The treated plastic strip (PVC or PET) was
placed on the table of a Ram&Hart goniometer.
A drop of deionized water (pH 5.8-6.2) was placed
on the surface of the PVC or PET strip using a
microsyringe. The drop size was made to increase
or decrease by adding or withdrawing a small
volume of water, and the water advancing and
receding contact angles, respectively, were measured
within 30-60 s. The contact angle measurements
for the particular system were done for five
to eight large drops having a drop base diameter
from 8 to 10 mm. The average values are reported.