Spatial distribution of surface treatment efficiency in coplanar barrier discharge operated with oxygen–nitrogen gas mixtures

The influence of the gas mixture of oxygen and nitrogen on the treatment efficiency distribution is investigated. The treatment efficiency is evaluated by contact angle measurement on polypropylene (PP) samples placed in varying distance from the coplanar barrier discharge electrode module. A planar electrode operated with 4 kHz signal and power of typically 10–21 W is used for treatment. A strong variation of contact angle as a function of distance from the CDB electrode surface is observed for samples treated 4 s in nitrogen discharge. Contact angle changes within 0.3 mm from 37.9 to 62.5° and it reaches 94.1° for 1.5-mm distance. It is already very close to the value of 103° measured on untreated PP. Much smaller treatment depth is obtained for mixture of nitrogen and oxygen. The experiments are performed without gas flow.