The effects of UVC irradiation on the properties of thermoplastics

The effect of UVC irradiation on plastics was investigated. This study first generates color and mechanical data on a large number of commercial plastics after irradiation. PP, HDPE and ABS undergo changes in color and mechanical properties. The effects are smaller for the other materials such as PC, PBT, PC/ABS, LDPE. Dark colors make the degradation processes less visible, but do not offer protection to chemical changes. Next, polycarbonate is studied in more depth by systematically screening antioxidants, colorants and UV absorbers. The aromatic polycarbonate backbone is a strong absorber for the short wavelength UVC. It discolors rapidly and forms a thin layer (<5 mu m) of degraded material on the surface which temporarily protects the bulk of the material against further changes in color and mechanical properties. Mechanical and electrical properties do not change significantly which shows proper resistance of PC towards UVC. Commonly used stabilizer additives have no effect on the degradation process of polycarbonate which implies that development of dedicated grades for UVC applications is currently not possible.