Blendas a base de biopolímeros para liberação controlada de agroquímicos

Abstract

The incorporation and encapsulation of fertilizers in polymers blends are methods that can be used to reduce losses and to minimize environmental pollution. In this work, blends of Soy Protein Isolate (SPI) and Polylactide Acid (PLA) were used to incorporate the granular fertilizer NPK (nitrogen, phosphorus and potassium). The blends were obtained from mechanical mixture in a Haake´s high shear mixer. The influence of concentration of the biopolymers in the blends, was examined by differential scanning calorimetry (DSC), Thermogravimetric Analysis (TGA) and Scanning Electron Microscopy (SEM). The morphology of the blends can control the diffusion of the fertilizers, also modulating the release. The effective incorporation of the nutrients to the soil is related to the control release control. However, the applications of these nutrients are linked to the methods and the soil conditions. One method for to reduce losses of nutrients is the slow-release. In this way, the preparation of biopolymers blends based in Soy Protein Isolate (SPI) and Polylactide Acid (PLA) for the controlled-release becomes viable. SPI and PLA or SPI, PLA and NPK were previously mixed whit plasticizers and submited to mechanical mixture, in a Haake high shear mixer. The process was performed at 165 ºC for 5 minutes at speed of 90 rpm. These parameters were applied for all blends containing SPI/PLA rate of 1.5, 2.3 and 4.0. For some blends 5 to 15% of plasticizer was added to study its effects. For the blend containing NPK the same method was utilized with addiction of the fertilizer, after the fusion of the PLA. The release rate of nutrients was estimated by the conductivity promoted by the ionization of thefertilizer salts. The ions concentration increase with time due to the release of the fertilizers. The dynamic tests were conducted in a beaker under continuously agitation with 100 mL of water, 1.6 ±0.2g. of sample and 180 hours. The release rate is a function of the blends morphology, and it can be controlled by the porosity. The use of blends as vehicle decreases the release of the fertilizer when compared to the pure component, for about eight times. The relationship increase with the amorphous phase which is related to the SPI.