Comparative study between UVB 313 nm, UVC 254 nm, and far UVC 222 nm light on the aging of polyamide 66

Polyamide-66 underwent substantial growth worldwide in the late 1930's. It can be found in several public spaces. After 2019, due to the coronavirus disease (COVID-19), the sanitization of the interior of aircraft and public spaces by using UV light became important. Most of all, the effect of the far UVC 222 nm became a research hot spot and is still a research blank. In the present work, a comparative study on the post-exposure damage of polyamide- 66 occurred when controlled ultraviolet irradiation (UVC 254 nm, far UVC 222 nm, UVB 310 nm) and moisture-condensation were carried out. Chemical (FTIR), thermal (DMA), and nano-mechanical properties were evaluated. FTIR analysis showed the formation of O-H and/or N-H bonds since there appeared absorptions at 3400 cm-1 along with the vanishing of other signals related to C-N bonding. These changes are more evident in samples exposed to UVC 254 nm followed by samples that were irradiated with UVC 222 nm. Samples that were aged with UVA 313 nm didn't show a change in FTIR spectra. FTIR on spectra and nanoindentation showed that UVB 313 nm produced a lower aging effect on this material. In contrast, UVC 254 nm light caused the highest degree of surface chemical-mechanical change attributed to cleavage/crosslinking reactions initiated by free radicals produced by UV light and moisture. On the contrary, far UVC 222 nm light presented moderate effects on Polyamide-66. Glass-transition temperature (Tg) diminished as the time to exposure increased attributed to water absorption and surface damage, being the highest change at -16.05 °C for samples irradiated with 245 UVC nm. However, the potential of far UVC 222 nm light for COVID-19 sanitization, with no significant degradation effects on polymeric materials, is a promising finding that should be further explored and could provide a hopeful solution in the fight against the pandemic.