where T600is the fractional transmittance at 600 nm and x is the corresponding film thickness (mm). The lower opacity value represents the higher transparency of films.
2.8. Film surface characteristics
The surface morphology of both the upper (drying surface) and lower (in contact with Petri dish) sides of films was observed according to Pagno et al. (2015), with some modifications. A scanning electron microscope (SEM) (JEOL, JSM 6060, Japan) was used. Samples were fixed on aluminum stubs, coated with gold and scanned with an accelerating voltage of 5.0 kV and a magnification of 1000×.
2.9 Thermogravimetric analysis (TGA)
The thermogravimetric analysis (TGA) of film samples was performed on a thermogravimetric analyzer (Shimadzu, TGA-50,Japan), operating from room temperature to 650◦C at a rate of 10◦C min−1, using nitrogen as the purge gas.
2.10. Statistical analyses
The experimental design was analyzed using a surface response methodology. An analysis of variance (ANOVA) and Tukey’s test of multiple comparisons were used at a significance level of 5% to compare the differences between the means of data from the analysis of peroxide values, using Statistica 12.0 software (StatsoftInc., Tulsa, USA).