Heat Shrink Tube Guide | Railwayscenics
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Heat Shrink Tube Guide

heat shrink

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.

There are several different types of heat shrink tube. We sell standard wall tube in a range of shrink ratios and colours, and also adhesive lined 3:1 ratio but only in black. Adhesive lind tube is manufacturered in the same way as normal tube hut has a hot melt glue on the inner surfaces which when heated melts and seals the tube. This type of tube is less flexible that normal tube but can be used where a water tight seal is required.

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 to +350 degrees Fahrenheit. This material is also highly resistant to chemicals and punctures.

What is heat shrink tubing used for?

Heat shrink tubing is used to insulate wires, and 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, protect wires or small parts from minor abrasion, and create cable entry seals.

How to select the right size of heat shrink tube

Size is very important when it comes to heat shrink tubing. If the diameter is too small, the wires will 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 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. All of our 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 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 heat shrink 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 a 2:1 shrink ratio. Shrinking temperature starts at +70 degrees C and totally shrunk at 115 degrees C.

We have started to stock shorter 240mm lengths of 3:1 adhesive lined heat shring tubes in black and red, and in 1.5, 2.4, 3.2, 4.8, 6.4, 7.9, 9.5, 12.7, 15 and 19.1mm sizes before shrinking.

We also have a small range of 3:1 non adhesive lines tube, sold in short 300mm lengths and available in red and black. It is available in 1.5, 2.4, 3.2, 4.8, 6.4, 7.9, 9.5, 12.7, 15 and 19.1mm sizes before shrinking.

We also sell a few heat shrink tube kits, which contain a handy assortment of sizes, but only in one colour.

Our full range of heat shrink tubing can be found byclicking here.

Applying heat to heat shrink tubing

Heat shrink will start to shrink at about 70degC, so heat over that temperature needs to be used. We recommend using a special warm air heat gun such as an electric paint stripper, but it is possible to use things like a very hot soldering iron or even a cigarette lighter. Just be careful using naked flames as too much heat can damage the tube, and the wire.

Heat should be applied evenly over the whole length of the tube to ensure that equal shrinkage takes place.

Do not touch the tube until it has cooled as it will be hot.

How to use heat shrink tubing

Heat shrink tubing is a 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. To get a secure fit, be sure that the tubing 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 it out of the way of any heat from soldering.

Tip: Silicone lubricant spray can be applied to wires or cords to guide heat shrink tube 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.

Creative uses for heat shrink tube

Why just use heat shrink tube as an insulation material on electrical joints. Here are a few other uses for this versatile material.

  • Stopping rattles
  • Preventing fraying of ropes, threads and shoe laces.
  • Colour coding just about anything that the tube will fit on.
  • As a replacement for insulation tape to bind cables together.
  • Adhesive lines heat shrink can be used to stop leaks in water pipes and hoses but only temporarily.
  • Fix broken glasses arms instead of tape.
  • Insulate screwdriver blades.

There may be more, but this list does show what can be done using this product.