.org/10.1002/mame.201300161 SN - 1438-7492 SN - 1439-2054 VL - 299 IS - 3 SP - 290 EP - 295 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Mellinger, Axel A1 - Mellinger, Olena T1 - Breakdown threshold of dielectric barrier discharges in ferroelectrets where Paschen's law fails JF - IEEE transactions on dielectrics and electrical insulation N2 - The piezoelectric activity of charged cellular foams (so-called ferroelectrets) is compared against simulations based on a multi-layer electromechanical model and Townsend's model of Paschen breakdown, with the distribution of void heights determined from scanning electron micrographs. While the calculated space charge hysteresis curves are in good agreement with experimental data, the onset of piezoelectric activity is observed at significantly higher electric fields than predicted by Paschen's law. One likely explanation is that the commonly accepted Paschen curve for electric breakdown in air poorly describes the critical electric field for dielectric barrier discharges in micrometer-size cavities. KW - Ferroelectrets KW - dielectric barrier discharges KW - piezoelectricity KW - Paschen's law Y1 - 2011 U6 - https://doi.org/10.1109/TDEI.2011.5704491 SN - 1070-9878 VL - 18 IS - 1 SP - 43 EP - 48 PB - Inst. of Electr. and Electronics Engineers CY - Piscataway ER - TY - JOUR A1 - Kappel, Marcel A1 - Abel, Markus A1 - Gerhard, Reimund T1 - Characterization and calibration of piezoelectric polymers in situ measurements of body vibrations JF - Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques N2 - Piezoelectric polymers are known for their flexibility in applications, mainly due to their bending ability, robustness, and variable sensor geometry. It is an optimal material for minimal-invasive investigations in vibrational systems, e.g., for wood, where acoustical impedance matches particularly well. Many applications may be imagined, e. g., monitoring of buildings, vehicles, machinery, alarm systems, such that our investigations may have a large impact on technology. Longitudinal piezoelectricity converts mechanical vibrations normal to the polymer-film plane into an electrical signal, and the respective piezoelectric coefficient needs to be carefully determined in dependence on the relevant material parameters. In order to evaluate efficiency and durability for piezopolymers, we use polyvinylidene fluoride and measure the piezoelectric coefficient with respect to static pressure, amplitude of the dynamically applied force, and long-term stability. A known problem is the slow relaxation of the material towards equilibrium, if the external pressure changes; here, we demonstrate how to counter this problem with careful calibration. Since our focus is on acoustical measurements, we determine accurately the frequency response curve - for acoustics probably the most important characteristic. Eventually, we show that our piezopolymer transducers can be used as a calibrated acoustical sensors for body vibration measurements on a wooden musical instrument, where it is important to perform minimal-invasive measurements. A comparison with the simultaneously recorded airborne sound yields important insight of the mechanism of sound radiation in comparison with the sound propagating in the material. This is especially important for transient signals, where not only the long-living eigenmodes contribute to the sound radiation. Our analyses support that piezopolymer sensors can be employed as a general tool for the determination of the internal dynamics of vibrating systems. KW - acoustic transducers KW - calibration KW - durability KW - electric sensing devices KW - piezoelectricity KW - polymers Y1 - 2011 U6 - https://doi.org/10.1063/1.3607435 SN - 0034-6748 VL - 82 IS - 7 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Altafim, Ruy Alberto Pisani A1 - Rychkov, Dmitry A1 - Wirges, Werner A1 - Gerhard, Reimund A1 - Basso, Heitor Cury A1 - Altafim, Ruy Alberto Pisani A1 - Melzer, Martin T1 - Laminated tubular-channel ferroelectret systems from low-density Polyethylene Films and from Fluoroethylene-propylene Copolymer Films - A comparison JF - IEEE transactions on dielectrics and electrical insulation N2 - A template-based lamination technique for the manufacture of ferroelectrets from uniform electret films was recently reported. In the present work, this technique is used to prepare similar ferroelectret structures from low-density polyethylene (LDPE) films and from fluoro-ethylene-propylene (FEP) copolymer films. A comparative analysis of the pressure-, temperature-, and frequency-dependent piezoelectric properties has been performed on the two ferroelectret systems. It is observed that the FEP ferroelectrets exhibit better piezoelectric responses and are thermally more stable. The difference between the piezoelectric d(33) coefficients of the two ferroelectret systems is partially explained here by their different elastic moduli. The anti-resonance peaks of both structures have been investigated by means of dielectric resonance spectroscopy and electroacoustic sound-pressure measurements. A difference of more than 10 kHz is observed between the anti-resonance frequencies of the two ferroelectret systems. KW - Ferroelectrets KW - piezoelectrets KW - piezoelectricity KW - electro-mechanical transducers KW - static-pressure dependence KW - temperature dependence KW - frequency response Y1 - 2012 SN - 1070-9878 VL - 19 IS - 4 SP - 1116 EP - 1123 PB - Inst. of Electr. and Electronics Engineers CY - Piscataway ER -