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

Abstract

The recent strategies in preparation of cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) were described. CNCs and CNFs are two types of nanocelluloses (NCs), and they possess various superior properties, such as large specific surface area, high tensile strength and stiffness, low density, and low thermal expansion coefficient. Due to various applications in biomedical engineering, food, sensor, packaging, and so on, there are many studies conducted on CNCs and CNFs. In this review, various methods of preparation of CNCs and CNFs are summarized, including mechanical, chemical, and biological methods. The methods of pretreatment of cellulose are described in view of the benefits to fibrillation.

Extending Cellulose-Based Polymers Application in Additive Manufacturing Technology: A Review of Recent Approaches

“…% and temperature of 60–70 °C, where high concentration and temperature will lead to the dissolution of cellulose [ 73 ]. Various methods have been considered in the isolation of CNC as a substitute to the acid hydrolysis method due to the difficult treatment of acid waste [ 74 ]. CNC possesses tremendously good properties such as high tensile strength, low density, optical transparency, and high surface area, which are suitable for many applications, such as biosensors, drug delivery, and water absorption [ 75 ].…”

Interest of Pickering Emulsions for Sustainable Micro/Nanocellulose in Food and Cosmetic Applications

“…High Pressure Homogenization (HPH) is another mechanical method used to produce CNFs and CNCs. In this method, cellulose passes through a small nozzle, with high pressure, causing cellulose cleavage at nanoscale [ 29 ]. Before to use HPH to produce nanocellulose, a pre-treatment, reducing cellulose size is often necessary, as grinding [ 46 ], hydrolysis with sulfuric acid [ 49 ], as well as ultra-sonication [ 56 ].…”

“…Thus, to separate cellulose nanofibers, it has been often necessary to use hard treatments [ 26 ]. The main treatment used was acid hydrolysis, but this method presents several drawbacks, in particular large use of water, equipment corrosion, and most importantly, production of great amount of acid wastes [ 27 , 28 , 29 ]. Thus, even if cellulose is an eco-friendly polymer, production of nanocellulose may not be so eco-friendly.…”

Ball milling: a green technology for the preparation and functionalisation of nanocellulose derivatives

“…Nanobers can be obtained by mechanical shearing actions such as high-pressure homogenization, cryocrushing, microuidization, high intensity ultrasonic treatments and grinding. 8,9 Chemical treatments (e.g. acid hydrolysis, TEMPO-mediated oxidation and enzymatic reactions) can facilitate this process as well as biological pretreatments (e.g.…”

“…The extraction of the crystalline regions contained within the cellulose microbrils allows collecting crystalline rod-like particles called cellulose nanocrystals (CNCs). 8,9 These particles have a well-dened shape and are mainly obtained by acid hydrolysis, which degrades the amorphous regions and disrupts the hydrogen bonds. Compared to CNFs, CNCs are highly crystalline and have a smaller aspect ratio (i.e.…”