Rheological behavior of high consistency enzymatically fibrillated cellulose suspensions

Abstract

High-consistency processing of fibrillated cellulose materials is attractive for commercial applications due to potential for lowered production costs, energy savings and easier logistics. The current work investigated structure–property relationships of fibrillated cellulose suspensions produced at 20% consistency using VTT HefCel (High-consistency enzymatic fibrillation of cellulose) technology. Morphological examination of the fibrillated materials revealed that enzymatic action on the cellulose substrates was not a direct function of enzyme dosage but rather was dependent on the raw material composition. Furthermore, shear viscosity of the HefCel suspensions was found to decrease with increasing enzyme dosage while the water retention increased. The shear viscosity followed power law relationship with the power law index varying in the range 0.11–0.73. The shear-thinning behavior decreased with increasing consistency. Moreover, suspension viscosity ($$\upmu$$ μ ) was found to be highly dependent on the consistency ($$\mathrm{c})$$ c ) as $$\upmu \sim {\mathrm{c}}^{\mathrm{m}}$$ μ ∼ c m , with $$\mathrm{m}$$ m ranging from 2.75 to 4.31 for different samples. Yield stress (τy) of the HefCel suspensions was measured at 7 and 10% consistencies. The performance of the fibrillated cellulose grades in a typical application was demonstrated by casting films, which were characterized for their mechanical properties. Graphic abstract

Production of High-Solid-Content Fire-Retardant Phosphorylated Cellulose Microfibrils

“…The films made from unmodified HefCel displayed rather good homogeneity with mechanical properties typical for this type of fibril grade. 22 Specifically, the tensile strength reached 60 MPa and the elongation at break was ∼1.8% (Figure 6c), giving values comparable to those reported in the literature. 18 In contrast, films made from phosphorylated HefCels exhibited rather poor mechanical performance.…”

“…Prior to the treatment, the carboxyl groups of pulp fibers were converted to their sodium form according to a standard process described elsewhere . Next, the pulp was fibrillated according to the HefCel technology developed at VTT. , Briefly, the pulp suspension at 25% consistency was first sprayed evenly with an enzyme cocktail comprising commercial cellulases in 0.1 M sodium acetate buffer and then transferred to a reactor equipped with a two-shaft sigma-type mixer (Jaygo Incorporated, Randolph, NJ, USA) and a temperature controller. The enzymatic treatment was carried out at 70 °C and pH 5 with a mixing speed of 30 rpm.…”

Bicomponent Cellulose Fibrils and Minerals Afford Wicking Channels Stencil-Printed on Paper for Rapid and Reliable Fluidic Platforms

“…HefCel is composed of relatively large fibrils and fibril size distribution and has low water content and a paste-like consistency. 29 Meanwhile, CNF has a high water-holding capacity and forms gel structures. We combined the two fibrillated celluloses to produce effective binding and achieve appropriate fluid flow properties combined with controlled water retention properties, which are not achievable in a paste when only a single cellulose component is used.…”

“…This effect is explained by the larger fibril size distribution and variation in fibril network entanglement. 29 The addition of perlite to the Ca–H paste at high solid content produced a solid-like behavior that prevented measurements. A greater shear-thinning behavior was noted for pastes that combined CNF and HefCel.…”

Production of Nanocellulose by Enzymatic Treatment for Application in Polymer Composites

“…It is also worth noting that the enzymatic process eliminates the use of harmful reagents, which are used, e.g., in chemical methods, in favor of the use of biodegradable cellulases, which are neutral and, consequently, have no emissions of harmful chemicals that affect ecology and laboratory equipment [ 20 , 30 ]. Cellulose, due to the presence of a large amount of hydrogen bonds in it, is a material whose enzymatic modification requires a synergistic correlation of cellulolytic enzymes [ 31 , 32 , 33 , 34 , 35 ]. Scientists in their works have proved that the effectiveness of this complicated process is influenced not only by the conditions of the hydrolysis reaction, such as temperature, pH of the reaction environment [ 36 ] or the type, activity level and concentration of the selected substrate [ 37 , 38 ], but also the type or degree of polymerization of the cellulose used, its crystallinity and porosity [ 39 , 40 ].…”