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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 wiring. 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. Heat-shrink tubing is ordinarily made of polyolefin, which shrinks radially (but not longitudinally) when heated, to between one-half and one-sixth of its diameter.
Heat-shrink tubing is manufactured in a multitude of varieties and chemical makeups with the exact composition of each type being dependent on the intended application.  From near microscopically-thin-wall tubing to rigid, heavy-wall tubing, each type has precise design and chemical additives that make it suitable for meeting any of a wide variety of environmental demands. Heat-shrink tubing is rated by its expansion ratio, a comparison of the differences in expansion and recovery rate.
The unshrunk tubing is fitted on the wire before making the connection, then slid down to cover the joint after it is made. If the fit is tight, silicone lubricant can be applied without compromising the heat-shrink material.  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 hot gas flow. 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.  If overheated, heat-shrink tubing can melt, scorch or catch fire like any other plastic. 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. There is also longitudinal shrinking, usually unwanted and to a lesser extent than narrowing, of typically around 6%.  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.
Some types of heat-shrink contain a layer of thermoplastic adhesive on the inside to help provide a good seal and better adhesion, while others rely on friction between the closely conforming materials. Heating non-adhesive shrink tube to very near the melting point may allow it to fuse to the underlying material as well[ citation needed ].
Heatshrink tubing is sometimes sold in pre-cut lengths, with a solder blob at the center of the length, as this configuration was specified by Daimler-Benz for automotive electrical repairs. 
One application that has used heatshrink in large quantities since the early 1970s is the covering of fibreglass helical antennas, used extensively for 27 MHz CB radio. Many millions of these antennas have been coated this way.[ citation needed ]
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 material called heat-shrink tubing. For outdoor use, heat-shrink tubing often has a UV stabiliser added.
Different applications require different materials:
Other special materials exist, offering qualities such as resistance to diesel and aviation fuels, and there is also woven fabric, providing increased abrasion resistance in harsh environments.
Heat-shrink tubing is available in a variety of colors for color-coding of wires and connections. In the early twenty-first century heat-shrink tubing started to be used for PC modding to tidy up the interior of computers and provide an appearance considered pleasing[ citation needed ]. In response to this opening market[ citation needed ], manufacturers started producing heat-shrink tubing in luminous and UV reactive varieties.
Although usually used for insulation, heat-shrink tubing with a conductive lining is also available, for use on joints which are not soldered.
Specialty heat-shrink tubing, known as "solder sleeves", have a tube of solder inside of the heat-shrink tubing, allowing the heat source to electrically join the two wires by melting the solder and simultaneously insulate the junction with the tubing. Solder sleeves also commonly contain a ring of heat-activated sealant on the inside of each end of the tubing, allowing the connection to also be made waterproof. 
Heat-shrink end caps, closed at one end, are used to insulate the exposed cut ends of insulated wires.
SAE AS23053 
ASTM D 2671 
ASTM D3150 
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A thermoplastic, or thermosoft plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling.
In physics and electrical engineering, a conductor is an object or type of material that allows the flow of charge in one or more directions. Materials made of metal are common electrical conductors. Electric current is generated by the flow of negatively charged electrons, positively charged holes, and positive or negative ions in some cases.
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Electrical wiring is an electrical installation of cabling and associated devices such as switches, distribution boards, sockets, and light fittings in a structure.
Polychlorotrifluoroethylene (PCTFE or PTFCE) is a thermoplastic chlorofluoropolymer with the molecular formula (CF2CClF)n, where n is the number of monomer units in the polymer molecule. It is similar to polytetrafluoroethene (PTFE), except that it is a homopolymer of the monomer chlorotrifluoroethylene (CTFE) instead of tetrafluoroethene. It has the lowest water vapor transmission rate of any plastic.
Shrink wrap, also shrink film, is a material made up of polymer plastic film. When heat is applied, it shrinks tightly over whatever it is covering. Heat can be applied with a handheld heat gun, or the product and film can pass through a heat tunnel on a conveyor.
Electrical tape is a type of pressure-sensitive tape used to insulate electrical wires and other materials that conduct electricity. It can be made of many plastics, but PVC is most popular, as it stretches well and gives an effective and long lasting insulation. Electrical tape for class H insulation is made of fiberglass cloth.
Ultra-high-molecular-weight polyethylene is a subset of the thermoplastic polyethylene. Also known as high-modulus polyethylene, (HMPE), it has extremely long chains, with a molecular mass usually between 3.5 and 7.5 million amu. The longer chain serves to transfer load more effectively to the polymer backbone by strengthening intermolecular interactions. This results in a very tough material, with the highest impact strength of any thermoplastic presently made.
Cross-linked polyethylene, commonly abbreviated PEX, XPE or XLPE, is a form of polyethylene with cross-links. It is used predominantly in building services pipework systems, hydronic radiant heating and cooling systems, domestic water piping, insulation for high tension electrical cables, and baby play mats. It is also used for natural gas and offshore oil applications, chemical transportation, and transportation of sewage and slurries. PEX is an alternative to polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC) or copper tubing for use as residential water pipes.
Mineral-insulated copper-clad cable is a variety of electrical cable made from copper conductors inside a copper sheath, insulated by inorganic magnesium oxide powder. The name is often abbreviated to MICC or MI cable, and colloquially known as pyro. A similar product sheathed with metals other than copper is called mineral insulated metal sheathed (MIMS) cable.
Fluorinated ethylene propylene (FEP) is a copolymer of hexafluoropropylene and tetrafluoroethylene. It differs from the polytetrafluoroethylene (PTFE) resins in that it is melt-processable using conventional injection molding and screw extrusion techniques. Fluorinated ethylene propylene was invented by DuPont and is sold under the brandname Teflon FEP. Other brandnames are Neoflon FEP from Daikin or Dyneon FEP from Dyneon/3M.
A pipe is a tubular section or hollow cylinder, usually but not necessarily of circular cross-section, used mainly to convey substances which can flow — liquids and gases (fluids), slurries, powders and masses of small solids. It can also be used for structural applications; hollow pipe is far stiffer per unit weight than solid members.
Plastics extrusion is a high-volume manufacturing process in which raw plastic is melted and formed into a continuous profile. Extrusion produces items such as pipe/tubing, weatherstripping, fencing, deck railings, window frames, plastic films and sheeting, thermoplastic coatings, and wire insulation.
Magnet wire or enameled wire is a copper (Cu) or aluminium (Al) wire coated with a very thin layer of insulation. It is used in the construction of transformers, inductors, motors, generators, speakers, hard disk head actuators, electromagnets, electric guitar pickups and other applications that require tight coils of insulated wire.
Heat-shrinkable sleeve is a corrosion protective coating for pipelines in the form of a wraparound or tubular sleeve that is field-applied.
Rulon is the trade name for a family of PTFE plastics produced by Saint-Gobain Performance Plastics. Rulon plastics are known for their low coefficient of friction, excellent abrasion resistance, wide range of operating temperatures, and chemical inertness. Common applications for Rulon include seals, piston rings, bearings, and electrical insulation.
Cold shrink tubing is an open ended rubber sleeve, made primarily from rubber elastomers with high-performance physical properties, that has been factory expanded or pre-stretched, and assembled onto a supporting removable plastic core. Cold shrink tubing shrinks upon removal of the supporting core during the installation process and the electrician slides the tube over the cable to be jointed, terminated or abandoned and unwinds the core, causing the tube to collapse down, or contract, in place. The following video demonstrates the installation process of using Cold Shrink to abandon power cables.
Soldering is a process in which two or more items are joined by melting and putting a filler metal (solder) into the joint, the filler metal having a lower melting point than the adjoining metal. Unlike welding, soldering does not involve melting the work pieces. In brazing, the work piece metal also does not melt, but the filler metal is one that melts at a higher temperature than in soldering. In the past, nearly all solders contained lead, but environmental and health concerns have increasingly dictated use of lead-free alloys for electronics and plumbing purposes.
Materials for use in vacuum are materials that show very low rates of outgassing in vacuum and, where applicable, are tolerant to bake-out temperatures. The requirements grow increasingly stringent with the desired degree of vacuum to be achieved in the vacuum chamber. The materials can produce gas by several mechanisms. Molecules of gases and water can be adsorbed on the material surface. Materials may sublimate in vacuum. Or the gases can be released from porous materials or from cracks and crevices. Traces of lubricants, residues from machining, can be present on the surfaces. A specific risk is outgassing of solvents absorbed in plastics after cleaning.