Nowadays, effect pigments are widely used in many printing industries. The colorful effects produced by light scattering of these types of pigments add an additional value to the prints and enhances the overall quality of color appearance. The aim of this study was to investigate the quality enhancement of printed specialty papers with various effect pigments in combination with offset inks. Four different effect pigments were used (one luster pigment-EP1, two interference pigments-EP2, EP3, and one multicolor pigment-EP4) as well as two types of paper substrates (film synthetic paper and wood-free paper). The effect pigments were overprinted on dried CMYK offset prints on both paper substrates. The following analysis were performed: scanning electron microscopy analysis of effect pigment particles, contact angles of papers and offset prints, Fourier transform infrared spectrocopy (FTIR), principal components analysis (principal components analysis (PCA)), and flop index analysis of overprinted effect pigments, and paper and print gloss. The results of the experiment indicate that effect pigments behaved differently on different printing substrates. From the FTIR and PCA, it was found that the different composition of effect pigments differently influence the behavior of these particles on the final prints. Effect pigments overprinted on offset CMYK inks on both paper substrates enhance print gloss, except interference pigment EP2 on film synthetic paper. It was also found that the ink color has the most pronounced influence on flop index, followed by the paper type and the type of effect pigment. Higher flop index was obtained at wood-free paper, especially by overprinted pigment EP2.
The research focused on the structural, sorption and dyeing properties of enzymatically treated viscose fibers and chitosan/cellulose fibers compared to the untreated fibers. First, both fibers were treated with cellulase enzymes for 30 minutes and 90 minutes and afterwards were dyed with the commercial sample of CI Reactive Red 238 at three different dye concentrations. Comparison of the structural and sorption properties of untreated and enzymatically treated fibers showed that the enzymatic treatment lowered the degree of polymerization, as well as crystallinity degree and influenced the surface structure of fibers, resulting in enhanced sorption properties and dyeability of enzymatically treated fibers. Although the values of exhaustion and fixation were higher for chitosan/cellulose fibers because of their initial less-ordered crystalline structure, the 90 minutes of enzymatic treatment has increased the moisture content and water retention capability more for the viscose fibers and hence their dyeability compared to chitosan/cellulose fibers. The 90-minute enzymatically pretreated viscose fibers reached the same exhaustion and fixation values at lower dye concentrations as chitosan/cellulose fibers.
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