Blends formulations of cellulose microfibers and cellulose nanocrystals

GUIDONI, MARIELA; CASADO, ULISES; ARANGUREN, M. I.; MUCCI, VERÓNICA L.

Buenos Aires

Congreso; WCCE11-11th World Congresses of Chemical Engineering-GS01 Global Symposium on Nanocellulose: Recent advances to unlock potential for Engineered Sustainable Materials (JE II CIBIQ); 2023

AAIQ

The objective of this work is to characterize mixtures from cellulose nanocrystals and cellulose fibers and the resulting casted films. The blends are prepared in order to improve the mechanical properties of the films obtained from neat CNC suspensions, while maintaining as much as possible some of the interesting optical properties of these suspensions. As is already known, nanocellulosic materials such as cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs) can form organized hierarchical structures with interesting optics properties [1,2]. In the present study, an aqueous suspension of CNC from CelluForce® and CNF obtained from local cellulose pulp were used to prepare the mixtures in different weight ratios. The macroscopic anisotropy of the suspensions was qualitatively investigated using two crossed linear polarizing plates with a back diffuse light source. Also, an optical microscope was used to observe the suspensions using crossed linear polarizers. A rheo-optical study was performed to characterize the neat CNC suspensions, and the order achieved applying shear rotation between transparent parallel plates. Additionally, the shear viscosity and complex viscosity of the mixed liquid suspensions prepared at different fiber ratios were measured. As expected, the viscosity increased with the cellulose concentration, but also was a function of the ratio of the fibers, increasing with the microfiber content due to the length effect of the microfibers. The study also showed that suspensions of rigid rod-like CNC suffer orientation due to shear during flow. Following this results, films were prepared casting the CNC suspensions in Petri dishes, and carrying the drying step in an orbital shaker, at different rpm and at room temperature. The films presented concentric zones with clearly different orientation and iridescence, which was related to color when microscopically observed between crossed polarizers. Similar characterization will be performed on the mixed films to investigate if the orientation can be partially maintained in the presence of the microfibers and the effect of the microfiber/CNC ratio.