Review on Nonconventional Fibrillation Methods of Producing Cellulose Nanofibrils and Their Applications

Abstract

The production of cellulose nanofibrils (CNFs) continues to receive considerable attention because of their desirable material characteristics for a variety of consumer applications. There are, however, challenges that remain in transitioning CNFs from research to widespread adoption in the industrial sectors, including production cost and material performance. This Review covers CNFs produced from nonconventional fibrillation methods as a potential alternative solution. Pretreating biomass by biological, chemical, mechanical, or physical means can render plant feedstocks more facile for processing and thus lower energy requirements to produce CNFs. CNFs from nonconventional fibrillation methods have been investigated for various applications, including films, composites, aerogels, and Pickering emulsifiers. Continued research is needed to develop protocols to standardize the characterization (e.g., degree of fibrillation) of the lignocellulosic fibrillation processes and resulting CNF products to make them more attractive to the industry for specific product applications.

Twin-screw extrusion for the production of nanocellulose-PVA gels with a high solid content

“…Cellulose nanofibrils (CNFs) constitute a class of nanocellulose with a wide range of lateral size, from 5 up to 50 nm and lengths up to several µm, essentially depending on the fiber pretreatment and, to a lesser extent, on the fiber origin. They are mainly produced via intensive mechanical shearing action to break down the strong interfibrillar bonding holding the elementary cellulose fibrils within the cell wall of the fibers and release the fibrils individually or in the form of bundles (Wang et al, 2021). Numerous merits have contributed to make CNFs a promising category of nanocellulose with increasing interest both from the academia and industry: the full conversion of cellulose fibers into CNFs after the disintegration process without generation of any by-products, the unnecessity to perform any post-purification treatments after the disintegrating process, the broad versatility in size depending on the extent of the disintegration, and the possibility to generate functionalized CNFs through a chemical pretreatment of the cellulose fibers.…”

Poly(3-hydroxybutyrate) Nanocomposites with Cellulose Nanocrystals

“…Reaction temperature and duration as well as the acid type and its concentration are the main parameters that determine the size and morphology of the isolated CNCs [ 76 ]. Thus, CNCs possess whisker or a short-rod-like morphology with uniform sizes ranging from 100 to 200 nm in length and 10 to 30 nm in diameter [ 77 , 78 ]. The use of weak acids leads to cellulose fibers with low crystallinity and fibrous morphology as a result of the low dissociation constant of these acids [ 76 ].…”

“…Top-down mechanical disintegration methods such as grinding, cryocrushing, high-intensity ultrasonication, and high-pressure homogenization are usually employed for the CNFs’ isolation. Through these techniques, dilute suspensions of cellulose fibers are subjected to high shear and impact forces, thus leading to mechanical cleavage along the longitudinal direction of the cellulosic source [ 78 , 81 , 82 , 83 ]. Specifically, the defibrillation methods yield nanostructures with both crystalline and amorphous regions.…”

Progress, Challenge, and Perspective of Fabricating Cellulose

“…The extraction methods of nano/micro cellulose suspensions could be found in recent reviews. [ 46–48 ] Among various nanocellulose, cellulose nanocrystal (CNC) suspensions [ 49 ] and cellulose nanofibers (CNF) suspensions [ 50 ] are two important types. The CNC suspension features high crystallinity and could form a helical structure via evaporation induced self‐assembly.…”