Explore the preparation steps of hydrophobic modified nanocellulose

Hydrophobic modified nanocellulose (HNC) is a material with good dispersion, enhanced mechanical properties and hydrophobic properties obtained by nano- and hydrophobic treatment of natural cellulose. It is mainly used in composite materials, coatings, oil-water separation, drug delivery and other fields. Here are the detailed preparation steps:

1. Pretreatment of cellulose raw materials

In order to make natural cellulosic materials suitable for nanoification and further chemical modification, pretreatment is first required:

Clean and remove impurities : Clean cellulose raw materials (such as wood pulp, cotton, rice husks, etc.) with water to remove impurities such as resin, sugar, protein, etc. This can be accomplished by acid-base washing, enzymatic lysis, or hot water treatment.

Chemical treatment : In order to improve the reactivity of cellulose, acid-base treatment is usually performed. Acid treatment (such as sulfuric acid) can destroy hemicellulose and lignin in cellulose, improving cellulose solubility. Alkaline treatment (such as sodium hydroxide) can remove lignin and make cellulose more pure.

Oxidation treatment : Sometimes oxidants (such as hydrogen peroxide) are used to treat cellulose to further decompose impurities and improve their reactivity.

2. Preparation of nanocellulose

The treated cellulosic material can be further decomposed into nano-scale fibers by the following methods:

High-pressure homogenization method : Through high-pressure homogenization equipment, the treated cellulose solution (usually in water) is homogenized under high pressure to decompose the cellulose into nano-sized fibers. This method is easy to operate and is suitable for large-scale production.

Ultrasonic method : Use ultrasonic vibration to break and disperse cellulose molecules into nano-scale fibers. Ultrasonic method can process cellulose more gently, but it is difficult to achieve large-scale production.

Mechanical refining method : The treated cellulose is degraded into nanofibers by means of friction by means of mechanical refining equipment. It is suitable for production with higher yields, but it takes a long time and higher energy consumption.

These methods can convert cellulose into nanocellulose with a large specific surface area and high surface energy, increasing its chemical reactivity and functionalization possibility.

3. Hydrophobic modification reaction

The is nanocellulose surface introduced into hydrophobic groups to enhance its hydrophobicity in an aqueous environment. Commonly used hydrophobization methods include:

Silenization reaction : The hydrophobic silane groups are formed by introducing silane compounds (such as triethoxysilane TEOS) and reacting with nanocellulose. The silanization reaction is usually carried out under anhydrous conditions, and the reaction will form a hydrophobic surface through chemical bonding with the hydroxyl group (-OH) on the surface of the cellulose.

Fatty acid modification : Fatty acid (such as stearic acid, lauric acid) and nanocellulose are esterified. The long carbon chain groups of fatty acids can provide significant hydrophobicity. The reaction is usually carried out under solvents (such as dichloromethane) or under anhydrous conditions.

Aminosilanization modification : amino groups are introduced into the cellulose surface by reacting amino silanes (such as γ-aminopropyltriethoxysilane) with nanocellulose. When these amino groups are bound to hydrophobic molecules, hydrophobic groups can be introduced through further reactions.

These modification methods can effectively introduce hydrophobic molecules or groups into the nanocellulose surface, improve their dispersion in water, and make them have better performance in oil-water separation, coatings and other applications.

4. Post-treatment: Washing and drying

Washing : After the modification reaction is completed, the product needs to remove unreacted reagents and by-products through repeated washing of water, ethanol washing, etc. to ensure the purity and stability of the product. During washing, deionized water and ethanol are usually used to remove excess reactants and solvents.

Drying : The washed samples need to be dried. Commonly used drying methods include:

Freeze-drying : Freeze-drying can maintain the structural and functional characteristics of nanocellulose to the greatest extent, and is suitable for applications with high precision requirements.

Vacuum drying : Remove moisture by vacuum suction at low temperatures to prevent nanocellulose from aggregating during drying.

5. Characterization and performance testing

Modified hydrophobic nanocellulose needs to be confirmed through a series of characterizations:

Surface morphology : Use scanning electron microscope (SEM) to observe the surface morphology and size of modified nanocellulose to confirm whether it maintains the nanostructure.

Functional group detection : Through Fourier transform infrared spectroscopy (FTIR) analysis, hydrophobic groups (such as silane groups, fatty acid groups, etc.) introduced on the surface are verified.

Contact angle measurement : measure the contact angle of the nanocellulose surface and judge its hydrophobicity. A larger contact angle indicates stronger hydrophobicity.

Water dispersion : By testing the dispersion and stability of modified nanocellulose in water, it evaluates its application effect in aqueous media.

Through these steps, the hydrophobic modified nanocellulose produced has strong hydrophobic properties and is suitable for use in many special applications, such as water-oil separation, coatings, reinforced composite materials and other fields. Nanjing Tianlu Nano Technology Co., Ltd. is specialized in the production of nanocellulose , cellulose nanofiber filaments, vitamin nanocrystals, bacterial cellulose, cellulose nanofiber filaments (CNF), cellulose nanocrystals (CNC), bacterial cellulose ( BC) manufacturer.