HEAT-SHRINK TUBING – FITCOTUBE®

Heat-shrink tubing, usually based on heat-resistant PTFE or PVDF, is drawn over the object to be protected and then heated with various processing devices. The heat applied shrinks the tubing into a tightly enclosing sleeve.

How far down the shrink tube shrinks depends on the shrinking rate, which is also called shrinking range or shrinking ratio.
The usual shrinking rates are from 2:1 to 4:1, although there are also other variations.

The material of a shrink tube is crosslinked after production. This step ensures that the molecular chains are connected to each other. Silanes or electron radiation can bring about this state. The respective plastic is extruded in the warm state and expanded to a desired diameter. This leads to tension between the molecular chains, and subsequent cooling then ensures that the diameter and the tensions are “frozen.” These dissolve under the influence of heat, and the diameter of the shrink tube returns to its original size.

A heat-shrink tube is made of plastic which contracts when heated. Depending on the material, it is usually used to electrically insulate something and/or to protect something from damage (thermal or mechanical). There are countless variations of heat-shrink tubing. For example, there are differences in the shrinking ratio (how much the tubing shrinks), the wall thickness (thin, medium, thick), the color, the approval (MIl, UL, CSA) and the material (polyolefin, fluoroplastics, elastomers, polyester, etc.) of the respective heat-shrink tubing. Depending on the design, the shrink tubing then exhibits specific properties.

The right choice of heat-shrink tubing is essential for the successful use of the product. Since there are a multitude of possible criteria that could be relevant for you, we have a four-figure repertoire of different products in the area of heat-shrink tubing alone. The wall thickness, the material used, the shrinking temperature, the necessary approvals or the possibility of printing are only a few of the most important characteristics that must be clear when selecting the shrink tubing. This is why we at GREMCO are not simply one of many shrink tubing manufacturers – we have specially trained personnel who will provide you with professional support in the decision-making process. Our individualized customer consultation service in the field of heat-shrink tubing helps you to avoid unnecessary incorrect purchases and ensures the smooth employment of the most suitable plastic tubing.

The usual temperature to shrink a heat-shrink tube is around 200°C. However, it is often not a problem to use a higher temperature, since the data sheet always indicates the minimum shrinking temperature. For example, if you use a hot-air blow dryer as a processing device, you will reach temperatures of around 400°C. In principal, the higher the temperature used, the faster the hose shrinks. However, be careful when storing because, even below the shrinking temperature, a shrink tube can begin to shrink (although not completely). A normal hairdryer is not suitable for this. Other possible products for shrinking are heat guns, soldering irons and shrinking/infrared ovens.

Heat-shrink tubes are used in various fields of application and industries. Therefore, you have a wide range of possible applications, such as protection against moisture (shrink tubing with inner adhesive), protection against mechanical as well as thermal environmental factors, electrical insulation or protection against chemical substances. They can also be used for connecting cables or as corrosion protection.

In general, a distinction can be made between a thin-walled, medium-walled or thick-walled wall thickness, and are indicated in mm on the data sheets after the complete shrinkage process.

The different categories of wall thickness are in turn characterized by different properties. For example, thin-walled heat shrinkable tubing usually has higher flexibility but can withstand only less severe mechanical stress in comparison, nevertheless the thin-walled FITCOTUBE has flame retardant and self-extinguishing properties. Heat shrinkable tubing with a high wall thickness, on the other hand, offers much more robust protection and can usually insulate against higher voltage (volts/kV), but with reduced flexibility. Medium-wall heat shrinkable tubing offers a middle ground, promising high shrinkability with consistently high flexibility.

Medium- and thick-walled shrink tubing is usually also available with an adhesive coating. The adhesive-coated material is used when the contents, i.e. cable harnesses or other electrical components, must be protected from liquids or withstand pressure.

Different combinations of materials and the shrink tube wall thickness sometimes determine how a tube can be extruded. The shrinkage rate in turn describes the ratio of how much the FITCOTUBE shrinks from the expanded state to the restored state (extruded state), during the heating process. The rate specification varies from 2:1 to 5:1, with the latter implying a higher shrinkage rate.

This means, for example, that the diameter of the expanded shrink tubing is 2 times larger at a 2:1 ratio than in the shrunk state. In this context, 2:1 to 4:1 are common shrink ratios. High shrink ratios, such as 5:1, are used when there are large average differences in the object to be insulated.

Optimal insulation results are achieved by following a simple 80:20 rule. This states that a shrink sleeve should be shrunk by at least 20%, but no more than 80%. You should always try to keep the shrinkage distance as small as possible, and it helps to choose a shrink tubing with a diameter just slightly larger than the contents to be protected.

Our competent sales consultants will also be happy to help you find the optimum shrink ratio for your application.

Length changes should be taken into account in the case of heat shrink tubing sections. When adapting blanks, an additional section should always be included in the calculation. The reason for this is that during the shrinking process, the tubing is not only reduced in diameter, but usually also marginally in length.

A low longitudinal shrinkage is a quality feature. The exact extent is always specified individually per shrink hose in the data sheet as a percentage, and thus the required extra length can be calculated.