Heat-shrink tubing was invented by Raychem Corporation in 1962. It is manufactured from a thermoplastic material such as polyolefin, fluoropolymer (such as FEP, PTFE or Kynar), PVC,neoprene, silicone elastomer or Viton.
The process for making heat-shrink tubing is as follows: First the material is chosen based on its properties. The material is often compounded with other additives (such as colorants, stabilizers, etc.) depending on the application. A starting tube is extruded from the raw material. Next, the tube is taken to a separate process where it is cross-linked, usually through radiation. The cross-linking creates a memory in the tube. Then the tube is heated to just above the polymer's crystalline melting point and expanded in diameter, often by placing it in a vacuum chamber. While in the expanded state it is rapidly cooled. Later, when heated (above the crystalline melting point of the material) by the end user, the tubing shrinks back to its original extruded size.
The material is often cross-linked through the use of electron beams,peroxides, or moisture. This cross-linking creates the memory in the tubing so that it is able to shrink back to its original extruded dimensions upon heating producing a term used called heat-shrink with a built-in thermal-memory.
For external use, heat-shrink tubing often has a UV stabiliser added.