Is it recommended to use a post-curing agent to improve the water resistance of nanocellulose food packaging film?

Post-curing agent is an effective method to improve the water resistance of nanocellulose food packaging film coating. The post-curing agent can with chemically react Here are some common strategies and suggestions:nanocellulose or other components in the coating to form a crosslinked structure, thereby enhancing the water resistance and stability of the membrane.

1. Effect of curing agent after use :

• Formation of cross-linking network : The post-curing agent can form chemical cross-links between nanocellulose molecules, build a more stable three-dimensional network structure, and reduce the invasion of moisture into the membrane.

• Improve the stability of the coating : The crosslinked structure can enhance the swelling and moisture resistance of the coating, preventing the nanocellulose from dispersing or dissolving after contacting water.

• Improved mechanical properties : Post-curing not only improves water resistance, but also increases the hardness and wear resistance of the coating.

2. Commonly used post-curing agent types :

• Multifunctional crosslinking agents : such as epoxy compounds, isocyanates or multifunctional crosslinking agents containing hydroxyl groups and amino groups. These compounds can react with hydroxyl groups on nanocellulose to form stable chemical bonds.

• Water-based polyurethane or polyamide curing agent : This type of curing agent can form hydrogen bonds or covalent bonds with nanocellulose, thereby improving water resistance.

• Metal ion crosslinking agents : such as calcium ions or aluminum ions, form coordination bonds or ion bonds with the hydroxyl groups on nanocellulose through metal ions, enhancing the water resistance of the membrane.

3. Other strategies to improve water resistance :

• Surface hydrophobic modification : Introducing hydrophobic groups (such as long-chain alkyl or fluoride) on the surface of nanocellulose can reduce the permeation of moisture on the surface.

• Composite coating technology : Add a layer of hydrophobic or waterproof coating (such as polyvinyl alcohol or polyurethane coating) to the nanocellulose coating to form a multi-layer structure to further improve water resistance.

• Heat treatment : Moderate heat treatment on the coated film can make the nanocellulose react more fully with the post-curing agent, thereby increasing the degree of crosslinking.

4. Things to note when using the curing agent :

• Choose food-grade safe curing agents : Ensure that the curing agent and the crosslinked products produced are harmless to the human body and meet safety standards for food contact materials.

• Control the amount and conditions of curing agent : The amount of curing agent and curing reaction conditions (such as temperature, time) need to be reasonably controlled to avoid affecting other properties of the film (such as transparency or flexibility).

To sum up, post-curing agents are an effective method to improve the water resistance of nanocellulose coating, but attention should be paid to food safety and optimization of process parameters.