Cassava starch films: effect of polyvinyl alcohol on films’ water diffusion, permeation and sorption behavior and mechanical properties

Abstract

In search of sustainable materials for food packaging, many studies are focused on the use of biopolymers and their blends. This trend is related to the resistance of non-biodegradable commercial plastics toward degradation and by their inadequate disposal, which results in environmental damage. To reduce the post-consumption impact of plastic packaging, it was found that the production of cassava starch and polyvinyl alcohol (PVOH) flexible films and their blends by solvent casting method was helpful. The volume concentrations used in the films elaboration were 100S0P, 90S10P, 80S20P, 70S30P, and 0S100P [where proportion of starch percentage (S) and PVOH% (P) film solutions], with the addition of 8% of citric acid. The films were characterized by mechanical properties and water sorption, diffusion, and permeation behavior. The PVOH insertion of 10, 20, and 30% to the films made them about 24, 58, and 80% more flexible and 36, 71, and 83% more puncture-resistant, respectively, compared to the starch film. However, the insertion of 20 and 30% of PVOH more than doubled the monolayer moisture content of the blends and increased their water diffusion coefficient by about 163 and 300%, respectively, compared to the starch film. For effective diffusion coefficient determination, a series and simplified solutions were suitable since the values presented the same order of magnitude and obtained a good fit among the data. Thus, the 10% of PVOH insertion was more advantageous as it strengthened the mechanical properties of the blend without decreasing its water barrier properties, compared to the starch film.