Surface modification of clay‐coated paper by atmospheric‐pressure plasma in air.

The aim of this work was the wettability improvement of clay‐coated paper by ambient air plasma exposure. Industrial corona with a volume dielectric barrier discharge in cylindrical configuration was used as a plasma source; the exposure times varied from 0.25 up to 5 s. Water contact angle (WCA) measurement and surface free energy (SFE) evaluation were carried out for the estimation of wettability changes. Plasma treatment in the duration of 0.25 s was sufficient to decrease the WCA almost to the half of the original value, which was 76°. SFE of paper has increased by 40%–50% after plasma treatment. Long‐term ageing effect study of treated samples was carried out up to 3 months after the treatment. WCA did not reach the original value even after 3 months, and it was still 20%–30% lower. O/C ratio increased from 0.7 to 1.8 in case of 5‐s plasma treatment, and the new chemical bonds (C=O, O–C=O) were created on the surface. [ABSTRACT FROM AUTHOR]