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Vacuum Plasma Treatment Systems for Functionalization of Films and Fabrics

Sigma was the first to develop and succesfully commericalize wide-web, high-speed, vacuum plasma treatment systems flexible packaging. Today, most metallized films are plasma treated to increase barrier performance. Sigma continues to develop new applications for vacuum plasma treatment - such as post plasma treatment of metallized films.

2 meter vacuum plasma treater typically installed in a new, or commercially active, vacuum metallizer/coater.Treater Design

Design of Sigma's VPT's take from Sigma’s patented dual magnetron hollow cathode design. This allows for an intense plasma region ideal for effectively treating most polymer substrates. Also, because Sigma VPT systems have magnets located on the opposite (untreated) side of the substrate, the plasma field is more directed toward the film surface. All of this leads to a higher performing plasma treater, with a more compact design.

SEM images of metallized polyester film, one without plasma pre-treatment (left), the other treated just prior to aluminum deposition (right). Note the increased aluminum coverage with the plasma treated sample - resulting in better adhesion and better barrier performance.Post Plasma Treatment of Metallized Films

Metallized aluminum is passivated mainly by exposure to air in the slitting/rewinding process.  Ambient air contains moisture (which varies seasonally and geographically) that leads to the formation of a hydrated aluminum oxide (Al2O3(H2O)) which has poor barrier properties, resulting in inferior corrosion resistance of the deposited Al layer.

Oxygen plasma treatment of the freshly metallized surface in the vacuum results in the formation of a high quality aluminum oxide layer (Al2O3 ) which improves  corrosion resistance and reduces bonding of the aluminum with the backside of the polymer film.  Reduction of bonding between the aluminum and the polymer film, reduces  pick-off of the aluminum  during the slitting/rewinding process which.  Pick-off reduction leads to significant improvement in the barrier properties of the metallized films.