Elucidating the Opportunities and Challenges for Nanocellulose Spinning

Abstract

In comparison to natural fibers, such as silk-, cotton-, or wool-fibers, man-made fibers refer to fibers fabricated from either synthetic or natural polymers. Man-made fibers from synthetic polymers (the largest volume of man-made fibers) are mainly produced from fossil-based resources, such as oil or gas. Examples of commonly used polymers are polyamides, polyesters, polyethylene, or polyurethanes. As a result of a century of developments within the area of polymer science and processing, it is currently possible to control the hierarchical structure of synthetic fibers, from the atomistic level up to the fiber level. Thus, one can address the properties and functionalities of the final fibers by developments on all hierarchical levels. Similar to synthetic fibers, natural fibers are synthesized from the atomic level up to the fiber level. The processes are designed by evolution, generally in the presence of water, to provide sufficient mechanical strength and toughness. Natural fibers are also biodegradable. When fabricating man-made fibers from natural polymers, the starting point is to use polymers extracted from biological sources, such as cellulose from wood pulp. Hence it is only possible to control the structure can thus only be controlled from the polymer scale and up. Cellulose represents the starting polymer for the first fabricated man-made fibers, i.e., Rayon, [1] also called regenerated cellulose fibers. In the preparation of regenerated cellulose fibers, highly purified cellulose is subjected to a dissolving process to extract individualized cellulose polymer chains. The biosynthesis in the plant cell wall forms nanofibrils from parallel polymer chains crystallized in a lattice referred to as Cellulose I, [2] and the dissolving process breaks the intermolecular bonds to individualize the chains to form a polymer solution. The cellulose polymer solution is spun using a spinneret and precipitated into continuous filaments to form the final regenerated cellulose fiber. The result of the precipitation process and drying is a different crystalline lattice called Cellulose II, which is more thermodynamically stable than Cellulose I. Regarding the mechanical performance as a building block, Cellulose I is significantly stiffer compared to Cellulose II. [3] The production of regenerated cellulose fibers depends on biological processes for producing the cellulose polymer since there are no industrial processes capable of producing synthetic cellulose polymer chains. Man-made continuous fibers play an essential role in society today. With the increase in global sustainability challenges, there is a broad spectrum of societal needs where the development of advanced biobased fibers could provide means to address the challenges. Biobased regenerated fibers, produced from dissolved cellulose are widely used today for clothes, upholstery, and linens. With new developments in the area of advanced biobased fibers, it would be possible to compete with high-performance synthetic fibers such as glass fibers and carbon...

Shear-free mixing to achieve accurate temporospatial nanoscale kinetics through scanning-SAXS: ion-induced phase transition of dispersed cellulose nanocrystals

“…An example, where flow-focusing with a detached core is achievable is the hydrodynamic focusing and spinning of filaments from nanocellulose. 31,[37][38][39] As an example, by applying the double flow-focusing technique, Mittal et al 37 demonstrated how the first focusing with the buffer caused an alignment of cellulose nanofibers (CNFs), and a second focusing with a gelation agent could make the CNFs aggregate in an aligned state. Drying this gel thread resulted in filaments exceeding mechanical properties of any known natural material.…”

Humidity‐Induced Nanoscale Restructuring in PEDOT:PSS and Cellulose Nanofibrils Reinforced Biobased Organic Electronics

“…In this context, cellulose nanofibrils (CNFs) are gaining more attention as a substitute for glass or carbon fibers due to their particular mechanical properties in combination with sustainable resources and biodegradability. [8] In detail, nanocellulose extracted from wood was shown to be a good reinforcing agent in polymer nanocomposites, while retaining flexibility, lightweight, and mechanical stiffness. [9,10] Chemical functionalization of nanocellulose can be used to further tailor barrier performance of films which might be of crucial benefit for considering nanocellulose as a template for organic electronics.…”

Understanding ion-induced assembly of cellulose nanofibrillar gels through shear-free mixing andin situscanning-SAXS

“…2D films in photonic applications 16 . The main advantage of CNFs, are their inherent ability to form volume-spanning networks at very low concentrations [17][18][19][20][21][22] , making them highly desirable as building blocks in membranes, barriers, aerogels, foams 1,2,4 , 3D-printed materials 23 and also for making filaments that can be used for reinforcing new biobased composites and high-performance textiles 22,[24][25][26][27][28][29][30][31][32] The properties of materials produced from the bottom-up reassembly of CNCs and CNFs are highly dependent on their spatial and orientation distributions within the material, which in turn are set by the processing conditions 14,29 . A common route for controlling the nanostructure of the final product includes hydrodynamic alignment with subsequent assembly (transition from dispersion to gel, i.e.…”

“…A common route for controlling the nanostructure of the final product includes hydrodynamic alignment with subsequent assembly (transition from dispersion to gel, i.e. gelation) by neutralizing the electrostatic repulsion between nanoparticles through the addition of salts or acids 25,28,29 . It has been found during spinning filaments from CNFs, that a system, which is aligned through a pure extensional flow with no shear, is highly desirable to obtain optimal mechanical properties 28,29 .…”

“…gelation) by neutralizing the electrostatic repulsion between nanoparticles through the addition of salts or acids 25,28,29 . It has been found during spinning filaments from CNFs, that a system, which is aligned through a pure extensional flow with no shear, is highly desirable to obtain optimal mechanical properties 28,29 . Nanoscale structures and assembly of CNFs and CNCs are commonly studied through small-angle Xray scattering (SAXS) of pre-mixed samples of CNFs 6,9,33,34 or CNCs [35][36][37] .…”