PTFE Heat Shrink Tubing: Wall Thickness After Recovery


Recently a customer wanted to use some PTFE shrink tubing to cover the shoulder of a bolt as a slip surface and had questions about the wall thickness of shrink tubing. In this customer’s application they were starting with a 0.140” mandrel (the shoulder of the bolt), and the tubing they were considering had a nominal recovered wall thickness of 0.010” with a tolerance of +/-0.003”.

The customer’s main question was: “After going through the heat shrink process, what would you estimate the wall thickness to be and how uniform is it?”

We frequently receive questions like this about estimating wall thickness. In this case, our customer was trying to work out if he would be dealing with a finished outside diameter on the low end of 0.154” (the mandrel plus the two walls, 0.140”+0.007”+ 0.007”) or on the high end of 0.166” (the mandrel plus the two walls, 0.140”+0.013”+ 0.013”). From the highest possible outside diameter to the lowest, a 0.012” swing can make a big difference so the concern is valid and raises two other questions. First, what is allowed in order for the product to be considered within specifications? Second, what do users need to make the product work for their application?

For this post, we are going to make the assumption that the products are going to be in spec because at Component Supply, we distribute quality products and, honestly, we are awesome pretty much all of the time. So, let’s go over the aspect of making the product work for the application. In general, we have found that the wall thickness is fairly true to the nominal or within +/-0.001”. So, for the typical application you can plan on that being the case. In the example we have been using, this would yield an overall outside diameter between 0.158” (the mandrel plus the two walls, 0.140”+0.009”+ 0.009”) or on the high end of 0.162” (the mandrel plus the two walls, 0.140”+0.011”+ 0.011”).

Just a side note: we would not suggest that you do something like design a product with tighter specifications than what is called out in our charts. That’s just a good way to disappoint a lot of people.

DuPont® Developed Teflon® Heat Shrink Tubing

Teflon® heat shrink tubing was developed by DuPont®. It is a synthetic material derived from a fluoropolymer called polytertafluoroethylene, useful for a wide variety of applications and purposes. You may have also heard of this type of tubing being called PTFE, which is simply the abbreviation of polytertafluoroethylene.

Teflon® has high heat resistances, which makes it suited for use in a variety of forms, ranging from coatings to cookware, to being used as regular tubing, as well as heat shrink tubing. Because it is a widely used material, it is vital you verify the type of tubing you order is exactly what you require. Sometimes people accidently order regular PTFE tubing in place of heat shrink. Regular PTFE does not shrink, and retains its original shape and diameter. It is beneficial for use in guide wire assemblies, fluid delivery and other such applications.

Many of the same benefits found in other forms of PTFE also apply to heat shrink tubing and include:


  • Lubricity
  • High durability and strength
  • Electrical insulating properties
  • Solvent resistance
  • Chemical resistance
  • Abrasion resistance
  • Shock resistance
  • Ability to withstand temperatures in harsh environments
  • Creation of a sealed barrier against water, moisture and other liquids

In addition to being offered as a single form heat shrink tube solution, PTFE is also available in a special type of shrink-melt tubing. This unique kind of tubing uses PTFE on the outer layer, and FEP in the inner layer. As the tubing is heated up, the inner layer of FEP melts and creates an additional seal around the objects where it is being applied, while the PTFE shrinks and creates its barrier of protection.


Teflon® Heat Shrink Tubing Is Designed for a Variety of Environments

Teflon® heat shrink tubing is used by a variety of industries for applications whenever they require a viable material which is able to withstand a wide range of temperatures, is chemically inert, provides excellent electrical insulating properties, and can be used in wet environments. For example, automobile manufacturers coat wires and cables with Teflon® shrink tubing that is connected directly to the engine. Because the engine gets extremely hot, other types of materials would melt away, leaving exposed wiring and cables. This could create a hazard, as water is able to get under the hood of a vehicle when it is raining or snowing outside, from different areas, including underneath the vehicle.

Automobile manufacturers also use Teflon® heat shrink tubing along with the various metal tubing used to deliver gasoline, oil and other lubricating fluids to different areas of the vehicle. This is because Teflon® is a chemically inert material which will not react if oil, gasoline or other fluids come into contact with the Teflon®. The heat shrink tubing also serves as a barrier in the event the metal tubing it is covering was to develop a crack as it helped to prevent leaks. Another area where Teflon® shrink tubing is used in vehicle production is to create wiring harnesses. Wiring harnesses help hold together a large number of wires and prevent them from becoming tangled. It is common for the harnesses to have a plug adapter at the end, where each individual wire is attached to a different connection on the adapter.

Teflon® Heat Shrink Tubing Is Available in Different Walls

Teflon® heat shrink tubing is available in several different walls to fit with your needs and requirements, including standard wall, thin wall and light wall. All three wall types are offered with a 2 to 1 heat shrink ratio, which means the tubing shrinks down to about half of its original size, as long as there are no restrictions. You are also able to find thin wall heat shrink tubing available with a 4 to 1 heat shrink ratio. A 4 to 1 shrink ration means the tubing will shrink down to about one quarter of its original size, without any restrictions.

Use a Heat Gun for Shrinking Teflon® Heat Shrink Tubing

There are different kinds of issues or problems which you may face when working with Teflon® heat shrink tubing. For example, one issue faced is being able to generate enough heat to shrink the Teflon® tubing. In most situations, it is possible to resolve this issue by making sure you have the right type of heat shrink equipment, such as a heat gun. A heat gun is similar to a hair dryer, in its shape and size, but is able to generate temperatures at a much higher level. These higher temperatures are required in order to start the shrinking process of Teflon® tubing. Heat shrink guns are also able to be used for other types of heat shrink tubing, including FEP, Raychem® polyolefin, Iridium class IV polyolefin, and Palladium Pebax® tubing, as most heat guns are able to generate a wide range of temperatures.

Create an Added Layer of Protection over Hypodermic Tubing by Applying Teflon® Heat Shrink Tubing

Teflon® heat shrink tubing can be applied over sections of hypodermic tubing to create an added layer of protection. Teflon® is able to withstand both extremely hot and cold environments and acts as a barrier between your tubing and the exterior conditions. You are also able to use this method anytime you want to protect the tubing from exposure to wet and damp conditions from water and other harsh liquid chemicals.

Use Teflon® Heat Shrink Tubing to Increase the Strength of Cabling and Wiring 

Another application for Teflon® heat shrink tubing is to increase the strength of cabling and wiring. Teflon® is able to help relieve some of the strain and stress placed on repeated movements. It also helps to prevent accidental breakage when it is securely and properly applied. You can even use heat shrink tubing to make repairs and splice sections of cabling and wire back together without having to replace an entire assembly.

You May See Teflon® Heat Shrink Tubing Listed by Its Chemical Name or Abbreviation

Teflon® heat shrink tubing may be identified by its chemical name or abbreviation since Teflon® is a brand name. You might see this type of tubing listed as PTFE or polytertafluoroethylene heat shrink tubing. Regardless of how the tubing is identified it functions and preforms the same. Any time the right amount of heat is applied to the correct size tubing it will shrink and create a firm fitting over various kinds of materials.

Make Sure to Select the Correct Shrink Ratio When Using Teflon® Heat Shrink Tubing

There are several different heat shrink ratios available with Teflon® heat shrink tubing. The heat ratios refer to the amount of shrinkage the tubing will provide after heat has been applied based on the starting size of the tubing. It is important to understand the differences between the ratios in order to select the right type of tubing for your applications. For example, a ratio of 2:1 means the tubing shrinks to about half of the starting size.

Teflon® Heat Shrink Tubing Is Also Called PTFE Shrink Tubing

Teflon® heat shrink tubing is another name given to PTFE shrink tubing. Teflon® is the brand name given to polytetrafluoroethylene which is a synthetic material. Specifically, PFTE is a fluoropolymer made from tetrafluoroethylene. Teflon® has several properties that make it an ideal product to use in a variety of applications. The tubing does require heating it to the correct melting temperature in order to shrink the tubing firmly in the locations where it is being applied.

Teflon® Heat Shrink Tubing Has Many Useful Purposes for Various Industries

A variety of industries have useful purposes and applications for Teflon® heat shrink tubing. This type of tubing is used as an insulating material for electrical wiring and is often used as part of manufacturing process to create bundled wiring harnesses. PTFE tubing can be used to create a barrier against chemicals, corrosions, bases, acids, and moisture. You are also able to use this tubing for increasing the amount of resistance against shock and strains created by moving components within various products.

Use the Preshrunk Diameter to Select Teflon Heat Shrink Tubing

Teflon heat shrink tubing is available with different size diameters. The size given refers to the preshrunk diameter size of tubing. You have to know this diameter in order to select the size tubing you require. You should select sizes based upon the diameter of cable or wires where you want apply tube. In addition to using the preshrunk diameter, you will also need to take the heat shrink ratio into consideration.  

Understand the Ratios Used with Teflon Heat Shrink Tubing

You will need to understand heat shrink ratios when working with Teflon heat shrink tubing. These ratios tell you how much the tubing shrinks from its original size to its shrunken state. For example, if you had a section of tubing with a ½ inch opening and a 4:1 ratio, the tubing would shrink down to about a 1/8 inch opening after fully shrunk. On the other hand, if you had the same size tubing, but with a 2:1 ration, the tubing would shrink down to about a 1/4 inch opening.

Teflon Heat Shrink Tubing Protects Wiring in Wet Locations

Both medical and electronic industries use Teflon heat shrink tubing. This type of tubing has several features which makes it suitable for a variety of environments and situations. Teflon is a good electrical insulating material, which keeps wires contained and sealed inside the Teflon. The Teflon acts as a barrier against water and other liquids, so it is possible to run electrical wiring through wet locations.

Teflon Heat Shrink Tubing Can Be Used Protect Devices and Equipment You Autoclave

Teflon heat shrink tubing can be used on the outside of devices and equipment, which are autoclaved. Since the melting point is much higher than the autoclaving process, the Teflon will remain solid and protects the objects it is used around. Teflon tubing provides the necessary thermal protection for sensitive devices and equipment so that they are able to reach the temperature needed for autoclaving processes without getting damaged.