Heat Shrink Tube Guide

What is heat shrink tubing

Heat shrink tubing is a flexible, pre-stretched tube, which is engineered from a range of polymers that will shrink to a fixed diameter when sufficient heat is applied. The thickness and diameter can vary. Heat shrink tube is rated by its shrinkage ratio.

How Heat Shrink Tubing Works

If you think about it, heat shrink tubing works in the opposite way that most would imagine. Many objects expand when heated and contract when cooled, so the term heat shrink tubing almost sounds like an oxymoron. However, the key to how it works lies in how it is made.
When heat shrink tubing is created its original diameter is what you would typically think of as the post-shrinking size. To make the tubing have a larger diameter it is heated to near its melting point and then expanded, typically by inflating it with a gas. After the tube is expanded it is then rapidly cooled so it retains its new shape. This is what makes heat shrink tubing work, as when you heat the tubing up it becomes soft and contracts to its original size in diameter but not length.

Heat Shrink Tubing Materials

The science bit. Among the common shrink tubing materials are elastometic, fluorinated ethylene propylene (FEP), polyolefin, polyvinylidene fluoride (PVDF), PTFE, PVC, silicone rubber, and Viton. Perhaps the most flexible is the PTFE, a fluoropolymer tube that functions in temperatures ranging from -130 degrees to 350 degrees Fahrenheit;. This material is also highly resistant to chemicals and punctures.

What is heat shrink used for

Heat shrink is used to insulate wires, provide abrasion resistance and environmental protection for stranded and solid wire conductors, connections, joints and terminals in electrical engineering. It can also be used to repair the insulation on wires or to bundle them together, to protect wires or small parts from minor abrasion, and to create cable entry seals.

How to Select the Right Size of Heat Shrink Tubing

Size is very important when it comes to heat shrink tubing. Obviously, if the diameter is too small, the wires do not fit inside the tube. However, a too large diameter presents problems as well. Heat shrink tubing only shrinks as far as it is designed to. Therefore, a ratio of 2:1 means the heat shrink tubing reverts to a size that is half of its current diameter. Similarly, other sizes, such as 3:1, 4:1, 5:1, and 6:1 shrink only to the intended extent. Heat shrink tubing circumferences range from 1.2mm up to over 60mm.

How to Buy Heat Shrink Tubing

We sell heat shrink tubing in the smaller sizes, as there is no real practical use for the larger sizes in railway modelling. We also only sell in one length, but in many colours. Al of out heat shrink tubing is of the 2:1 variety, which means it will shrink to half of its original size.
All you have to do is to measure the wires you wish to protect and find a suitable size covering to meet your requirements.

The heat shrink tubing we sell

We stock tubing in 1.6mm, 2.4mm 3.2mm, 4.8mm and 6.4mm un-shrunk sizes in black, blue, clear, green, grey, purple, red, white and yellow. All are available in 1.2m lengths in 2:1 shrink ratio. Shrinking temperature starts at +70 deg C and totally shrunk at 115 deg C.
Our full range of heat shrink tubing can be found by clicking here.
We also sell a few shrink tube kits, which contain a handy assortment of sizes, but only in one colour.

Using heat shrink tubing

Heat shrink tubing is one versatile product. Insulating your cables with heat shrink tubing can be an easy do-it-yourself activity. Just use the following helpful how-to guide for a smooth-running project which will give great results.

Step 1

Select the proper size of heat shrink tubing for your project. In order to get a secure fit, be sure that the tubings recovered diameter (the diameter after shrinking) is smaller than the diameter of the area you are going to insulate. At the same time, the tubings expanded diameter (the diameter before shrinking) needs to be large enough to easily fit over the area to be insulated, as well as any connectors attached to it.

Step 2

Cut the heat shrink tubing to the required length, and be sure to allow for a minimum 8mm overlap over any existing insulation or connectors.
If joining wires remember to slide the tubing onto one of the wires and keep out the way of any heat from soldering.
Tip: Silicone lubricant spray can be applied to wires or cords to guide heat shrink over them without compromising the heat shrink material.

Step 3

Slide the cut tubing over the object that you are covering. If you are covering a splice slide the tubing over the centre of the splice, and allow for equal overlap on both sides.

Step 4

Evenly apply heat over the whole length and around the entire diameter of the tubing, until it is uniformly shrunken and conforms to the shape of the cable, hose, or splice that it is covering. Immediately remove the heat source, and allow the tubing to cool slowly before you apply physical stress to it.
Avoid overheating the heat shrink tubing, because it will become brittle and/or charred.