🔌 Shrink wire: what are the characteristics, selection criteria

Discoverer of the effect of heat shrinkage is considered to be a chemical engineer Paul Cook. First-shrink plastic insulation materials was started by Raychem Corporation, starting with the 50-ies of XX century. In the USSR, the release of such products started in 1977 by the "Zagorski pilot plant of plastics". Due to the high cost they have long been the special means used in electrical work and military aerospace industry. At the moment, for shrinking wires It is widely used as an alternative to conventional PVC insulating tape, and thanks to its high performance characteristics practically replaced the traditional insulation materials.

What is shrinking: the principle of action

The principle of operation is based on the shrinking shape memory effect. In the manufacturing process the polymer is exposed to a flow of charged electrons, whereby molecules material prepared additional compounds in the transverse direction of the article (crosslinking technology).

1. Starting position of the polymer chains in the material.
2. Irradiation of the polymer and separation of the hydrogen atoms.
3. Combining carbon atoms and the cross-connections.

Thus, during exposure the temperature of the polymer returns its original size, while not changing the linear (longitudinal) and radial (transverse) direction. This tube has a long shelf life without compromising its basic performance.

Important! In the market of electrical products, this product may be known by different names: termokembrik, Heat-, shrink (shrinks) insulation.

Purpose and field of application of the heat shrinkable tube

At the moment, most often used in shrinking electrical work. To comply with applicable SAE standards, it is recommended to use heat-shrinkable tubing, corresponding to GOST 17675-87 and GOST 19034-82 (the standards are relevant as of 30.12.2018g). Shrink materials are used in the following installations:

• contact isolation and wires under standard operating conditions;
• isolation of the compounds at higher negative impact of the environment;
• high humidity;
• temperature changes in the range -65 ° C... + 260 ° C;
• dynamic effects - moving machinery, vibration;
• cable protection areas exposed to high temperature and the (limited) open flame. The labeling or description of such articles present the words Teflon and / or PTFE;
• contact protection against corrosion, chemical and mechanical action, contact marking (termokembriki).

Helpful information! Besides electrical shrink materials as tubes or ribbons have been applied as a replacement for paint products for the protection of wooden and metal structures (water pipes, underground part of transmission towers, and the like) from external impacts. One can buy shrink tube with ribbed or grooved to improve the ergonomics of the hand tool handles.

Shrink tubing for wires: strengths and weaknesses

By analyzing the advantages and disadvantages of heat-shrinkable insulating material, their fair compared to classical PVC tape.

Shrink	Insulating tape
Fast installation: to reliably isolate the compound sufficient 5-10 seconds	In one simple isolation of the compound may take 2-5 minutes, depending on the convenient access
Tight to the ground, it is impossible to shift in the direction of	A perfect seal to the base is relative and depends on the strength and skills of an electrician, you can move to the side
Completely seals the connection for the entire period of operation cable	After some time, the connection protection loses tightness
The polymer was compacted, giving the joint an extra strength and resistance to mechanical stress	It does not improve the strength characteristics
The junction thin, does not occupy a lot of space	Takes a lot of space, can not fit in the box, corrugated or not to go into the hole in the wall
Retains insulation properties under various external influences long period of time	It is better not to external influences, the protection level of the mediocre
High product cost in terms of the isolation of the compound	affordable
The need for additional tools or equipment: construction hairdryer, lighters, matches	Application of the knife for cutting the strip of the desired length
Narrow size range (diameter) of the heat-shrinkable tube TUT	It is possible to insulate the connection whatever thickness

Types of heat-shrinkable tube for the wires

Heat shrinkable tubes are characterized by three fundamental parameters:

1. Material.
2. The presence inside the adhesive layer.
3. The wall thickness after shrinking.

In material manufacturing

Polyolefin - the most common material for the manufacture of heat-setting. It consists of polyethylene subjected to chemical or radiation treatment (cross-linked). Also, it is composed of colorants and flame retardants. Recommended operating temperature -50 ° C... + 125 ° C / + 150 ° C. Resistant to benzene and oxidants. Prolonged contact with fuel can destroy the structure.

PET (polyester) - Thin and sverhtonkostennye shrink tube of large diameter. High chemical resistance and mechanical strength.

Synthetic rubber (elastomers) - resistance to fuel and high temperatures (up to 175 ° C). They have a rather high price.

PVC (thermoplastic PVC) - good insulation properties. Small operating temperature range: -20 ° C... + 80 ° C. Material combustible, combustion provides carcinogens.

silicone - flexible, non-toxic, chemically inert, have high strength. Decompose under the influence of organic solvents.

PTFE heat shrink tubing - features unique performance, but because of the difficulty in manufacturing technology has a high cost.

According to the principle of installation

glueless - provide reliability and tightness of the joint is only due to pressure and density girth.

With glue - tesmousazhivaemaya tube, on the inner surface of which is applied a layer of thermosetting adhesive, providing additional strength to the connection.

With additional longitudinal seal - have in their structure of butyl rubber mastic tape (e.g. Deray® Duomelt 105).

Wall thickness

• Thin-wall;
• srednestennye;
• thick-walled

Heat-shrinkable tubing HERE: basic and further

There are a number of operating parameters of which are the following:

• shrinkage ratio - expressed as a percentage or proportional relation and is from 2: 1 to 6: 1;
• diameter before and after temperature exposure;
• resilience:

• chemical;
• electric;
• petroleum products;
• UV;
• open flame.

As labeled tube

The marking, in varying degrees, there is information on the size of the product and the coefficient of shrinkage. This may be a direct indication of the diameter before and after thermal exposure, and may be an initial diameter and the shrinkage factor. Dimensions for shrinking the wires indicated by a diagonal line, the coefficients - a colon.

In addition, there may be mentioned additional information about the characteristics of: fluorescent, with a corrugated surface, high density (up to 1000V), nonflammable, etc.

How to choose a heat shrinkable tubing - the recommendations of our editorial

If there are no special requirements for resistance to external influences and the coefficient of shrinkage, the heat shrinkable tubing is selected in diameter. It is often the rule for choosing the "minus 10 plus 20" or "80:20". What does this mean?

The size of the isolated compound should be greater than the minimum size of the tube after shrinking a multiplicity of 20 (20%, 40%, 60%), but not less than 10%.

Tubes with shrinkage ratio of 2: 1 can be seated is not less than 20% and no more than 80% of its original diameter.

Important! If the connection has been a sharp jump size, it is recommended to buy heat shrink wire by a factor of 6: 1 or more.

How to use heat shrink tube

If you have a lot of work to shrink, it is advisable to purchase a building with a hairdryer to set the temperature. Although most of the heat-shrink products may be exposed to an open flame - lighters, matches. Process shrink insulation of wires is performed in such a sequence.

Preparatory stage

1. In step preparation of shrink tubing is cut into pieces of the required size. On each side of the isolated portion must be not less than 1.5-2 cm of the tube over the old insulation. Cut the pipe must be carefully to avoid breakage and burrs, because they can break the shell in the process of shrinkage.
2. Pipes of large diameter, thick-walled or recommended preheated, approximately half of the reaction temperature. This will allow a more uniform shrinkage.

Installing the Heat Shrink Tubing with their hands

1. The tube is put on one of the cable and shifted to the side.
2. Wiring is performed in accordance with the electrical work.
3. Shrink moves in the opposite direction to its center coincides with the center of the compound.
4. Heating produced a stream of hot air directed from the center toward the edges compound.

The approximate cost of heat shrink tubing

At the moment, heat shrink tubing can be purchased at any hardware store or ordered online. The most popular manufacturers are DSG-Canusa, Raychem, Zeus, 3M, Sumitomo, LG. However, the branded products are very expensive.

For example, 1 running. m DERAY HB - 6.4 / 3.2 mm worth 78 rubles. (Prices as of January 2019)

But the Chinese brand Woer, quite popular manufacturers producing quality products, ISKE2- (2X) G D: 6.4 / 3.2 costs only 30 rubles / rm.. m.

The most popular Russian manufacturers of heat shrink products are firm:

• TMARK;
• Metatron;
• Thermoforming.

findings

Shrink tubing for wires gained widespread popularity due to its reliability and ease of use. In the future, its value will decline because of the high competition in this segment, and expand the range of products.