2.4.8. Tensile testing
Tensile properties of the film samples were tested using a
5965 universal testing machine (Instron, USA) according to ASTM
standard method D882-12 (2012) with modified storage conditions.
Samples were cut into rectangular shapes with a dimension
of 3 cm × 15 cm and then conditioned at ambient temperature with
different relative humidity (RH) of 62 ± 2% and 42 ± 2% for at least
two days prior to the test. Five specimens were tested for each
sample. Thickness of the films was measured by an ID-C112BS
micrometer (Mitutoyo, Japan), with an accuracy of 0.0001 mm. The
average thickness of each film was calculated from five points for
each specimen. Tensile strength (MPa), modulus of elasticity (MPa)
and elongation at break (%) were recorded as mean ± SD (n = 5). The
initial grip distance was set at 100 mm and the crosshead speed was
50 mm/min.