Obtenção e caracterização de nanoceluloses a partir da fibra de tucum (Astrocaryum chambira Burret.)

Abstract

Tucum fibers are widely used and known by families of indigenous communities in the Amazon, although it is widely used in handicrafts, there is still little information about the potential of this fiber. Therefore, this study presented, in an unprecedented way, the properties of Tucum (Astrocaryum chambira Burret.) as a source for obtaining nanocellulose. The plant part used was the stem, being analyzed firstly the chemical composition in percentage of cellulose (66.77%), hemicellulose (14.21%) belonging to holocellulose (81.00%), moisture content (5.92% ), ash (2.94%), extractives (3.93%) and lignin (11.47%). Based on these contents, it was possible to confirm that this fiber was suitable for pulping. The cellulose extraction was carried out by the mercerization process and the product of this extraction was used to obtain cellulose nanocrystals, through acid hydrolysis with sulfuric acid at 64% and, to obtain cellulose nanofibrils, in which the mechanical defibrillation process using the Super Mass Colloder defibrillator mill. After that, the resulting materials were lyophilized for characterization. Tucum in natura and cellulose samples were characterized by X-ray diffraction, Fourier transform infrared, thermogravimetric analysis and scanning electron microscopy. The materials resulting from acid hydrolysis and mechanical treatment were cellulose nanocrystals and micro/nanofibrils, respectively, in which they were characterized by the same techniques mentioned, with the exception of scanning electron microscopy and including dynamic light scattering and atomic force microscopy. The crystallinity index for nanocrystals was 66.79% and for micro/nanofibrils 43.95%. In the topographic images of the Atomic Force Microscopy it was possible to observe that the nanocrystals presented a structure similar to a needle. As for micro/nanofibrils, as a hybrid material is obtained, suspensions of microfibrillated cellulose are normally heterogeneous with particles of irregular diameter, varying between micrometric and nanometric scales. In the analysis of dynamic light scattering referring to micro/nanofibrils, cycle 10 was the optimal point, with a higher frequency around 11 – 13 nm, and with a higher concentration of nanoscale particles. Thus, due to research in search of new sources of biomass, this work may enable new discoveries.