Prospects of atmospheric pressure plasma technology for improving barrier and anti-microbial properties of flexible packaging

By combining atmospheric pressure plasma technology with nano-sized (electrostatic) precursor addition, an in-line production process for the deposition of high-performance, multi-functional barrier coatings on plastic foils could be developed. It has been demonstrated that the basic concept of plasma assisted curing and in-situ deposition of nano-sized precursors of sol-gel systems is superior over conventional thermal or UV curing of wet-chemically applied coatings. The barrier properties that could be obtained were within the range of currently available atmospheric technologies (EVOH coating and PVdC lamination) and the most commonly used vacuum technology (evaporation of a thin aluminium coating). Advantages of the newly developed technology include the improved flexibility to implement the coating process in-line (especially compared to vacuum processes), the possibility to apply other functional or multifunctional coatings using the same equipment and the fact that the process is environment friendly since no solvents are used. The combination of tailored chemical surface activation by means of cold atmospheric plasma treatment and subsequent wet-chemical coating using a chitosan solution resulted in coated plastic foils with good anti-microbial activity and improved barrier properties against oxygen transmission. Chitosan is a food approved compound derived from chitin, the second most abundant natural polymer after cellulose. The reduction of bacterial growth observed, indicates that the amount of preservatives can be reduced significantly by applying this type of treatment