The tensile properties were studied using a material testing
machine (Universal tensile strength tester) with 3 kg load
cell, according to ASTM standard method D882-91 (1996). Film
sample strips, with a size of 100 mm
×15 mm, were cut from
each kind of tapioca starch films. Before testing, the thickness
of the samples was measured with a micrometer at 10 arbitrary
points of the film and the average of these values was used
to calculate the cross-sectional area (equal to thickness multiplied
by width) of each sample. The samples were held tightly
between pneumatic clamps. The ends of each specimen were
mounted using a utility tape to prevent and cracking and slippage
of films during testing. Force (N) and deformation (mm)
were recorded during extension at 40 mm min−1. The machine
was capable of maintaining a uniform rate of grip separation. Ten
replicates of each film were tested. Experiments were run within
3 min of removing films from desiccators to minimize adsorption/
desorption of water by films. The parameters determined to
be: tensile strength (MPa), elongation (%), and Young’s modulus
(MPa).