Heat-shrink tubing
A heat shrink tube is a plastic tube which (usually by supplying hot air ) greatly shrinks when exposed to heat. Here the before heating introduced into the tube product against its environment is electrically insulated and protected from mechanical damage.
Properties
Shrinkable tubes are with a diameter of 1 mm to a maximum. 1100 mm. An alternative form are shrinkable caps that are already closed at one end, and Schrumpfaufteilkappen who have three or more openings.
The shrinking range, ie the maximum size change during shrinkage is strongly dependent on the plastic used. The shrinkage ratio is 2:1 to 6:1, with special plug seals and up to 10:1. In order to achieve the best possible sealing, many shrink on the inner side are coated with a hot melt adhesive. Manufacturers recommend a ratio of 4:5 between the diameter of the object to be isolated and the shrink tube to get best results.
The plastics used are thermoplastics. In order to achieve a shrinkage of the material upon heating ( at a temperature range typical for the material ), the plastics must be crosslinked after production in the extruder. By cross-linking the molecular chains are connected with each other, which can be done for example with silanes, or by electron beams. Now the extrudate thus treated can in the hot state (temperature range approximately extrusion temperature ) are expanded. By cooling, the material is frozen with respect to the reshaping of the last expansion, so to speak, the expanded diameter is maintained, and thus stress in the power jumpers on the molecular level. Only by heating the shrink tube is able to orient. Since this is crosslinked plastics for shrink tubing, these are not to be used as regrind. Exception are shrink PVC, since PVC must not be networked. With inexpensive shrink tubing arrangement is due to the van der Waals forces, with higher quality plastics hoses with dipole -dipole effects used (example: Teflon ) observing this behavior, you can also eg yoghurt cups ( polystyrene ) obtained by heating again coincide in itself.
Shrink films, which are often used for fixing of stacked goods on pallets or boxes may shrink uni-or bidirectional, depending on the manufacturing process, therefore, draw upon heating only longitudinally or transversely along also.
Meanwhile, there are also so-called " cold -shrink " ( EPDM or silicone ). They are based on a different technology to come out without any heat and can thus be imported also be used under water.
Species
In shrink tubing are categorized according to wall thickness, diameter, and after shrinkage ratio.