Efeito do plastificante na cinética de liberação de ureia a partir de filmes de zeína obtidos pelo método casting

Abstract

One of the most used fertilizers in agriculture is urea, because it contains a high nitrogen content and has a low cost. However, it has the disadvantage of suffering losses by leaching, volatilization, among others, causing damage to the producer and the environment. One way out of this inconvenience is the use of fertilizers that have a sustained release system, which are those that have at least one substance that delays the availability of the nutrient for absorption and use by plants. This work aimed to develop a controlled urea release system and verify the release kinetics. The films were prepared by the casting method using zein and urea in the proportion of 30% (m/v) of hydroalcoholic solution and plasticized with triethylene glycol (TEG) at concentrations of 0, 5, 10, 15 and 20% (m/v). Differential scanning calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD) were used to characterize the films. Release kinetics were evaluated in aqueous solution and it was evaluated whether the First-order and Peppas-Salim models were adequate. Due to the FTIR, DSC and XRD results, it can be concluded that urea was encapsulated by the zein films. The addition of the plasticizer caused a reduction in the glass transition temperature of zein from 153°C to 135°C, 125°C, 127°C and 103°C respectively, as the TEG concentration increased. In the XRD of the zein films, a peak at 9° and 20° was observed, which correspond to the interplanar spacing. The zein and urea films showed the characteristic diffraction patterns of urea. The release of urea in aqueous solution after 3 days was between 28 and 65%, and the results of the release kinetics were better suited to the First Order model, indicating that the release occurs through the urea dissolution process. Thus, the developed system has the potential to be used in agriculture.