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.
Working with PTFE heat shrink tubing is not difficult, as long as you have the proper tools available. First you need a ruler and razor blade or another tool to cut the tubing. It is important to understand how the tubing shrinks and melts, in order to cut the tubing to the correct length. Sometimes the tubing might increase in length as it shrinks in diameter. The main piece of equipment, which is also the most important you will need, is a heat gun. A heat gun is able to reach the required temperatures needed to shrink PTFE tubing. The minimum shrink temperature of PTFE is around 654 degrees Fahrenheit. Heat guns come in a variety of models and styles with various options. In situations where you work with multiple types of shrink tubing, you may want to consider a model able to accommodate all of your heat shrinking needs.
PTFE Heat Shrink Tubing Can Be Applied to a Variety of Metals
There are all types of metal materials, parts and components where you are able to apply PTFE heat shrink tubing. Some industries use heat shrink tubing as insulation on electrical wires. The tubing also is used in industries where exposure to moisture and chemicals are an issue. PTFE has both excellent insulation properties and is chemically inert. While the most common applications is to apply the tubing over a piece of wire, it can also be used as a protective coating over various materials, including screws and nuts that are left exposed after manufacturing processes.
Because PTFE heat shrink tubing has such a high shrink temperature, you need to make sure the underlying wire or cable is also able to withstand this level of heat. The minimum shrinkage temperature for the tubing ranges between 654 degrees Fahrenheit, to 670 degrees Fahrenheit. Metals which have melting points significantly greater than this temperature range include brass, copper, steel and stainless steel. The tubing also works well when it is applied over glass tubing, as glass has a much higher melting point than is needed to shrink the tubing. In situations where there is an existing layer of coating of PVC or other plastic over the wire or cable, it is better to strip away the existing coating before applying the PTFE, because the existing coating will melt.
There Are Benefits to Using PTFE Heat Shrink Tubing for Your Applications
Using PTFE heat shrink tubing in various industries provide benefits that work with several different applications and processes. A common application of heat shrink tubing is to use it as a coating over cables and wiring. PTFE has corrosion resistance and is chemically resistant, so it will not degrade if it is exposed to certain types of chemicals and other corrosive agents. PTFE also creates a barrier of protection against wetness and moisture. This kind of heat shrink tubing offers excellent insulation properties when used as a coating over electrical cables carrying high voltages. Another suitable application for PTFE shrink tubing is to supply protection to underlying materials any time they are used in extremely hot or cold environments.
Bundling wires together can be accomplished by using PTFE heat shrink tubing. The process could involve cutting piece of tubing to size and first applying it to the individual wires. Once each wire has its own tubing on it, they are able to be held together and in place by using a larger piece of tubing and shrinking it around the group of wires.
Make Sure to Fully Shrink PTFE Heat Shrink Tubing on All Sides
A heat gun is commonly used to provide the necessary heat required to shrink PTFE heat shrink tubing. You need to make sure to evenly apply the heat by moving the gun back and forth to all sides of the tubing in the location where the tubing is placed. If the tubing is not shrunk correctly there could be sections of the tubing which do not seal fully. In situations where the tubing needs to be applied in tight locations you will want to remove the wire or cable, apply the tubing and then reattach it.
PTFE heat shrink tubing can be used to add support and strength to wiring and cabling when it is used in high temperature locations. PTFE has a high shrink temperature, so once it is fully attached it will remain in place, unless temperatures become extremely hot and melt the tubing. In order to actually melt the tubing off it would need to be exposed to very high and constant heat levels beyond the shrink temperature range.
Keep a Supply of PTFE Heat Shrink Tubing on Hand
In manufacturing and production industries, you should keep a supply of PTFE heat shrink tubing on hand. This type of tubing can be used to make a variety of repairs to machinery and equipment. Whenever there is a production issue, you can avoid having to shut down an entire line because you lack the right parts to make the repair. Instead, you can make the repair using this kind of tubing to get your line back up and running.