Thermochromic prints on beverages packaging: The resistance of printed labels upon ethanol

Abstract

Today, the packaging industry is increasingly transforming, especially in terms of development of new sustainable materials and smart solutions in order to attract customers when choosing products, and to be competitive in the market. The use of colour changing packaging can give added value to the product since this kind of packaging can in that way interact with the consumer and provide a massage upon the product. During its lifecycle, the packaging can be exposed to the influence of various agents, for example the spilling of beverages over the printed labels. For this reason, the prints need to be resistant to certain agents, in this case, ethanol. In the end, the spill of ethanol can cause visual alterations of the print due to the colourants or the substrate itself not being resistant to the particular agent. Thermochromic inks are widely used as indicators for beverage packaging which can often be exposed to different concentrations of alcohol that may affect the functionality of that same indicator. Thermochromic inks differ in their composition from classic printing inks, which in the end results in lower stability when exposed to UV radiation and various chemicals. Thus, this study explores the influence of ethanol on the functionality of TC prints on labels. Different label papers were printed with one TC ink, with an activation temperature of 12°C. The samples were exposed to different concentrations of ethanol (8%, 12%, 25%, 35%, 42% and 96%) to simulate the real conditions in which it is possible to spill different alcoholic beverages on the thermochromic print on the packaging of an alcoholic product. It can be concluded that alcohol affects the stability of microcapsules even in the smallest concentrations because the largest changes of colour were observed at low temperature, while smaller colour changes determined at 23 ° C indicate that the classic process ink is more stable to the influence of alcohol. The results of this test showed that the chemical stability of the thermochromic print depends on both, the printing substrate and the external conditions to which the print is exposed. The results show that the proper choice of printing substrate can improve the stability of the thermochromic print in reaction with ethanol.