Gel Point as Measurement of Dispersion Degree of Nano-Cellulose Suspensions and Its Application in Papermaking

Abstract

The dispersion degree of cellulose micro and nanofibrils (CMFs/CNFs) in water suspensions is key to understand and optimize their effectiveness in several applications. In this study, we proposed a method, based on gel point (Øg), to calculate both aspect ratio and dispersion degree. This methodology was validated through the morphological characterization of CMFs/CNFs by Transmission Electronic Microscopy. The influence of dispersion degree on the reinforcement of recycled cardboard has also been evaluated by stirring CMF/CNF suspensions at different speeds. Results show that as stirring speed increases, Øg decreased to a minimum value, in which the aspect ratio is maximum. Then, Øg increased again. Suspensions with lower Øg, in the intermediate region of agitation present very good dispersion behavior with an open and spongy network structure, in which nanofibril clusters are totally dispersed. Higher stirring speeds shorten the nanofibrils and the networks collapse. Results show that the dispersion of the nanocellulose at the minimum Øg before their addition to the pulp, produces higher mechanical properties, even higher than when CNFs and pulp are agitated together. This method allows for the determination of the CMF/CNF dispersion, to maximize their behavior as strength agents. This knowledge would be crucial to understand why some industrial trials did not give satisfactory results.

Dataset for facilitating the calculation of aspect ratio of fibrillated cellulose suspensions based on gel point data

“… No. Raw Material Pretratment Main Treatment Reference and Comments 1–5 Recycled paper from newsprint TEMPO-mediated oxidation (5 mmol NaClO/g pulp) High pressure homogenization (HPH) 600 bar, 4 passes [9] Stirring agitation of CMNFs: 3, 70, 125, 500, 2500 s − 1 6–9 Recycled paper from newsprint Refining PFI mill 5 K rpm HPH 600 bar, 6 passes [9] Stirring agitation of CMNFs: 50, 500, 900, 2500 s − 1 10–13 Recycled bleached de-inked pulp – Refining PFI mill 0, 10 K, 30 K, 50 K rpm [5] 14–16 Triodia pungens grass (spinifex) plants Hot water + NaOH, Delignification with NaClO 2 No HPH, HPH 1 pass 300 bar and HPH 1 pass 500 bar [10] 17–20 Bleached Eucalyptus Kraft Pulp – Refining PFI mill 0, 10 K, 30 K, 50 K rpm [5] 21–22 Bleached Eucalyptus Kraft Pulp Refining PFI mill 10 K rpm HPH at 500 and 1000 bar 1 pass [10] 23 Bleached Eucalyptus Kraft Pulp TEMPO-mediated oxidation (5 mmol NaClO/g pulp) High pressure homogenization (HPH) 600 bar, 4 passes Not published 24 Thermomechanical pulp Water disintegration Brecht-Holl 200 mesh screener (Fines <76 µm) Not published 25 Kraft Water disintegration Brecht-Holl 200 mesh screener (Fines <76 µm) Not published …”

A Facile One-Pot Preparation and Properties of Nanocellulose-Reinforced Ionic Conductive Hydrogels

“…This material is non-toxic, harmless, lightweight, and has good biocompatibility. More importantly, the surface of nanofibers is rich in hydroxyl groups, with high elastic modulus, stiffness, and low thermal expansion coefficient, which can be stably dispersed in water-soluble polymers or as matrix composites dispersed in water [ 8 , 9 , 10 , 11 , 12 , 13 ]. In this regard, cellulose is often combined with conductive fillers to make conductive nanocomposite complexes, which play an important role in toughening, crosslinking, and acting as network support with excellent mechanical properties.…”

Dynamic Light Scattering Plus Scanning Electron Microscopy: Usefulness and Limitations of a Simplified Estimation of Nanocellulose Dimensions

“…This is the case for cellulose nanofibers (CNFs) and, to a lesser extent, cellulose nanocrystals (CNCs) [ 1 , 2 ]. The former are present in aqueous suspensions as networks of entangled fibrils with a high aspect ratio (length/diameter), usually between 20 and 200 [ 3 , 4 ]. CNF entanglement hinders the determination of their length even by the most advanced microscopy techniques, as distinguishing both ends of each individual fibril is often impossible.…”