Influence of plasma activation on absorption of ink components and dampening water in sheet-fed offset printing

The influence of plasma activation oil offset printability was investigated. Four different model pigment coated papers were treated with corona, experimental pilot scale argon plasma. and laboratory scale nitrogen plasma. Surface characterization was made by contact angle measurements, X-ray Photoelectron Spectroscopy (XPS) mid Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). Five different model inks with different portions of linseed and mineral oils, and one commercial ink were Used in ink setting evaluation with Ink Surface Interaction Tester (ISIT) and laboratory scale printing. In addition, samples were printed in a Pilot scale sheet-fed printing press Using the same commercial ink as in laboratory scale. According to results. plasma activation increased surface wettability and polarity due to oxidation of high Molecular weight dispersion chemicals of pigment and latex particles. Therefore, the dispersion system of different pigments seemed 10 influence thee effectiveness of the plasma treatment: Talc containing paper had the greatest change in O/C ratio determined by XPS, whereas ground calcium carbonate (GCC) containing paper had the smallest. Plasma treatment had a clear impact oil ink setting with all the papers, but the response depended oil the ink composition. The ink setting rate decreased with linseed oil dominating inks, probably due to increased acid-base interaction between ink oil and polar plasma treated coating. With mineral oils ink setting accelerated. Pilot scale plasma treatments did not have an impact oil print density and gloss, bill the laboratory scale plasma treatment led to a significant print density variation. Ga focused ion beam (FIB) and optical microscope images, showed that micro-picking Was occurring ill the surface layers of the coating, leading to a decrease in the print density with laboratory plasma treated samples.