Pyroelectricity in Nylon 7 and Nylon 11 ferroelectric polymers

Pyroelectricity is the electrical response of a material to a change in temperature. It exists in polymers which contain spontaneous or frozen polarization resulting from oriented dipoles. This review describes the physical basis for the existence of the pyroelectric effect and discusses its behavior in a number of amorphous, semicrystalline, crystalline and liquid crystalline polymers. Some of the techniques for measurement of the pyroelectric effect are presented and its use in pyroelectric relaxation spectroscopy and thermal analysis is described. The spatial distribution of polarization and space charge through the thickness of polymer films can be determined by several thermal pyroelectric techniques. Recent developments in the integration of pyroelectric polymer infrared detectors with solid-state silicon devices are described. One of the most important recent applications of polymers is in photopyroelectric spectroscopy which can be used for the determination of a number of thermal and optical properties of materials. Finally, some miscellaneous applications in physics, chemistry and biology are presented.Polar liquid crystals (LC) seem to,be very interesting materials for pyroelectric applications, due to the strong orientation of

Section: Polyamidesmentioning

confidence: 84%

Pyroelectric polymer electrets

Bauer

Lang

1996

“…One of the first reported alternatives to PVDF is the odd nylon system, which consists of a planar -CH 2 -backbone with polar carbonyl -C=O dipoles sticking out of the same side of the chain. The odd nylons [53][54][55][56][57][58], which have all the carbonyl groups on the same side of the molecule, are indeed ferroelectric, with polarizations increasing with carbonyl content, ranging from 40 mC/m 2 to 130 mC/m 2 [56], which is comparable to the range for PVDF and its copolymers. The odd nylons are inexpensive and easy to process and make good piezoelectric [53][54][55] and pyroelectric [53,57,59] materials.…”

Section: Other Ferroelectric Polymersmentioning

confidence: 73%

Why ferroelectric polyvinylidene fluoride is special

Poulsen

Ducharme

2010

Ferroelectric polymers entail a number of constraints, which together limit the useful compositional variations. These constraints include the following: a stable molecular dipole moment, compact crystal structure, conformational flexibility, and minimal steric hindrance. They are well satisfied by the prototype ferroelectric polymer, polyvinylidene fluoride, and yet almost every other conceivable molecular structure is limited by comparison.

“…Polyamide 11, [-NH-(CH 2 ) 11 -CO] n commonly known as Nylon 11 (N11), exhibits piezo/pyro/ferroelectric properties [11][12][13]. The electroactive properties of N11 are similar to those of PVDF, if their responses are compared above the respective glass transition temperature.…”

Section: Introductionmentioning

confidence: 97%

Space charge and dipolar charge contribution at polar polymers polarization

Neagu

Lança

Dias

et al. 2015

The thermally stimulated discharge current, the final thermally stimulated discharge current, DC conductivity and the final thermally stimulated discharge current with partially blocking electrode measures were used to analyze electrical behavior of Nylon 11. The objective was to discriminate between dipole related effects and space charge related effects. The space charge effects are dominant in the temperature range from room temperature to 170  C. By using a Teflon-FEP partially blocking electrode, the space charge injected in the sample is diminished and the effects related to dipole movement can be observed. Beside the two known relaxations for Nylon 11, one associated with the glass transition around 60  C and a second one associated with a molecular motion in the rigid-amorphous phase at 96  C, a weak relaxation was observed around 168  C. The peak around 96  C is quite broad been composed of two narrow peaks. The final thermally stimulated discharge current method allows a better selection of the experimental conditions for sample charging (polarization) to have only a partial overlap between the nearby peaks. The peak's maximum current and temperature are dependent on the ratio between the charging and discharging time and temperature given a possibility to discriminate between dipolar and space charge effects. A pyroelectric current changes sign around 140  C indicating that the amidegroup dipoles are frozen in opposite directions when the sample temperature is below 140  C (amorphous and rigid-amorphous phase) or above (crystalline phase). The conductivity is controlled by the competition between n(E,T) and μ(E,T) indicating a space charge controlled conductivity mechanism.