Varnish MD-92: characteristics, properties, use

Varnish MD-92: characteristics, properties, use Characteristics of ML-92 electrical insulating varnish and its application

There are many paints and varnishes, and it costs separately consider varnishes for electrical insulation. Before you learn about the properties and characteristics of ML-92 electrical insulating varnish, we suggest finding out what this type of paintwork is.

Such compositions are colloidal solutions of various film-forming agents in correctly selected organic types of solvents.

Film-forming substances can be called those substances which, upon evaporation of solvents and upon hardening (i.e.

, polymerization), can form a solid film.

Electrical insulating varnishes - what is it

These substances include resins of natural and artificial origin, drying plant masses, cellulose ethers and others. In the role of solvents for film-forming substances, volatile (that is, easily evaporating) liquids are used - toluene, benzene, xylene, acetone, alcohols, turpentine and others. To make an electrical insulating varnish that will satisfy a number of requirements, several film-forming substances should be selected, which will form the basis of the varnish.

For perfect dissolution of the varnish base, as well as good drying of the varnish, sometimes it is necessary to use several types of solvents at once.

To dilute thickening varnishes, thinners are added to them, and they differ from solvents in a lower degree of volatility. Moreover, they are ways to dilute the lacquer base only in a mixture with solvents. Gasoline, varnish type of kerosene, turpentine and several other types of liquids can be used as diluents. As part of such a varnish, driers and plasticizers can also be introduced. The latter are substances that give elasticity to the lacquer film.

Desiccants are solid or liquid substances that are added to certain types of varnishes to speed up drying.

When drying the lacquer layer, which is applied to the surface, the organic solvents contained in it evaporate (that is, volatilize), and the film-forming substances during polymerization form a lacquered solid film. It can be elastic, or inflexible and brittle - much depends on the properties of the substances that make up the lacquer base. According to their purpose, such varnishes can be divided into cover, impregnating and adhesive. Compositions for impregnation are used for impregnating windings in apparatus and electrical devices for cementation (connection) of winding turns with each other, and also to eliminate porosity in insulating windings.

The varnish for impregnation, getting into the pores of the winding insulation, displaces air from there and, after polymerization, creates a winding that is resistant to moisture. This will increase the electrical strength of the winding, as well as its thermal conductivity coefficient. One of the main characteristics of varnishes will be their penetrating ability.

Details

Covering agents

..

. are used to obtain on the surface of already impregnated windings of low strength or moisture resistant coatings with lacquer finish. The coating compositions include enamel varnishes, which are used to enamel winding wires, as well as means that are used to insulate sheets of electrical steel in magnetic wires. Adhesives are used for gluing various electrical insulating materials - mica sheets (for the production of layered mica insulation), plastics, ceramics and others. The main requirement for adhesive varnishes is that such varnishes have excellent adhesion and create a strong seam.

Note the fact that in practice there are cases when one and the same varnish can be used as an impregnating and coating, or as an adhesive and coating composition.

When drying, all varnishes can be divided into two groups:

  • Composition of air (i.e. cold) drying.
  • Composition of oven (hot) drying.

For electrical insulating air-cured varnishes, the film cures at room temperature. Cold drying varnishes include ether cellulose, shellac and other types. For compositions for drying in an oven, curing of the film will only work at high temperatures (from +100 degrees and above). In varnishes for drying in an oven, thermosetting film-forming substances (resole, glyphthalic and other resins) are used, the curing of which is caused by the polymerization process, which requires high temperatures. "Hot" varnishes generally have improved mechanical / electrical properties.

According to the lacquer base, varnishes can be divided

... into oil, resin, oil-bitumen and cellulose ethers. Resin lacquer compositions are a solution of synthetic and natural resins in an organic solvent.

Resin varnishes include glyphthal, shellac, bakelite, organosilicon and others. Resin agents are thermoplastic (polyvinyl chloride, polyvinyl acetal and others), as well as thermosetting (bakelite, glyphtal). Oil varnishes are solutions of vegetable (semi-drying and drying) oils in an organic type of solvent. Drying oils include linseed and tung oil. The latter is made of tung tree nuts, dries quickly, creates a moisture-resistant and elastic film.

Linseed, on the other hand, is made from flaxseeds, and it is boiled to a certain density to be the basis for oil varnishes. Desiccants are usually added to oil varnishes, which were mentioned earlier - substances that accelerate the polymerization process. The films of oil varnishes are thermosetting, which means they do not soften when heated.

The scope of use of oil varnishes in electrical engineering is limited in comparison with resin compositions.Oil products are used for impregnation of electrical insulating varnished cloths, enameling of winding wires and as coating agents that are resistant to moisture.

Yes, a special varnish is required to coat and protect electrical parts well. To insulate various electrical equipment, ML-92 electrical insulating varnish is often used, which has excellent characteristics, low cost and many positive reviews. This type of varnish is used for different areas of industry, so we suggest considering it in more detail.

Properties and purpose of ML-92

This composition is an insulating type varnish, which is made in accordance with GOST 15865-70. It is made from glyphthalic lacquer solution, organic solvent and melamine formaldehyde resins.

The technical characteristics of the ML-92 varnish make it possible to use it in places where there is an electric voltage. The varnish will not lose its original properties under the influence of electricity, and even discharges of electricity, and can withstand high temperatures without defects. It can be used at a temperature of +135 degrees, and the minimum threshold is -60 degrees.

This is a varnish that is often used to cover and protect electrical windings and can be used:

Quite often, such varnish is used to apply to the windings of electric type machines, devices, various priors, transformer installations, small parts, including for car parts that need good insulation.

This varnish has a lot of advantages:

  • Helps to preserve products that work in negative conditions, under the aggressive influence of chemical acids, alkalis, various salts and gases.
  • ML-92 has a long service life, a durable layer is obtained that is resistant to oil.

  • Has thermal plasticity.

And now a little about the properties.

Characteristics of paintwork materials

All technical specifications are regulated by GOST, and the main list is as follows:

  1. Drying time varnish composition is about 1 hour, provided that the temperature is from +104 to +112 degrees. If the layer of the mixture is thick, it will dry for 10 to 16 hours.
  2. Visually, the protective film of the varnish looks like a uniform, glossy and even layer that does not have extraneous craters or inclusions.

  3. The consumption of the product is excellent - about 0.05 kg per square meter, when applied in one layer.
  4. The layer thickness is 20-30 microns.
  5. The viscosity of the composition at room temperature is 25-50 s, and the data are taken from the VZ-246 device.
  6. The proportion of dry non-volatile residue will be about 50%.

  7. The electric strength at a temperature of +20 degrees will be 70 MV / m, at a temperature of +135 degrees, the strength will be approximately 40 MV / m, under the influence of water during the day, the strength at room temperature is 30 MV / m.
  8. Thermal elasticity at high temperature (more than 130 degrees) is 48 units.
  9. Pendulum hardness index at room temperature 0. 4 units.

Other characteristics of the ML-92 varnish are prescribed in the state standard 15865-70.

After drying, the mixture acquires a yellow-brown hue.

Process features

Application rules

Varnish MD-92: characteristics, properties, use The surface must be properly prepared before the insulating varnish is applied. All types of contamination must be removed from it, including dirt, dust, oil stains and grease. A solvent is used for degreasing, and as a result, the surface must be clean and dry. If the composition is very thick, it can be diluted to the required consistency level with a solvent such as xylene, white spirit or toluene.

It is not necessary to prime before applying the varnish mixture.

The agent can be applied by dipping small-sized parts, or by pouring. If there is a need, then it will be possible to apply not even 1, but 2 layers of paint and varnish. In this case, the next coat should only be applied after the first coat has dried. The best option would be the usual drying of the varnished product at room temperature for about 1/3 hour, and then hot drying for 1 hour at a temperature of +110 degrees.

Next, you can apply a second layer of varnish, and if necessary, the second layer can be made thicker, and then dry the product for no more than 16 hours using the hot method, at a temperature of +120 degrees.

Features of storage and packaging

This varnish solution is usually packed in industrial types of containers (metal or plastic), and their volume is consistent with the customer's requirements. The shelf life and storage period is 1 year from the date of manufacture, and during this time the invariability of the properties and technical characteristics of the solution will be guaranteed. So that it does not deteriorate, storage should be carried out in a sealed and sealed factory-type container, which should not be exposed to sunlight. The lacquer composition should be stored indoors at temperatures from -45 degrees to +40, and the humidity level should not exceed 80%.

Also, there should be no heating devices and sources of fire nearby.

Precautions

Before starting work with the ML-92 varnish, you should wear personal protective equipment, as well as tight clothing suitable for work ... It is possible to apply the varnish composition only with a respirator, glasses and gloves to protect the skin, respiratory organs and eyes.

In the room where work will be carried out with the paint and varnish product, there must be good ventilation or even ventilation. Please note that this composition is flammable and therefore should not be applied near sources of fire or sparks. If the varnish gets on the eyes or on the skin, then it should be rinsed as soon as possible with clean cold water, and the ingress of varnish fumes and human respiratory organs should not be allowed.

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