Demands on the permeation properties of beverage packages are nowadays important criteria for choosing the right packaging material. These demands do not only depend on the filled good, but are also severely aggravated by current developments and trends like the use of biopolymers or light weighting of bottles. In order to meet those challenges, the Institute of Plastics Processing (IKV) at RWTH Aachen University has been working for now more than 20 years on the field of plasma-assisted barrier coating of polymers. Besides the conception and development of processes for the interior and exterior coating of beverage bottles or coating of foils and plastic parts, the focus of the investigations is upon the development of suitable layer systems to enhance the permeation properties of plasma-polymer coatings.
Currently IKV is investigating in a process to enhance the barrier performance of plasma-polymer layers by the use of a substrate-bias. Studies on foils already have shown that the deposition of barrier coatings using a substrate bias leads to a significant increase in the barrier properties because the negative effect of layer defects is reduced. Therefore a plasma reactor providing the possibility to bias the inserted polyethylene terephthalate (PET) bottle has been built up recently. Studies on this new technology are currently carried out. After a successful validation of the process a transfer to other materials such as polylactide (PLA) is targeted.
Besides the influence of the substrate bias on the coatings’ performance its influence on the coatings’ flexibility will be evaluated as well. A possible influence on the strain tolerance is crucial for applications such as carbonated soft drinks, since the occurring stress that is caused by the internal bottle pressure may lead to a stretching and even cracking of the barrier coatings. This may result in a higher permeation of gases. For this purpose, investigations will be carried out to determine to what extent the deposition of multifunctional coatings consisting of hard and soft layers may increase the strain tolerance of the whole composite while maintaining good barrier properties at the same time.
The research project 16306 N has been sponsored as part of the industrielle Gemeinschaftsforschung und -entwicklung (IGF) by the German Bundesministerium für Wirtschaft und Technologie (BMWi) through the AiF.
Reactor for the substrate-biased interior plasma coating of plastic bottles
|Dipl.-Ing. Karim Bahroun|
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