Caracterização de filmes elaborados por compressão térmica à base de misturas de amidos e plastificantes: biodegradabilidade em função do tempo e tipo de solo

Abstract

Films as a function of mixtures of starches can present a great potential for the formation of biodegradable products together with the insertion of plasticizing agents. Biodegradability is an important factor in determining how long the film can be fully degraded in the environment. The objective of this work was to optimize the elaboration of biodegradable films by thermal compression as a function of mixtures of starches and plasticizers and to evaluate the biodegradation of the films by means of digital image processing. Initially, the physicochemical characteristics of the starches (maize, banha-degalinha, fruta-do-lobo, lírio-do-brejo and parreira-do-mato) were analyzed. Previously, films of starch mixtures were prepared using water as plasticizer, using the simplex network design {5,2}. The film-forming solutions were prepared based on mixtures of starch and water, irradiated in microwaves and molded by thermal compression. Solubility in water was determined from the produced films, which was used as a parameter to select four films with different solubility values. Plasticizing agents (glycerol and citric acid) were added to the selected films. The combination of these variables was performed in a 4 x 2 x 2 triple factorial scheme. The films were also prepared as in the previous case. The studied response was water solubility, which was used as a parameter to select five best films for the evaluation of biodegradability. In addition to solubility, physicochemical, optical and mechanical properties were evaluated. For the biodegradation test, a 5 x 3 x 7 triple factorial scheme was carried out: 5 types of films, 3 types of soils and 7 days of analysis. ImageJ and Octave software were used for image analysis and processing to evaluate the biodegradability of the films. The insertion of plasticizing agents (citric acid and glycerol) provided an increase in moisture, solubility, strength and tensile strength and reduced water activity, water vapor permeability and film elongation. The TF2 film (mixture of fruta-do-lobo with 30% glycerol and 2% citric acid) was the most biodegradable treatment, and the TF4 films (mixture of banha-de-galinha and lírio-do-brejo starches more 30% glycerol and 3% citric acid) and TF5 (a mixture of banha-de-galinha and lírio-do-brejo starches with 40% glycerol and 2% citric acid) based on a mixture of lard starches de-chicken and lily-of-the-brejo were the least biodegradable treatments. Therefore, the films based on mixtures of banha-de-galinha and lírio-dobrejo starches (TF4 and TF5) presented chemical, physical and mechanical aspects that show the potential of these polymers in the use of packaging.