Paper Microelement Composition and its Effect on Components of the Color Difference dE94 in the Paper Shade

摘要

In the printing industry, whiteness and shade of paper significantly affect the final print. However, the term "whiteness" still does not have a precise definition. Different international standards define whiteness differently. The composition of the paper obviously affects whiteness, but little is known about the effect on whiteness that a particular chemical element produces in paper. Not all paper is recycled by industrial means, so some of the impurities from paper can penetrate into the soil and water. If these impurities are unsafe, this may create an additional threat to the environment and people. In this work, we have established a link between the whiteness of paper and its component composition. We compared 255 paper samples by their dE94 color difference versus standard paper with CIE Lab coordinates (95/0/-2). X-ray fluorescence analysis revealed the presence of 25 chemical elements in paper samples. Based on this, clustering of papers and further discriminant analysis revealed four clusters with distinct composition and whiteness of paper. We identified 12 elements that have the greatest impact on the whiteness of paper (S, Ti, Mn, Zn, Rb, Sr, Y, Zr, Sb, I, Ba, Th), and also built a model of the influence of the composition of the paper on its whiteness, based on artificial neural networks.