Solid Foams from Cellulose
Doctoral thesis, 2025
The development of lightweight materials such as foams highlights the human drive to optimize material functionality and minimize energy expenditure. At the forefront of modern foam materials are highly versatile fossil fuel-based plastics; a technological triumph which is producing a spiraling ecological disaster. To solve this problem, we can turn to renewable materials such as cellulose. However, several challenges appear when transitioning to these materials: Solid foams from cellulose can suffer from lackluster mechanical performance, sensitivity to environmental conditions such as moisture and fire, and require significant energy to dry. This thesis explores structural features in cellulose foams which introduce multi-functionality such as enhanced mechanical strength and fire-retardancy.
Two distinct phenomena affecting the strength of cellulose networks were evaluated: i) degradation/cross-linking, and ii) structural rearrangement. The degradation of non-crystalline cellulose fiber regions weakened fiber networks via phytic acid or endo-xylanase enzymatic hydrolysis. To counteract this, fibers were cross-linked through the physical adsorption of extrinsic xylan or by covalently binding phytic acid to cellulose via dehydration synthesis reactions. Phytic acid also changed the foaming behaviour of wet systems applying an ionic surfactant, and imparted thermal stability and fire-retardancy to dried cellulose fibers. The structural arrangement of cellulose nanocrystals in suspensions and during freezing was modified by leveraging interactions between tert-butanol and water. The disrupted assembly and unique ice crystal formation led to tailorable strength and surface areas in freeze-dried cryogels.
With these studies, we unveil methods and mechanisms to strengthen fiber networks with the goal of expanding the use-cases of cellulose foams. In our pursuit of a sustainable future, we must overcome our dependence on non-renewable plastics by finding and exploiting effective solutions found in nature.
Two distinct phenomena affecting the strength of cellulose networks were evaluated: i) degradation/cross-linking, and ii) structural rearrangement. The degradation of non-crystalline cellulose fiber regions weakened fiber networks via phytic acid or endo-xylanase enzymatic hydrolysis. To counteract this, fibers were cross-linked through the physical adsorption of extrinsic xylan or by covalently binding phytic acid to cellulose via dehydration synthesis reactions. Phytic acid also changed the foaming behaviour of wet systems applying an ionic surfactant, and imparted thermal stability and fire-retardancy to dried cellulose fibers. The structural arrangement of cellulose nanocrystals in suspensions and during freezing was modified by leveraging interactions between tert-butanol and water. The disrupted assembly and unique ice crystal formation led to tailorable strength and surface areas in freeze-dried cryogels.
With these studies, we unveil methods and mechanisms to strengthen fiber networks with the goal of expanding the use-cases of cellulose foams. In our pursuit of a sustainable future, we must overcome our dependence on non-renewable plastics by finding and exploiting effective solutions found in nature.
cellular solids
biopolymer
Natural fibers
aerogel
porous
Lecture hall 10:an, Kemivagen, Gothenburg
Opponent: Dr. Prof. Tatiana Budtova, Mines Paris, France
Author
Eliott Orzan
Chalmers, Chemistry and Chemical Engineering, Applied Chemistry
Foaming and cross-linking of cellulose fibers using phytic acid
Carbohydrate Polymers,;Vol. 347(2025)
Journal article
Role of intrinsic and extrinsic xylan in softwood kraft pulp fiber networks
Carbohydrate Polymers,;Vol. 323(2024)
Journal article
Elucidation of cellulose phosphorylation with phytic acid
Industrial Crops and Products,;Vol. 218(2024)
Journal article
Tert-butanol as a structuring agent for cellulose nanocrystal fluids and foams
Throughout the development of our civilization, the human passion for problem solving and efficiency has inspired technological progress. As a result, we discovered the potential of cellular structures, also known as foams. We began mimicking lightweight constructions found in nature to engineer modern solutions for the construction, transportation, and packaging industries. By encapsulating air within materials, we could minimize weight, costs, and waste while maintaining a functioning design. Now, we are entering an era where developing a circular bioeconomy is a pressing issue. Foams are an excellent solution, yet the widespread use of fossil fuel plastics for these materials demands an alternative.
We have become overly reliant on plastics, and for good reason. As materials, they are efficient; abundant, cheap, easy to produce, and perfectly tailorable to almost any application. However, in our transition towards more sustainable practices, the use of materials originating from renewable resources is a key ingredient toward our success. One enticing option is cellulose, the structural core of all plant material. We use this common material every day in paper products, textiles, and packaging. On the other hand, it struggles to find use in applications that require strength, such as in the transportation sector. The network of fibers which defines cellulose-based materials is inherently weaker than plastics, such as polyurethane, and is affected by environmental conditions such as moisture and fire.
This thesis aims to provide solutions to strengthening cellulose foams. By introducing additives that change the chemical or physical structure of fiber networks, it is possible to determine which methods are the most effective and why. Along the way, foam formation and functionalities such as fire-retardancy are explored as a way to bolster the potential for cellulosic materials.
We have become overly reliant on plastics, and for good reason. As materials, they are efficient; abundant, cheap, easy to produce, and perfectly tailorable to almost any application. However, in our transition towards more sustainable practices, the use of materials originating from renewable resources is a key ingredient toward our success. One enticing option is cellulose, the structural core of all plant material. We use this common material every day in paper products, textiles, and packaging. On the other hand, it struggles to find use in applications that require strength, such as in the transportation sector. The network of fibers which defines cellulose-based materials is inherently weaker than plastics, such as polyurethane, and is affected by environmental conditions such as moisture and fire.
This thesis aims to provide solutions to strengthening cellulose foams. By introducing additives that change the chemical or physical structure of fiber networks, it is possible to determine which methods are the most effective and why. Along the way, foam formation and functionalities such as fire-retardancy are explored as a way to bolster the potential for cellulosic materials.
Upgrading of cellulose fibers into porous materials (BreadCell)
European Commission (EC) (EC/H2020/964430), 2021-04-01 -- 2025-03-31.
Driving Forces
Sustainable development
Subject Categories (SSIF 2025)
Paper, Pulp and Fiber Technology
Areas of Advance
Materials Science
ISBN
978-91-8103-218-5
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5676
Publisher
Chalmers
Lecture hall 10:an, Kemivagen, Gothenburg
Opponent: Dr. Prof. Tatiana Budtova, Mines Paris, France