The thickness of films was measured at five random positions on
the film strips using a micrometer (Digimatic Micrometer, QuantuMike
IP 65, Mitutoyo, Japan) with an accuracy of 0.001 mm. The
average values of five random measurements were taken for the
thickness of each film. Tensile properties such as tensile strength
(TS), elongation at break (E), and elastic modulus (EM) of each
film were measured according to the method of ASTM D 882-88
using Instron Universal Testing Machine (Model 5565, Instron Engineering
Corporation, Canton, MA, USA). The films were cut into
rectangular strips (2.54 cm × 15 cm) andthemeasurement wasperformed
in a tensile mode with an initial grip separation of 50 mm
and a crosshead speed of 50 mm/min. The TS (MPa) was determined
by dividing the maximum load (N) by the initial cross-sectional area
(m2) ofthe film. The E (%) was determined by dividing the extension
at the rupture of the film by the initial length of the film (50 mm)
multiplied by 100, and the EM (GPa) was determined from the slope
of the linear portion of the stress-strain curve, which corresponds
to the stress divided by the strain of the film sample. Ten specimens
from each film were used and the average values were presented.