UV-Accelerated Aging of PLA and PP-Based Biocomposites: A Spectral and Colorimetric Study

In this work, biocomposites of polylactic acid (PLA) and polypropylene (PP) with micronized cellulose (MC) were produced by mold injection and subjected to accelerated aging with ultraviolet (UV) radiation. The tests took place over 10 weeks, during which the produced specimens were exposed to a total of 1050 h of ultraviolet light. During the UV aging test, images were captured, and spectral reflectance and colorimetric measurements were carried out on the specimens exposed to UV and on specimens of the same materials kept in the dark (originals). As expected, only residual color differences were observed in the original specimens with values of ΔE*ab always below 0.5. On the other hand, spectral reflectance and colorimetric changes were noticed over time in the specimens subjected to UV radiation. In particular, the values of ΔE*ab increased over time and were found to be higher for PLA with MC compared to PP with MC. Values of ΔE*ab = 4.7, 9.0, and 10.4 were obtained for weeks 1, 5, and 10, respectively, for the specimens of PLA with MC, whereas ΔE*ab = 4.5, 6.8, and 7.3 were obtained for weeks 1, 5, and 10, respectively, for the specimens of PP with MC. Therefore, it was found that the specimens of PLA with MC showed greater color fading compared to the specimens of PP with MC when subjected to UV exposure. In addition, it was also found in this work that besides the color differences noted in the tested specimens, those made of PP with MC also showed signs of surface damage.