One of the keys to improving print quality is to experimentally characterize the paper surface, structure and printability to obtain quality control mechanisms. In multi-color prints, determining the differences in the acceptance of the next color ink by the surface of the paper or the ink film that was previously printed is important for print quality. The criteria, such as ink setting, adhesion, color, gloss and density, in the printing process, depend on the wettability and absorbency of the paper. The surface structure of the paper is the most important factor in determining the hydrophobic properties. In this study, wetting and absorption dynamics of the printed partially hydrophobized paper surface were investigated. The aim was to measure the effect of the printed ink film on the wetting (surface free energy) and liquid absorption behavior of the paper. Liquid absorption changes on printed/unprinted paper surfaces were measured by the sessile drop method, using a contact angle-measuring device. The surface energies of the papers were calculated and evaluated according to the surface contact angle of the droplet.

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The main objective of this study was to evaluate the potential of sodium percarbonate and sodium perborate utilization during repulping of old news and magazine paper mixture. A series of experiments were performed to determine the effects of bleaching agents on ISO brightness and ink removal efficiency of pulp after flotation deinking. Conventionally, with other parameters are constant, the ISO brightness of pulp was increased from 45.24% to 54.10% and ink elimination ratio at 950 nm of pulp was increased to 69.12% with 1% sodium hydroxide and 1% (as active oxygen content) hydrogen peroxide usage. However, when sodium percarbonate was utilized instead of hydrogen peroxide (as 1% active oxygen content) without alkaline addition, the ISO brightness of the pulp was increased to 55.00%. Also, unlike the other bleaching agents, a favorable effect of sodium percarbonate on ink detachment was observed. The ink elimination ratio of floated pulp was increased to 74.31% with 1% (active oxygen) sodium percarbonate addition without alkaline usage. There were no additive effects of sodium perborate usage on brightness, and ERIC value of pulp could be determined. In this respect, sodium percarbonate utilization without sodium hydroxide addition was proposed for effective repulping, deinking, and prebleaching of waste papers, in a similar manner to the use of hydrogen peroxide.

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