Introduction
Heat Shrink Tubing is, in the simplest sense, a plastic tube that shrinks when heated. It is used for the insulation of wires and it provides abrasion resistance. It can also be used to bundle groups of wires, or, in some cases, provide identification.The one great feature of heat shrink tubing is that there is little or no shrinkage along the length, only shrinkage along the diameter, when heated to a specific temperature.
Some materials for heat shrink tubing are Polyolefin, PTFE, Viton, Silicone Rubber and PVC, of which polyolefin is the most commonly used. [1]
Single v/s Dual Heat Shrink [1]
Single / Thin wall tubing is the most common. This tubing provides a good seal thereby providing protection against water and other contaminants. Connections are also strengthened, decreasing the chances of them pulling apart. However it does not bond with the material it shrinks to. The strength is increased by friction only.
Dual Wall or adhesive Lined tubing features an adhesive lining, which melts as the tubing contracts forming a truly sealed connection. Thus, here a bond is established with the material the tube shrinks to. It drastically increases the strength of connections, taking it beyond the strength of the wires themselves.
Applications [1]
Heat Shrink tubing has many uses. Some are listed below:
- It protects against water and other contaminants.
- It provides electrical insulation. Heat shrink material is an insulator.
- It protects against extreme heat.
- It can be used for identification if the tubing is color coded.
- It can help to bundle multiple wires together.
- It helps cleanly terminate ends of braided sleeving
- It helps improve the aesthetics of large amounts of wiring
Why should we use heat shrink tubing instead of traditional insulation?
As explained above, heat shrink tubing increases strength, providing increased durability, and also improves heat resistance. Therefore, in most cases, it performs better than basic insulation. Additionally, heat shrink tubing does not come off with age or use, and it made to provide perfect fit (which cannot be said for electrical tape). Heat shrink tubing is also generally easy to install. Some can be installed manually, but some require extra machinery. [2]
Additional Information
Heat shrink tubing was invented by Raychem Corporation. It is manufactured from a thermoplastic material such as polyolefin, fluoropolymer (such as FEP, PTFE or Kynar), PVC, neoprene, silicone elastomer or Viton.[3]
The material is quite often cross-linked using electron beams, peroxides, or moisture. This helps creates the memory in the tubing which helps it shrink back to its original dimensions after heating. [1]
Heat Shrink Insulated Terminals
These terminals offer superior performance over standard crimp terminals. After crimping, the hot-melt glue lined heat shrink sleeve is heated and shrunk down onto the cable. This increases the mechanical strength of the termination and its resistance to corrosion, as the melted glue effectively seals the joint.
An image for female insulated terminals can be found here.
Buying Heat Shrink Tubes
Heat shrink tubing comes in a wide range of colors and sizes. It also comes with a variety of protection levels, including heavy wall, multiple wall, and single wall.
Here are some things to consider if you’re buying heat shrink tubing:
- Maximum diameter of your cable bundle: This will help you choose the correctly-sized heat shrink tubing.
- Temperature range of your environment : Some heat shrink tubing is rated to extremely high and low temperatures, while other tubing is designed for more moderate environmental conditions.
- Wall thickness: Heat shrink tubing is typically categorized by heavy wall, multiple wall, and single wall tubes. Thicker walls provide enhanced durability, rigidity, and abrasion resistance – but come at an extra cost and can unnecessarily thicken your cable arrangement.
- Required resistance properties: For example, your wires may be exposed to chemicals and oils
It’s also a good idea to buy heat shrink tubing that is slightly longer than you need. When heat is applied, you’ll notice that the tubing slightly shrinks lengthwise as well as widthwise, though ideally they are expected to shrink only along the diameter.
Additional Information
Heat shrink tubing comes with a range of different ratios. You’ll see these ratios advertised directly on heat shrink product descriptions or packaging. Here are the most common ratios and their uses:
2:1 ratio: These tubes shrink to half its original size when heat is applied
3:1 ratio: These tubes shrink to one third of its original size when heat is applied
Types of Heat Shrink Tubes
Elastomeric Tubes
They maintain high flexibility even at low temperatures and meet stringent international specifications. Their operating temperature range is -75 to 150 °C. A common shrink ratio is 2:1.
Fluorinated Ethylene Propylene (FEP)
It is a versatile electrical insulator and is inert to most chemicals and solvents. Additionally, it is highly resistant to extreme heat, cold, and ultraviolet radiation, making it an excellent material for heat-shrink tubing applications.
Polyolefin Tubes
The are most commonly used and have maximum use for temperatures from -55 to 135 °C, and are used by the military, aerospace and railway industries. They are flexible and fast-shrinking, and manufactured in a wide range of colors (including clear), which can be used for color-coding wires. Polyolefin tubing shrinks at 143°C. Polyolefin heat-shrink tubing typically shrinks 2:1 diametrically, but high-grade polyolefin heat-shrink is also available with a 3:1 ratio. Polyolefin tubing may withstand being touched with a soldering iron.
References
- http://ramproducts.com/6-things-need-know-heat-shrink-tubing/
- http://www.jttproducts.com/jt-t-tech-articles/An-Introduction-to-Heat-Shrink-Tubing
- https://en.wikipedia.org/wiki/Heat-shrink_tubing
- https://www.youtube.com/watch?v=ak-9BxjWMlw
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