How to Choose the Right Heat Shrink Tubing

 When working on cabling and other similar components, sometimes you need to take a step or two back in order to correct certain mistakes, which we all make. Re-wiring is oftentimes the most common solution and for this, you need to splice wires and patch them up afterwards.

This is where heat shrink tubes are used in order to keep the wires in place but also to protect them from any external factors. A shrink tube is a long plastic sleeve that goes over the cable and it shrinks when heat is introduced, solidifying and at the same time securing the wiring in place. Simple and easy to use, shrink tubes come available in different sizes and are made from different materials too.

What to Look for in Heat Shrink Tubing

Diameter

The diameter of the sleeve is going to determine how thick of a cable or wiring you'll be able to use it with. The larger the diameter of the tube when shrunken the more it can accommodate but you don't want it to be too large as it will be loose. The diameter of heat shrink tubing shouldn't be too small either as it will apply too much force on the wiring.

Wall

The thickness of the wall or the tubing overall is going to determine how well-insulated the wiring will be. Thicker walls often mean better protection and insulation but that's not always the case as both also depend on the material the shrink tube is made of.

Shrink Ratio

The shrink ratio represents how much the tubing will reduce its diameter when heat is applied. A good rule of thumb is to never use a higher shrink ratio than what's needed. For instance, a 2:1 ratio means you get 50% of the original diameter reduced. If you buy heat shrink with a 3:1 ratio you will get more than 60% of shrinkage.

Longitudinal Shrinkage

This type of shrinkage refers to the total length of the tubing that's going to be reduced down to the shrink ratio it has. This is expressed in percentage and it's in relation to the original tubing. While there is a small loss of length there is usually between 5% and 15% of longitudinal shrinkage depending on the material the tubing is made of. 

Seal

It's not all about how much the tubing shrinks or how thick it is, sometimes the seal it provides is also important. While not always the case, when sealing plays an essential role, you should look to buy heat shrink with an inner layer that will melt and one that's made of a material that can withstand contaminants. 

Requirements

Although all of the above features are important, they are not going to be as important as the requirements of the environment the shrink tube will be used as well as the electrical requirements of the property. All of these need to be satisfied by the properties of the tube in order for their use to be effective and safe.

Types of Heat Shrink Materials

PVC

PVC or polyvinyl chloride is quite a common material used for shrink tubing which is mainly because of its smooth surface and highly versatile nature to conform to any surface and still offer great levels of protection.

FEP

Also known as Fluorinated ethylene propylene, FEP shrink tubing is resistant to chemicals and it has excellent sealing properties. It also shrinks at a much lower temperature than PTFE.

PTFE

Talking about PTFE or polytetrafluoroethylene better known as Teflon makes for highly resistant shrink tubing when it comes to chemical spills with a low coefficient of friction. Anything that drops on it will slide off almost immediately. 

Polyolefin

The most commonly used shrink tubing is polyolefin since it's resistant to high temperatures as well as chemical contamination. It may not be the most impressive but it gets the job done most of the time.

PVDF

PVDF or polyvinylidene fluoride is known to be a very robust material and to withstand corrosive chemicals, industrial fuels as well as flames. If you want tubing that won't get perforated easily, PVDF is the way to go.

Elastomeric

Known for its extreme flexibility and abrasion resistance, elastomeric shrink tubing is used in the most demanding industrial environments. If diesel fuel or hydraulic fluids are present, elastomeric tubing is recommended. 

Silicone

Just like elastomeric shrink tubing, silicone tubing is quite flexible but it's also resistant to extreme temperatures both high and low. This makes silicone tubing ideal for the insulation of heating elements and for the bundling of fibre optic cables. You'll also find silicone shrink tubing used in the medical field as it can survive sterilisation conditions.

Viton

Viton shrink tubing is made from a unique material known as fluoroelastomer which is essentially synthetic rubber. It's not only resistant to high temperatures and quite flexible, but Viton tubing is also able to provide excellent sealing properties against oils, lubricants and fuels.