Figure 9. Evolution of WCA of the samples produced in the Ar, N2, CO2, SF6, vacuum and O2 and aged up to 30 days in ambient air. LP is the polarization direction of laser field perpendicular to the direction of scanning beam. CP is the circularly polarized laser beam.
The samples prepared in SF6 showed slowest WCA transition speed. Also notice that surface of the samples prepared in SF6 being tested in the defined spot for WCA, change the wetting properties after contact with water droplet. The repeated tests at the same place of these samples demonstrated higher WCA.
Figure 10 presents the summary of semi-quantitative analysis of variation of weight percentage relation for laser-treated samples in different gas media and untreated surfaces after 30 days of ageing in atmospheric air. The marks below corresponding bars denote the used gases (from Ar to O2, VAC means vacuum). HP and CP correspond to the polarization type, and the numerical values (1 and 2) correspond to the 50 mm/s and 300 mm/s scan speeds. In the case of O2 (from O2 HP1 to O2 CP2 bars in Fig. 10, panel c), one can admit a pattern similar to Fig. 8, where stronger oxidation is accompanied with the increased presence of carbon, that can be associated with higher WCA.