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Views: 0 Author: Site Editor Publish Time: 2025-04-23 Origin: Site
Cellulose Nanocrystals CNC ，is a nano-scale crystalline substance extracted from natural cellulose. It has significant physical and chemical characteristics. These characteristics make CNC have a wide range of application prospects in various fields, including high-performance materials, environmentally friendly products, medical electronic devices, etc. Due to its excellent mechanical properties, high specific surface area biodegradability and renewability, CNC is considered a green and sustainable nanomaterial. This article will discuss in detail the analysis of the structural characteristics of CNC and the application fields.
Nanocellulose crystals are crystalline parts obtained by natural cellulose through acid hydrolysis and other methods. The cellulose itself is composed of glucose molecules connected through β-1,4 glycosidic bonds to form a linear chain structure. The molecular chains are formed by hydrogen bonding. CNCs have the following significant structural characteristics:
High crystallinity : The crystallinity of CNC is usually as high as 60%-80%. This characteristic makes CNC harder and tougher than non-crystalline cellulose parts, with high mechanical strength and rigidity.
Nanoscale : CNCs are usually long needle-shaped or rod-shaped, generally from nanometers 100to 500nanometers in length, and diameters 5between 20nanometers. Due to their nanoscale size, CNCs have extremely high specific surface area, which can provide rich reaction sites for different applications.
Surface functionality : The CNC surface has a large number of hydroxyl ( -OH ) groups, which makes it highly hydrophilic and good surface reactivity. Through chemical modification, different functional groups can be introduced on the CNC surface, thus giving it specific properties and functions.
The preparation of nanocellulose crystals usually involves acid hydrolysis or other physical and chemical methods. The most common preparation method is acid hydrolysis. The amorphous part of the cellulose is selectively hydrolyzed by acidic solution and retaining the crystalline part. The specific preparation process is as follows:
Acid hydrolysis method : Acid hydrolysis is the most commonly used method for preparing CNC . Commonly used acids include hydrochloric acid and hydrofluoric acid. During the hydrolysis of acid, the amorphous areas in the cellulose molecule will be hydrolyzed by acid, while the crystallization area remains intact due to its highly ordered structure, so as to obtain a crystallized part with a nanoscale. By adjusting the reaction time and temperature of the acid concentration, the morphological size and crystallinity of the final CNC can be controlled.
Sulfuric acid hydrolysis method : The acid concentration commonly used in the sulfuric acid hydrolysis method is 60%-70%. During this process, cellulose will produce a hydrolysis reaction under the action of acid, and some amorphous parts are removed. Finally, the crystalline nanocellulose crystals are hydrolyzed. After the CNC is hydrolyzed, the CNC will appear in a rod-shaped or needle-shaped form, and the particle size is usually 5-20 nanometers.
Hydrofluoric acid hydrolysis method : Hydrofluoric acid hydrolysis method has higher selectivity than sulfuric acid hydrolysis method, which can better retain the crystalline part of the cellulose and obtain higher crystallinity CNC. This method can sometimes obtain purer nanocellulose, which is especially suitable for some high-demand applications.
Enzymatic solution : Compared with acid hydrolysis, enzymatic solution is a gentle preparation method. By using cellulase or other degradation enzymes, the amorphous portion of cellulose can be selectively degraded, and the advantages of obtaining a purer CNC enzymatic solution are mild conditions, low energy consumption, and avoid the use of strong acids, but their efficiency is low and cost is higher.
Mechanical method : Mechanical method directly grinds cellulose raw materials through physical means such as high-pressure homogenizer ball milling or ultrasonic wave to reach nanoscale size. This method is often used in combination with acid hydrolysis or enzymatic method to improve the yield and performance of CNC.
The unique properties of nanocellulose crystals make them widely used in multiple fields. The following are its main properties:
High mechanical strength and elastic modulus : CNC has extremely high tensile strength and elastic modulus, usually between 3-5 GPa , which is much higher than most natural polymer materials. Due to its excellent mechanical properties, CNC has a wide range of application prospects in reinforced composite materials.
Transparency : CNC has good transparency, especially when preparing films, which shows a high light transmittance, which makes CNC have application potential in fields such as transparent electronic material optical films.
Excellent moisture adsorption : The surface of CNC contains a large amount of hydrophilic groups, which can adsorb a large amount of water. Therefore, CNC has a wide range of applications in water-based coating cellulose-based composite materials and other fields.
Biodegradability and environmental friendliness : As a natural polymer, CNC has excellent biodegradability and can naturally degrade in the environment, meeting the needs of sustainable development
Adjustability : The size and morphology of CNCs can be controlled by adjusting the preparation conditions, for example, by controlling the hydrolysis time, acid concentration or mechanical treatment conditions, CNCs of different sizes and morphology can be obtained to meet the needs of different applications.
Due to its excellent performance, nanocellulose crystals are widely used in the following fields:
High-performance composite materials : CNC is often used as a reinforcement material. As a reinforcement for polymer-based composite materials, CNC can significantly improve the mechanical properties of composite materials, especially in the fields of aerospace and automobiles and building materials.
Transparent films and coatings : CNC has good transparency and can be used to make transparent films and coatings. These films are not only superior in optical performance, but also have good mechanical properties and protective effects. Therefore, they have important applications in the fields of display solar cells and photoelectric materials.
Biomedical field : CNC is increasingly used in the field of biomedical. Its good biocompatibility and degradability make it an ideal drug carrier tissue engineering scaffold material and wound dressing CNC can slowly release drugs and have the effect of promoting wound healing.
Water treatment : CNC can act as an adsorbent to remove pollutants in water, especially harmful metal ion dyes and organic substances. In addition, CNC can be used as a filter membrane material and is widely used in the fields of water treatment and environmental purification.
Food and cosmetics : Due to its natural source of low toxicity and degradability, CNC has been applied in the food and cosmetics industry. It can be used as a component such as thickener stabilizer emulsifiers, etc., to enhance the texture and performance of the product.
As the research on nanocellulose crystals continues to deepen, it is expected to play a role in more fields in the future. By further optimizing the preparation process and reducing production costs, CNC will be expected to be widely used in many fields such as high-performance materials, biomedical and environmentally friendly products, and smart materials. In addition, the commercial production of CNC will further promote its application in green and sustainable development, providing strong support for the development of environmentally friendly materials.
In general, nanocellulose crystals, as a renewable green and environmentally friendly material, have excellent performance and wide application prospects, and will play an increasingly important role in many industries and fields in the future.
