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Abstract

Content

Introduction

The electrets — electric analogue of the permanent magnets currently widely used. Their range of uses stretches from the home appliance (a well – known high – quality electret microphones) to special equipment (for example, electret dosimeters, electret hydrophones, etc.). Practical need of obtaining electrets with desired properties has stimulated and continues to stimulate physical tests of a sufficiently complex phenomena underlying the so – called electret state of the dielectrics [1].

1. The relevance of the topic

Polymer materials rapidly entered and occupied a significant place in human life, plastics surround us every step of the way, from packaging, plastic tableware and finishing construction materials and parts of equipment and machines. Perhaps when the idea was to produce plastic products, and she was entirely positive in nature, as the introduction of plastics allowed greatly to reduce the consumption of natural resources. In addition, such production is a great source of income, because the production costs of these materials are minimal and selling them brings manufacturers a huge profit.

Despite all the positive aspects of the introduction of plastics in human life, there is a reason why in recent years scientists from many countries are seeking ways of disposing and recycling plastic waste lies primarily in the fact that for the decomposition of polymeric materials requires not a century, and the rate of production of plastics each year is rapidly increasing.

One option of recycling of plastic wastes is receiving electret materials, which can then be used as alternative sources of energy, production of which today plays an equally important role.

2.The purpose and research tasks, planned results

Key tasks:

1) comparative analysis of using different types of waste household plastics (packaging, PET, etc.);

2) Designing the facility to conduct electroterapia polymer under high voltage;

3) Create termoelectrica based on natural dielectrics for further study and comparison of the properties possessed by the "artificial" and "natural" electrets;

4) analysis of the characteristics of electrets made of different polymeric compositions;

5) Practical application of the obtained samples.

Expected results: the result of the study is planned to thermoelectret with "quasiphotons" electric field, which will be prototypes for demonstration of the properties possessed by the electret.

3. Literature review

3.1 Basic information about the electrets

In the history of science knows of cases where some of the similarities between the different nature, but with a formal external similarity of the phenomena contributed to the discovery of new effects.

In 1732 S. Gray mentioned electret behavior of dielectrics, pointing to "the eternal power of attraction" of some of them, especially waxes, resins and sulfur. Static electricity in these materials, it was obtained by contact electrification in the cooling of their melt in an iron crucible.

More than a century later, in 1839 Electret properties due to the superposition of the external electric field, have attracted the attention of Faraday, who in his theoretical descriptions have referred to a "dielectric material that retains an electric moment after switching off the external field". The term "electret" was the use of O. Heaviside in 1892 [2].

The electret is a dielectric that has on the surface electric charges, long lasting in time. Electret properties of polymers are closely associated with electrostatic properties, and, in fact, they could be considered together. However, in the process of development of the science of electrets was that the development of electrets with high settings, theory of electrostatic properties of dielectrics can be used only very limited, and on the contrary it is the development of the science of electrets has contributed to the development of ideas about electrostatic phenomena in insulators. During the research of the electrets was found so much new that justified the consideration of electret properties apart from electrostatic, the more that the electrostatic properties are considered primarily as something negative, disturbing production processes, leading to fires, defects, and electret — like positive characteristics that influence the suitability of a dielectric for the manufacture of products [3].

If electrostatic charges occur primarily by chance, then an electret — as a result of special processing of the dielectric. Depending on the technology for there are different types of electrets:

– Termoelectrets — et-cooled pre–heated dielectrics in an electric field of high tension to temperatures below the glass transition temperature or curing;

– Crioelectrets is obtained by drying of a solution of a dielectric in an electric field (without preheating);

– Radiation electrets is obtained by irradiation of dielectrics charged particles (electrons, protons) and neutral particles or γ–radiation by simultaneous or subsequent exposure to a constant electric field;

– Cronoelectrets — they get charged in a corona discharge under heating or without heating;

– Electroelectrets get exposure (without heating) to the dielectric constant electric field with intensity close to the breakdown;

– Chemoelectrets — get chemical crosslinking (vulcanization) of the polymer dielectrics in the electric field or by polymerization in an electric field;

– Mechanoelectrets is obtained by pressing or other methods of molding polymer samples without the influence of an electric field from an external source;

– Magnetoelectrets — obtain thermomagnetic processing of dielectrics without the influence of an electric field from an external source.

The electrets have their surfaces equal and opposite charges, however, recently appeared the so&ndashcalled nanoelectrode — the samples of insulators, having equal charges of the same sign from different angles. The stability of electret charge is provided (in addition to low electrical conductivity of the electret material and a large relaxation time of the dipole orientation) the presence of protivoparaz on the opposite charged surface or by electrodes located in close proximity to a charged surface. In these cases, the system capacity increases sharply, and correspondingly increases the relaxation time.

The electrets obtained after the static electrification or friction, sometimes called "static electrets" or "triboelectrets".

In addition to these methods for producing electrets there is still a way of charging with liquid electrodes, in which a high voltage is applied to sputtered on the surface of the polymer to the metal electrode, and on the other to the fluid surrounding the opposite surface. The liquid is then drained, surface dried, and obtained an electret with a surface potential, corresponding exactly to the applied voltage.

All the electrets can be divided into two groups: electrets that have dipole charges, and electrets that have injectionem from outside charges. In the first case the sign of the charge on the surface opposite to the sign of the voltage at the adjacent electrode, so this kind of charges also referred to as heterokaryon; in the second case, the sign of the charge on the surface is the same as the voltage at the adjacent electrode, this charge is called homearama. However, heterothera may occur not only due to the dipole orientation, but also from the displacement of ions in the polarization process [4] .

3.2 Application of thermoelectrets

The electrets, and in particular termoelectrets, find the application:

1) as a dielectric, which is the source of the external electric field,

2) as a dielectric, having an internal polarization,

3) as the piezoelectric materials ,

4) as pyroelectric.

As the dielectrics are the sources of the external electric field, the electrets are widely used in filters, to control electron beams, in particular for their focus in electromechanical transducers — microphones, vibration sensors.

The most widely electret condenser microphones, which are produced in millions of pieces per year. Their use greatly simplifies the design, reduces the size of the microphones to the size of ~5 mm while improving their quality (for example, the linearity characteristics of commercially available microphones is maintained in the range of 50 — 16, 000 Hz). Made and special electret microphones for the study of ultrasound and infrasound. Widespread fibrous electret filters L90J, produced abroad under the title “filtret”. These filters are cheap, several times faster than the previously used fibrous filters are effective for respiratory protection from industrial and radioactive dust.

Imparting electret properties of artificial blood vessels and artificial parts of the heart and reduces blood clots.

In the second capacity that the electrets can be used as a kind of battery. Heating of the electret, for example in an emergency situation, may give the TSD current, sufficient to power the transmitter .

As piezoelectric materials polymer electrets used in stereo headphones, cartridges, lighters, for the manufacture of fans. Currently patented over 40 different examples of the application of piezoelectric polymer film of polyvinylidene fluoride just. Of particular interest is its use in hydroacoustics, switching systems in fiber optics for generating a focused ultrasonic signal, to prevent fouling of hulls by algae and mollusks .

As pyroelectrical promising application of polymer electrets (e.g., based on polyacrylonitrile) for the direct conversion of solar energy into electrical energy for visualization of infrared radiation (polyvinylidene fluoride) in different produtcion and other areas [9].

4. The experimental installation

4.1 Description of the experimental setup

One of the main elements of the experimental setup (Fig. 1) is the electric furnace 1 with a device for setting and maintaining at the set temperature of the heating surface 2. Oven placed on a metal cylinder 3, inside of which will be the melting and electroterapia polymer composite. On the surface of the material 4 is overlaid structure consisting of a metal disk 5, stock with needle 6 and the spring 7. The spring and the disk is necessary for leveling the surface of the sample in the melting process. To minimize heat exchange with the environment, the cylinder is covered with a lid 8, and then on top of the rod fits over the latch speed 9. Simultaneously with the melting is conducted electrotrauma, the cylinder body 3 and the end of the rod 6 is attached to electrodes leading current from the high voltage generator 10 to be installed.

On the surface of the material 4 is overlaid structure consisting of a metal disk 5, stock with needle 6 and the spring 7. The spring and the disk is necessary for leveling the surface of the sample in the melting process.

To minimize heat exchange with the environment, the cylinder is covered with a lid 8, and then on top of the rod fits over the latch speed 9. Simultaneously with the melting is conducted electrotrauma, the cylinder body 3 and the end of the rod 6 is attached to electrodes leading current from the high voltage generator 10 to be installed.

Экспериментальная установка

1 —the electric furnace , 2 — temperature regulator,3 — metal cylinder ; 4 —the surface of the material , 5 —metal disk , 6 — stock with needle, 7 — the spring , 8 — a lid , 9 — the latch speed , 10 — the high voltage generator

Figure 1 — The experimental intallation
(animatio: 8 frames, 10 cycles of repeating, 28,1 kilobytes)

4.2 Experiment

Experiment is performed in several stages.

Step 1: Create a sample of natural polymers. As natural polymers taken wax and rosin in the ratio of 35: 65 %. The method of manufacture of electrets is widely distributed, and is described in detail in the literature [7].

"Natural" electret serves as a model for comparison of the main indicators, such as the electric field and surface charge density.

Step 2: Development of polymer composition, electrotrauma, measurement of key indicators and analysis of the obtained results.

Step 3: implementing practical applications of electrets made.

Insights

Getting the electret materials of polymer may be considered as one of the ways of solving the problem of disposal of plastic waste, according to the results of the experiments of many scientists working in this direction.

When writing this abstract the experimental part of the master's work is in progress. A full description of the experiments and the results of their conduct can be obtained from the author or scientific adviser after this date.

The list of sources

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  2. Мяздриков  О.А., Манойлов  В.Е. Электреты. — М.; Л.: Госкомэнергоиздат, 1962. — 99 с .
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  4. Лущейкин  Г.А. Методы исследования электрических свойств полимеров. — М.:Химия, 1988. — 160 с.
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  6. Бартенев  Г.М., Зеленев  Ю.В. Физика и механика полимеров. — М.: Высш. Школа,1983. — 391 с.
  7. Губкин  А.Н. Электреты. — М.:Наука, 1978. — 192 с.
  8. Сесслер  Г. Электреты. — М.: Мир, 1983. — 487 с.
  9. Лущейкин  Г.А. Электретный эффект в полимерах. Достижения в получении и применении электретов. // Успехи химии. 1983. — Т. 52. — Вып. 8. — с. 1410—1431.
  10. Дудышев  В.Д. Новые методы извлечения скрытой энергии потенциального электрического поля в кинетическую энергию и электроэнергию. [Электронный ресурс]. — Режим доступа: Изобретения Дудышева