Master of Science Matias Lakovaara defended his thesis at the University of Oulu on improving the water resistance of cellulose nanomaterial-based films and coatings using deep eutectic solvents.
“Deep eutectic solvents are a new type of liquid that is obtained by combining two solid components that form hydrogen bonds with each other. The components used are common, inexpensive and low-toxic chemicals, so they are environmentally safer than the volatile organic compounds commonly used in chemical cellulose modification processes,” he explains.
Lakovaara studied the modification of nanocellulose films in his master's thesis in process technology. The dissertation consists of four sub-publications.
Water resistance improved easily
Films made from nanocellulose have many favorable properties for packaging materials – they are transparent and flexible, and oxygen and grease do not easily pass through them. However, they are not waterproof.
The first two sub-publications focused on the modification of nanocellulose membranes.
“With deep eutectic solvents, water resistance could be improved with a simple and short modification process – water resistance improved with just a 15-minute reaction time.”
When the nanocellulose membrane is exposed to water, oxygen permeability also increases, which was attempted to be prevented.
“Unfortunately, we haven't been able to solve this problem yet,” Lakovaara says.
Rice packaging and protective film for printed electronics
In the latter two sub-studies, cellulose fibers were first modified, and the newly modified cellulose fibers were used to make waterproof membranes.
“The modification process was the same as for nanocellulose membranes, but after the process, the modified pulp was treated with ultrasound in ethanol.”
Highly transparent nanocellulose films were made from cellulose modified with ultrasound.
“The optical properties were good and the water resistance was clearly better than with unmodified nanocellulose films. The material could also be heat-sealed.”
The functionality of the material was tested by making a package for rice from it.
“However, the material is fragile and cannot withstand mechanical processing, so it still requires further development.”
In the fourth sub-study, the same material was used to make a coating for an unmodified nanocellulose film as a waterproofing material for printed electronics applications.
“We demonstrated this with a conductive water-soluble paint, so it was easy to see if it would spread when the material was exposed to water. The results were promising.”
Dissertation
Matias Lakovaara's dissertation Water-resistant nanocellulose Films and coatings via deep eutectic solvent modifications, University of Oulu Graduate School; University of Oulu, Faculty of Technology Acta Univ. Oul. C 1019, 2025.
https://oulurepo.oulu.fi/bitstream/handle/10024/57984/nbnfioulu-202508085234.pdf
