Research and development of nanocellulose in the field of functional coatings

1. Introduction

Functional coating is a type of surface covering material that combines decoration and specific functions (such as waterproof, anti-fog, anti-UV rays, barriers, conductivity, etc.), and is widely used in packaging, electronics, medical, textiles and construction industries. With the increasing demand for green and environmentally friendly and high-performance materials, natural, renewable and functional nanocellulose ( Nanocellulose ) sources have gradually become an important substrate or additive for functional coatings.

Nanocellulose provides excellent adhesion, film formation and functionalization potential for coatings with high mechanical strength, high transparency, controllable surface chemical structure and biocompatibility.

2. The mechanism of action of nanocellulose in coating

Skeleton enhancement

High aspect ratio and high crystallinity form a dense mesh structure to improve the wear resistance and stability of the coating.

Improved barrier performance

The tightly arranged nanonetwork significantly extends the permeability path of gas or water vapor and improves barrier performance.

Functional vector

The surface hydroxyl, carboxyl or sulfonic acid groups can be combined with metal nanoparticles, inorganic materials or organic molecules to achieve antibacterial, ultraviolet ray protection, electrical conductivity and other functions.

Transparency and adhesion

The nanoscale reduces light scattering, and the coating maintains high transparency while enhancing adhesion to the substrate.

3. Typical preparation process

1. Water-based nanocellulose coating

Formula : Nanocellulose suspension + functional additives ( TiO₂ 、ZnO 、AgNPs , graphene, etc.)

Construction method : spraying, scraping, dipping

Features : Green and environmentally friendly, no organic solvent required

2. Nanocellulose-polymer composite coating

Formula : Mixed with water-based polyurethane, 、PVA PLA , etc.

Features : It has both polymer toughness and nanocellulose barrier properties

3. Surface chemically modified coating

Modification methods : silanization, esterification, graft polymerization, etc.

Use : Give hydrophobic, antifouling, antibacterial or conductive properties

4. Application direction and performance

The application of nanocellulose in the field of functional coatings covers many aspects such as packaging, optics, medical, electronics and corrosion protection, and its performance has been verified in many experiments.

1. Application cases

Application areas	Functional coating properties	Examples /Case
Food packaging	High barrier ( O₂, H₂O), transparent, degradable	CNC/PVA coated paper instead of aluminum foil
Anti-fog and anti-cream	Super hydrophilic to prevent water droplets from beading	CNC + TiO₂ Photocatalytic anti-fog glass
UV protection	Absorb or scatter UV light	CNC/ZnO Transparent Sunscreen
Antibacterial coating	Inhibit bacteria and fungal growth	CNC/AgNPs Medical coatings
Conductive coating	Transparent conductive film for flexible electronic devices	CNC/graphene/carbon nanotube composite coating
Anti-corrosion coating	Barrier water and oxygen to inhibit metal corrosion	CNC-epoxy resin composite coating

2. Performance test data (typical experimental results)

Coating system	Function Type	Oxygen transmittance OTR (cc/m²·day·atm)	Water vapor transmittance WVTR (g/m²·day)	Visible light transmittance (% @550 nm)	Antibacterial rate ( E. coli)	Pencil hardness	Adhesion (a hundred grid test)
CNC/PVA coated paper	High barrier packaging	0.8	2.1	89	-	HB	100%
CNC/TiO₂ Glass Coating	Anti-fog and UV	-	-	92	-	H	100%
CNC/ZnO Transparent Film	UV protection	1.5	3.4	88	-	HB	100%
CNC/AgNPs Medical coatings	Antibacterial	1.2	2.8	85	>99.9%	HB	100%
CNC/graphene conductive film	Transparent conduction	1.7	3.0	82	-	B	100%
CNC-epoxy resin composite coating	Anti-corrosion	0.5	1.8	80	-	2H	100%

Data interpretation:

The lower the OTR and WVTR values, the better the barrier performance (PET films are usually 50–150 cc/m²·day·atm)

Visible light transmittance ≥80% can be considered highly transparent

Antibacterial rate >99% indicates significant antibacterial effect

Pencil hardness and adhesion directly reflect the durability of the coating

5. Summary of performance advantages

Green and renewable : natural source, environmentally friendly and non-toxic

Adjustable functions : easy to modify, customizable performance

Wide applicability : adapted to paper, plastic, glass, metal and other substrates

High transparency : suitable for optical and display fields

Excellent mechanical properties : wear resistance, scratch resistance, strong adhesion

6. Development trends and challenges

Development trends

High performance : developing towards superhydrophobic, self-cleaning, and photoelectric integration

Greening process : Promoting full-water system and low-energy consumption preparation

Nanocomposite : Combining two-dimensional materials and functional nanoparticles to expand functional boundaries

Facing challenges

Cost and mass production issues

Stability under high temperature and high humidity conditions

Increased surface adhesion of hydrophobic substrates

7. Conclusion

Nanocellulose has shown great potential in the field of functional coatings. It can not only significantly improve the mechanical, barrier and optical properties of the coating, but also impart antibacterial, anti-fog, and anti-ultraviolet properties through functional modification. With the optimization and industrialization of green preparation technology, the application prospects of nanocellulose functional coatings in packaging, electronics, construction, medical care and other fields will be broader.