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

Abstract

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.

Keywords:

• UV-C irradiation
• 3D-printing
• polylactic acid
• carbon fiber-reinforced composites
• fluorescence spectroscopy

Disclosure of potential conflicts of interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors would like to thank the Department of Advanced Fibro-Science, Faculty of Fiber Science and Engineering, Kyoto Institute of Technology for all supports provided.