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.

PTFE Heat Shrink Tubing Provides Protection to Electrical Components, Wires and Cables

There are several different benefits gained by sealing wires and cables within PTFE heat shrink tubing. First, this type of tubing provides excellent electrical insulating properties. Next, the tubing creates a solid sealed barrier to prevent moisture, liquids or other fluids from reaching the cables or wires. Additionally, this barrier also keeps out solid particles and gases, and prevents them from coming into contact with your cables or wires.

Besides being applied to the outside of cables and wires, PTFE heat shrink tubing may also be used as a coating over other various electrical parts and components. When used in this manner, the parts and components receive the same protections experienced by your cables and wires. Further, due to the high temperature needed to melt Teflon® tubing, any object covered in it is protected from exposure in high heat environments.

When working with Teflon® shrink tubing, it is important to understand how it will react once you apply heat to it using an approved heat gun. Once the tubing reaches its shrink temperature, it starts to decrease in size and diameter. During this time, it is important to ensure the heat is evenly distributed, in order for the tubing to shrink neatly and to avoid kinking. The amount of shrinkage achieved does depend upon the shrink ratio and whether there are any restrictions. For example, a section of standard wall tubing with a 2 to 1 shrink ratio in AWG size 10 has a starting minimum inner diameter of 0.191 inches. If it is allowed to fully shrink without any restrictions, the recovered inner diameter is 0.112 inches. It should be noted that it is possible for the tubing to increase in length as it shrinks.


The Amount PTFE Shrink Tubing Shrinks Depends On whether There Are Any Restrictions

The amount of shrinkage obtained when working with PTFE shrink tubing depends upon several factors. The biggest one is the diameter of the object where the tubing is being applied. You need to determine the diameter of the object and use this information to help you select the right size of shrink tubing. Shrink tubing wall thicknesses and inner diameters are based upon both preshrunk and shrunken states. The resulting insider diameter and wall thickness depends on whether there are any restrictions. Restrictions prevent the tubing from fully shrinking.

For example, shrink tubing with a 2 to 1 shrink ratio normally has about a half reduction in the starting inner diameter and the recovered diameter. If you were to shrink a piece of tubing with a 0.50 inch starting diameter, with no restrictions, the resulting diameter would be around 0.25 inches. However, if the diameter of the object where the tubing is being applied is greater than 0.25 inches, then the actual resulting diameter will be larger. Further, the recovered wall thickness is less if the tubing is restricted during shrinkage.

Restrictions are just one issue you might face when working with PTFE shrink tubing. Another problem which sometimes occurs is where the tubing is allowed to fully shrink without restrictions, but ends up not fitting firmly around the object. This mistake is the result of using shrink tubing that is too large to fit around the object. It is easily fixed by determining the actual diameter of the object and matching tubing with a recovered inner diameter as close to this measurement as possible.

Verify PTFE Shrink Tubing Will Work Correctly by Testing

PTFE shrink tubing can be applied to a variety of metal materials in order to create a protective barrier. Because of the high temperatures required to shrink PTFE, it is worth your time to verify it properly works as desired, before fully utilizing it for your processes. For instance, you might be placing the shrink tubing around a piece of metal tubing that has fiber optic cabling running through the interior. While the metal could easily withstand being heated to around 650 degrees Fahrenheit, the fiber optic cable may not be able to withstand this amount of heat as it is transferred from the metal. In most cases, since fiber optic cable is made from glass, there should be no issues, as glass has a much higher melting point. However, you may still want to test a small section of the tubing, first, so you can ensure the fiber optic cable is not damaged and performs as required.

Measure and Cut Your PTFE Shrink Tubing to the Right Lengths

When working with PTFE shrink tubing, you will want to make sure you carefully measure and cut the tubing to the desired lengths. For some applications, you have to make sure the tubing has a slight overlap, in order to fully cover and seal the area where it is being applied. For instance, if you are making a repair to a wire harness, with a three inch crack in the protective coating, you would want to use a section of shrink tubing at least 3 ½ to 4 inches in length. This provides you with ¼ inch to ½ inch overlap on each side of the crack.

Different Wall Sizes Are Offered on 2:1 PTFE Shrink Tubing

PTFE shrink tubing with a 2 to 1 ratio is available is different wall sizes. You can choose from standard wall, thin wall and light wall, depending upon your needs and requirements. For example, with AGW size 20, the minimum expanded inner diameter is 0.060 inches and the recovered inner diameter is 0.039 inches for all three wall sizes. However, the thickness of the recovered wall will vary, with regular wall being 0.016 inches, thin wall being 0.010 inches, and light wall being 0.006 inches, plus or minus 0.003 inches.

Recovered Wall Sizes of PTFE Shrink Tubing Are Less If They Are Restricted 

The recovered wall size of PTFE shrink tubing can be less if the tubing is restricted in some manner during shrinkage. This is true regardless of whether you use standard wall, thin wall or light wall tubing. One cause for restrictions in the recovered wall size is when the tubing is placed around wire that has a larger diameter than the recovered wall diameter.

Protect Cables and Wires from Chemical Corrosion by Using PTFE Heat Shrink Tubing

You can help protect wires and cables from corrosion by applying PTFE heat shrink tubing to the outside. PTFE is chemically inert which means that it does not react or change properties when exposed to certain types of chemicals. Because your wires and cables are protected inside the tubing, they continue to provide the functionality required in chemically harsh environments.

Repair Exposed Electrical Wires with PTFE Heat Shrink Tubing 

Anytime the protective coating comes off of electrical wires, it creates a hazard. If the bare wire were to be exposed to water, accidently touched by bare hands or come into contact with another metal object accidents will occur. While you could replace the entire length of wire with brand new wire, this is not the most cost effective manner. Instead, PTFE heat shrink tubing is commonly used to make repairs to the existing wire in the areas where protective coating is missing.

Create Solid Encapsulation by Using PTFE Shrink Tubing with an Inner Layer of FEP Shrink Tubing

For certain applications you might need to use PTFE shrink tubing has an inner layer of FEP shrink tubing. The reason for using this type of dual layered heat shrink tubing is for situation where you require an almost solid encapsulation around the location where the tubing is being applied. As the PTFE tubing shrinks the inner layer of FEP tubing melts. Once the tubing fully cools the inner layer becomes solid. The dual layer tubing is well suited for applications where stress from vibrations and pulling can be severe.

Many Different Industries Use PTFE Shrink Tubing for Their Applications

PTFE shrink tubing is used for a variety of applications in many different industries. For instance, this type of tubing is used to manufacture wire harness assemblies used in the automotive industry. Because the tubing has a high heat tolerance it can be used to cover wiring and cables used in close proximity to the engines in vehicles. The tubing creates a protective barrier around the wiring and cables to prevent them from being damaged from exposure to high heat levels, as well as moisture.


Determine the Correct Size of PTFE Heat Shrink Tubing by Performing Tests

Deciding which size of PTFE heat shrink tubing will be suited for your applications may require some prior testing. By testing different sizes you are able to determine the ones that work best. You can often request small samples of various sizes in order to conduct your testing. Once your testing is completed you are able to order larger quantities of the desired size for your business.

You Can Order PTFE Heat Shrink Tubing in Standard and Custom Lengths

You can order PTFE heat shrink tubing for your business in standard four foot lengths whenever you cut your tubing to length yourself. Another option which will save you time is to order your heat shrink tubing already custom cut to the lengths you require. You are also able to use a combination of both of these ordering options in situations where you desire customized cuts and standard lengths for specific applications and purposes.

You Can Order PTFE Shrink Tubing Already Cut to Custom Lengths

Any time you use a large amount of PTFE shrink tubing in the same lengths, you should consider ordering it already cut to size. By taking advantage of this optional service you can eliminate having to cut your tubing before being about to use it. Instead, you save time and are able to complete tasks faster while ensuring you have a proper supply and stock of tubing on hand whenever you need it.

PTFE Shrink Tubing Creates a Protective Barrier over Cables and Wires

PTFE shrink tubing can be used for electrical and medical components. Since this type of tubing has a higher shrink temperature it helps to create a protective barrier over cables and wires that could be exposed to high temperatures. Further, the tubing does provide insulation properties as well as protects surrounded materials from exposure to water and moisture.

Use PTFE Shrink Tubing for a Variety of Applications

You can use PTFE shrink tubing for a variety of applications and purposes. This type of tubing helps with such situations like bundling cables and wires, electrical insulation, wire and cable splicing, protection against corrosion, moisture and abrasion, as well as protection against the elements when it is used in outdoor settings. The size of tubing you require does depend upon how and where you intend to use it. You will need to choose tubing with a large enough opening to fit around the items where you plan to shrink it.

You have to Cut PTFE Shrink Tubing to Size When You Order it in Bulk

If you order your PTFE shrink tubing in bulk, you have to cut it to size when you want to apply it. You should start by measuring the length of the section you require in the area where it is to be placed. Now use this measurement on the tubing and cut it to the correct size. You may choose to cut the piece of tubing slightly larger in order to have a slight overlap. Before sliding the tubing over the location, hold it up and visually inspect it will fit correctly. Now slide it over the cable or wire to the area you want it applied. The final step is to shrink the tubing using a heat gun or other suitable appliance.