Industry challenges
Packaging films and functional coatings must balance oxygen barrier, transparency, mechanical properties, coating processability and sustainability. Some bio-based films lack gas barrier, while high-barrier coatings are sensitive to layer uniformity, thickness, flexibility and humidity. Building barrier performance with a thin, continuous and dense functional layer is therefore a key development direction.
What nanocellulose does
CNC and CNF combine nanoscale size, high specific surface area and good film-forming and compounding ability, forming a dense nanostructure in the layer that lengthens the diffusion path of oxygen and other small molecules.
Carboxylated cellulose nanocrystals (C-CNC) add high crystallinity, nanoscale size and good water dispersibility, suiting water-based oxygen-barrier coatings, transparent functional coatings, bio-based composite films, paper packaging coatings and multilayer barrier structures.
Recommended grade
Recommended: carboxylated cellulose nanocrystals (C-CNC).
For systems whose main goals are lower oxygen transmission, retained transparency and a thin dense barrier layer, evaluate carboxylated CNC first. Its small particle size and high crystallinity favour a uniform, dense nano-barrier under suitable dispersion, coating and drying conditions, and its water dispersibility eases compounding with PVA, starch, chitosan and other water-based polymers.
CelluBio offers grades at roughly 2%–15% solids and 50–500 cP viscosity, selected by coating method, target coat weight and processing requirements.
Solids and viscosity selection
Different coating processes need different solids and rheology; use the table as a first orientation.
| Requirement | Suggested solids | Reference viscosity | Typical use |
|---|---|---|---|
| Low viscosity, easy levelling | 2%–5% | about 50–150 cP | thin coats, spraying, low coat weight |
| Standard barrier coating | 5%–10% | about 100–300 cP | rod, blade and general water-based coating |
| Higher coat weight | 8%–12% | about 200–400 cP | higher coverage, thicker functional layers |
| High-solids processing | 10%–15% | about 250–500 cP | lower water and drying load |
Do not simply chase high solids or high viscosity: for barrier coatings, continuity, uniformity and defect control usually matter more than adding more CNC. Viscosity depends on concentration, temperature, shear and grade; refer to the product data sheet.
Application test reference
Carboxylated CNC has been tested in packaging films and barrier coatings; one test system reached an oxygen transmission rate (OTR) of 0.0298 cm³/(m²·24 h), showing strong oxygen-barrier potential.
This result was obtained under a specific formulation and test conditions. Real performance depends on substrate, formulation, coating thickness, film-forming process and humidity, so verify it in your own system.
Other grades
- Reinforcement and continuous fibre networks: evaluate CNF / C-CNF.
- Transparent thin layers and oxygen barrier: evaluate C-CNC first.
- Non-polar composites or humidity resistance: evaluate hydrophobically modified CNC/CNF.
- Free-standing bio-based membranes: evaluate BC membranes.
CNC and CNF are not simple substitutes for each other; select on barrier, reinforcement, transparency, rheology, humidity resistance and processing method together.
Trial suggestions
For water-based barrier coatings, first fix the substrate, target OTR, coating method and target dry thickness, then choose the C-CNC grade by solids and viscosity. In the first round compare C-CNC grade → coating solids → coat weight and dry thickness → drying conditions, with a blank substrate and coat-weight controls.
Test OTR, WVTR, transparency and haze, adhesion, flexibility and barrier at different humidities. When compounding with PVA, starch or chitosan, screen CNC-to-polymer ratios to find a suitable film-forming and barrier system.
Common issues
- Barrier drops at high humidity: nanocellulose is hydrophilic; improve with a hydrophobic top layer, a multilayer structure or a humidity-resistant polymer.
- Coating cracks: coat applied too thick in one pass, dried too fast or layer too stiff; adjust coat weight, drying or add flexible components.
- High-solids grade hard to coat: match solids and viscosity to the equipment, higher is not better.
- OTR results scatter: check for pinholes, cracks, thickness variation or poor substrate wetting; tiny defects strongly affect high-barrier films.
Note
These suggestions are for material selection and preliminary trials, not fixed formulations or final process parameters. Results depend on grade, surface groups, solids, dispersion, substrate, compounding materials, coat weight, dry thickness, drying conditions and test environment. Run blanks and process gradients to confirm the grade and process for your system. For food and food-contact packaging, confirm regulations, purity, testing and market access separately.
