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Title of the thesis: Development of biobased coatings incorporating lignin nanoparticles for packaging and textile applications

Thesis defender: Sahar Babaeipour
Opponent: Associate Professor Marc Delgado-Aguilar, University of Girona
Custos: Professor Monika Österberg, Aalto University School of Chemical Engineering

Development of bio-based coatings incorporating lignin nanoparticles for packaging and textile applications  

The widespread use of plastics in packaging and textiles has created major environmental challenges, particularly due to their fossil origin and limited recyclability. At the same time, cellulose-based materials such as paper, board, and cotton offer a renewable alternative but lack sufficient resistance to moisture. This doctoral thesis addresses this challenge by developing fully bio-based coatings that enhance performance while maintaining recyclability. The study focuses on lignin, a major but underutilized by-product of the pulp industry, and explores its use in the form of lignin nanoparticles as a functional coating component . The main objective was to design simple and scalable coating systems for cellulose-based materials, with applications in both packaging and textiles, while considering industrial adaptability and circular material design.

Two types of coatings were developed: open and breathable coatings, and closed barrier coatings. The open coatings were designed for textile applications, where maintaining air permeability is essential. These coatings provided water repellency, antibacterial properties, and stain resistance, while preserving the comfort and breathability of the fabric.

In contrast, closed barrier coatings were developed for packaging applications, where protection against oxygen, moisture, and oils is critical. These coatings formed dense, continuous layers that significantly improved barrier performance, even under humid conditions. By combining lignin nanoparticles with cellulose-based materials, the coatings reduced moisture sensitivity and enhanced resistance to gas and liquid permeation. Importantly, these coatings were successfully applied to both flat paper materials and complex 3D-molded fiber packaging using scalable techniques such as spray coating, while maintaining recyclability

The main contribution of this thesis is the development of multifunctional, fully bio-based coating systems that combine high performance with circular design principles. The research also provides new understanding of how lignin nanoparticles can be modified, processed, and integrated into coating structures to achieve desired properties.

In conclusion, this work demonstrates that lignin nanoparticles can enable high-performance, recyclable materials and support the transition toward a circular bioeconomy.

Thesis available for public display 7 days prior to the defence at .