Heat shrink tube (or more commonly called a heat shrink or heat shrink) is a shrinkable plastic tube used to insulate wires and provide wear resistance and environmental protection for stranded and solid wires, connections, joints and terminals in electrical engineering. It can also be used to repair the insulation of wires or tie them together, to protect wires or small parts from minor wear and tear, and to make cable inlet seals to provide environmental seal protection. Heat shrink tubes are usually made of polyolefin and shrink radially (but not longitudinally) when heated to between one-half and one-sixth of their diameter.

Heat shrink tube come in many varieties and chemical compositions, and the exact composition of each type depends on the intended application. From near-microscopic, thin-walled tubes to rigid, thick-walled tubes, each type has precise designs and chemical additives that make it suitable to meet a variety of environmental needs. The heat shrink tube is rated according to its expansion rate, which is a comparison of the difference between the expansion rate and the recovery rate.


Before the connection is made, the unshrunk tube is fitted to the wire and then slipped down after the connection is complete to cover the joint. If the fit is tight, silicone lubricants can be used without affecting the heat shrink material. The tube is then tightly wrapped around the joint by heating it in the oven or with a heat gun or other hot air source. Convenient but less consistent ways to shrink a tube include using a soldering iron close to but not touching the tube, or using the heat of a lighter. Uncontrolled heating can lead to uneven shrinkage, physical damage, and insulation failure, and these methods are not recommended by heat shrink tube suppliers. If overheated, heat shrink tubes can melt, burn, or catch fire like other plastics. Heating causes the tube to shrink to between half and one-sixth of its original diameter, depending on the material used, providing a tight fit for the irregularly shaped joint. The tube also has longitudinal shrinkage, which is usually not needed, and the degree of shrinkage is smaller than the degree of reduction, usually about 6%. The tubes provide good electrical insulation against dust, solvents and other foreign objects, as well as mechanical stress relief, and are mechanically held in place by their tight fit (unless incorrectly sized or not properly shrunk).


The heat shrink tube was invented by Raychem in 1962. It is manufactured from thermoplastic materials such as polyolefins, fluoropolymers (such as FEP, PTFE, or Kynar), PVC, neoprene, silicone elastomers, or fluororubbers.