FIBRE IS THE FUTURE – ARE WE READY TO COAT IT?

Packaging is a major domain in the food-processing industry. It considers not only commercial value, but also waste reduction and shelf-life extension. In recent years, plastic packaging has raised more concerns because of environmental issues driven by the alarming growth of single-use plastic, food-packaging waste. The EU Packaging and Packaging Waste Regulation (PPWR) is driving a major transformation in the packaging industry. The PPWR requires all packaging to be recyclable by 2030. Alongside, there are new rules such as mandatory recycled content for plastics and the Plastic Tax. Combined with growing environmental pressures and regulatory requirements, moulded fibre packaging has gained increasing attention. It is a sustainable alternative to single-use plastics because of its renewable origins, recyclability and potential for biodegradability. 

Alongside the advantages of moulded fibre packaging, there are also some challenges.1 Paper- or fibre-based materials have little to no barrier properties. This is because they are inherently porous and hydrophilic, limiting performance potential. To overcome these limitations, paper- or fibre-based packaging must be combined with specific coatings to create a sufficient barrier between the contents and the package. Developing proper barrier properties on the paper-substrate surface is the main challenge in scaling up moulded fibre packaging for commercial use. 

Creating effective barrier layers for different paper products – tailored to specific application requirements – involves careful selection and application of coating technologies, primers and coatings to match substrates.

Among the elements of the coating process, there has been little attention paid to substrate-controlled liquid transport. During coating, droplets land first, followed by simultaneous spreading and penetration into the pore system. Surface chemistry and contact angle are important in controlling droplet evolution after landing. Substrate structure – such as surface roughness and pore-size distribution – can control penetration. The competition between spreading and penetration determines the amount of coating that remains on the surface and whether a continuous barrier layer forms. Therefore, characterisation of paper substrates provides key parameters for understanding coating penetration and barrier-layer formation. These include density, wettability, absorption, moisture content, surface chemistry, roughness and surface morphology.

“Moulded fibre packaging has gained increasing attention”

Surface roughness influences coating coverage and film formation. On rough surfaces, liquid coatings may accumulate in recessed areas, leaving thinner layers on raised features. Alternatively, raised features can stop coating spreading and create a shade. This leaves the recessed region’s surface with poor coverage. As illustrated in Figure 1, all specimens are cellulose, fibre-based substrates exhibiting notable variations in surface roughness. The brown marks indicate the pinholes through which iodine has penetrated. The roughness of the recycled paper tray on the right is about 
41.1 ± 6.1µm, while the Bagasse pot shows a roughness of about 3.52 ± 0.23µm. Roughness modifies the local liquid-spreading behaviour and influences the effective capillary pathways within the fibre network. Exploration of the roughness of the fibre-packaging surface shows that the coating weight probably needs to be increased to achieve good coverage of the barrier layer for the rougher surface. 

The roughness and moisture content correlate with wettability. A rougher surface tends to have higher moisture content. This is related to the pore structures in the paper substrates. Higher water content in the substrates tends to result in better wetting and a lower contact angle. 

Substrate properties play an extremely important role in coating performance. Dr Zhongnan Duan’s work at Archipelago is focussed on mapping substrate properties to assess their potential to enable the formation of good barrier layers.

The coating itself is essential for better barrier properties. Currently, polyethylene (PE) layers are used for paper-based packaging, particularly to provide resistance against moisture and liquids.2 However, increasing attention is being given to plastic-free and bio-based alternatives. These could provide the required barrier performance while improving the sustainability of the final package.3

Cellulose derivatives, such as cellulose nanofibrils (CNF), can be used to coat paper and impart adequate water and oxygen barriers on paper substrates.4 Chitosan – a natural polysaccharide derived from shellfish shells – can provide a water or oxygen barrier when coated on paper.5

A commercial barrier coating (BARV656) (7), supplied by Sun Chemical, can provide resistance to grease, oil, water, moisture and oxygen when applied as a pin-hole free layer applied using PowerdropTM technology. However, selecting an effective barrier coating is only part of the challenge. 

“The coating itself is essential for better barrier properties”

The condition of the underlying fibre surface can strongly influence how successfully that coating forms a continuous barrier layer. On substrates with high-surface roughness or large pores, the coating may penetrate into the fibre structure and fail to cover the surface evenly. In these cases, introducing a primer layer can help prepare the surface for subsequent barrier coating. Microfibrillated Cellulose (MFC) is a natural, renewable material derived from plant fibres. It is known for its high surface area, which enhances mechanical properties such as strength and stiffness. Importantly, it can form a dense network on the paper substrate surface, making it more receptive to the next-step coating.6 This is demonstrated by the recycled paper bowl, whose uncoated roughness is about 30.1µm. After MFC coating, the roughness decreased to 4.1µm. Confocal microscopy further demonstrates this change, showing a substantially more uniform surface after MFC application, as shown in Figure 2. 

“PowerdropTM is a patented industrial inkjet coating technology”

PowerdropTM is a patented industrial inkjet coating technology created by Archipelago Technology Group Ltd. The product can produce pinhole-free, waterproof and oil-proof layers. This non-contact, continuous coating process can deliver precise material doses and apply high-quality coatings with minimal waste, making it suitable for high-value materials. The PowerdropTM technology can coat both flat and 3D objects. The technology can strongly support industrial-scale production of moulded fibre packaging. 

In summary, fibre-based packaging has significant potential to replace primary plastic packaging in many applications with the right coatings. To compete with conventional packaging, it must also provide reliable and consistent barrier performance. While developing barrier coatings is essential, their performance cannot be considered independently of the fibre substrate beneath them. Ultimately, replacing plastic with fibre is not simply a material substitution. The real opportunity lies in designing the substrate, surface treatment, coating technology and barrier coating as an integrated system. This combination allows fibre packaging to deliver both the environmental benefits and functional performance required by the next generation of packaging. 

REFERENCE

1. Pulikkalparambil, H et al. Recent Advances in Natural Fibre-Based Materials for Food Packaging Applications. Polymers vol. 15 Preprint at https://doi.org/10.3390/polym15061393 (2023).
2. Pagnotta, L Paper and Cardboard Packaging: From Cellulosic Substrates to Functional and Hybrid Architectures. Materials 19, 2801 (2026).
3. Kunam, PK, Ramakanth, D, Akhila, K & Gaikwad, KK. Bio-based materials for barrier coatings on paper packaging. Biomass Conversion and Biorefinery vol. 14 12637–12652 Preprint at https://doi.org/10.1007/s13399-022-03241-2 (2024).
4. Yook, S et al. Barrier coatings with various types of cellulose nanofibrils and their barrier properties. Cellulose 2020 27:8 27, 4509–4523 (2020).
5. Tanpichai, S et al. Mechanical and antibacterial properties of the chitosan coated cellulose paper for packaging applications: Effects of
6. molecular weight types and concentrations of chitosan. Int J Biol Macromol. 155, 1510–1519 (2020).
7. Lavoine, N, Desloges, I, Dufresne, A & Bras, J. Microfibrillated cellulose – Its barrier properties and applications in cellulosic materials: A review. Carbohydr Polym 90, 735–764 (2012).
8. Direct Food Contact Inks and Coatings (DFC) | Sun Chemical