Wiring must be safe. This is one of the main conditions for its operation.
At the junction, contact disruption, overheating, or even fire occur most often. Therefore, it is precisely at these points that reliable insulation is especially important. Reliability can be ensured by insulation of wires by heat shrink. This type of protection has many more advantages compared to other types of insulation compounds.
What is a heat shrink tube
Heat Shrink Tubing (TUT) is a thin-walled tube made of polymeric materials that is capable of being compressed under high temperatures without collapsing. It is such a tube that has found wide application in everyday life and is often used by home craftsmen.
Heat shrinkage for wires, the dimensions of which can vary significantly when heated, is good because it tightly, without voids, fits the junction of the wiring elements, does not create unnecessary thickenings, such as ordinary tape. However, this is not the only advantage of tubes made of polymer materials.
Shrink Benefits
A heat-shrinkable tube, in comparison with other methods of insulation of conductive wires, has several more advantages.
Firstly, since it fits snugly, it does not shift under various kinds of mechanical influences. Secondly, it is installed quite simply. Thirdly, after shrinkage, the tube material becomes stronger, giving additional mechanical stability and rigidity to the junction of the wires. In addition, it retains its properties for a long time, much longer than the same insulating tape.
Shrink Drawbacks
The only drawback that heat shrinkage for wires has, the dimensions of which change irreversibly when heated, is the inability to reuse it after dismantling, since it is impossible to remove it without damage.
The price of the heat-shrinkable tube is higher than the price of ordinary insulating tape, but not so much as to become a decisive moment when choosing an insulating material.
Other possible disadvantages are, rather, the shortcomings of a particular manufacturer.
Shrink Tub Properties
The main property of the tube, which determines its use, is the ability, by changing the diameter and thickness, to compress under the influence of high temperatures in the range of 80-120 ° C. Tubes whose initial heating temperature is not higher than 70 ° C are used in electronics.
The heat-shrinkable tube differs in a wide range of operating temperatures ranging from -45 ° to + 125 ° . There are materials with an even higher operating temperature, up to 135 ° C. They are used in the automotive industry to isolate joints in the vicinity of the engine.
The standard color is black, non-standard - red, green, blue, yellow, white. Transparent heat shrink tube is used in places where it is necessary to monitor the condition of the connection.
Main characteristics
Depending on the properties of the polymer, the ability to compress, which is characterized by heat shrinkage for wires, changes. The size of the tube can be reduced by half or even six. The shrinkage coefficient usually varies from 2: 1 to 6: 1.
Another characteristic is the presence of an adhesive layer. Heat-shrink adhesive tube is used in cases where contact joints must be reliably sealed and protected against moisture from corrosion. In addition, hot-melt adhesive on the inner surface of the tube gives additional strength to the connection.
It characterizes the shrink tube and resistance to light and aggressive environments. The material can be chemically or oil-resistant, light stabilized (resistant to ultraviolet radiation) or with the effect of photoluminescence.
Shrink tubes differ in the composition of the polymer. They are made of PVC, polyolefins, elastomers and other materials, which determine the resistance to ultraviolet rays or fire, mechanical properties and color solutions.
With different connection requirements, tubes with similar characteristics can be made, both in black and in transparent polyolefin. The color scheme is also a characteristic of heat shrinkage for wires.
Application area
Heat-shrinkable tube (HERE) can serve not only for insulation of electric circuit wires, although this is its main purpose.
It seals and protects against moisture, chemical corrosion, dirt and mechanical stress. The tube protects the wires from deformation and protects the places of bends.
It can repair damaged insulation and the sheath of cables and wires, bind harnesses.
A heat shrink tube, the dimensions of which allow you to put on a small ring cut from it, on wires of any thickness, is made in a large number of colors, therefore it is very convenient for marking. For example, a piece of red tube is worn over the end of the wire over the insulating layer, and this means a plus in the DC circuit. A ring of black color is installed on the “minus”, yellow-green on the ground, in a three-phase circuit for the corresponding phases - red, yellow and green.
A thin heat-shrink tube that withstands a fairly high operating temperature is convenient for repairing the vehicle's electrical system, installing alarms, car radios, and speakers.
Multi-colored tubes made of polymeric materials are used for decorative purposes, and for repairing home appliances and electrical wiring.
Shrink Tubing Dimensions
All manufacturers label their products. The main parameter that distinguishes any heat shrink tube is the diameters before and after shrinkage.
Usually, the inner diameter before shrinkage is indicated first, and through the fraction, either the diameter or the coefficient by which it can be calculated. The most common is a standard 2: 1 ratio.
Asian and Russian manufacturers produce tubes with a diameter of multiple 0.5 mm or 1 mm. European manufacturers indicate the diameters in inches, so when converted, a diameter is obtained, for example, 1.6 mm or 4.8 mm.
If two tubes of close diameters are suitable, you need to choose the largest of them.
The heat shrink tube can be sold in slices of one meter or, which is inconvenient for home use, in bays of 25.50,100 and more meters.
Types of Heat Shrink Tubing
Diameter before and after shrinkage and length are not all 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, the wall thickness of which 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 coefficient from 2: 1 to 4: 1) are used not only for insulation of wires, but also for marking. As a rule, they have heat resistance, a relatively low temperature of shrinkage, increased resistance to sunlight and suppress combustion.
- Thick-walled and medium-wall adhesives, the wall thickness of which after shrinkage is from 1.5 to 4.5 mm (shrinkage coefficient from 2: 1 to 6: 1) are used for insulation and moisture protection objects with a large difference in diameters, high-voltage cables, protection against corrosion not only electrical contacts, but also steel pipes, sealing contact couplings.
Mechanical characteristics
Since the main task that the heat shrink tube has to perform is electrical insulation, the main characteristic is its dielectric strength, which should be at least 20 kV / mm. The strength characteristics of the material are also important. The tensile strength should not be less than 1.0 kgf / sq. mm (9.81 MPa), and elongation of at least 200%. The most durable is heat shrinkage for wires, the dimensions of which decrease when heated by six times, its tensile strength is already more than 14.5 MPa.
In many cases, heat shrink tubes must ensure the tightness of the joints, so another characteristic is important - equilibrium water absorption. It should not exceed 0.2%.
Preparation for installation
The process does not require a special tool. You need a sharp knife or scissors to cut the necessary pieces of the tube without any burrs and some kind of device for heating the tube. Industrial hair dryers are used by professional electricians who install a large number of connections. A home master can very well do with a gas burner or an ordinary lighter, the flame of which is quite enough to heat shrink for the wires.
Sizes are harder to pick. The initial diameter is important in order to put the tube on the wire connection without interference. Shrinkage coefficient or final diameter, which should be less than the diameter of the connection, you need to know in order to ensure tightness and reliable protection.
And the greater the shrinkage, that is, the higher the coefficient, the greater the thickness of the tube, and therefore its strength after heating.
Shrink Mounting
So, according to the properties and dimensions, a suitable thin-walled heat-shrink tube was selected. How to use it for insulation of wires? Firstly, you need to cut a piece from it so that it overlaps the length of the area that must be insulated taking into account the longitudinal shrinkage when heated. It is 5-10% and is also indicated by the manufacturer. There should be no burrs or deep damage on the sections and the surface of the cut tube so that the material does not collapse under the influence of high temperature.
First, a tube is put on the wire, then the connection is made on which it should be worn. 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 section is long enough.
You can’t warm up the tube at both ends at the same time - air bubbles may remain under it, which is undesirable, and wrinkles form on the surface.
The tube must be heated evenly, making sure that there is no overheating, carbonization, breaks or bubbles on its surface.
Temperature and heating rate are determined empirically. You should not rush, especially if there is no experience in such work. Too high temperature or heating rate can lead to marriage.
Work takes a little longer if, according to operating conditions, an adhesive heat-shrink tube is needed. How to use it to seal the joint? First you need to prepare the joined wires or products: to clean the sharp edges, clean and degrease, as with conventional bonding, the surface. Warming up the tube must be carried out from the middle to the edges.
Shrink tube prices
It is impossible to name a specific price range. The cheapest heat shrink tube, the price of which is slightly more than three rubles per linear meter, is usually a black thin tube with a diameter of 2 mm, the shrinkage coefficient of which is 2: 1 and the wall thickness is 0.6 mm, Russian or Chinese production.
Prices depend on the manufacturer, sizes, the presence of an adhesive layer, color, other additional properties.
Thick-walled heat shrinkage for wires, the dimensions of which are 230 × 4.8 mm, with an adhesive layer, with a shrinkage coefficient of 6: 1, black from the German manufacturer ACS with a world name is already worth more than 160 euros per meter.
Learning to install a heat shrink tube at home is not difficult. It can reliably protect the connections of wires, the installation location of terminals and other elements. But you can use this material for a wide variety of purposes, for which only enough imagination. For example, for decorative finishing of metal products, rubberizing of rollers or sealing of holes during repair.