Heat shrink sizing and materials
What is Heat Shrink Tubing?
Heat shrink tubing, also referred to as heat shrinking or heat shrink wrap, is the process of encasing wires or cables in plastic tubes that shrink when heated to form a close-fitting casing.
When it comes to heat shrink technology, understanding the intricacies of sizes and your material is pivotal. Our experts have put together this guide to shed light on how this unique cable management solution works and what you need to know when it comes to measuring heat shrink tubing. We’ll cover:
What is Heat Shrink Tubing?
What are the Benefits of Heat Shrink Tubing?
Heat Shrink Tubing Material
Color Coding
Sizing: Heat Shrink Tubing
The heat shrink process involves using a heat gun or specialized heat shrink oven. When applied to the heat shrink tube material, the tubing undergoes controlled contraction, reducing in size and conforming closely to the shape and dimensions of the wires and cables it’s covering or insulating. Heat shrink tubing is commonly used in electronics, automotive, aerospace, and marine for tasks such as wire bundling, cable identification, and enhancing the durability and safety of electrical connections.
What are the Benefits of Heat Shrink Tubing?
This shrink fitting process ensures the reliability and longevity of electrical systems and components. There are several advantages to this.
Protect Wires and Cables
Shrink fit tubing provides mechanical protection by adding an extra layer around the wires or cables. This layer helps prevent abrasion, bending, and damage caused by physical stress. It acts as a buffer, reducing the risk of wires or cables breaking or wearing out at critical points. This is especially helpful for cables in moving parts and areas that see a lot of use.
Wire and cable shrink tubing also protects cables and wires from damage caused by environmental effects, including liquids like oil, water and acids and also atmospheric factors, such as humidity, and temperature.
Heat shrink tubing is one effective way to protect cables. Learn about the others in our guide, How to Protect Cables.
Insulation
Heat shrink tubing sizes vary, ensuring the perfect fit for cables and wires. This fit means that in most cases, it performs better than basic insulation products. It’s also more reliable due to the tight fit that it provides – it won’t come off with age, in contrast with other insulation solutions.
Heat shrink material is typically made with excellent insulating properties, such as polyolefin. When the tubing is shrunk and tightly conforms to the wires or cables, it creates a barrier that insulates them, helping to prevent electrical leakage and short circuits.
Relieves Strain on Wires and Cables
Cables and wires are often stretched or put under strain due to insufficient length or being squeezed into confined spaces. This can adversely affect the lifespan of cable and wiring.
One of the benefits of heat shrink tube is its ability to provide strain relief. It reinforces cable connections, particularly at connectors or junctions, where wires are susceptible to bending and pulling. This prevents the wires from breaking due to mechanical strain.
Our experts explain other components that can help, in our Guide to Cable Strain Relief and Protection.
Bundling Cables Together
Bundling cables in heat shrink tubing presents both practical and aesthetic advantages. With so many heat shrink sleeve sizes available, you can bundle multiple cables and wires within a single tube. This approach not only yields a tidier and more organized appearance but also enhances the overall efficiency of cable arrangements. By centralizing the cables, it minimizes clutter, reduces the risk of tangling or snagging, and simplifies tasks related to maintenance and issue identification.
Heat Shrink Tubing Material
What material is heat shrink tubing? The most popular material that shrinks when heated is polyolefin, which is especially favored by the military, aerospace, electronics and railway industries. This should give you an idea of its durability. Polyolefin’s advantage derives from the cross-linking polymer chains and offers an outstanding combination of characteristics as a shrink tube material.
Heat shrink material properties: Polyolefin
| Standard application | Insulation, mechanical protection and marking |
| Features |
|
| Heat shrink ratio High-grade shrink ratio |
2:1 3:1 |
| Shrink temperature | 100°C (212°F) transparent, 3" and 4" > 100°C (212°F) |
| Maximum continuous-use temperatures | -55 to 135°C (-67 to 275°F) |
Color coding
Color-coded heat shrink tubing enables engineers to quickly and safely determine the function of cables, avoiding the dreaded cable spaghetti. This helps repairs and system management to be conducted efficiently and makes your cable and wiring appear organized and professional.
Color coding allows for easy and quick identification of different wires or cables within a bundle or assembly. This is especially valuable in complex systems where numerous connections need to be made, traced, or serviced. For example, in electrical wiring, color-coded tubing can distinguish between power cables, signal cables, ground wires, or specific circuits.
What is adhesive-lined polyolefin heat shrink tubing material?
This is a specialty solution. It’s a standard polyolefin tube with an inner-liner of adhesive that melts and flows at the same temperature at which the polyolefin tubing shrinks. When heat is applied, the tubing shrinks. The adhesive flowing fills the voids and conforms to the underlying shape to form a seal. The seal protects the interior components from moisture, debris and other contaminants.
● Typical applications: Wire harnesses and splices that need insulation and sealing in the automotive industry. Also popular with the marine sector.
Browse Adhesive-lined Heat Shrink Tubing
Sizing: Heat Shrink Tubing
You need to know these terms to determine your heat shrink sizing, which appear on technical data sheets.
Inside, or Inner, Diameter (I.D.) Supplied
This is the minimum I.D. of the tubing – before it’s heated – as supplied by the manufacturer.
Recovered Inside, or Inner, Diameter (Recovered I.D.)
Nominal recovered wall thickness has to do with your heat shrink tubing thickness. Specifically, it’s the target thickness of the wall after complete recovery.
The wall thickness of the tubing is measured in inches. When heat is applied to expanded tubing, the tubing shrinks, or recovers. The nominal recovered wall thickness, or recovered I.D., is the the measurement of the tubing’s Inside Diameter after it shrinks back to its original extruded size.
The diagram here shows you the information you’re looking for to get the right shrink tube sizes.
How to Size Heat Shrink Tubing
Before you can determine the correct shrink sleeve sizes, you’ll need to collect some information first.
Step 1: What’s the diameter of the tubing?
To get the heat shrink diameter you’ll need, measure the widest area of the materials that your expanded sleeve will slide over.
● When selecting your tubing, look at the technical sheet. You should allow an additional 20—30% allowance on your supplied I.D., which will provide enough space for the heat shrink tubing to fit over any protrusions.
Step 2: What’s the shrink ratio?
Common shrink ratios include:
● 2:1
● 2.5:1
● 3:1
This tells you that the tubing has been expanded twice, two-and-a-half times or three times it’s full recovered size. The bigger the size variations of the underlying materials that you’re covering, the larger the shrink ratio you’ll need.
Example: 3:1 shrink ratio: 3/4" will recover to 1/4" — which is 67% shrinkage.
You should know:
● A high ratio heat shrink indicates that the tubing is more suitable for connectors. The reason: it can encase the connector body and still shrink to cover a wire or cable.
● In general: the tubing’s supplied I.D. and the size of the object you’re protecting should NOT exceed a 40% ratio, in order to allow effective coverage.
Step 3: What’s the length of the tubing?
During the recovery process, the tubing will experience a small loss of length, which you’ll need to account for. Longitudinal shrinkage varies, anywhere from between 5—15%. Here again, the technical data should be able to supply you with that information.
Step 4: What’s the wall thickness?
When anything stretches, it thins out. The more stretched, the thinner it gets. In heat shrink tubing, the opposite also occurs. The more it shrinks, the thicker it gets. If it’s not allowed to return to its specified Recover I.D., then it won’t recover to its specified thickness either. You’ll find it too thin. If wall thickness is an issue for you, then take note.
Questions? We’re here to help
Download free CADs and order samples to make sure you’ve chosen exactly what you need. If you have questions about choosing the right heat shrink tubing or need any advice, email us at sales@essentracomponents.com.
You might also find it helpful to read our guide, Heat Shrink Tubing vs. Cold Shrink Tubing and Electrical Tape.
We can help you with different types of heat shrink products. You can also speak to one of our experts for help or more information on the appropriate hinge for your application: 800-847-0486.