Tensile properties were determined by a tensile test with a
texturometer (Shimadzu, Japan). Sample films of 5 2 cm were
loaded in the equipment. The crosshead speed was set at 10 mm/s.
The ultimate tensile strength (tensile strength) and elasticity
modulus were determined by using a Trapezium X software.
Film thickness was obtained by direct measuring of the film.
A micrometer (Mitutoyo, Japan) was used.
Opacity measurements were performed according to Gomez-
Estaca, Gimenez, Montero, and Gomez-Guillen (2009). A film
piece was loaded in a spectrophotometer (VIS spectrophotometer,
Jenway, UK) and the absorbance was determined at 600 nm. The
opacity was determined according to