Aplicação de filmes de amido termoplástico (TPS) como substrato de liberação controlada de fertilizantes NPK

Abstract

The plasticization of starch makes it possible to obtain thermoplastic starch (Thermo Plastic Starch - TPS), a multifunctional bioplastic with high biodegradability. TPS can be added to fertilizers, such as those based on nitrogen, phosphorus and potassium (NPK), which when applied in controlled release devices allows for a slower release of the fertilizer, and consequently a lower loss by leaching, among other processes. For the present work, thermoplastic starch films were developed with NPK fertilizers in their composition, using the casting method. Soil leaching and controlled release of fertilizer into water from the films were monitored using UV-vis Spectrophotometry and Flame Photometry techniques. The releases do not occur at a constant rate, however, it was possible to prove their efficiency in releasing these ions in a controlled manner. The films were also characterized by contact angle and by the Fourier Transform Infrared Spectroscopy (FTIR) technique, before and after undergoing accelerated degradation, using the photodegradation technique. In this last analysis, it was possible to notice that the addition of fertilizers to the film reduces their moisture loss through evaporation. After three months of analysis, samples with approximately 1 cm in diameter were completely biodegraded in soil. Despite not maintaining a constant rate of release, NPK was released into water within one hour, indicating the success of the starch films in releasing the fertilizer.