Heat-shrinkable materials in electrical engineering

Heat-shrinkable materials are widely used in many industries and primarily in electrical engineering, due to a sufficiently high electrical resistance. In addition to electrical engineering, they are also used in the automotive, aircraft, instrumentation, energy, and many other industries. This is a new promising and easy to use material with very good performance properties. First of all, it is a high electrical resistance, resistance to low temperatures and aggressive environments: acids, alkalis and oil products.

The most famous and common heat shrink tubing or as they are called shrink. The main property of the tubes is the ability to compress under the influence of high temperature. Moreover, compression occurs only in the transverse direction (the diameter of the tube decreases), but there is no noticeable increase in length. Such properties of the tubes are obtained through the use of materials that have undergone special processing.

It should be noted that in addition to the tubes cable sleeves of various designs, heat-shrinkable TUP gloves, heat-shrinkable tubes with glue, heat-shrinkable NG tubes (non-combustible), cable hoods and much more are also manufactured from heat-shrinkable materials.

Heat-shrinkable TUP gloves are not intended to be worn at all. This is an element that allows branching to be sealed when cutting cable with oil-soaked insulation. The appearance of such “gloves” is shown in Figure 1.

Figure 1. Heat-shrinkable TUP gloves

What are heat-shrinkable materials made of?

Heat-shrinkable materials are made from compositions based on polyolefelins, better known as polyethylene, which have undergone special treatment with radiation exposure. Under the influence of irradiation in polyolefelin, some hydrogen atoms are separated, and in these places cross-links form. Under the influence of such radiation treatment, a product made of polyolefelin acquires a new physical property - shape memory.

A part of such a material, for example, a cable box, is made in the size and shape that it must acquire after shrinkage. Then the workpiece is subjected to radioactive treatment, heated, stretched and left to cool in a stretched state. The cooling mode is maintained such that hard crystalline bonds are again restored in the substance.

When mounting the clutch is installed in place, and heated. As a result of heating, the crystalline bonds melt, and the material acquires its original shape, which is obtained due to the property already mentioned above - “shape memory”. Thus, the heat-shrink sleeve is mounted on the cable. In this case, of course, the dimensions of the cable and the coupling must correspond to each other.

Fig. 2. Installation of heat shrink sleeve

Despite such a variety of shapes and sizes, products made from heat-shrinkable materials are often called simply heat-shrinkable tubes or simply heat-shrinkable. Actually this is the case: any part from heat shrinkage has an opening into which the part to be crimped is inserted. Which side do not go up - you still get the phone.

In addition to the aforementioned polyolefelin (aka polyethylene), silicone rubber (silicone), fluoroplast-4, polyvinyl chloride, fluorine-containing elastomers and others are used as materials for the production of heat shrinkage.

Where are heat shrink tubes used?

The main field of application of heat-shrinkable tubes is electrical engineering.In the energy sector, these are, first of all, cable joints that provide not only electrical insulation, but also mechanical protection, as well as shielding from electromagnetic fields (when using special materials).

Heat-shrinkable tubes are widely used in the installation of electrical wiring, repair and restoration of insulation of damaged wires.

Special cuffs are produced for corrosion protection of welded pipe joints, as well as for sealing joints.

Heat-shrinkable tubes are so versatile that they find application in various fields of industry, while there are no boundaries for the imagination of developers and technologists. Perhaps the use of tubes for marking cable cores. At the same time, they are marked by thermal printing or just by hand with special inks.

Tubes are used to rubberize conveyor rollers, to cover handles of sports and household equipment, to give products a presentation and a different color.

History of the invention of heat-shrinkable tubes

The first samples of heat-shrinkable tubes were invented in the USA by Raychem Corporation in the late 50s of the XX century. It was then that the chemical engineer Paul Cook conducted experiments in the field of radiation chemistry. The name of the laboratory itself consists of two English words Ray Ray and Chemistry Chemistry. As a result of these studies, a lightweight electric cable was born for the aviation industry and the technology for the production of heat-shrinkable tubes.

Thanks to these technologies, the company Raychem Corporation became a pioneer in the development of heat-shrinkable tubes, secured a priority. Currently, there are several companies engaged in the production of heat shrink tubes, of which Sumitomo Electric Industries, 3M Corp., LG Woer, DSG-anusa, Alpha, Zeus, etc. are the most famous.

Fig. 3. Heat shrink tubing Sumitomo Electric Industries

In the former USSR, heat-shrinkable tubes began to be engaged only in the 60s. There is practically no information about this; all studies were carried out within the framework of the defense industry, as always at the highest level of secrecy. It is known that the first studies were conducted on the basis of the Moscow Research Institute of Plastics, located in Zagorsk (now Sergiev Posad).

Some data suggest that the first experimental work using heat-shrinkable tubes in the USSR was carried out in 1977 during the installation of communication lines. At the same time, the heat-shrinkable tubes were not known at all to the general public and even to many specialists, since they were made for the space and military industries.

Heat-shrinkable tubes in Russia began to appear in the mid-90s due to the efforts of the aforementioned foreign companies. It was then that the heat-shrinkable tube began to get into Russia in small batches.

Over time, the production of heat-shrinkable tubes was established in Russia. The total production volume is quite large, but at the same time the price turned out to be the most attractive factor for these pipes - at the level of inexpensive Chinese companies. Consumer properties and the appearance of domestic tubes so far leave much to be desired.

Although, in fairness it should be said that in some cases it was possible to catch up with Western competitors. For example, the Podolsk plant of electrical products mastered the production of heat-shrinkable tubes for high-voltage power. This is just the case where the reliability and durability of the product are required in the first place, and a presentable appearance is in second place.

TUT heat-shrinkable tubes

Often in various descriptions you can find just such a designation HERE. Is this some kind of new brand? No, it's just an abbreviation like this: Thermo Shrink Tubes - (HERE). In this case, this is not at all a specific brand of a product, but simply a designation of a wide class of products. The name HERE has become simply a household name, which means Heat-shrinkable tubes and nothing more.True, there is also the designation HERE ng, which stands for Heat-shrinkable tubes of non-combustible material.

Boris Aladyshkin