Polyolefin heat shrink tubing is a form of protective tubing that is often used as an insulator in electrical appliances. This tubing has a built-in thermal memory, and will shrink in diameter when it is heated.
The tubing is very thin when in its larger form, but when it shrinks in diameter, the thickness of the tube walls increases, making it tough and durable. The most common way of shrinking the tubing is by applying heat directly using a hot air gun, although some hobbyists use “easy shrink” varieties of tubing which will shrink at lower temperatures – for example the heat of a standard home hair drier.
Polyolefin heat shrink tubing is used to protect electrical cables from abrasion and general wear and tear. It is often used in outdoor electrical cabinets to act as a weather seal.
Polyolefin heat shrink tubing is designed to shrink at approximately 90 degrees Celsius. Once it has been shrunk, it is designed to be used in all weathers, and can cope with extremely high and extremely low temperatures.
Some heat shrink tubing is lined with an adhesive to ensure that it sticks to the wires that it is supposed to protect. Commercial grade polyolefin heat shrink tubing – which is designed for general outdoor use – is usually flame retardant, and has a continuous operating temperature range of between -55 degrees Celsius to +135 degrees Celsius.
In contrast, high grade polyolefin heat shrink tubing is designed for use in the aerospace, offshore, and rail industries, and can be used at even more extreme temperatures.
Most specialist electronics retailers sell commercial grade polyolefin heat shrink tubing, however if you require something more hardwearing you will most likely need to order direct from the manufacturer. Companies producing polyolefin heat shrink tubing include Raychem, Tyco, 3M, and Sumitomo Electric Industries.
Tubing is available in a variety of colours, and usually has a 2:1 shrink ratio, although some products have a 3:1 shrink ratio instead. Common lengths of tubing range from 1 metre to 5 metres, and many companies will offer longer continuous lengths of tube on request.
The colours offered by most brands are clear (for use where the tubing will be covering labelled components), black, white, blue, brown, red, yellow, and green/yellow. These match the standard colours of electrical wiring.
Commercial users should take care to ensure that the cabling they purchase complies with all relevant standards, including ROHS (Restriction of Hazardous Substances). In recent years there has been a move towards halogen free tubing, because of environmental concerns.