Heat-shrink tubing
Encyclopedia
Nylon
Nylon is a generic designation for a family of synthetic polymers known generically as polyamides, first produced on February 28, 1935, by Wallace Carothers at DuPont's research facility at the DuPont Experimental Station...
or polyolefin
Polyolefin
A polyolefin is a polymer produced from a simple olefin as a monomer. For example, polyethylene is the polyolefin produced by polymerizing the olefin ethylene. An equivalent term is polyalkene; this is a more modern term, although polyolefin is still used in the petrochemical industry...
, which shrinks when heated in an effort to return to the original relaxed diameter as when it was extruded. 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 microscopic thin wall tubing to rigid heavy wall tubing, each type has precise design and chemical additives that are suited for a wide variety of environmental demands. Heatshrink tubing is rated by its expansion ratio, a comparative of the differences in expansion and recovery rate. Heat shrink is used to insulate wires offering abrasion resistance and environmental protection for stranded and solid wire conductors, connections, joints and terminals in electrical engineering
Electrical engineering
Electrical engineering is a field of engineering that generally deals with the study and application of electricity, electronics and electromagnetism. The field first became an identifiable occupation in the late nineteenth century after commercialization of the electric telegraph and electrical...
. 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 between bulkheads and adding sealability to electrical junction boxes.
Utility
The tubing is placed over the connection to be protected and then heated with an oven, hot air gun or similar tool. Convenient, but less effective, methods for shrinking the tube include a soldering ironSoldering iron
A soldering iron is a hand tool most commonly used in soldering. It supplies heat to melt the solder so that it can flow into the joint between two workpieces.A soldering iron is composed of a heated metal tip and an insulated handle...
(held in close proximity, but not touching the tube) or the heat from a lighter
Lighter
A lighter is a portable device used to generate a flame. It consists of a metal or plastic container filled with a flammable fluid or pressurized liquid gas, a means of ignition, and some provision for extinguishing the flame.- History :...
. These processes cause the tubing to contract as far as one sixth of its original diameter (dependent on the heat shrink, 2:1 is the most common), providing a snug fit over irregularly shaped joints. This provides good electrical insulation, protection from dust, solvent
Solvent
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...
s and other foreign materials, as well as strain
Deformation (mechanics)
Deformation in continuum mechanics is the transformation of a body from a reference configuration to a current configuration. A configuration is a set containing the positions of all particles of the body...
relief. If overheated, heat shrink tubing can melt, scorch or catch fire like any other plastic.
Some types of heat shrink contain a layer of thermoplastic
Thermoplastic
Thermoplastic, also known as a thermosoftening plastic, is a polymer that turns to a liquid when heated and freezes to a very glassy state when cooled sufficiently...
adhesive
Adhesive
An adhesive, or glue, is a mixture in a liquid or semi-liquid state that adheres or bonds items together. Adhesives may come from either natural or synthetic sources. The types of materials that can be bonded are vast but they are especially useful for bonding thin materials...
on the inside to help provide a good seal and better adhesion, while others rely on friction from the closely conforming materials. Heating plain, non-adhesive shrink tube to very near the melting point may allow it to fuse to the underlying material as well.
One application that has used this product 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 with this versatile plastic shrink tube product.
Manufacture
Heat-shrink tubing is manufactured from a thermoplasticThermoplastic
Thermoplastic, also known as a thermosoftening plastic, is a polymer that turns to a liquid when heated and freezes to a very glassy state when cooled sufficiently...
material such as polyolefin
Polyolefin
A polyolefin is a polymer produced from a simple olefin as a monomer. For example, polyethylene is the polyolefin produced by polymerizing the olefin ethylene. An equivalent term is polyalkene; this is a more modern term, although polyolefin is still used in the petrochemical industry...
, fluoropolymer
Fluoropolymer
A fluoropolymer is a fluorocarbon based polymer with multiple strong carbon–fluorine bonds. It is characterized by a high resistance to solvents, acids, and bases.-History:Fluoropolymers were accidentally discovered in 1938 by Dr. Roy J...
(such as FEP, PTFE or Kynar), PVC
Polyvinyl chloride
Polyvinyl chloride, commonly abbreviated PVC, is a thermoplastic polymer. It is a vinyl polymer constructed of repeating vinyl groups having one hydrogen replaced by chloride. Polyvinyl chloride is the third most widely produced plastic, after polyethylene and polypropylene. PVC is widely used in...
, neoprene
Neoprene
Neoprene or polychloroprene is a family of synthetic rubbers that are produced by polymerization of chloroprene. Neoprene in general has good chemical stability, and maintains flexibility over a wide temperature range...
, silicone elastomer or Viton
Viton
Viton is a brand of synthetic rubber and fluoropolymer elastomer commonly used in O-rings and other molded or extruded goods. The name is a registered trademark of DuPont Performance Elastomers L.L.C.....
.
According to the exact material used, there are two ways that heat shrink may work. If the material contains many monomer
Monomer
A monomer is an atom or a small molecule that may bind chemically to other monomers to form a polymer; the term "monomeric protein" may also be used to describe one of the proteins making up a multiprotein complex...
s, then when the tubing is heated the monomers polymerise. This increases the density of the material as the monomers become bonded together, therefore taking up less space. Accordingly, the volume of the material shrinks.
Heat shrink can also be expansion-based. This process involves producing the tubing as normal, heating it to just above the polymer's crystalline melting point and mechanically stretching the tubing (often by inflating it with a gas); finally, it is rapidly cooled. Later, when heated, the tubing will relax back to the un-expanded size.
The material is often cross-link
Cross-link
Cross-links are bonds that link one polymer chain to another. They can be covalent bonds or ionic bonds. "Polymer chains" can refer to synthetic polymers or natural polymers . When the term "cross-linking" is used in the synthetic polymer science field, it usually refers to the use of...
ed through the use of electron beams, peroxide
Peroxide
A peroxide is a compound containing an oxygen–oxygen single bond or the peroxide anion .The O−O group is called the peroxide group or peroxo group. In contrast to oxide ions, the oxygen atoms in the peroxide ion have an oxidation state of −1.The simplest stable peroxide is hydrogen peroxide...
s, or moisture. This cross-linking helps to make the tubing maintain its shape, both before and after shrinking.
For external use, heat shrink tubing often has a UV stabiliser
UV Stabilizers in plastics
UV light stabilizers are used frequently in plastics, including cosmetics and films. The primary function is to protect the substance from the long-term degradation effects from light, most frequently ultraviolet light...
added.
Materials
Different applications require different materials:- PTFE (fluoropolymer) tubes have a wide operating temperatureOperating temperatureAn operating temperature is the temperature at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the device function and application context, and ranges from the minimum operating temperature to the...
range (-55 to 175 °C), a low coefficient of friction, and high resistance to chemicals and punctures.
- VitonVitonViton is a brand of synthetic rubber and fluoropolymer elastomer commonly used in O-rings and other molded or extruded goods. The name is a registered trademark of DuPont Performance Elastomers L.L.C.....
, another fluoropolymer with high chemical resistance, is widely used in hydraulic equipment. It is highly flexible, with a very high operating temperature of -55 to 220 °C, making it suitable for protecting sensitive devices against heat.
- Polyvinylidene fluoridePolyvinylidene fluoridePolyvinylidene fluoride, or PVDF is a highly non-reactive and pure thermoplastic fluoropolymer.PVDF is a specialty plastic material in the fluoropolymer family; it is used generally in applications requiring the highest purity, strength, and resistance to solvents, acids, bases and heat and low...
(PVDF) tubes are intended for high temperature applications.
- Fluorinated ethylene propyleneFluorinated ethylene propyleneFluorinated ethylene propylene or FEP is a copolymer of hexafluoropropylene and tetrafluoroethylene. It differs from the PTFE resins in that it is melt-processible using conventional injection molding and screw extrusion techniques. Fluorinated ethylene propylene was invented by DuPont and is sold...
(FEP) is a lower-cost alternative to PTFE.
- Elastomeric tubes maintain high flexibility even at low temperatures, and meet stringent internation specifications. Their operating temperature range is -75 to 150°C. The material is resistant to many chemicals (including diesel and petrol) and has good resistance to abrasionAbrasion (mechanical)Abrasion is the process of scuffing, scratching, wearing down, marring, or rubbing away. It can be intentionally imposed in a controlled process using an abrasive...
, even in severe environmental conditions. Common shrink ratio is 2:1.
- Silicone rubberSilicone rubberSilicone rubber is an elastomer composed of silicone—itself a polymer—containing silicon together with carbon, hydrogen, and oxygen. Silicone rubbers are widely used in industry, and there are multiple formulations...
offers excellent resistance to scrape abrasion and high flexibility.
- PolyolefinPolyolefinA polyolefin is a polymer produced from a simple olefin as a monomer. For example, polyethylene is the polyolefin produced by polymerizing the olefin ethylene. An equivalent term is polyalkene; this is a more modern term, although polyolefin is still used in the petrochemical industry...
tubes, the most common kind, have maximum continuous use temperature from -55 to 135 °C, and are used by the military, aerospace and railway industries. They are flexible and fast-shrinking, and manufactured in a wide range of colors (including clear), which can be used for color-coding of wires. With exception of black, they tend to have lower resistance to ultraviolet light; only black is suggested for outdoor applications. Common shrink ratio is 2:1, while high-grade polyolefin heat shrink is available in 3:1.
- PVC tubes are available in several colors, and can be used outdoors.
Other special materials exist, offering qualities such as resistance to diesel and aviation fuels, or woven fabric for increased abrasion resistance in harsh environments.
Heat shrink types
Heat shrink tubing is available in a variety of colours to allow easier colour codingElectronic color code
The electronic color code is used to indicate the values or ratings of electronic components, very commonly for resistors, but also for capacitors, inductors, and others...
of wires and connections. Recently heat shrink tubing has been used more in PC modding
Case modding
Case modification is the modification of a computer chassis , or a video game console chassis. Modifying a computer case in any non-standard way is considered a case mod...
to tidy up the interior of computers and provide a more aesthetic finish. As a reaction to this new market opening up, manufacturers have started producing heat shrink tubing in luminous
Luminosity
Luminosity is a measurement of brightness.-In photometry and color imaging:In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. The SI unit for luminance is candela per square metre.The luminosity function...
and UV
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
reactive varieties.
Although most heat shrink is used to provide insulation, heat shrink tubing is also available with a conductive lining to avoid the requirement to solder a joint before covering it. This may be considered poor engineering practice.
Similar to heat shrink tubing is heat shrink end caps. Shaped like small mugs, these may be used to insulate cut ends of wires or cables.
Heat Shrink Tubing was invented by Raychem
Raychem
Raychem Corporation was founded in Menlo Park/Redwood City, California in 1957 by Paul Cook, James B. Meikle, and Richard W. Muchmore. The original name of the company was RayTherm Wire and Cable and later formed a subsidiary named RayClad Tubes. The company changed names to avoid confusion with...
Corporation.
See also
- Cold shrink tubingCold shrink tubingCold 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...
- Heat-shrinkable sleeveHeat-shrinkable sleeveHeat-shrinkable sleeve is a corrosion protective coating for pipelines in the form of a wraparound or tubular sleeve that is field-applied.- History :...
- SolderingSolderingSoldering is a process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, the filler metal having a lower melting point than the workpiece...
- Electrical wiringElectrical wiringElectrical wiring in general refers to insulated conductors used to carry electricity, and associated devices. This article describes general aspects of electrical wiring as used to provide power in buildings and structures, commonly referred to as building wiring. This article is intended to...