Heat Shrink Tubing

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Short Definition
A polymer tube which shrinks when exposed to heat. Used to insulate and protect connections.
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Heat-shrink tubing (or, commonly, heat shrink or heatshrink) is a shrinkable plastic tube used to insulate wires, providing abrasion resistance and environmental protection for stranded and solid wire conductors, connections, joints and terminals in electrical work. 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, offering environmental sealing protection.

The unshrunk tubing is slipped on to the wire before making the connection, then slid down over the joint after it is made. The tubing is then shrunk to wrap tightly around the joint by heating in an oven or with a hot air gun or other source of heat. Convenient but less consistent methods for shrinking the tube include a soldering iron held close to but not touching the tube, or the heat from a lighter. Uncontrolled heat can cause uneven shrinkage, physical damage and insulation failure, and these methods are not recommended by heatshrink suppliers.

Heating causes the tubing to contract to between half and one sixth of its original diameter, depending on the material used, providing a snug fit over irregularly shaped joints.

The tubing provides good electrical insulation, protection from dust, solvents and other foreign materials, and mechanical strain relief, and is mechanically held in place (unless incorrectly oversized or not properly shrunk) by its tight fit.