Plasma treatment strengthens cellulose films for future packaging

Researchers at North Carolina State University have developed a plasma-based treatment that could improve the water resistance of cellulose nanofibril films, addressing one of the main barriers to replacing conventional plastic packaging with plant-based materials.

The study uses dielectric barrier discharge plasma to modify the surface of cellulose-based films and control how they interact with liquid water and water vapour.

The results demonstrate that plasma treatment can significantly alter the moisture behaviour of cellulose films without requiring the material to be replaced with a conventional petroleum-based polymer.

Water resistance remains a major challenge for cellulose packaging

Cellulose offers several advantages as a packaging material, including renewable sourcing, biodegradability potential and compatibility with fibre-based packaging systems.

However, cellulose is naturally hydrophilic, meaning that it readily absorbs water. This can cause swelling, loss of mechanical strength and deterioration of barrier performance when the material comes into contact with moisture.

These characteristics limit the use of untreated cellulose films in applications involving wet or high-moisture foods.

DBD plasma changes the surface properties

The researchers used dielectric barrier discharge plasma to apply layered protective treatments to cellulose nanofibril films.

Plasma generates energetic species capable of modifying the chemistry and structure of a material surface without requiring the entire material to be chemically reformulated.

This makes the technique particularly interesting for bio-based packaging, where surface modification can potentially add specific functional properties while retaining the underlying characteristics of the renewable substrate.

Water absorption falls below 1%

One of the plasma-treated coatings reduced liquid water absorption in the cellulose nanofibril films to less than 1%.

The result demonstrates the potential of surface engineering to overcome the inherent sensitivity of cellulose to liquid water.

However, not all treatments produced the same effect. Another coating weakened the film’s moisture barrier and allowed greater water-vapour transmission, showing that plasma parameters and coating architecture must be carefully controlled.

Plasma provides precise control over moisture behaviour

The researchers found that plasma treatment can be tuned to produce different interactions between the cellulose surface and moisture.

This ability to control surface properties is important because packaging applications require different levels of resistance depending on the product.

A dry-food package, for example, may require protection against atmospheric humidity, while a chilled or wet-food application may require resistance to direct liquid contact.

Plant-based films could replace selected plastic formats

The research is part of a broader effort to develop packaging materials capable of providing the functionality of conventional plastics while using renewable resources.

Cellulose nanofibrils are particularly attractive because they can be produced from abundant biomass and can form thin, strong films.

Improving their moisture resistance could expand their potential use in food packaging, where water sensitivity has traditionally limited cellulose-based materials.

Surface treatment avoids redesigning the entire polymer

An important advantage of the approach is that plasma treatment acts primarily at the material surface.

Rather than introducing a large quantity of another polymer throughout the film, researchers can potentially create a thin functional layer that changes the interaction between the package and its environment.

This could help preserve the renewable character of the underlying cellulose material while adding the performance required for specific packaging applications.

Industrial scale-up remains to be demonstrated

The research is still at the development stage and further work will be required before the technology can be considered for commercial packaging production.

Future studies will need to evaluate coating uniformity, processing speed, mechanical durability, food-contact safety, oxygen and grease barrier performance and compatibility with existing converting equipment.

The economics and energy consumption of continuous plasma treatment will also determine whether the process can compete with established coating technologies at industrial scale.

Plasma could become an enabling technology for fibre packaging

The study demonstrates how advanced surface engineering can address one of the fundamental weaknesses of plant-based packaging without abandoning the cellulose substrate.

If the process can be scaled efficiently, plasma treatment could become an enabling technology for producing fibre-based films with the moisture resistance required for a wider range of food and consumer packaging applications.

The development reinforces a broader trend in sustainable packaging: the next generation of bio-based materials may depend as much on advanced surface engineering as on the underlying renewable material itself.