The surface properties of polyethylene can successfully be altered using argon plasmas. In this work, the surface modification of low density polyethylene (LDPE) using an argon atmospheric pressure plasma jet (APPJ) is profoundly investigated. The surface modification is examined using different analysing techniques namely, water contact angle (WCA) measurements for the wettability and X-ray photoelectron spectroscopy (XPS) for the chemical composition. Particular attention is paid to the treatment distance between the plasma jet capillary and the LDPE foil and the applied treatment time. At treatment distances between 5 and 15 mm, the WCA can be reduced with more than 70% within a treatment time of a few ms. XPS measurements reveal that this is due to the incorporation of oxygen containing groups and especially the increased implementation of the O-C=O group has a big influence. At treatment distances above 15 mm, the wettability decreases with increasing treatment distance. The wettability can however be enhanced by increasing the treatment time. Ageing considerations show that the loss in treatment efficiency is restricted to only 25%, meaning that even after 14 days of ageing the WCA reduction upon plasma treatment is still more than 40%. Based on the above mentioned results, the most appropriate parameters can thus be selected to provide an efficient plasma treatment of LDPE using the argon APPJ.3

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In this paper, water vapor up to 41% is added to an argon dielectric barrier discharge at medium pressure to profoundly investigate the effect of water vapor addition on the surface modification of polyethylene (PE). Contact angle measurements show that the wettability of PE significantly increases after a pure argon plasma treatment. However, the addition of water vapor to the argon feeding gas can give an extra 30% decrease in water contact angle. This extra decrease is due to the incorporation of additional oxygen containing groups such as CO, CO, OCO, and OCO. AFM results reveal that the surface roughness of PE only increases for plasma treatments with no or low water vapor concentrations. All this indicates that a water vapor based plasma can be an excellent tool for the surface activation of PE.

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