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Diffusion barriers

The percentage of food packaging materials made of polymers is steadily growing due to their advantages like low specific weight and environmental compatibility. High-barrier polymer packaging mostly consists of a multi-layer structure of different polymers. Due to the increasing commodity prices for polymers, more and more enterprises active in the food packaging industry are looking for cheap homo-polymeric materials to replace the expensive multi-layer polymer packaging currently in use.

One of the major requirements concerning the cheap homopolymeric materials is the need for multi-functional surfaces and barrier properties comparable to multilayer polymer packaging. Particularly efficient barriers towards the permeation of water vapour and of gases like oxygen or carbon dioxide are necessary to extend the shelf life of the food stuff. Quartz-like (SiOx) layers for example represent an excellent barrier material with regard to significantly reducing the permeation of water vapour and most gases as well as providing optical transparency. Plasma Enhanced Chemical Vapour Deposition (PECVD) is a very suitable technology to produce SiOx barrier layers by use of oxygen and vaporised silicon oils like hexamethyldisiloxane (HMDSO).
Another very important topic in the automotive industry is the decrease of the permeability of plastic tanks. For the use of polyethylene tanks the permeability of gasoline must be reduced by a factor of 100 compared to the untreated material. An alternative solution to the problematic treatment of polyethylene with the aggressive fluorine gas is the deposition of a thin plasma polymerised barrier layer on the surface of the plastic tank. Compared to uncoated polyethylene the permeability towards gasoline can be reduced by a factor of 3000.

Contact Person
Name: Dr.-Ing. Matthias Walker