Amido termoplástico: obtenção de nanocompósitos de amido de araruta termoplastificado com nanopartículas de óxido de zinco

Abstract

The search for new materials with comparable performance to synthetics has driven the development of sustainable and biodegradable materials. The growing demand has stimulated the creation of innovative materials, such as starch-based films, biopolymers, and others, which offer excellent mechanical and barrier properties while being environmentally friendly. To achieve higher levels of sustainability, starch-based films, enriched with new components, gain prominence as possible candidates for food packaging applications. In this context, the present study aims to obtain and characterize thermoplasticized nanocomposites with arrowroot starch (TPA) and zinc oxide nanoparticles (ZnO NPs) in different proportions (1%, 3% and 5%). Films without ZnO NPs were used as controls. The thermoplasticized starch films were made using the casting solution technique (solvent evaporation). They were evaluated for the concentration of ZnO NPs, and were also submitted to laboratory techniques, such as moisture, solubility and swelling tests. In addition, they were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and tensile, strain at break and modulus of elasticity tests. For the moisture test, the results revealed that the addition of 1, 3 and 5% of ZnO NPs to the polymeric matrix provided a gradual decrease in the percentage of moisture when compared to the control TPA film. This fact is attributed to the interfacial interaction between the ZnO NPs and the arrowroot starch matrix, which in turn hinders the interaction of water molecules with the nanocomposite film. For the percentage of solubility of the films, a small change was observed after the addition of the NPs ZnO to the starch matrix, which becomes important for the maintenance of products stored in food packaging as well as the stability of the polymeric films. As for the swelling test, for the 1% TPA, 3% TPA and 5% TPA films, it was verified that when the SPL was added, they presented smaller variations compared to the TPA film containing only arrowroot starch in the polymeric matrix. In view of the above, the micrographs obtained by SEM revealed the presence of randomly dispersed aggregates of ZnO NPs in the polymeric matrix of arrowroot starch. The stress properties tests were conducted in 5 replicates, with a speed of 5 mm/min. The TPA film showed an average of 0.34 MPa and 59.80% for tensile strength and deformation at break, respectively. The incorporation of ZnO nanoparticles into the arrowroot starch matrix resulted in an increase in the tensile strength and deformation of TPA 1%, TPA 3% and TPA 5% films compared to TPA film. The mean strength for the films TPA 1%, TPA 3% and TPA 5% were 0.42 MPa, 0.45 MPa and 0.60 MPa, respectively. In addition, the mean strain at break for TPA 1%, TPA 3% and TPA 5% films were 77.14%, 86.34% and 86.05%, respectively. The FTIR spectra exhibited the same spectral behavior. This phenomenon is due to the presence of high starch content in the polymeric matrix of the films. The thermal stability for TPA, TPA1%, TPA 3% and TPA 5% films was investigated by thermogravimetric analysis (TGA). The results obtained for the TPA1%, TPA 3% and TPA 5% films presented similar data to the thermal stability of the TPA film and showed that the addition of ZnO NPs to the polymeric matrix did not cause a significant decrease in them. The results showed that it is possible to use the films produced in this work in the packaging sector.