Decontamination of polymer foils with a combined UV-plasma source at atmospheric pressure

Currently, polymer packaging is sterilised by chemical means like hydrogen peroxide or by hot steam. Thermally sensitive foils with thickness of few tens of µm may require efficient and environmentally friendly sterilisation processes which work with web speeds up to several meters per second. UV-emitting plasmas at atmospheric pressure generated in dielectric barrier discharges (DBD) show low working temperature of the plasma gas and can therefore be used for treatment of polymeric materials. By combination of a flat excimer UV source and a second plasma discharge gap, a cascaded dielectric barrier discharge (CDBD) set-up is built. The lower gap provides direct plasma exposure to the packaging foil and may be flowed by reactive or oxidative plasma gases. The efficient excimer UV source is emitting narrow-band UV light near to the packaging which results in high angles of incidence of the light. We compare spore reduction properties of "standard" DBD set-ups with one gap and of cascaded DBDs using different gas atmospheres. The CDBD showed to be more efficient in terms of treatment duration and power consumption compared to the "standard" barrier discharges.