Evaluation of degradation of ultraviolet-C irradiated polylactic acid/carbon-fiber composites using fluorescence spectroscopy

In this study, the effects of ultraviolet-C (UV-C) exposure on polylactic acid/carbon-fiber (PLA/CF) composite and PLA were evaluated using Fourier transform infrared spectroscopy (FT-IR), 3D fluorescence spectroscopy, differential scanning calorimetry (DSC) and tensile testing. The PLA specimens irradiated with UV-C for 0-15 days were not only oxidized on the surface, but also showed a decrease in the thermal and mechanical properties as the number of days of UV-C exposure increased, due to the cleavage of PLA chains. On the other hand, for the PLA/CF specimens, although surface oxidation was induced by UV-C irradiation, they did not undergo chain breakage, and their thermal and mechanical properties were retained. Therefore, carbon fibers play an important role not only as a reinforcement for PLA but also as a barrier to UV degradation. Furthermore, our results suggest that 3D fluorescence spectroscopy can be useful for the evaluation of accelerated degradation of polymer samples.