Amido, álcool polivinílico e ácidos carboxílicos na produção de biofilmes

Abstract

Plastics are widely used in the production of food packaging, household items, hygiene and cleaning products, cosmetics, pharmaceutical and industrial applications. However, conventional plastics are responsible for generating large amounts of waste that are deposited to the environment and require a long time to completely degrade. Because of the need to replace plastics from non-renewable sources, in this context we studied the junction of cassava starch, polyvinyl alcohol, glycerol and carboxylic acids (citric and succinic acids) in the preparation of biodegradable films by casting method. Furthermore, this study optimized the methodology developed by Shi et al. (2008), evaluated the effect of adding carboxylic acids to the properties of the films of PVOH and starch and characterized in relation to the thickness, moisture, water solubility, water vapor permeability, mechanical properties and morphological analysis (scanning electron microscopy ). We conducted a complete Factorial Design 22 with 3 replications at the central point for studying the effect of time of blend (starch-PVOH) and time of crosslinking of citric acid on the properties of moisture and water solubility of the films. Other formulations of films were prepared with the best time (2 hours of blend and 15 minutes of crosslinking) compared to control (starch-PVOH-glycerol) and the interaction of acids (citric and succinic) in films about the significant difference (p ≤ 0.05). The average film thickness was 0.12 ± 0.02 mm. The biofilms had around 14g/100gfilm moisture content and water solubility up to 31% of total dry mass. The tensile strength varied from 16.4 to 25.1 MPa, elongation at break from 6.37 to 15.91% and the Young's modulus of 451.8 to 670.6 MPa. The water vapor permeability is moderate (0,20 a 0,25 g.mm/m2.dia.kPa), typical of highly hydrophilic films. The morphology of the films was observed by scanning electron microscopy and observed that the control presented a relatively compact and homogeneous structure, suggesting the polymer compatibility between starch and PVOH. However, it was observed also the presence of starch granules not disrupted in control and film-containing succinic acid. In the film containing citric acid verified the presence of "donuts", as detected by other authors. From the analysis results it is considered that in general, the films produced were homogeneous, transparent, visually attractive (without presence of air bubbles) and flexible, and that the addition of PVOH has improved properties when compared to films containing only starch.