2.3.2. Contact angle
The samples (4 cm
×
4 cm
×
1 cm) of the industrially coated
tiles were used for the determination of the photo-induced
hydrophilicity. The changes of the water contact angle were
monitored by a sessile drop method (Surface Energy Evaluation
System, Advex Instruments).The measurements were performed
by putting
∼10 m3 water droplets at ten different spots
on each tile surface in environmental conditions, and the measurement
results were averaged. During the measurements the
samples were illuminated by UV lamp (Osram Eversun, 40 W,
320–400 nm), light intensity 0.80 mW/cm2 at a distance of 33 cm
(Radiometer Solar Light PMA 2100, UV-A detector PMA 2110,
Photopic detector PMA 2130 H for visible light, Solar Light co.,
INC Glenside, PA 19038). The UV illumination time was up to
24 h. The changes in the water contact angle were related to the
values of photo-generated superhydrophilicity.