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Investigation of migration from decorative shrink-sleeves
Project Code: A03048
Lord, A ; Obhrai, S
This project investigated the migration of chemical substances from shrink sleeves used on flexible plastic food containers. Shrink sleeves are manufactured from a polymer sheet that has been stretched during manufacture. The sheet is printed and welded at one side to form a tube and then placed over the food container. Heat is applied and the sleeve then shrinks back towards its original dimensions. In doing so, the sleeve takes the form of the food container.
Shrink sleeves have gained considerable market share over other forms of pack labelling. They offer the advantage of high gloss, high quality images at low cost on a wide range of containers, on surfaces which would otherwise be difficult to print on.
There has been very little work published that has considered the possibility of migration of components from shrink sleeves, through the food container to which it is applied, into the food. However, shrink sleeves are printed and welded using solvents and the print is applied on the inner surface that is in contact with the food container. The polymers used to manufacture the sleeves are good barriers to solvent migration, whilst the polymers used in the food container may be poor barriers. Thus solvents in the sleeves may be trapped at the food container surface rather than being lost to the outside air and may migrate through the container into the food. A variety of decorative novel inks, such as ultra violet (UV) cured inks are being introduced.
Whilst the importance of using low migration and low taint inks on primary packaging is well understood in the UK, secondary packaging such as shrink sleeves is not subject to the same controls as primary packaging. It is also possible that, because sleeves are used on metal and glass containers and non-food applications where migration is either not possible or of no importance, due consideration is not given to the use of similar sleeves on flexible food containers where migration is possible.
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