A Shrink Film can shrink forming as single direction (unidirectional or mono-directional) or bi-directional (bidirectional)
When the initial coincidental state of the molecules of the film production material is expanded with the heat, the material takes the desired shape. When subjected to cooling process the characteristic structure of the film occurs. In the case of reheating, the film returns to its initial dimensions.
Molecules of a plate or cylinder material which is moving according to the direction of the shrink process tangle just like a bowl of spaghetti. In this case, the molecules are in completely random sequences and there are no specific placements. However, when a force (heat) is applied to the molecules, the molecular chains in the amorphous regions are activated, and they form appropriately in the direction in which the force is applied. When cooling is applied in the right ratio the molecules freeze in the same way they stay. Heat/power must be applied again in order for the molecular chains to revert to their original state. You can imagine a rubber band which is hand-strapped stay in that form when it falls into liquid nitrogen to imagine the process. As long as that liquid nitrogen remains in the cold the rubber band will remain in its expanded position. However, when the heat is applied again the rubber band may return to its original state.
Shrinkage in the production volume at the commercial dimension can be carried out by preferring one of the two processes; Tenterframe or Bubble Process. Tenterframe technology is used to produce “heat-set” products in various specifications and it is preferred to use polypropylene which is shrunk in two directions. The Bubble Process – also called Tubular Process – is the production of the material in the tube form which is moved on a spool. Tube heat and cooling are usually ensured by using water. And after the main material has formed and cooled down it will be reheated and inflated just like a balloon. After the inflation, the tube can form by shrinking in two directions.
Shrink Films which have been produced have been developed over the years. Today, multi-layer films are sold. Many films also offer different options such as printability, stylish appearance, hardness and slippery besides the ability to shrink. Apart from these, there are detailed options and features such as the maximum heat tolerance, see shrinkage, shrinkage strength, shrinkage heat range, memory, and general package view.
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