Master's thesis: Stabilizing Fiber Suspensions with Cellulose Nanofibrils for High-Concentration Processing

Master's thesis: Stabilizing Fiber Suspensions with Cellulose Nanofibrils for High-Concentration Processing

Cellulose fibers have long been used in packaging applications, hygiene products, and printed media. Today, there is strong interest in expanding their use to new areas where they can replace plastics—such as in 3D-shaped products like trays.

The versatility of cellulose fibers comes from their ability to form strong networks. To create these networks, the fibers are suspended in water and processed at low concentrations, typically below 1 wt%. Even at these levels, fiber flocculation (entanglement) occurs, leading to uneven material structure and reduced mechanical properties. Much effort has gone into developing processing equipment that prevents flocculation by hydrodynamically breaking apart the flocs. However, the need for low processing concentrations still remains.

Developing new methods to process fibers into uniform networks at higher concentrations would significantly reduce energy and water usage. It would also lead to stronger load-bearing networks for high-performance fiber products, and enable new material forming processes where flocculation is currently a limiting factor—such as for low-density porous materials.

At KTH, we have shown that cellulose nanofibril networks at just 0.1 wt% concentration can effectively prevent the flocculation or sedimentation of nano- and microparticles. These nanofibrils create a fine mesh that hinders particle motion, working efficiently at low concentrations due to their high slenderness. In this master thesis project, you will use nanofibrils to prevent fiber flocculation, enabling processing at higher concentrations—up to 5 wt% or more—for both existing and new fiber-based materials.

This master thesis project is part of a collaboration between KTH, RISE, and the Scandinavian pulp and paper industry, under the BioFunChem (BFC) research and education program. BFC focuses on developing biobased paper chemicals and additives for both current and future fiber processes. Project results will be shared at BFC research progress meetings, providing a valuable opportunity for industry connections.

Part 1 – Flocculation studies

RISE has a flow-loop setup designed for studying flowing fiber suspensions. The first step will be to adapt an existing imaging-based method for characterizing fiber flocculation, making it suitable for the higher concentrations targeted in the project. This will involve designing a modified measurement section for the flow loop, as well as adapting image processing scripts.

Once ready, the setup will be used to study fiber suspension flocculation at various concentrations with different levels of added cellulose nanofibrils. This will help quantify how the nanofibrils affect the flocculation state. In parallel, rheological characterization of the suspensions will be performed at KTH.

Part 2 – Application to wet-moulded products

The potential of using high-concentration pulp suspensions with nanofibrils in wet moulding applications will be evaluated. It is hypothesized that the de-flocculating effect of the nanofibrils, along with their ability to enhance stiffness and strength, will offer significant advantages in both the processability and performance of 3D-shaped cellulose fiber products. This part of the project will make use of RISE's wet-moulding pilot equipment.

The project will be supervised by:

• Tobias Benselfelt at KTH, Division of Fibre Processes
• Claes Holmqvist at RISE Bioeconomy

The examiner is:
Professor Daniel Söderberg, Division of Fibre Processes

Terms
Location: RISE, Drottning Kristinas väg 61

Application deadline:

Starting date: As soon as possible or at latest January 2026.

Contact: Claes Holmqvist, RISE, and Anna Sjöstedt, RISE,

Credits: 30 points

Compensation: For an approved thesis project worth 30 credits, we pay a compensation of

Welcome with your application
Candidates are encouraged to send in their application as soon as possible but at the latest by the 31th of January 2026. Suitable applicants will be interviewed as soon as applications are received.