Heatshrink Tubing is most commonly used as an insulation in wiring applications, where wires need to be spliced or repaired, and has replaced Electrical Tape and wire nuts in many applications. Heatshrink tubing comes in a wide variety of sizes, from as little as 1/16 of an inch, to as large as 3 inches or more, in a range of wall thicknesses. Heatshrink tubing, as its name suggests, is designed to shrink when heat is applied to it. When doing electrical assembly, this is a useful property, since it allows a continuous band of insulation to be neatly formed around a splice in a wire. Electrical tape has a tendency to come unraveled, and it is difficult to get it wrapped neatly and tightly around smaller gauge wires.
How is heatshrink tubing made?
Electrical heatshrink tubing is made by extruding a polymer such as polyolefin through a die. More sophisticated types of heatshrink tubing can have several layers, usually an inner layer of a meltable thermoplastic adhesive, along with one or more outer layers chosen for abrasion resistance, rigidity, shrink ratio, or insulation properties. By stretching the newly formed tubing before it fully cools, the tubing's molecular structure is disturbed in such a way that the tubing shrinks in diameter when heat is applied and starts to break down some of the cross-linked bonds which maintain its larger diameter, and the tubing softens and shrinks, to as little as a quarter of its original diameter.
Applications around the house and car
Regardless of how it is made, heatshrink tubing is something that belongs in just about every do it yourselfer's toolbox. for a typical home owner, good sizes to have are 3/32" and 1/4" diameter tubing, which will repair wires from #22 AWG to #12 AWG, but other sizes are available. Its most common use is to repair wiring, such as a chafed wire inside an appliance, under the hood of a car, or for splicing wires when installing a car stereo or other accessories.
How to use Heatshrink Tubing
The main thing to remember about heat shrink tubing is that it requires a little advance planning. If you have to repair a broken wire, you need to slip the tubing over the wire before soldering it together. Also, make sure you slide the tubing at least an inch or two away from the splice, or else the heat of the soldering iron will start to shrink the tubing before you are ready. Use a neatly twisted lap joint in the wire, and make sure no solder whiskers or bits of stranded wire are sticking up. Let the joint cool and slip the tubing over the joint, making sure it overlaps intact insulation on both sides of the splice. Apply heat to the tubing with a lighter, hair dryer or heatgun, and make sure it shrinks evenly around the joint. Voila an instant neat splice as good as new! With a little planning, multiple layers of tubing can be used to beef up the insulation in vulnerable areas, or to build up the diameter of a cable so it can be held firmly by a strain relief clamp. While it won't replace electrical tape for every application, its continuous band of insulation that will stay where its put will improve the safety and reliability of whatever equipment you build, install, or repair with it.