Technique and installations for electromagnetic treatment in the formation of composite polymer coatings

ABSTRACT

In the present machine-building industry in Uzbekistan, innovative work has appeared on changing the properties of various polymers due to the influence of an external electromagnetic field, which makes it possible to obtain coatings with an oriented structure. The processes of processing coated parts in an electromagnetic field are technologically advanced and safe, as well as cheaper in comparison with other chemical and physical modification methods.

АННОТАЦИЯ

В настоящее машиностроительном производстве в Узбекистане появились инновационные работы по изменению свойств различных полимеров за счет воздействия внешнего электромагнитного поля, которое позволяет получать покрытия с ориентированной структурой. Процессы обработки деталей с покрытием в электромагнитном поле технологичны и безопасны, а также более дешевые по сравнению с другими химическими и физическими методами модификации.

Ключевые слова: Полимеры, композиционные материалы, электромагнитная поля, жидких и твердых тел, механические, соединение, метод, постоянный ток, напряжение, электромагнитная установка.

Keywords: Polymers, composite materials, electromagnetic fields, liquids and solids, mechanical, compound, method, direct current, voltage, electromagnetic setting.

Electromagnetic installation for processing composite polymer coatings. Analysis of published works shows that existing devices for magnetic processing of liquids and solids are diverse in design and principle of operation. However, the considered devices are quite complex in design, require special cooling and do not withstand long-term operation, while for polymeric materials it is necessary to carry out treatment with a magnetic field for a long time of curing. [4, 108, 109].

By the nature of the magnetic field, all devices can be divided into two groups:

1) for processing substances in a constant magnetic field;

2) for processing in a variable field.

By the method of creating magnetic fields - by four:

1) with permanent magnets;

2) in the form of magnetizing coils (solenoid type);

3) with DC electromagnets;

4) with alternating current electromagnets.

Devices with permanent magnets have a field strength of up to 4000 A / m, an annular gap of no more than 15 mm. The length of the magnetic zone is 20-40 mm.

The rejection of devices with permanent magnets is due to the fact that the magnetic flux created by them is unstable - it changes over time and when exposed to external conditions of magnetic fields, mechanical loads, temperature, radiation, the effect of ferromagnetic masses, as well as change in magnetic resistance.

Magnetizing coils - solenoids of the required voltage (about 40,000 A / m) are difficult to manufacture, consume a lot of power and require special devices for cooling. Devices with DC electromagnets are quite simple to manufacture, low power consumption and long-term operation (without forced cooling) makes them convenient for operation. The processing area of such devices is outside the coil and has an ambient temperature, i.e. not higher than 313 K in the conditions of Central Asia. Considering this, the temperature regime in the processing zone was considered satisfactory. Diverse and numerous designs of apparatus used for magnetic processing of substances contributed to the development of various methods for their calculation.

However, when designing the apparatus, we did not use any of the methods proposed above, due to the fact that our apparatus has a completely different design and a large air gap (80 mm). The considered methods are intended for devices with constant electromagnets and a gap of up to 15 mm, for devices with a gap of up to 20-30 mm.

In this regard, we used methods for calculating electromagnets of widespread use (electromagnetic relays, brake and traction machines). At the same time, it should be noted that these methods also do not fully satisfy the requirements for calculating our apparatus, since they are intended for electromagnets with a small air gap. But they seem to us more approved. We base our calculation on the basis of the book by B.S. Sotskova [109]. A complete calculation of the parameters of the electromagnetic installation is presented in Appendix 1.

Figures 2.5 and 2.6 show the design, electrical and magnetic circuits of the electromagnetic installation.

Figure. 2.5. Electromagnetic installation for processing polymeric materials and coatings based on them

A - electro magnet; B - rectifier; C - voltage regulator; 1-base 2-magnetic wire 3 – magnetizing coils 4-pole lugs  5-heating element 6 – rack for rectifier and voltage regulator

Figure 2.6. Electrical and magnetic circuit of the installation

K1, K2 - magnetizing coils; V - voltmeter; A - ammeter; B - rectifier; RN - voltage regulator; AB - circuit breaker 1-yoke 3-pole lugs 2 - extreme rods 4 - core

The design and principle of operation of the installation. The electromagnetic installation consists of a magnetic wire, magnetizing windings, an alternating current rectifier and an autotransformer for measuring the magnetic field strength in the air gap (Fig. 2.5).

The armored magnetic wire is assembled from electrical steel plates. Electrical steel is an alloy of iron with silicon. This steel has good magnetic characteristics - high saturation induction, low coercive force and low hysteresis losses.

The magnetic wire serves to strengthen the magnetic field and increase the magnetic flux, and also allows you to direct and focus the magnetic flux.

The electrical steel plates are bolted together. An armored electromagnet is characterized by the fact that its core covers the winding and thereby protects it from mechanical damage. The magnetic wire consists of three cores and a yoke. The cross-section of the outermost cores and the yoke is the same along the entire length. The middle core has a working extreme in the middle. The ends of the middle core are beveled in order to increase the air gap of 80 mm. The cross section of this core is twice the uniformity of the magnetic field in the working air gap. Magnetizing coils are placed on the middle cores. Each core has four coils with a gap between them. The gaps between the coils are made to improve the cooling conditions.

windings. In total, the installation contains 8 magnetizing coils. All coils are included in the opposite direction.

The magnetizing coils are made on a frame made of electrical cardboard. The winding of the bobbins is multilayer. There is insulation between the layers. All coil leads are connected to two branded panels. This allows the switching on of the magnetizing coils to be changed.

The electromagnetic installation is completed with a rectifier for obtaining direct current.

A permanent magnetic flux created by the magnetizing coils travels through the yoke of the magnetic wire, the middle core and the air gap.

The coating to be processed in a magnetic field is placed in an air gap and stays in it for a certain time.

The optimal parameters for processing coatings in a magnetic field are selected in each individual case, depending on the polymer system to be processed.

The electrical diagram of the installation is shown in Fig. 2.6 and consists of magnetizing coils, a rectifier (B) and an autotransformer (tr). The magnetizing coils are divided into two groups. In each group, the coils are connected in series and opposite. The inclusion of groups of coils is parallel. The magnetizing coils are connected to a rectifier, which in turn is connected to an autotransformer.

The electrical parameters of the installation are monitored using a C-50 DC voltmeter (V) with measurement limits from 0 to 1000 V and an ammeter (A) with measurement limits from 0 to 15A. It is possible to monitor the electrical parameters of the installation on the AC side. In this case, the voltmeter and ammeter are connected between the rectifier and the autotransformer. Preparing the installation for work. Before starting work on the installation, it is necessary to connect the coils to the rectifier, and the latter to the autotransformer. Flexible wires with copper conductors of the SHRPS or PVG type with a conductor cross-section of 1.5 or 2.5 mm2 were used as connecting wires.

Then, the dependence of the magnetic induction in the air gap on the value of the supply voltage and the consumed current is removed. To do this, using an autotransformer, voltage is supplied through a rectifier, a certain voltage is applied to the windings of the coils, and the current consumption and magnetic induction in the air gap are measured.

Measurement of magnetic induction is carried out using an induction meter of type E – II or millivebro meter M – 119. Then another voltage is set and similar measurements are made.

After a series of measurements, a curve of the dependence of the magnetic induction on the current is drawn (Fig. 2.7.) In the air gap, the magnetic field strength is calculated by the formula

where H is the magnetic field strength in A / m;

B - magnetic induction in tesla;

µ - relative magnetic permeability;

µ is the magnetic constant in H / m.В

If the unit operates with a field strength in the air gap of not more than 240,000 A / m, the unit is powered at a voltage of 220 V through an autotransformer.

To obtain a field strength of 360,000 A / m, the rectifier is connected directly to a network with a voltage of 330 V. The design of the installation provides for a change in the magnetic field strength by changing the switching circuits of magnetizing coils.

Figure 2.7. Curve of magnetic field strength in the air gap depending on the current in the magnetizing coils

Technical data of the unit:

1. Maximum magnetic field strength in the air gap

H = 360,000 A / m;

2. Supply voltage V = 220, 380 V;

3. Kind of current - constant and alternating;

4. Power consumption - 22 kW;

5. The total number of turns - 12692;

6. The number of coils - 8;

7. Wire grade PEVT;

8. Wire diameter - 1.06 mm;

9. Working air gap between pole pieces 80 mm;

10. The working area of the cross-section of the pole pieces is 90x100mm;

11. Overall dimensions - 300 x 140 x 560 mm;

12. Weight - 250 kg.

Conclusions:

1. A scientifically grounded choice of research objects for obtaining polymer coatings has been carried out. As objects of research, we chose a thermosetting polymer - epoxy resin ED-16, ED-20, pentoplastic - PNP, polyethylene - HDPE, hardener - polyethylene polyamine and plasticizer - dibutyl phthalate, and as fillers - talc, iron powder, flake graphite, powder graphite and soot. Steel, aluminum sheet, and copper sheet were chosen as substrates.
2. A method for obtaining samples of polymer coatings has been determined, which includes the preparation of a polymer binder, a substrate, application of coatings and their heat treatment.
3. The methods for determining the physical and mechanical properties of composite polymer coatings in accordance with GOST are presented.

References:

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