What is pre stretch?

Prestretch is the process that allows stretch film to be stretched before
being applied to a load.

The film threads past two rollers (Primary and Secondary) in which the second rollers'
rotational speed is faster than the first, thus stretching the film between the two.

General

Stretch wrapping of palletised goods started in the 70s and has become the most common form of transport packaging. One reason for this is the low consumption of material compared to shrink wrapping, another is the strength and elastic properties of the material. There are many types of machines and stretch film available which will make it difficult for the first time user to choose the best combination.

The following may help to facilitate the choice of machine and film to achieve the best economy and packaging of your goods. In those cases where the examples are not sufficient, your supplier of machine and stretch film will of course assist you.

Why do we package?

During transport the goods is subjected to different kinds of stress against which it has to, be protected, e g wind and weather, shocks and blows.

Different ways of transporting affect the goods with forces of different strength and during shorter or longer time. Shunting of train wagons e g means very strong forces during a short time, but sea transport means low forces during a long time.

A transport packaging must handle all kinds of forces during a long time. A transport packaging must handle all kinds of forces emanating both from static forces and dynamic forces as well as having a sufficient safety margin.


Static forces and dynamic forces


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