What Is Heat Shrink Tubing?
Heat shrink tubing is a special type of plastic sleeving that shrinks when you apply heat from a heat gun. Heat shrink tubing is used to permanently cover and protect cable terminations, wire splices, and electrical connections. Shrink tubing is an electrical insulator but also provides mechanical and environmental protection to electrical wires. In use, the tubing shrinks to snugly fit the dimensions of the item, leaving a permanent, professional, and aesthetically pleasing finish.
How Does Heat Shrink Tubing Work?
The manufacturing process for heat shrink tubing is deceptively simple. Initially, the manufacturer extrudes a continuous length of tubing using an appropriate thermoplastic material together with various additives. After cooling, the manufacturer irradiates the material to create links between different molecules (cross-linking). Using heat and vacuum forming, the manufacturer stretches the tube to its expanded diameter. When placed over a wire and heated, the tube shrinks back to its initial diameter (recovery size) creating a neat and tight seal.
Where Do You Use Heat Shrink Tubing?
You can use heat shrink tubing to cover and protect electrical wires, leads, terminals, and electrical connectors. Applications for heat shrink tubing include:
| Electrical Insulation: | to insulate exposed connectors and wires |
| Mechanical Protection: | to provide strain relief and protect wiring and harnesses from mechanical damage, cuts, and abrasion |
| Environmental Protection: | to create a chemical and waterproof seal around components |
| Organization: | to group individual wires into a neat and managable harness |
Heat Shrink Tubing Characteristics
Characteristics to note include the extended and recovery diameter, shrink ratio, and wall thickness.
Diameter
Two key parameters for selecting heat shrink tubing are the expanded diameter and recovery diameter:
- Expanded diameter: This is the size of the tubing as purchased. It should be large enough to fit over the components you're protecting, including plugs and receptacles.
- Recovery diameter: This is the smallest diameter the tubing will shrink to after heating and should be smaller than the minimum diameter of the items you're covering for a tight fit.
Shrink Ratio
The shrink ratio is the difference between the expanded (initial) diameter and recovery (final) diameter of the tubing. Typical values include:
| 2:1 | The most common type where the tube shrinks to half its initial diameter |
| 3:1 | Useful for covering items with different diameters, the tube shrinks to one-third of its original diameter |
| 4:1 | Best for covering wires and receptacles that have significantly different diameters, or when you need to slide the tube over a bulky item before shrinking |
Wall Thickness
The nominal wall thickness represents the thickness when the tube is fully shrunk to its recovery diameter. Because the tube diameter after shrinking will generally be larger than the recovery diameter, the final wall thickness will be slightly less than the stated wall thickness.
Shrinkage
When you heat the tubing, you should expect a degree of overall shrinkage. You can counter this property by heat shrinking one end first.
Different Types of Heat Shrink Tubing
Standard Applications
The most popular types of heat shrink materials are polyolefins and polyvinyl chloride (PVC). Both offer good performance and are economical. Polyolefin heat shrink is flexible, durable, and fast shrinking. It shrinks at 90 degrees Celsius and has a maximum usable temperature of 130°C. PVC tubing is more economical than polyolefin but has a lower maximum working temperature of 105°C. PVC is abrasion-resistant and has good tensile strength.
Special Applications
Allied Wire & Cable (AWC) stocks an assortment of specialty heat shrink materials for specific applications where standard materials aren't suitable. These include:
- High temperatures
- Superior chemical, fuel, and oil resistance
- Greater strength.
Adhesive-Lined Heat Shrink
Otherwise known as dual wall tubing, adhesive-lined tubing has an internal layer of glue that's activated when heated to form a permanent, tight, and impermeable seal.
Contact us to learn more about the best heat shrink tube for your project.