A Fast Dissolution Pretreatment to Produce Strong Regenerated Cellulose Nanofibers via Mechanical Disintegration

Abstract

This study investigates a fast dissolution and regeneration pretreatment to produce regenerated cellulose nanofibers (RCNFs) via mechanical disintegration. Two cellulose pulps, namely, birch and dissolving pulps, with degree of polymerizations of 1800 and 3600, respectively, were rapidly dissolved in dimethyl sulfoxide (DMSO) by using tetraethylammonium hydroxide (TEAOH) as aqueous electrolyte at room temperature. When TEAOH (35 wt % in water) was added to the pulp–DMSO dispersion (pulp:DMSO and TEAOH:DMSO weight ratios of 1:90 and 1:9, respectively), 95% of the dissolving pulp and 85% of the birch pulp fibers dissolved almost immediately. Addition of water caused the regeneration of cellulose without any chemical modification and only a minor decrease of DP, whereas the crystallinity structure of cellulose transformed from cellulose I to cellulose II. The regenerated cellulose could then be mechanically disintegrated into nanosized fibers with only a few passes through a microfluidizer, and RCNF showed fibrous structure. The specific tensile strength of the film produced from both RCNFs exceeded 100 kN·m/kg, and overall mechanical properties of RCNF produced from birch pulp were in line with reference CNF produced by using extensive mechanical disintegration. Although the thermal stability of RCNFs was slightly lower compared to their corresponding original cellulose pulp, the onset temperature of degradation of RCNFs was over 270 °C.

Effects of Glucose and Coagulant on the Structure and Properties of Regenerated Cellulose Fibers

“…In general, the crystal structure of cellulose I disappears after dissolution and becomes amorphous. Then in the regeneration process, the cellulose molecular chains are rearranged through hydrophobic interactions to form new crystal planes . It is theorized that different coagulation baths will have a great influence on the crystal shape of RCFs.…”

“…Then in the regeneration process, the cellulose molecular chains are rearranged through hydrophobic interactions to form new crystal planes. 33 It is theorized that different coagulation baths will have a great influence on the crystal shape of RCFs. Besides, the crystallinity of cellulose fiber will significantly affect its breaking strength and elongation at break.…”

Cellulose based Nano-Composites and Applications

“…One of the major drawbacks that have deterred the use of CNFs in many other applications is the need for use of excessive energy during their production. CNFs are produced via mechanical disintegration of cellulose microfibrils to form nanofibers [29,30]. However, this can now be circumvented through the use of pretreatment processes such as mechanical refining, enzymatic hydrolysis and catalytic oxidation to name a few.…”

Pickering Emulsions and Hydrophobized Films of Amphiphilic Cellulose Nanofibers Synthesized in Deep Eutectic Solvent

“…DESs derived from organic compounds have intensively been revealed in the valorization and modification of biomaterials . Particularly, they provide a sustainable and efficient medium to create functionalized cellulose nanomaterials for advanced applications …”

“…3 Particularly, they provide a sustainable and efficient medium to create functionalized cellulose nanomaterials for advanced applications. 4 Previous studies on DES-mediated nanocellulose preparation have focused on non-derivatizing cellulose swelling prior to the mechanical liberation of cellulose nanofibers (CNFs). DESs of choline chloride, urea, or glycerol, and potassium carbonate promoted the swelling of the cell wall of cellulose fibers.…”