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

Abstract

In the past, the direct production of lignincontaining nanofibers from wood materials has been very limited, and nanoscale fibers (nanocelluloses) have been mainly isolated from chemically delignified, bleached cellulose pulp. In this study, we have introduced a newly adapted, heat-intensified disc nanogrinding process for the enhanced nanofibrillation of wood nanofibers (WNF) with a high lignin content (27.4 wt%). The WNF produced this way have many unique and intriguing properties in their naturally occurring form, for example, being able to be dispersed in ethanol and having ethanol solution viscosities higher than water solution viscosities. When WNF nanopapers were formed with ethanol, the properties of the nanofibers were recoverable without a notable decrease in the viscosity or mechanical strength after redispersing them in water. The preservation of lignin in the WNF was noticed as an increase in the water contact angles (89°), the rapid removal of water in the fabrication of the nanopapers, and the enhanced strength of the nanopapers when subjected to high pressure and heat. The nanopapers fabricated from the WNF were mechanically stable, having an elastic modulus of 6.2 GPa, a maximum stress of 103.4 MPa, and a maximum strain of 3.5%. Throughout the study, characteristics of the WNF were compared to those of the delignified and bleached reference cellulose nanofibers. We envision that the exciting characteristics of the WNF and their lower cost of production compared to that of bleached cellulose nanofibers may offer new opportunities for nanocellulose and biocomposite research.

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.…”

“…4 Recently, heat-intensified disc nanogrinding of mechanical pulp was introduced to produce wood nanofibers (WNFs). 5 In addition, acid hydrolysis of lignin-containing pulp has been shown to be an efficient way to produce both CNCs and CNFs. 6 However, information is still scarce about the production of chemically functionalized WNFs to obtain nanosized lignocellulose materials with an adjustable surface charge.…”

High-strength cellulose nanofibers producedviaswelling pretreatment based on a choline chloride–imidazole deep eutectic solvent

“…The lateral dimensions of CNFs produced with CCIMI are in line with previous studies with CNFs produced using nonderivatizing DES treatment 21,23 and pure mechanical disintegration. 49 Thermal properties of CNFs TG analysis showed CNFs produced using CCIMI and CCUrea exhibited a slightly lower onset temperature compared to the original cellulose pulp (288°C of original pulp vs. 273°C-278°C of CNFs), indicating marginally lower thermal stability (Fig. S4 †).…”

Research on the Strengthening Advantages on Using Cellulose Nanofibers as Polyvinyl Alcohol Reinforcement

“…Nanocellulose (NC) presents high specific surface, aspect ratio, transparency, low density (similar to native cellulose), high intrinsic mechanical properties, and a reactive surface due to the presence of hydroxyl groups [11][12][13][14]. As in the case of common cellulosic fibers, they can be obtained either from softwood, hardwood, plants, or even agriculture residues, and by means of different treatments [15][16][17][18][19][20]. NC can be even obtained from bacteria, such is the case of bacterial cellulose (BC).…”