Cellulose Nanofibrils from Nonderivatizing Urea-Based Deep Eutectic Solvent Pretreatments

Abstract

Deep eutectic solvents (DESs) are a fairly new class of green solvents applied in various fields. This study investigates urea-based DES systems as novel pretreatments for cellulose nanofibril production. In the experiments, deep eutectic systems having urea and ammonium thiocyanate or guanidine hydrochloride as a second component were formed at 100 °C and then applied to disintegrate wood-derived cellulose fibers. The DES-pretreated fibers were nanofibrillated into three different levels of mechanical treatments with a microfluidizer, and their properties were analyzed. Moreover, nanofibril films were fabricated by solvent casting method. Both DES systems were able to loosen and swell the cellulose fiber structure as indicated by the increase in the lateral dimension of the fibers. Nonpretreated birch cellulose fibers had difficulties in mechanical nanofibrillation as clogging of the chamber occurred often. However, cellulose nanofibrils with widths ranging from 13.0 to 19.3 nm were successfully fabricated from DES-pretreated fibers with both systems. Translucent nanofibril films generated from DES-pretreated cellulose nanofibrils had good thermal stability and mechanical properties, with tensile strengths of approximately 135-189 MPa and elastic modulus of 6.4-7.7 GPa. Consequently, both urea-based DESs showed a high potential as environmentally friendly solvents in the manufacture of cellulose nanofibrils.

Anionic wood nanofibers produced from unbleached mechanical pulp by highly efficient chemical modification

“…5 The tensile strengths of the AWNFs were in the same range as, though slightly lower than, those of CNF films obtained from non-chemically modified, DES-treated bleached fibers. 12 The tensile strengths of nanopapers with lignin contents of ∼14% have previously been reported as 116 ± 7, which is similar to the properties of AWNF1. 39 The AWNF films had tensile strengths comparable to those of previously studied 2,2,6,6-Tetramethylpiperidin-1-yloxyl (TEMPO)-oxidized CNF films produced from bleached fibers.…”

“…DESs have been used in nanoparticle fabrication [9][10][11] and recently in nanocellulose fabrication. [12][13][14][15] In this study, a DES based on imidazole and triethylmethylammonium chloride (TEMACl) was used as a reaction medium for the chemical modification of nonbleached mechanical pulp (groundwood pulp, GWP). Succinic anhydride was chosen as a reagent, as it allows the production of carboxylated wood material through the formation of a halfester of succinic acid.…”

Recent Strategies in Preparation of Cellulose Nanocrystals and Cellulose Nanofibrils Derived from Raw Cellulose Materials

“…Sirviö and workers proposed a bio-based DES consisting of urea and choline chloride (molar ratio of 2 : 1) which could be used to the pretreatment of cellulose pulp [233]. Li and coworkers used the urea-based DES as the pretreatment for the preparation of CNFs [234]. In this work, DES was composed of urea and ammonium thiocyanate or guanidine hydrochloride and was used to treat wood-derived cellulose fibers.…”

Mechanical fabrication of high-strength and redispersible wood nanofibers from unbleached groundwood pulp

“…The cross-sections from the nanopapers showed structural differences between the specimens. REF 150 showed a layered structure that is typical for nanopaper (Li et al 2017), while WNF 150 had layers with grooves and a less-aligned horizontal positioning (high-magnification images of the cross-sections can be seen in Fig. S4).…”