Dynamics of thermochromic color change of pressure sensitive labels facestock made from environmentally friendly materials

Abstract

To maintain a circular economy and better sustainability, it is important to minimize the use of synthetic polymers. Nowadays, agricultural and industrial wastes or by-products are increasingly being used as raw materials in industrial processes. It has been determined that agro-industrial wastes have a high potential of cellulose fibers, which makes them an excellent resource for paper production. Recently, potential resources from non-wood raw materials for paper production, as well as cheap raw materials, have become the interest of various researchers. Since our main focus is on the study of thermochromic inks (TC) and the influence of substrate characteristics on their dynamic color change, this paper will examine the possibilities of a commercially available offset TC ink printed on several environmental friendly pressure sensitive labels (PSL) facestock compared to commonly use in PSL production. For the purpose of this study, a commercially available TC ink with an activation temperature (TA) of 29°C was used. The effect of color change, from blue to colorless, was measured through one heating and cooling cycle at several selected temperatures at six different PSL materials. Three fiber-based facestock of PSL used in this research are produced with 15% agroindustrial byproducts, 40% post-consumer recycled paper and 45% virgin wood pulp to form a high-quality natural paper. In addition, one material made from biogenic polymers facestock and two materials commonly used in labels production were used as well. The results of this research show that TC ink printed on alternative materials has a similar trend of color change and may be a good choice. Also, the influence of the color of fiber-based paper substrates on the change of TC color was noticed, which indicates the importance of colorimetric analysis of paper and TC ink before their printing.