Impact of Aging and Recycling on Optical Properties of Cardboard for Circular Economy

This study investigates the effects of aging and recycling on the optical properties of paperboard, which is key to advancing circular economy practices in packaging. Methods included deinking flotation of cardboard made from sea algae and eco-conventional cardboard of unexposed and exposed samples in a xenon test chamber. Optical measurements were performed on the obtained laboratory paper sheets. Measurements for the chromatic coefficients ΔL*, Δa* and Δb*, as well as the CIE whiteness from comparison of the fluorescent component in the cardboard, were carried out under two light sources, D65 and UV. Regression analysis was used to quantify the statistical significance of these changes over time, i.e., in the aging process. The results revealed significant effects of both aging and recycling on the chromatic coefficients, with ΔL* and Δa* decreasing, while Δb* initially increased before decreasing. The influence of the fluorescent component is reduced by recycling the samples. Opacity measurements showed an initial increase in values that decreased with the aging of the samples, which indicates structural changes in the material. This research contributes to the circular economy by providing insight into the durability and optical properties of recycled cardboard, helping to develop sustainable packaging solutions.