Most commonly made of polyolefin, heat shrinkable tubing shrinks when exposed to a high temperature. The amount that the tubing shrinks depends on the heat shrink ratio of that particular tube, with common heat shrink ratios including 2:1, 3:1, and 4:1. These ratios tell how much smaller compared to the original size the tube will become. For example, with a 2:1 ratio, the tube shrinks to half the original size, and with a 3:1 ratio, it shrinks to a third of the original size.
With heat shrink tubing, you can protect wires by allowing the heat to do the heavy work instead of having to wrap them manually.
When buying heat shrink tubing, consider both the expanded (exp.) and recovered (rec.) size. You want the tube to fit snugly over the wiring, so choose tubing with a smaller shrink diameter than the wires or other item you put the tube or sleeve on.Additionally, consider the application in which you plan to use the heat shrink tube. Heavy wall heat shrink tubing uses an adhesive lining and flame retardant heavy wall material to ensure maximum protection in harsh environments and areas with a high maximum operating temperature, while thin wall heat tubing works for light duty applications and has a non-adhesive lining. Dual wall heat shrink tubing provides a water-tight seal for connectors and splices and uses a semi-rigid material.
Besides heat shrink tubing, other electrical tubing options include split wire loom flex tubing and spiral wrap tubing. Split wire loom tubing has a full length split to simplify wire installation, which, once installed, closes with a tight seam enclosure for a permanent covering. Spiral wrap tubing “spirals” around the wires, making them easy to organize, provides abrasion resistance and protects them from cuts and UV wear.