1. Structural essence and material properties of nanocellulose

Nanocellulose ( Nanocellulose ) is a nanoscale fiber structure material obtained by physical defibration or chemical selective modification using natural cellulose as raw material. Its basic unit is a cellulose chain connected by β-1,4- glucosidic bonds, which forms a highly ordered crystal structure under the action of intermolecular hydrogen bonds.

1.1 Molecular structure and crystal characteristics

Natural cellulose mainly exists in the form of cellulose type I crystals, with crystalline regions and amorphous regions alternately distributed. The formation of nanocellulose is essentially a hierarchical deconstruction of cellulose microfibril bundles, making them close to the scale of a single microfibril ( elementary fibril ).

Typical structural parameters:

parameter	Numerical range
diameter	5–50 nm
length	500 nm – several microns
aspect ratio	50–200+
Crystallization degree	60–90%
elastic modulus	100–150 GPa

The high crystallinity gives it excellent rigidity and strength, while the high aspect ratio determines its network-building ability in the system.

2. Interfacial behavior and rheological mechanism of nanocellulose

2.1 Hydrogen bond network and three-dimensional structure formation mechanism

In an aqueous system, multiple hydrogen bonds and electrostatic repulsion balance are formed between a large number of hydroxyl groups ( –OH ) and carboxyl groups ( –COO⁻ ) on the surface of nanocellulose, causing self-assembly to form a three-dimensional network structure.

This network structure has the following characteristics:

High viscosity at low shear

Shear Thinning​

Thixotropy​​

Good anti-settling ability

From a rheological perspective, nanocellulose systems usually behave as pseudoplastic fluids, their storage modulus ( G' ) is higher than their loss modulus ( G'' ), and they exhibit obvious elastic-dominated behavior.

2.2 Suspension stability mechanism

The suspension stability of nanocellulose comes from two mechanisms:

Spatial network hinders particle settling (physical barrier effect)

Surface charge creates electrostatic repulsion

Compared with traditional thickeners, its advantages are:

Does not rely on polymer swelling

Not prone to failure due to temperature changes

Does not produce obvious sticky feeling

3. Technical control points of nanocellulose preparation process

The performance of nanocellulose is highly dependent on the preparation process and pre-treatment methods.

3.1 Mechanical defibration technology

The high-pressure homogenization method dissociates fiber bundles through high shear and cavitation.

Key control parameters:

Homogenization pressure ( 600–1500 bar )

Number of cycles

Raw material pretreatment degree

Solid content control (usually 1–3% )

Excessive homogenization will cause fiber breakage and reduce the aspect ratio, thus affecting the reinforcement effect.

3.2 TEMPO selective oxidation method

The TEMPO oxidation method selectively oxidizes the C6 hydroxyl group to generate carboxyl groups, thereby improving the electrostatic repulsion between fibers.

Control points:

Maintain pH at 10–11

Degree of oxidation ( mmol COOH/g )

Subsequent washing and purification

The carboxyl content is usually controlled between 0.5–1.5 mmol/g , which can significantly improve dispersion stability.

Advantages:

High nanotechnology efficiency

More uniform particle size distribution

Transparent dispersion systems available

3.3 Preparation of CNC by acid hydrolysis

The amorphous region is removed by sulfuric acid hydrolysis and the crystalline region structure is retained.

Features:

Shorter particle size ( 100–300 nm )

High crystallinity

With sulfate group, charge stability

4. Reinforcement mechanism of nanocellulose in functional materials

4.1 Principle of mechanical enhancement

Nanocellulose reinforcement is based on:

High modulus filling effect

stress transfer network

Enhanced interfacial hydrogen bonding

The formation of in the polymer matrix ' nano-skeleton ' can significantly improve:

tensile strength

Flexural modulus

Impact toughness

The enhancement effect is closely related to dispersion uniformity and interface compatibility.

4.2 Functional positioning in water-based systems

In pesticide suspension agents, water-based coatings, graphene dispersion systems, and daily chemical products, nanocellulose is mainly responsible for:

structure builder

Anti-settling stabilizer

thixotropy regulator

Micro reinforced skeleton

Its advantage lies in its dual functions of structural support and rheology regulation.

5. Industrialization challenges and technology development direction of nanocellulose

Although nanocellulose has excellent properties, industrialization still faces:

High energy consumption problem

Difficulty in increasing solid content

cost control issues

Difficulty in drying and dispersing

Future technology development priorities include:

Low energy consumption continuous production

Development of high solid content stable dispersion system

Precise functionalization of surfaces

Construction of multi-material composite collaborative system

With the promotion of green materials policies and the increasing demand for high-performance materials, nanocellulose is gradually moving from the laboratory to the large-scale application stage.

6. Summary

Nanocellulose is a natural nanomaterial with high strength, high specific surface area and sustainable properties. Its core advantage is that it can achieve multi-scenario application adaptation through structural control and surface modification.

In the fields of composite reinforcement materials, suspension system construction, new energy materials and medical materials, nanocellulose is showing broad development prospects. With the optimization of preparation technology and the reduction of costs, its industrialization process will be further accelerated.