Shrink Tube: An Ultimate Guide For Beginners

FACTS CHECKED BY  Jose George​

In 1962, Raychem Corporation came up with the idea of a heat shrink tube. It’s suitable for electrical insulation, protection, abrasion, and wire sealing. Different applications need different types of electrical shrink tubing. How do I choose one?

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What is a shrink tube?

It’s a type of electrical insulation tubing called heat shrink tubing. It bends to fit the structure of the surface below, making it easier to put on quickly. When you apply heat to it, the tubing activates and shrinks. It has a high expansion ratio; thus, it can fix many destroyed jackets with the connectors. 

Moreover, it is better than another type of electrical insulation tubing because you can make heat shrink to fit the shape of the cable or wire connection point better than other types of tubing. As a result, they will be able to withstand a lot of different things that happen outside. 

As there are so many cables and hoses, the heat shrink tube comes in a wide range of sizes, thicknesses, colors, and materials. For example, single-wall tubing and double-wall tubing. Also, you can see heat shrink tubing in spools, pieces of 1.2m lengths, and cutouts.

Shrinkable heat pipes

Caption: Shrinkable heat pipes

Shrink tube manufacture

First, choose the appropriate material for the intended usage. Then, compound the material with additional ingredients such as colors, stabilizers, etc. Next, transform the raw material into a start tube via extrusion. The process follows up a cross-linking step, in which they subject the radiation line. Here, create a tube memory via cross-linking. Afterward, heat the tube to a temperature up to the polymer crystal’s melting point and enlarge it in diameter. During the process, the machines rapidly chill while it is expanded. The tubing returns to its original shrinking size when the end-user heats it.

Heat-shrink tubing with a UV stabilizer added for outdoor use is standard. Here, you can use electron beams, peroxides, or moisture to cross-link the material. Heat-shrink tubing results from this cross-linking, making the tubing shrink back to its pressed dimensions when heated.

shrink tube materials

Here is the list of raw substances you can use to manufacture the shrink tubes.

  • Elastomer
  • neoprene
  • Fluorinated ethylene propylene (FEP)
  • Polyolefin
  • PVC
  • thermoplastics
  • Polyvinylidene Fluoride
  • Silicone Rubber
  • PTFE (fluoropolymer)
  • Viton

Other heat shrink tubing materials and woven fabrics offer additional resistance to moisture, fuel, and abrasions in harsh environments. These are made-to-order and not commonly accessible in-store.

How to use a heat shrinking tube?

You can use a heat shrinking tube in the following way. First, slide the unshrunk tubing onto the wire before making any connection. If the line is tight, you can use a silicone lubricant for a smooth fix.

Then, heat the tube using a heat gun or put it in the oven for some time. You can also heat it by holding the soldering iron or a lighter close to the tube. However, uncontrolled heat can cause uneven shrinkage, physical damage, less abrasion resistance, and insulation failure. On the other hand, exposing the line to overheating can melt it or form scorches on the surface.

Moreover, heating can cause the tube to shrink about half, or up to one-sixth of the original size. You can also shrink it longitude-wise, but it might be uneven and not snugly fit on the wire correctly. In some cases, the electricians use a layer of thermoplastic adhesives to firm the tube and provide a good seal for abrasion and moisture protection.

Shrink tube types

As for the types, you can get color heat-shrink tubes for color-coding of cables. In the early 21st century, people used heat tubing for PC modification to make the interior less messy and offer a beautiful appearance. Manufacturers responded by manufacturing shrink tubes with bright and UV-reacting properties.

Shrink tubes with a conductor liner are offered for application on non-solder junctions. The heat source melts the solder inside the shrink tube, electrically joining the wires and insulating its connection. Solder sleeves often have a heat-activated sealing ring on the ends of the tubing, making the connection watertight. Heat-shrink end caps also protect the disjoints on the ends of the wires.

Tips for Selecting the Right Type of Heat Shrink Tubing for Your Needs

Here are some tips you need to consider while selecting the correct type of heat shrinking tube for your intended application

Heat Shrink Ratios

Consider the heat shrink ratios as the higher the shrink ratio, the lesser the shrinking of the tube upon heating. For example, the 2:1 shrink ratio means that the line will reduce to half after heating, and 4:1 means shrinking up to one-fourth of the original. That way, you can buy the best-fit tube.

The Wall Thickness

Thicker is the wall; better is the protection against abrasions and other outer factors. Thus, if you need rigidity, go for a thick shrinking tube.

The Stiffness

Every sleeve is available in different levels of flexibility. So, if you want to achieve strain relief in connectors and terminals, go for stiff shrink tubes.

Sealing Ability

Heat shrinking tube seals the area between the tubing and the object. In some lines, there is a layer of meltable glue present inside. Thus, when you heat the tube, it shrinks, and the glue inside makes a firm layer taking the sealing ability one step further.

Shrink Temperature

There is a fixed shrinking temperature for every material. For example, polyolefin temperature ranges from 90 degree Celsius, whereas other like Teflon materials has 250 degree Celsius. So, consider the shrinking temperature while you buy a heat shrinking tube.

Heating Methods

Usually, people heat the shrinking tubes with a hand-held gun. However, if you want to do it on a higher level, you can use a flow-through oven. The flow-through oven ensures that the tubing is completely cool before fixing the wires.

 You can also use focused lights to heat the tube. For that, you will use halogen bulbs, and as the temperature gets higher, the tube shrinks.

The Sleeve Diameter

Said, don’t shrink the sleeve. It’s critical to utilize heat shrink tubing with a final shrink diameter smaller than the sleeved item. If the object is smaller than the final shrink diameter, the sleeve will not fit tightly.

Choosing the optimum heat shrink tubing size for the electrical setups that require accurate measurements. The length of the shrink tube needed depends on the components to be wrapped. The tube ID should be around 25% greater than the most significant component to be covered. It enables easier tube sliding over the element. The minor component’s measurement determines the tubing’s shrink ratio.

The material

Various shrink sleeves are required for different situations. Due to their chemical resistance, 2:1 High Temp Viton Heat Shrink Tubing and diesel resistant heat shrink are ideal for industrial applications.

Due to its temperature and chemical resistance, the 2:1 Polyolefin Heat Shrink is also a standard for packaging and shielding wires. Moreover, Dual wall adhesive lined heat shrink sleeving protects against moisture. Some fabric shrink sleeving contains a blend of Polyolefin Materials and Polyester strands to withstand water.

Kynar heat shrink tubing is perfect for small spaces like fuse covers since it is heat resistant and flexible. The military and aerospace use these shrink tubes because they are flame-resistant and resistant to lubricants and hydraulic fluids. But heat shrink tubing resistant to diesel is also an option.

Conclusion

Heat shrink tubes provide an insulation layer to the top of the wire. With its help, you can join two conducting wires and cover the area between them. Moreover, heat shrink tubes are available in many materials, and you can choose what best suits you. Here at Bloom, we offer wiring harnesses and cable assemblies. Our connection is made with attention to detail.

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