Investigação de redução da cristalinidade da celulose sob a influência de diferentes misturas eutéticas.

Abstract

Since cellulose is a biodegradable raw material that is practically inexhaustible, it has been the subject of several studies in order to find alternative applications to conventional raw materials. Its derivatization on an industrial scale occurs mostly through heterogeneous reactions, which complicates the reaction process. On the other hand, this limitation can be overcome by using homogeneous conditions. The heterogeneous system is mainly controlled by structural factors that regulate cellulose access, such as the crystallinity index. Thus, reducing the crystallinity of cellulose is not a trivial process, due to its supramolecular structure which prevents the process from being carried out in conventional solvents. This work studied the reduction of the crystallinity of commercial cellulose and sugarcane bagasse in different types of eutectic mixtures: lactic acid/trimethylammonium chloride; lactic acid/glycine; glycerol/potassium carbonate and glycerol/betaine, over a period of 4 h at a temperature of 80ºC and molar ratios of 5:1 and 10:1. The celluloses obtained in the procedure were analyzed using various techniques, such as: Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TG). The eutectic mixtures developed in the laboratory to reduce the crystalline phase of cellulose showed satisfactory results in the process. In the system involving the lactic acid/glycine mixture, a reduction in the crystalline phase of 19.71% was obtained and with the glycerol/betaine mixture 18.85%, which were superior results compared to the comparison mixtures (lactic acid/trimethylammonium chloride and glycerol/potassium carbonate). In cellulose extracted from sugar cane bagasse, crystallinity was reduced by 19.23% in the lactic acid/glycine mixture and by 17.85% in the glycerol/betaine mixture, which was also higher than the other mixtures previously worked on. The mixtures developed in the laboratory to reduce cellulose crystallinity obtained a good result in terms of cellulose crystallinity index (CI), but the lactic acid/glycine mixture obtained a lower index (40.5%) for commercial cellulose and (27.2%) for cellulose from sugarcane bagasse, when compared to cellulose that was not subjected and that was subjected to interaction with lactic acid/trimethylammonium chloride