In-depth comparison between nanocellulose whiskers and nanocellulose crystals: structure, performance and application analysis

Nanocellulose whiskers (NFC) and nanocellulose crystals (CNC) are two important nanocellulose forms, and they have significant differences in structure, performance, manufacturing methods and applications. In order to further understand their differences, we can discuss them in more detail from the following aspects:

1. Structure and form

Nanocellulose Whisker (NFC) :

Morphological characteristics : NFC usually exhibits a strip-like or fibrous structure with a large surface area. Its form is composed of cellulose microfibers that may vary in length and width.

Irregularity : The structure of NFC does not have strict crystallinity and contains a large number of amorphous regions, which do not have regular atomic arrangements. These amorphous regions of NFC are its advantages in dispersion and flexibility, although this makes its mechanical properties relatively low.

Cellulose molecular chain : The molecular chain of NFC is linear and can easily form hydrogen bonds with water molecules, which makes it highly hydrophilic.

Nanocellulose crystals (CNC) :

Morphological characteristics : CNC has a more defined morphology and usually appears as needle-shaped, rod-shaped or sheet-shaped crystals. Its size is smaller than that of NFC, but it has obvious order due to the existence of crystalline regions.

Crystality : CNC is mainly composed of crystalline parts of cellulose. These crystalline regions are arranged neatly, and the arrangement between atoms and molecules is relatively regular. The high order of CNC determines its advantages in mechanical properties.

Molecular arrangement : The molecular chains of CNCs are usually highly crystalline, and the structure of this crystalline region is relatively stable, which helps to improve the mechanical strength and thermal stability of the material.

2. Differences in crystallinity

Nanocellulose Whisker (NFC) :

NFC has a low crystallinity, usually between 30% and 60%**. The crystalline part and the amorphous part are alternately distributed, resulting in the overall structure not being tight enough and having high surface energy. This allows NFC to better combine with other substances in many applications, especially in the production of composite materials, with better adaptability.

Low crystallinity means that NFC has poor mechanical properties and its tensile strength, stiffness and compressive strength are lower. Its structure is more flexible, can be made into films, fibers or other forms, and has good hygroscopicity and scalability.

Nanocellulose crystals (CNC) :

CNC has very high crystallinity, usually between 60% and 90%**. High crystallinity imparts CNC excellent mechanical properties, especially in terms of rigidity and strength, far exceeding NFC.

Because the crystallization region of CNC is more compact and orderly, its tensile strength, compressive strength and heat resistance are better. The high order of the crystalline region gives it a lower surface energy, which may lead to poor dispersion.

3. Differences in mechanical properties

Nanocellulose crystals (NFC) :

NFC has good flexibility and expansion. Due to the existence of its amorphous region, NFC can be bending or deformed well when subjected to external forces, showing good plasticity.

NFC has relatively poor mechanical properties, especially in terms of compressive and tensile strength, which limits its application. NFC has a high dispersion and low density properties that make it very valuable in certain specific applications, such as flexible films, thermal insulation materials, etc.

Nanocellulose crystals (CNC) :

CNC has excellent mechanical properties due to its high crystallinity. Its rigidity, tensile strength and compressive strength are much higher than that of NFC. The rigidity of CNC mainly comes from the structure of its crystalline part, and the high order of atoms or molecules arranges it with extremely high mechanical stability.

The high rigidity of CNC makes it very popular among high-strength composite materials, especially in areas where it needs to withstand high stresses, such as high-strength films, composite materials, etc.

4. Surface characteristics and hydrophilicity

Nanocellulose Whisker (NFC) :

NFC is highly hydrophilic, which allows it to be dispersed better in aqueous solutions. Because its surface is rich in oxidation groups (such as hydroxyl groups, aldehyde groups, etc.), hydrogen bonds can form between NFC and water or other polar molecules, thereby enhancing its dispersion.

The surface energy of NFC is higher, which allows it to better interact with other substances (such as polymers, metals, etc.) in the composite material to form a more stable composite structure.

Nanocellulose crystals (CNC) :

The CNC surface is also hydrophilic, but due to its high crystalline nature, the surface energy is relatively low. This makes the dispersibility of CNCs worse than that of NFCs, especially without surface modification.

The fewer active groups on the surface of the CNC limit their interaction with other substances, so in some applications, CNC may need to be chemically modified to improve its compatibility with polymers, other nanomaterials or fillers.

5. Manufacturing process

Nanocellulose Whisker (NFC) :

The preparation of NFC is relatively simple, and common methods include mechanical abrasive 、acid hydrolysis 、, etc. Through these methods, the crystalline part and the amorphous part in the natural cellulose can be separated to obtain nano-scale cellulose with a large surface area.

The manufacturing process of NFC is relatively mild and does not require too much chemical treatment, so the production cost is relatively low.

Nanocellulose crystals (CNC) :

The preparation of CNCs usually requires strong acid hydrolysis, such as sulfuric acid hydrolysis , which can effectively remove amorphous areas in cellulose and retain only the crystalline part. Due to the intense treatment of cellulose by the acid hydrolysis process, the production process of CNC is more complicated and expensive.

Due to the need for strict control of hydrolysis conditions, the production process of CNC is usually more refined and has a higher cost.

6. Application areas

Nanocellulose Whisker (NFC) :

NFC is widely used in areas where high surfactivity and good dispersion are required, such as reinforced plastics, coatings, paper, food additives, drug delivery systems, etc.

Due to the high dispersion of NFC, it can be used to prepare hydrocolloids, films, cellulose composites, etc.

Nanocellulose crystals (CNC) :

CNC is mainly used in fields that require high mechanical properties and high strength, such as composite materials, high-strength films, liquid crystal displays, electronic devices, etc.

Its high rigidity gives it great potential in the preparation of high-performance composite materials, transparent films, nanomaterial reinforcement, etc.

Summarize:

Nanocellulose whiskers (NFC) : characterized by lower crystallinity and high dispersion, have good flexibility and scalability, and are suitable for applications that require high flexibility and dispersion.

Nanocellulose crystals (CNC) : characterized by higher crystallinity and stronger rigidity, have better mechanical properties, and are suitable for applications that require high strength and high stability.

Through in-depth comparison, we can see the significant differences in the two in terms of structure, performance, application, etc., which makes them play an important role in different fields.