PREPARATION AND CHARACTERIZING OF CELLULOSE MICRO/NANO FIBRILS USING OXALIC ACID AND DIFFERENT MECHANICAL PRE-TREATMENTS.

BASTIDA, GABRIELA ADRIANA; MIGUEL A. ZANUTTINI; GALVÁN, MARÍA VERÓNICA

Girona

Congreso; CIADICYP 2022 Iberoamerican Congress on Pulp and Paper Research; 2022

Riadicyp, LEPAMAP, Universidat de Girona, Ciadicyp

In the last decades, the production of nanocellulose obtained from the cell walls of wood fibers and plants through different process, has gained a lot of attention due to their interesting properties [1]. In this study, we examined the production of cellulose micro/nano fibrils (CMNFs) obtained from bleached eucalyptus pulp (BEP). For this, a chemical pre-treatment was performed using oxalic acid at two concentrations: 25% and 50 wt.%, considering two different mechanical treatments: a) a rotating homogenizer Ultra-turrax-type after chemical treatment or b) a PFI mill refining prior to chemical treatment. Finally, the mechanical fibrillation for production of CMNFs was performed by pressurized homogenization considering 5 and 15 passes. The FTIR spectrum and the increase in carboxylic groups determined by conductometric titration of CMNFs confirm the carboxylation of cellulose produced by the chemical treatment. The CMNFs were characterized by determination of nanofibrillation yield, transmittance and surface charge. The results show that, the best performed values of nanofibrillation yield (76.5%), transmittance (72%) and charge surface (73 µeq/g) of CMNFs were obtained for PFI refining, 50 wt.% of oxalic acid and 15 passes by pressurized homogenization. Besides, the morphology of the microfibrillated cellulose (CMF) and nanofibrillated cellulose (CNF) fractions were analyzed by SEM and TEM microscopy, respectively. The aspect ratio (p = length/diameter) of CMNFs were determined by sedimentation and shear viscosity methods. The highest aspect ratio determined by TEM was observed for the CNF obtained through PFI mill refining and 25wt.% of oxalic acid (p = 96.3), and no significant difference was observed by increasing the number of steps. The aspect ratio values determined by sedimentation method agree with those of TEM microscopy. Besides, a strong relationship between the intrinsic viscosity of the CMNFs dispersions and their aspect ratio was observed. Films of CMNFs were formed and it was observed that, the nanofibrillation yield, more than their aspect ratio, has influence on the film strength.