Public defence in Bioproduct Technology, MSc Hamidreza Ahadian

Title of the thesis: Dewatering of single- and multilayer nanopaper

Thesis defender: Hamidreza Ahadian
Opponent: Dr. Elias Retulainen, Megatrex Oy, Finland
Custos: Prof. Thaddeus Maloney, Aalto University School of Chemical Engineering

One of the important research directions in paper manufacturing is the development of nanopapers—an emerging grade of paper that incorporates nanomaterials as one of the main components. These papers aim to provide new functional properties that enable them to replace plastics in applications such as packaging, electronics, energy storage, membranes, diagnostics, and medical uses. A key component in many nanopapers is nanocellulose, which, at a small scale, has shown significant potential as a furnish component for fabricating a new range of eco-friendly, natural fiber products with enhanced functionality compared to traditional paper grades. However, there are major roadblocks to the large-scale application of nanocellulose in papermaking. The primary challenges include a very slow dewatering rate, poor retention, and high shrinkage. These issues arise from the small dimensions, large surface area, and high water-binding capacity of nanofibers. The overall objective of this thesis was to develop a technical strategy for forming and dewatering nanopapers. The work particularly focuses on the role of paper structure in enhancing dewatering efficiency. In this context, the permeability of the structure is a key parameter that must be maintained to enable efficient water removal. Approaches investigated in this thesis include modifying nanofibrils, optimizing their distribution within the paper matrix, and direct structuring of the paper. They proved to be successful approaches for the optimisation of the structure during the preparation of nanopapers.

Keywords: Nanopaper, microfibrillated cellulose, nanocellulose, papermaking, dewatering, cationic bubbles, multilayer forming, fiber fibrillation, swelling

Thesis available for public display 10 days prior to the defence at Aaltodoc. 

Contact information: 
hamidreza.ahadian@vtt.fi