Electret polymer

The described advantages of electret polymer coatings have not been called for until recently chiefly due to the lack of information and inaccessibility of electret techniques. It is taken for granted today that the electrically polarized state is a natural physical state of polymer dielectrics. The realization of merits that are intrinsic to polymer coatings may open new... 

Fig. 3.20. A scheme for a combined polymer antirust coating. (1) metal substrate, (2) passivating layer, (3) a layer of organic metal, (4) a layer containing corrosion inhibitors, (5) electret polymer layer...

The polarization induced in polymer dielectrics by the application of an electric field or by other charging treatments can, in a few cases, persist for long (ca. months) periods at room temperature. The polymers thus treated are termed electrets. Polymer films that have been subjected to this polarization treatment or poled manifest piezoelectric and... 

Looking beyond ceramic materials to electrets, polymer and elastomeric piezoelectric materials, and so-called electroactive materials, a wide-open field of research in high-strain piezoelectric materials is appearing. Using the same technology to manipulate the chemical and physi-... 

Electret Polymer Ferroelectret Dipole Charge Stability... 

Mellinger A, Camacho Gonzalez F et al (2004) Photostimulated discharge in electret polymers an alternative approach for investigating deep traps. IEEE Trans Dielectr Electr Insul 11 218-226... 

Arakawa Y, Suzuki Y, Kasagi N (2004) Micro seismic power generator using electret polymer film. 

They produced high performance electrets from thin polymer films metallized so as to yield high capacitance. Both electrical and mechanical properties of these transducers have been remarkable examples of how applications of science of solids, including knowledge of electron traps, conduction processes in insulators and the viscoelastic phenomena of semicrystalline polymers, can be combined.(6) Incidentally, similar ideas have been applied to optimization of the properties of particle microphones, through assemblies of perfectly microspherical polymer carbon systems. These have shown what limits of performance... 

Consideration of the structure of polyvinylidene fluoride (65) assuming a barrier of 3 kilo cal per mole for rotational minima of conformation of the chain by A. E. Tonelli (66) led to detailed conformation and its implications for dipole structure (Fig. 22). Indeed, the material can approximate a ferro electric. It is thus of interest in our expectations of the environments that polymers can provide for the creation of new phenomena. The total array of dipoles in polyvinylidene fluoride will switch in about 3 microseconds at 20°C with 200 megavolts per meter field. The system becomes much slower at lower temperatures and fields. But we do have a case of macroscopic polarization intrinsic to the polymer molecules, which thus supplements the extensive trapping and other charge of distribution phenomena that we have discussed in connection with electrets. 

Some of the insulating polymers such as poly (1, 1-difluoroethylene) meet the requirements of electret materials (the electric analogue of a permanent magnet) they respond to applied electric fields by limited movement of charge, and the charge does not leak back when the field is removed. 

Piezoelectricity in polymer films is greatly increased by polarizing the film under a high d.c. field at high temperatures. This effect, the piezoelectricity of a polymer electret, has attracted the attention of many investigators from the scientific as well as industrial point of view, since the early work by Kocharyan and Pachadzhyan (1963,1966) on PMMA and PVC. 

Murayama.N. Piezoelectric and pyroelectric effects of polymer electrets. Microsymposium on Electrical Properties of Polymers, Tokyo (Jan. 1972). 

Sturm H, Geuss M, Schulz E (1999) Scanning force microscopy investigations on electroactive polymer films. In Kosta AA (ed) Tenth International Symposium on Electrets (ISE10). IEEE, Piscataway, p 465... 

A spectacular relaxation phenomenon of polymeric materials is exhibited in a field-temperature treatment phenomenon. As was shown above, the polarisation of a polymeric material after application of an electric field increases after an instantaneous polarisation to the relaxed polarisation. If the electric field is subsequently released the polarisation decreases again with time. However, if the polarisation took place at a temperature above the glass transition temperature after which the temperature was decreased to a temperature well below Tg, then depolarisation is not possible, due to the immobilisation of the polymer molecules. In this way a so-called electret maybe formed, the electric counterpart of a magnet. 

Van Turnhout J, "Thermally Stimulated Discharge of Polymer Electrets", PhD Thesis, Leiden, 1972 as book published by Elsevier, Amsterdam (1975). 

Elastic effects in polymer melts, 578 Elastic moduli of some materials, 732 Elastic parameters, 383,386,391 Elastic shear deformation, 500, 531 Elastic shear quantities, 556 Electret, 329,331... 

It took a long time for this somewhat complicated behaviour of electrets to be sorted out, and in the meantime high-grade insulating polymers had been developed. The question then to be settled was what system would give the most stable electret, and this prompted a study of the relevant decay processes in polymers. 

Table IV. Charge Storage/Lifetimes of Some Polymer Electrets...

Wetton, R. E. Electret Thermal Analyses of Polymers, Society of Chem. 

Recent Advances in the Improvement of Polymer Electret Films... 

Keywords Charge storage properties Commodity polymers Corona charging Electret materials High performance polymers Physical aging Polymer films... 

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