Introduction to cellulose nanocrystals

Cellulose nanocrystals (CNCs) , also known as cellulose nanowhiskers, are nano-scale materials extracted from natural cellulose. They have high crystallinity and excellent mechanical properties. The following is a detailed introduction to cellulose nanocrystals:

• Preparation method

1. Acid hydrolysis: The most common method is to hydrolyze natural cellulose (such as wood pulp, cotton or bamboo fiber) using strong acids (such as sulfuric acid, hydrochloric acid or phosphoric acid). Acid hydrolysis selectively removes the amorphous region of cellulose, leaving crystalline regions to form nanoscale cellulose crystals.

2. Mechanical treatment: In some cases, mechanical treatment (such as high-speed stirring, ultrasonic treatment) can be combined with chemical methods to further improve the dispersion and nanoification of cellulose .

• Physical characteristics

1. Size: The diameter of CNCs is usually between 5-70 nanometers and the length is between 100 nanometers and a few micrometers.

2. Crystallinity: Since the amorphous region is removed, CNCs are highly crystalline, which gives them high strength and rigidity.

3. Surface chemistry: The surface of CNCs can introduce various functional groups, such as carboxyl, sulfate or phosphate groups, through chemical modification, thereby imparting different surface properties and reactive activities to them.

• Performance and Advantages

1. Mechanical strength: CNCs have extremely high Young's modulus (about 100-150 GPa ), close to or even exceeding the strength of steel.

2. Lightweight: Due to its nanoscale size and low density, CNCs are an ultralight material suitable for applications with high lightweight requirements.

3. Biocompatibility: CNCs are derived from natural cellulose, have good biocompatibility and biodegradability, and are suitable for use in the field of biomedical medicine.

4. Thermal stability: High crystallinity makes CNCs have good thermal stability within a certain temperature range.

• Application areas

1. Composite material reinforcement: CNCs are often used to enhance polymer-based composite materials, significantly improve their mechanical properties, and are used in aerospace, automobiles and construction fields.

2. Transparent film: Due to its nanoscale size and high transparency, CNCs can be used to prepare transparent reinforced films for use in flexible electronic devices and displays.

3. Medical materials: The biocompatibility of CNCs makes it suitable for the preparation of drug delivery systems, tissue engineering stents and wound dressings.

4. Coatings and inks: CNCs can be used as thickeners and stabilizers in coatings, inks and cosmetics, providing excellent rheology and stability.

• Prospects and Challenges

1. Cost: The cost of mass production of CNCs is relatively high, and further optimization of the preparation process is required to reduce costs.

2. Dispersion: The dispersion of CNCs in polymer matrix is ​​the key to affecting their enhancement effect, and effective dispersion methods and surface modification technologies are required.

3. Standardization: The properties of CNCs (such as size and surface chemistry) have an important impact on their performance, and the formulation of standardized production and testing methods is crucial to their application promotion.

In short, cellulose nanocrystals are nanomaterials with excellent performance and wide application prospects. With the continuous advancement of research and technology, their application scope and market potential will continue to expand.