The preparation and characterization of novel piezoelectric and pyroelectric electrets is discussed with respect to their electret properties. Charged heterogeneous electrets, like closed-cell microporous polypropylene (pp) foams and 'soft-hard' fluoropolymer hybrids are shown to yield large quasi-static and dynamic piezoelectric responses, indistinguishable from true piezoelectricity. Piezoelectric coefficients comparable to that of ceramic counterparts have been achieved. For the investigation of the piezoelectric and pyroelectric properties of the electret materials, the thermal-pulse technique has been extended towards temperature-dependent investigations and measurements on planar, cylindrical or spherical samples. The potential of the thermal-pulse technique not only for the measurement of electric-field and polarization distributions, but also for acoustical, electromechanical and pyroelectric properties is outlined.

Preparation and characterization of novel piezoelectric and pyroelectric polymer electrets

Scientific advancement is highly inspired and imitative of natural phenomenon’s, which exhibits extremely developed and well-organized nanostructures to cope with challenges under different environmental circumstances, such as moth eyes protuberances for efficient antireflective (AR) performance Innovative researches have been performed in the past to exterminate the undesirable reflectance in common optical components and optoelectronic industrial applications by biomimetic and replicating moth eye nanostructures creating gradient effect using metal oxides, composites, or polymers in multilayer AR coatings However, in few multilayer AR designs, the properties mismatch at interfaces, high cost, low mechanical durability, wetting issues, or thermal stability bounds their practical applicability Herein, we develop an approach for fabricating efficient, high-performance Teflon (polytetrafluoroethylene [PTFE]) AR nanostructures for glass-based supporting materials Nanotailoring, the morphology and structu

Al2O3 Encapsulated Teflon Nanostructures with High Thermal Stability and Efficient Antireflective Performance

Publisher Summary This chapter discusses polymer electrets for electronics, sensors, and photonics. Charging and poling can be viewed as an additional degree of freedom in the design of polymer electret devices. As a result, flexibility is achieved with which other materials—such as inorganic crystals or semiconductors—can hardly compete. The survey on measurement techniques presented in the chapter concentrates on new experimental analysis schemes—based on piezo-, pyro-, as well as linear and nonlinear optical effects—that complement traditional techniques from electret research. Charge electrets carry a quasipermanent excess charge trapped at their surface or in their bulk. Bulk trapping is possible in amorphous phases and crystalline phases and in semicrystalline polymers at interfaces between the amorphous and crystalline regions. Charge electrets are based on good insulating polymers with small dielectric losses. Dipole electrets show a preferential orientation of molecular dipoles—that is, frozen, quasipermanent dipole orientation polarization in amorphous phases and permanent dipole orientation polarization in crystalline phases.

Polymer electrets for electronics, sensors, and photonics

The piezoelectric coefficient of commercial polyvinylidene fluoride piezoelectric film was found to decrease with increasing preload due to a stress-dependent modulus; preload had no effect on the pyroelectric coefficient, in keeping with current theory. Both coefficients demonstrated an irreversible rise on heating due to amorphous phase depolarization at the T g, near 80°C in this highly oriented material, following which these values were temperature-independent in the range 20–100°C.

Piezo- and pyroelectric properties of polyvinylidene fluoride

Preliminary measurements of the piezoelectric effect in commercially produced Teflon cables have been performed using simple static methods. The effective piezoelectric constants for both uniaxial strain and torsional strain were determined. The effect, though 2–3 orders of magnitude smaller than those of good piezoelectric materials, is potentially useful as the basis of inexpensive but sensitive strain transducers.

S. T. Liu

Papers

Piezoelectric Effect in Teflon Cable