Recycled wood vs. virgin non-wood fibers in paper – Impact on the chemical stability of black screen prints

There are a number of factors to consider when choosing a paper substrate for a fiber-based graphic product. Physical, optical, strength and various properties of paper are limiting factors in the use of paper, especially when it is used as a packaging material. The requirements are additionally increased if the papers are subjected to printing in the creation of the graphic product. The print on the selected paper substrate must be stable to the influence of temperature, light, pressure and different chemical agents. Considering the depletion of forest resources, the demands for alternative resources for the traditional use of cellulose fibers in paper production are increasing. Thus, selecting the appropriate alternative source of biomass is a big concern. In this research, the changes in colorimetric values of black prints were analyzed after exposure to four chemical agents: water, sodium hydroxide, acetic acid and ethanol. Using black conventional and UV inks, prints were made with screen printing technology on paper substrates in which 30% of the pulp from recycled wood fibers was substituted with virgin fibers from wheat, barley or triticale straw. Compared to a paper substrate made from recycled wood fibers subjected to the same printing technique, it was observed that the replacement of part of the recycled wood pulp with virgin fibers of cereal straw in the paper substrate gave UV black prints a higher chemical stability, while the same replacement for conventional black prints caused reduced chemical stability to all observed chemical agents. In general, regardless of the printing substrate composition, black prints made with UV ink were more stable to all chemical agents than those made with conventional ink with the exception of ethanol.