Caracterização de adesivos de taninos reforçados com nanofibrilas de celulose

Abstract

The objective of this work was to characterize adhesives developed based on tannins with the addition of cellulose nanofibrils (CNF) in different proportions. In the tannin-based adhesives, 1%, 5% and 10% cellulose nanofibrils were added in order to improve the adhesive qualities for bonding. Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) were performed. The tannins used in the manufacture of the adhesives were extracted from bark of the Angico-red tree (Anadenanthera peregrina). The extraction of the tannins from the barks of red Angico was carried out with 3% sodium sulphite. Four adhesives, the control and three other adhesives were analyzed, varying the proportions of cellulose nanofibrils. The cellulose nanofibrils were obtained by the shear method, using a mechanical defibrillator (Grinder), which consists of breaking the structure of the fibers by friction, transforming the fibers into cellulose nanofibrils. The adhesives were characterized as to their molecular bonds, besides the thermal capacity of the material and its qualities for the application, such as viscosity, pH, gel time and solids content. It was observed that the greater influence of the addition of cellulose nanofibrils on the adhesive occurred in the viscosity, providing an increase of this property with the addition of NFC in the adhesives. Raman spectroscopy has identified that the higher the NFC ratio in the adhesives, the more they become amorphous and possibly more fluorescent, making it difficult to read the laser, as well as to identify the interaction of the tannins with the cellulose nanofibrils with the peak displacements. In the FTIR, one of the results was observed in the adhesive with 5% NFC, with a lower O-H binding band, and therefore the adhesive probably has lower amounts of O-H bond. With the thermogravimetric analysis it was observed that the adhesives did not alter the thermal capacity with the increase of the proportion of the cellulose nanofibrils in their compositions. The present work contributes with information for the characterization of adhesives of tannins reinforced with NFC and with the possibility of producing adhesives based on tannins more resistant to mechanical efforts with the purpose of increasing the use of these adhesives.