Filmes de álcool polivinílico reforçado com nanocelulose proveniente da casca de arroz

Abstract

The development of biodegradable materials has been stimulated in recent years, in the search for sustainable alternatives to the use of resources from fossil sources. Allied to this is the possibility of using raw materials from agro-industrial residues, which are often environmental liabilities, have low cost and high potential for the development of new materials. Thus, this work aimed to develop biodegradable films of polyvinyl alcohol matrix (PVA), reinforced with nanocellulose extracted from rice husk for application in packaging. For this, the rice husk in natura form was submitted to two processes for cellulose extraction: the alkaline treatment and bleaching. Soon after, nanocellulose was obtained from an acid hydrolysis with sulfuric acid. Rice husk, cellulose and nanocellulose were characterized through Fourier transform infrared (FTIR), X-ray diffraction (DRX) and thermogravimetric (TGA) spectroscopy analyses. Through these analyzes it was possible to notice that there was a change in the structures of the materials after the treatments performed. Subsequently, through the solvent casting technique, films of PVA (Pure), PVA reinforced with rice husk, PVA reinforced with cellulose and finally the PVA film reinforced with nanocellulose were developed. In this way, it used a content of 1% by mass of reinforcement as a standard for all films. From the analysis of thickness, weight and density of the films, it was identified an increase in the results for the films with reinforcements compared to the PVA film (Pure). By analyzing the transparency of the films, it was found that the only film that did not show changes in this aspect was the film reinforced with nanocellulose. When analyzing the flexibility of the films, it was found that the presence of reinforcements in the PVA matrix did not influence this property. The film reinforced with nanocellulose proved to be less soluble, it also exhibited the lowest water vapor permeability rate. Through optical microscopy it was observed a surface free of defects for the film reinforced with nanocellulose, unlike the films reinforced with cellulose and rice husk, which showed some defects such as roughness and agglomerates. When evaluating the thermal behavior of the films, a certain thermal instability was noted for the cellulose reinforced film in relation to the other films. In the biodegradability test, the film with nanocellulose reinforcement was the only one that withstood the test conditions for a period of 45 days. Finally, when analyzing the mechanical properties, it was seen that the modulus of elasticity and tensile strength of the reinforced nanocellulose films increased 295.45% and 29.6%, respectively, in relation to the pure PVA film. Therefore, the PVA film reinforced with nanocellulose, indicates to be a great alternative to be applied as biodegradable packaging.