A novel wood bark-based packaging coating material

In the COCOBIN project, coordinated by the University of Oulu, coating materials are being developed from suberin, a natural compound found for example in birch bark. In plants, suberin acts as a protective layer and prevents the loss of water. Up to 1500 meters of a bio-based coating material prototype have been produced at semi-pilot scale.

The material can be applied especially in fiber-based packaging materials such as paper or paperboard as a moisture barrier, as well as in other products requiring durable and functional surfaces. One key application area is food packaging, where the role of the coating is to prevent moisture from passing through the packaging material and to protect the product.

“The material can be applied especially in fiber-based packaging materials such as paper or paperboard as a moisture barrier, as well as in other products requiring durable and functional surfaces,” says professor Henrikki Liimatainen from the University of Oulu.

“Suberin-based coatings can be used as a water vapor barrier in food packaging applications. Current coating materials are typically fossil-based and can present challenges for recycling. Suberin-based coatings can offer an alternative while achieving comparable performance,” adds Rajesh Koppolu, Senior Scientist at VTT.

Toward more sustainable materials

The development of the coating has progressed step by step toward practical applications. The starting point was birch bark, from which suberin was extracted at semi-pilot scale. The extracted suberin was received as a moist material, then dried and further processed into a fine powder. This enabled it to be mixed into a uniform coating formulation.

From this powder, a water-based coating was prepared, where suberin particles are evenly distributed in the liquid. Additional components were included to help the coating spread evenly and to achieve the desired functional properties. The formulation is based on approximately one and a half years of research and development work. The work demonstrates the feasibility of the concept at semi-pilot scale.

The coating was produced and tested using semi-pilot-scale equipment that represents industrial production at a smaller scale. This allowed the team to observe how the material behaves under conditions similar to real manufacturing.

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Source & image credit: University of Oulu