Through green chemistry and smart processing, cellulose can be given new properties that result in stronger paper and improved barrier materials. This is demonstrated in a new doctoral thesis from Karlstad University.
Plastic is currently widely used in paper‑based packaging, such as milk and food cartons, to protect against air and moisture. However, plastic is fossil‑based and difficult to recycle together with paper. In her doctoral thesis, Mozhgan Hashemzehi shows how pulp can be modified in a more sustainable way to reduce the need for plastic in packaging.
The thesis focuses on how cellulose can be sustainably activated and modified to improve paper packaging materials. It investigates how environmentally friendly solvents, enzymatic pretreatments, and controlled drying methods can increase the reactivity of cellulose. The increased reactivity makes it easier to modify the cellulose and tailor its properties for specific applications. The modified cellulose was then used as additives and coatings to improve paper strength and barrier properties, while still being compatible with industrial papermaking processes.
“Cellulose is a renewable material that is already well established in industry, but its full potential is not fully utilised today. Our research demonstrates how pulp can be given new functionalities through more environmentally friendly chemical methods,” says Mozhgan Hashemzehi.
The thesis also shows that the green solvents used in the cellulose modification process, known as deep eutectic solvents (DES), can be recovered and reused several times without loss of efficiency, further enhancing the sustainability of the method.
An important part of the work involves understanding and mitigating hornification- the structural changes that occur when pulp dries and is rewetted, permanently altering its properties. By controlling how the pulp is treated and dried, the cellulose structure can be better preserved, resulting in improved reactivity and performance.
The results are particularly relevant for the pulp, paper and packaging industries, where interest in fossil‑free and circular materials is growing rapidly.
“By preserving the fibre structure while increasing its functionality, we were able to strengthen the paper and improve barrier properties without disrupting the papermaking process,” says Mozhgan Hashemzehi.
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