Heat-shrink for wires: dimensions, characteristics, application. Heat-shrink tubing

Wiring must be safe. This is one of the main conditions for its operation.

In the places of connection, contact disruption, overheating or even fire occur most often. Therefore, it is at these points that reliable insulation is particularly important. Reliability can provide insulation of wires by heat shrinkage. This type of protection has a lot of advantages in comparison with other types of insulation compounds.

What is a heat shrink tube

Shrink tube (TUT) - a thin-walled tube made of polymer materials, which is able to shrink under the influence of high temperatures, without breaking at the same time. It is such a tube that has found wide application in everyday life and is often used by domestic craftsmen.

Heat-shrink for wires, the dimensions of which can change significantly when heated, is good in that it is tight, without voids, it fits the place of connection of the electrical wiring elements, does not create unnecessary thickenings, such as an ordinary insulating tape. However, this is not the only advantage of pipes made of polymer materials.

Advantages of heat shrinkage

Heat-shrinkable tubing, in comparison with other methods of insulation of conductive wires, has several advantages.

Firstly, once it fits snugly, it does not shift with different kinds of mechanical influences. Secondly, it is installed quite simply. Thirdly, after shrinkage, the tube material becomes stronger, imparting additional mechanical stability and rigidity to the connection of the wires. In addition, it retains properties long enough, much longer than the same tape.

Disadvantages of heat shrinkage

The only drawback with the heat shrinkage for wires whose dimensions change when heated is irreversible is the impossibility of reuse after dismantling, since it is impossible to remove it without damage.

The cost of the heat-shrinkable tubing is higher than the price of an ordinary electrical tape, but not enough to be the deciding factor in choosing an insulating material.

Other possible shortcomings are, rather, the shortcomings of a particular manufacturer.

Heat Shrink Properties

The main property of the tube, which determines its use, is the ability, by changing the diameter and thickness, to contract under the influence of high temperatures in the range of 80-120 ° C. Pipes, the initial heating temperature of which is not higher than 70 ° C, are used in radio electronics.

The heat-shrinkable tube differs and a wide range of operating temperatures in the range from -45 ° C to + 125 ° C. There are materials with an even higher operating temperature, up to 135 ° C. They are used in the automotive industry to isolate the connections in the vicinity of the engine.

The standard color is black, non-standard - red, green, blue, yellow, white. Heat-shrinkable transparent tube is used in places where it is necessary to observe the state of the connection.

Main characteristics

Depending on the properties of the polymer, the ability to shrink, which is characterized by heat shrinkage for wires, also changes. The dimensions of the tube can be reduced by half or even six times. The shrinkage factor varies usually from 2: 1 to 6: 1.

Another characteristic is the presence of an adhesive layer. The shrink sleeve is used in cases where the contact junctions need to be reliably sealed, protect against moisture from corrosion. In addition, the hot melt adhesive on the inner surface of the tube imparts additional bond strength.

Characterizes the shrink tube and resistance to light and aggressive media. The material can be chemically or oil-and-oil resistant, light stabilized (resistant to ultraviolet radiation) or with the effect of photoluminescence.

There are different shrink tubes and polymer composition. They are made of PVC, polyolefins, elastomers and other materials, on which depends the resistance to the action of ultraviolet rays or fire, mechanical properties and color solutions.

With different requirements for connections, tubes with similar characteristics can be made, both in black color and transparent polyolefin. The color solution is also a characteristic of heat shrinkage for wires.

Application area

The shrink tube (TUT) can serve not only to isolate the wires of the electrical circuit, although this is its main purpose.

It seals and protects against moisture, chemical corrosion, dirt and mechanical influences. The tube protects the wires from deformation and protects the places of kinks.

It can restore the damaged insulation and sheath of cables and wires, and connect the tows.

Heat shrinkable tubing, the size of which allows you to put a small ring cut off from it on wires of any thickness, is performed in a large number of color solutions, so it is very convenient for marking. For example, a piece of red tube is put on the end of the wire over the insulating layer, and this means "plus" in the DC electric circuit. On the "minus" a black ring is installed, on the ground - yellow-green, in a three-phase circuit for the corresponding phases - red, yellow and green.

A thin heat-shrinkable tubing, which withstands a sufficiently high operating temperature, is convenient for repairing the on-board electrical network of the car, installing alarms, radio and acoustic systems.

Multicolored tubes of polymeric materials are used for decorative purposes, and for the repair of home appliances and electrical wiring.

Dimensions of shrink tubes

All manufacturers label their products. The main parameter by which any shrink tube differs is the diameters before and after shrinkage.

Usually the inner diameter is specified first before shrinkage, and through the fraction - either the diameter or the coefficient by which it can be calculated. The most common is the standard ratio of 2: 1.

Asian and Russian manufacturers produce tubes with a multiple of 0.5 mm or 1 mm in diameter. European manufacturers, however, indicate diameters in inches, so when recalculating, a diameter of, for example, 1.6 mm or 4.8 mm is obtained.

If two tubes of similar diameters are suitable, a large one should be chosen.

Heat-shrinkable tubing can be sold in slicing one meter or, which is inconvenient for home use, in coils of 25,50,100 and more meters.

Types of heat shrink tubes

The diameter before and after shrinkage and length are not all the geometric parameters that characterize a heat shrink tube. Its dimensions also include thickness before and after heating.

The thickness of the tube can be divided into two types:

- Thin-walled, whose wall thickness after shrinkage does not exceed 1 mm. They are the most popular, including for domestic use. Colored, black and transparent tubes without an adhesive layer (shrinkage ratio from 2: 1 to 4: 1) are used not only for wire insulation, but also for marking. As a rule, they have heat resistance, relatively low shrinkage temperature, increased resistance to sunlight and suppress combustion.

- Thick-walled and medium-sized glue, the thickness of the walls after shrinkage from 1.5 to 4.5 mm (shrinkage ratio from 2: 1 to 6: 1) is used for insulation and protection against moisture objects with a large difference in diameters, high-voltage cables, protection from Corrosion of not only electrical contacts, but also of steel pipes, sealing of contact couplings.

Mechanical characteristics

Since the main task that the shrink tube must perform is electrical insulation, the main characteristic is its dielectric strength, which must be at least 20 kV / mm. Strength and strength characteristics of the material are also important. The strength at break should not be less than 1.0 kgf / sq. Mm (9.81 MPa), and the elongation is not less than 200%. The most stable is heat shrinkage for wires, the dimensions of which decrease with heating six times, its breaking strength is already more than 14.5 MPa.

In many cases, shrink tubes should ensure the tightness of joints, so another important characteristic is the equilibrium water absorption. It should not exceed 0.2%.

Preparing for installation

The process does not require a special tool. You need a sharp knife or scissors to cut off the desired pieces of pipe without burrs and any device for heating the tube. Industrial hair dryer is used by professional electricians who mount a large number of connections. A home wizard may well manage a gas burner or a conventional lighter, the flame of which is enough to heat up the heat shrinkage for the wires.

The sizes to pick up are more difficult. The initial diameter is important in order to put the tube on the connection of the wires without interference. The shrinkage factor or the final diameter, which should be less than the diameter of the joint, is necessary to know in order to ensure tightness and reliable protection.

And the more shrinkage, that is, the higher the coefficient, the greater the thickness of the tube, and consequently its strength after heating.

Mounting of heat shrink

So, by the properties and sizes, a suitable thin-walled shrink tube has been chosen. How to use it to insulate the wires? First, you need to cut off the piece so that it overlaps the length of the section, which must be insulated with allowance for longitudinal shrinkage when heated. It is 5-10% and is also indicated by the manufacturer. The cuts and the surface of the severed tube should not have any burrs and deep damage, so that the material does not collapse under the influence of high temperature.

First, a tube is put on the wire, then a connection is made, to which it is to be put on. After that, it is heated from one edge to the other so that there is no large longitudinal shrinkage, or from the middle to the edges, if the area is long enough.

You can not warm up the tube at the same time from two ends - under it there may be air bubbles, which is undesirable, and wrinkles form on the surface.

Warm up the tube evenly, making sure that there is no overheating, charring, tears or bubbles on its surface.

The temperature and the rate of heating are determined experimentally. It is not necessary to hurry, especially if there is no experience of similar works. Too high a temperature or a heating rate can lead to a marriage.

A little longer work is carried out if a heat-shrinkable tubing is required by operating conditions. How to use it to seal the joint? First you need to prepare the jointed wires or products: clean the sharp edges, clean and degrease, as with conventional gluing, the surface. The tube is always heated from the middle to the edges.

Shrink tube prices

It is impossible to name a specific price range. The cheapest shrink tube, whose price is a little over three rubles per meter, is usually a black thin tube 2 mm in diameter, the shrinkage ratio of which is 2: 1 and the wall thickness is 0.6 mm, of Russian or Chinese origin.

The prices depend on the manufacturer, the sizes, presence of an adhesive layer, color, other additional properties.

A thick-walled shrink for wires whose dimensions is 230 × 4.8 mm, with an adhesive layer, with a shrinkage factor of 6: 1, black color from the German manufacturer ACS with a world-wide name costs more than 160 euros for one meter.

It is not difficult to learn how to mount a heat shrink tube at home. It can reliably protect the wire connections, the location of the terminals and other elements. But you can use this material for a variety of purposes, just enough for your imagination. For example, for decorative finishing of metal products, rubberizing rollers or sealing holes during repair.