A group of young researchers from Canada, Finland, Japan and Sweden attended the MWP Prize Event in Stockholm in September 2015. The young researchers contributed to the MWP Symposium by presenting their own research in a poster exhibition, see the below abstracts.
- Highly charged cellulose surfaces: The interface of the future?
Author(s): Tobias Benselfelt, Jonatan Henschen, Torbjörn Pettersson, Lars Wågberg.
Corresponding author: Tobias Benselfelt
Affiliation: Wallenberg Wood Science Center KTH
Highly charged cellulose materials, e.g. TEMPO-oxidized cellulose nanofibrils (CNF), have gained a lot of attention during the latest decade. Going from micro to nano-size increases the surface to volume ratio with three orders of magnitude, increasing the importance of the surface properties. Oxidation and fibrillation of pulp fibres leaves us with a highly charged surface to be tuned for various applications. One straightforward way to tailor/functionalize the surface or control the assembly of such materials is using a layer-by-layer (LbL) approach. However, knowledge on how surface charge affects the multilayer assembly remains a crucial scientific challenge in understanding how to tailor materials from the nano-scale.
In this project we investigate the build-up of LbL assemblies at highly charged cellulose (NMMO) model surfaces prepared from TEMPO-oxidized pulp. We also investigate the surface potential at different ionic strength, the swelling and surface structure (wet and dry) of these model films. This fundamental knowledge is very important for the future use of TEMPO-oxidized cellulose materials in a wide range of applications. The research also provides fundamental knowledge within the rapidly advancing research field of layer-by-layer assemblies where the use of well characterized, differently charged surfaces is still lacking in the literature.
Key words: Tailored cellulose surfaces, TEMPO-oxidation, NMMO-surfaces, surface charge, Layer-by-Layer (LbL), Multilayer build-up
- Structure and function of hemicellulose
Author(s): Jennie Berglund, Francisco Vilaplana, Martin Lawoko, Gunnar Henriksson, Mikael Lindström
Corresponding author: Mikael Lindström
Affiliation: Wallenberg Wood Science Centre, Department of Fiber and Polymer Technology, KTH Royal Institute of Technology, Stockholm, Sweden
E-mail: Mikael Lindström: firstname.lastname@example.org and Jennie Berglund: email@example.com
Hemicelluloses represent about one third of wood and constitute a large source to renewable materials. Wood hemicelluloses are to some extent separated and used today, but mostly for low value products like biofuel, and in the common kraft pulping process a large part of the hemicelluloses are not recovered. However, these polymers have potential to be used for value-added products besides pulp in the Swedish pulping industry. Plastic hemicellulose films have for example showed good barrier properties, and food packaging is one interesting product application. Nevertheless, the difficulty to separate the hemicelluloses from the rest of the wood is still a problem, and especially if high yields and large polymers are desired. Therefore more research about hemicelluloses properties is necessary.
I am studying the relation between, structure, function and properties of hemicelluloses. I modify the structures and evaluate how properties like solubility and interactions with other wood polymers are affected. I believe that my fundamental research will result in important knowledge that is needed in order to develop the utilization and usage of hemicellulose as a substitute for oil based plastics. I believe that this would be positive for our Swedish forest industry and make our society more environmentally friendly.
Key words: Hemicellulose, Wood, Renewable materials, Relate structure and properties
- From fiber to product: Computational modeling of the mechanical response of paper-based materials
Author(s): Eric Borgqvist, Mathias Wallin, Matti Ristinmaa, Johan Tryding
Corresponding author: Eric Borgqvist
Affiliation: Lund University
Product development within packaging industry relies today to a large extent on experiments on simplified load situations. The correlation between these simplified setups and the actual behavior in converting is not always evident. It is therefore crucial to obtain more knowledge about the deformation mechanisms in complicated load situations. To increase the understanding of fibrous materials in general and packaging materials in particular, it is essential to develop reliable computational models. As an example, the mechanical response of paperboard as it is converted into a package is complex and involves several processing steps which are difficult to analyze when only using experiments. The ability to predict the response in converting will significantly reduce the cost and time for the development of new products. One important result of the research so far is a 3-dimensional numerical model that can be used to simulate converting procedures.
My vision is to push the research front for fibrous materials and converting procedures from physical testing to the virtual world. This new paradigm which I will refer to as ‘from fiber to product’ will lead to reduced development time, improved cost efficiency and the ability to tailor new products.
Key words: Computational Modelling, Constitutive Model, Continuum, Finite Strains, Paperboard, Anisotropy, Creasing, Folding
- Chemical modification of biopolymers for improved or changed properties
Author(s): Mikaela Börjesson and Gunnar Westman
Corresponding author: Mikaela Börjesson
Affiliation: Chalmers University of Technology, Gothenburg, Sweden
The society has become increasingly aware of the limited nature of fossil-fuels and the importance of sustainable sources of materials. The demand for replacing non-renewable products with bio-based products requires knowledge and tools on how to utilize the resources in a more effective and sustainable way. Cellulose and hemicellulose can be extracted from side products such as low-value waste water streams and crop residues that otherwise is burnt to give a small energy contribution. Chemical modification of the polysaccharides can be useful for finding new application areas for the biomaterials and from the extracted cellulose there are possibilities for production of nanocellulose. Nanocellulose has found interest in many application areas due to its many attributes. By chemical modification of the surface of nanocellulose, a better incorporation between filler and matrix in for example bio-composites could be achieved and in turn improved functionalities of the final material. The research focus is on chemical modification on biopolymers for improved or changed properties for use in new products but also the extraction of cellulose and hemicellulose from crop residues for the use of a, so far, undeveloped source.
Key words: Chemical modification; Extraction, Hemicellulose, Nanocellulose
- Production of low molecular weight cellulose II using supercritical water treatment
Authors: Jean Buffiere 1), Patrik Ahvenainen 2), Marc Borrega 1), and Herbert Sixta 1)
Corresponding author: Herbert Sixta
Affiliation: 1) Aalto University School of Chemical Technology, Department of Forest Products Technology, Espoo, Finland.
2) University of Helsinki, Department of Physics, Helsinki, Finland
Biomass, the main component of which is cellulose, is recognized as the most promising raw material for production of sustainable materials, fuels and chemicals in the future. However, the development of cellulose-based products has repeatedly been hindered by its recalcitrance towards deconstruction and hydrolysis, which leads to the necessary use of highly concentrated acid or high amounts of costly enzymes.
Supercritical water is high-temperature, pressurized water above its critical point (374 °C and 221 bar). These conditions trigger the fast, uncatalytic hydrolysis of cellulose as well as the dissolution of its low molecular weight polymer chains. Different treatment intensities result in various product yields and molar mass distributions; therefore, the supercritical water treatment is a convenient alternative pathway for the controlled, partial depolymerization of cellulose.
When applied to microcrystalline cellulose (MCC) this process yielded two solid cellulosic product fractions: an insoluble MCC-like residual fraction, and a second fraction that had dissolved and reprecipitated. The precipitated fraction had a gel-like structure and was composed of narrowly distributed, low molecular-weight cellulose II. These results open the way for the rapid and environmentally-friendly production of otherwise unavailable higher cello-oligosaccharides and low molecular weight cellulose II in water.
Key words: Cellulose hydrolysis, cello-oligosaccharides, cellulose II, supercritical water
- Millisecond Catalytic Pulp Bleaching
Author(s): Naveen Kumar Chenna and Tapani Vuorinen
Corresponding author: Naveen Kumar Chenna
Affiliation: Doctoral candidate, Aalto University, Finland.
Pulp bleaching is an oxidation process which oxidizes residual lignin, hexenuronic acid (HexA), chromophores and removes other contaminants in pulp which eventually increases the brightness of the pulp. Currently typical bleaching sequence requires several hours to achieve the full brightness of pulp and uses stoichiometric excess of oxidants. The new catalytic bleaching technology (Hcat) uses chlorammonium cation as the main bleaching agent which is formed in a reaction between hypochlorous acid and tertiary amine catalyst. The formed cation rapidly oxidizes lignin and HexA in 100ms. Catalytic stage works efficiently with any oxygen delignified hard/softwood pulp over wide range of pH and industrial temperatures. Hcat stage uses only quarter of the chemicals used in the present day best available bleaching technology. As oxidation reactions are very fast, there is no time for the over oxidation which prevents the formation of volatile organochlorine compounds and also Hcat stage drastically lowers the environmental load. Catalytic bleaching process has been successfully demonstrated in both the laboratory and pilot trials. This method has a strong potential to increase the profitability of the pulp mills by saving chemicals, reaction time and energy.
Key words: Catalytic bleaching, Tertiary amine, Hexenuronic acid, Residual lignin, Hypochlorous acid
- Overcoming obstacles to biofuel production: discovery of compounds enhancing rooting of propagated trees
Author(s): Siamsa M. Doyle, Thomas Vain, Adeline Rigal, Stéphanie Robert
Corresponding author: Stéphanie Robert
Affiliation: Umeå Plant Science Centre, Swedish University of Agricultural Sciences (SLU)
In forestry, genetic improvements of trees are limited by slow growth and long generation time. However, clonal propagation via rooting of shoot cuttings, can rapidly multiply commercially interesting genotypes. Poplar (Populus) is a tree of great economical and industrial importance in Sweden, used for pulp, timber and bioenergy, but improved genetic varieties are needed to enhance biofuel production. We aim to identify new agrochemicals that can be used both for research and industrial purposes. We identified synthetic hormone-like compounds in the model plant Arabidopsis by screening for chemicals active in the wild type but not in a mutant deficient in hormone signalling. We discovered two developmental regulators that increase adventitious and lateral rooting in Arabidopsis seedlings. These compounds also increase adventitious rooting in poplar cuttings, thereby significantly accelerating their propagation, without decreasing overall root length, which is in contrast to commercially available compounds currently used for stimulating rooting. We aim to utilize these compounds as research tools for understanding the cellular and molecular mechanisms of rooting, which will be invaluable to the forestry sector for future improvements to clonal propagation. Furthermore, these compounds are themselves powerful tools for improving industrial clonal propagation of poplar, thereby potentially accelerating biofuel production.
Key words: Poplar, clonal propagation, adventitious rooting, agrochemicals
- Single-step method for producing cellulose based nanocomposites with outstanding dispersion
Author(s): Shiyu Geng, Kristiina Oksman
Corresponding author: Kristiina Oksman
Affiliation: Division of Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-971 87 Luleå, Sweden
E-mail: firstname.lastname@example.org, email@example.com
Cellulose nanomaterials are promising as reinforcement in composites, which is attributed to their high mechanical properties, large interfacial area and biodegradability. However, obtaining good dispersion is challenging since nanomaterials tend to form aggregates and lose their merits. In this study we developed a single-step method based on in-situ polymerization, to produce cellulose nanocrystals reinforced polyvinyl acetate with good dispersion. Compared to normal nanocomposites prepared only by mechanical mixing, better dispersion of cellulose nanocrystals using this new method has been confirmed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Furthermore, mechanical testing showed that the in-situ nanocomposites with same cellulose content had higher strength and longer elongation at break compared to mechanically mixed nanocomposites. Crosslinking the cellulose and partially hydrolysed polyvinyl acetate with tetrahydroborate ions in aqueous dispersion, further improved the reinforcing efficiency. The cellulose based nanocomposites produced by in-situ polymerization are potential materials to replace fossil based polymers used in packaging and coating applications.
Key words: In-situ polymerization; Cellulose nanocrystals; Mechanical properties; Atomic force microscopy (AFM); Casting
- Advanced characterization of cellulose solutions
Author(s): Joel Hagman, Luigi Gentile, Christian Moestrup Jessen, Manja Behrens and Ulf Olsson
Corresponding author: Joel Hagman
Affiliation: Lund University
We have characterized microcrystalline cellulose (MCC) in dilute cold alkali (2 M NaOH(aq)) solutions using a combination of NMR, small angle X-ray (SAXS) and static light scattering (SLS). While the NMR data indicate that the cellulose is fully dissolved, the scattering data demonstrate the presence of large (>µm) cluster-like aggregates in solution, consistent with attractive cellulose-cellulose interactions. At 25 °C the solution structure remains unchanged on the time scale of weeks. However, upon heating the solutions above 35 °C additional aggregation occurs on the time scale of minutes. Decreasing or increasing the NaOH concentration away from the “optimum” 2 M also leads to additional aggregation. With these examples, I will show how scattering methods can be used to assess the quality of solvents for cellulose. I will also briefly show the ongoing work where correlations between solution and spun fibre are sought. The long term goal of the present research is to develop an environmentally friendly, sustainable and economically competitive production of high quality cellulose textile fibres. It is considered that controlling solution structure and cellulose interactions in the spin dope, as assessed by scattering experiments, is a very important part in the optimization of fibre spinning conditions.
Key words: MCC, Cellulose, Cold Alkali, NaOH, SAXS, SLS, NMR
- Cellulose nanofibril films as templates for functional membranes
Author(s): Minna Hakalahti 1), Andreas Mautner 2), Tuomas Hänninen 1), Eero Kontturi 3), Alexander Bismarck 2,4), Tekla Tammelin 1)
1) VTT Technical Research Centre of Finland Ltd
2) University of Vienna, Institute for Materials Chemistry & Research
3) Aalto University, School of Chemical Technology
4) Imperial College London, Polymer and Composite Engineering group
Corresponding author: Minna Hakalahti
Affiliation: VTT Technical Research Centre of Finland Ltd
Renewable and sustainable membrane systems are required in technological fields ranging from water purification to biosensors and analytics. Tunable membrane materials are demanded for such systems, as each application entails its own characteristic performance requirements. Wood-based cellulose nanofibrils are intriguing building blocks for such materials due to their large surface area, strong film-forming tendency and numerous reactive groups. Reactive groups on fibril and film surfaces can be used for customizing mechanical and surface characteristics of the membrane material by chemical modification, enabling their utilization as for example organic solvent nanofilters and ion capturing materials. In this work, TEMPO oxidized cellulosic nanofibrils were covalently bonded with poly(vinyl alcohol) to render water stable films with adjustable mechanical properties. Stimuli-responsive poly(N-isopropylacrylamide) was grafted in order to control the hydrophilic-hydrophobic balance and adhesion properties of the membrane. Film characterization performed using surface sensitive methods showed that grafting could be carried out effectively as a surface reaction, without affecting the morphological features of the film. The nanocellulosic film developed here offers a template for diverse chemical modifications and can be tailored to meet the requirements of membrane applications.
Key words: Cellulose nanofibrils, films, membranes, TEMPO oxidation, poly(N-isopropylacrylamide), stimuli-responsive polymers
- From forest-based industrial residue, to oxygen barrier coatings for packaging applications. An ecological approach to build high quality bio-based materials from waste
Author(s): Martha A. Herrera, Aji P. Mathew, Kristiina Oksman
Corresponding author: Martha A. Herrera
Affiliation: Luleå Tekniska Universitetet
More than half of the packaging materials used nowadays are made of petroleum-based polymers, because of their low cost, ease manufacturing and good barrier properties. However, they are highly contaminant and non-biodegradable materials, causing an increasing ecological problem. To reduce the environmental contamination caused by these non-biobased polymers, we have designed a system where nanocellulose are extracted from forest-based industrial residues, and used as coating on cellulose-based porous substrates. The final application of this study is the replacement of plastic packaging for paperboard coated with a nanocellulose barrier layer. Nanocellulose were successfully isolated from purified bioethanol residue by high-pressure homogenization. The nanocellulose had quality and properties comparable to nanocellulose obtained from commercially available microcrystalline cellulose. This nanocellulose was mixed with sorbitol and a cross-linker, and used to coat paperboard. The barrier properties were dramatically improved, reaching oxygen permeability below 1.9 mLμmday-1m-2kPa-1 and water vapour permeability below 0.6 gmmday-1m-2kPa-1. The nanocellulose coating with sorbitol resulted in better barrier properties than some petroleum-based polymers which are used as coating materials. These results indicate that nanocellulose isolated from industrial residues have great potential as green coatings, stimulating the research towards a more ecological and biobased approach to the packaging industry.
Key words: Nanocellulose, Industrial residues, Coatings, Barrier properties
- Cellulose based electrical insulation- advanced fibre engineering
Author(s): Rebecca Hollertz, Lars Wågberg
Corresponding author: Rebecca Hollertz
Affiliation: KTH, Royal Institute of Technology
Electrical energy generation and transmission will be increasingly vital to meet growing societal needs. An increased demand of electrical insulation materials with improved performance has evolved with the challenges associated with integration of renewable materials and the demand for increasing voltage levels in electrical systems. The major failures in oil-filled high voltage transformers, a key component in power transmission networks, are related to the insulation material and an improved insulating capability would provide increased reliability and efficiency. The scope of this interdisciplinary PhD-project is to utilize novel modification routes for wood-fibres, such as nano fibrillation and layer-by-layer adsorption to (1) investigate the influence of chemistry and morphology on relevant electrical phenomena and (2) improve the electrical insulating capability of wood-fibre based electrical insulation. These modification routes provide a diversified tool-box with possibilities to tailor the insulating and mechanical properties with methods relevant for our process and application. With a better understanding of the mechanisms responsible for failure of the components and with improved insulation capability the goal is to contribute to a competitive product and an efficient and sustainable power system by providing the possibility to increase transmission efficiency, decrease material consumption and outperform petroleum-based products.
Key words: Electrical insulation
- Environmental-friendly antibacterial fibres
Author(s): Josefin Illergård, Lars Wågberg, Monica Ek
Corresponding author: Josefin Illergård
Affiliation: KTH Fiber and Polymer Technology
One of the largest societal challenges is the increasing number of antibiotic-resistant bacteria. This development is not only driven by the overuse of antibiotics, but also of the steadily increasing use of antibacterial consumer products, not least the products containing silver.
But what if there was a better way to fight bacteria, that was safer, environmentally friendly and cheap? At KTH we made this possible, as we have developed antibacterial polyelectrolyte multilayers on cellulose fibres. In a water-based process, we make a permanent modification where no toxic pollutants are released, in contrast to e.g. materials with silver. The modified fibres works as a ‘bacteria-magnet’, which makes it excellent for e.g. dry wipes for both household and professional use. Our research has shown that the technique works on several types of fibres and products and offers new opportunities and increased competiveness to forest-based products.
We have a number of academic successes, including theses and scientific articles. Now we want to take our research into the ‘real’ world and make a commercialisation possible, which means new challenges. We hope to go through this journey in close cooperation with the industry, to get an accelerated development by combining the two worlds.
Key words: Antibacterial, multilayers, layer-by-layer, fiber functionalization
Author(s): Sana Jahanshahi-Anbuhi, Kevin Pennings, Vincent Leung, Meng Liu, Carmen Carrasquilla, Balamurali Kannan, Yingfu Li, Robert Pelton, John D. Brennan, and Carlos D. M. Filipe
Corresponding author: 1. Carlos D. M. Filipe, 2. John D. Brennan
Affiliation: Departments of (1) Chemical Engineering, and (2) Chemistry & Chemical Biology, McMaster University
E-mail: 1. firstname.lastname@example.org , 2. email@example.com
When enzyames, proteins, and in general labile bio-reagents are shipped around the world, they are shipped in ice. This is to preserve their activity since some of these molecules are fragile and are not able to withstand ambient conditions. Moreover, working with these fragile reagents mainly taking place only in equipped laboratories due to their high instability when either stored at room temperature or exposed to open air (oxygen). We have proposed a technology which in summary an inexpensive and simple method is suggested for room storage of labile reagents over long periods of time. This allows for a more convenient method of shipping the labile bio-reagents around the world without any extra-care. No refrigeration. No loss of chemical activity. No fancy tools. The technology we developed is expected to have significant public health applications.
The method features ready-to-use, water-soluble tablets made with pullulan, a natural, water-soluble polysaccharide. We have found that pullulan is an excellent natural material to make bioassay tablets containing labile reagents (bacteria, viruses, enzymes, proteins, functional nucleic acids and small molecules). Pullulan tablets provide exceptional protection for entrapped reagents against thermal denaturation or chemical modification. Tablet strategy also provides a general platform for carrying out bioassays with minimal steps and user intervention, which is ideal for resource-limited regions, particularly in the developing world.
Key words: Bioassays, Stability, Labile Reagents, Preservation, Pullulan, Tablet, Pill, Cold Chain
- Mesh size analysis of cellulose nanofibril hydrogels with solute exclusion and PFG-NMR spectroscopy
Author(s): Leila Jowkarderis, Theo G. M. van de Ven
Corresponding author: Leila Jowkarderis
Affiliation: Chemical Engineering, McGill University
The pore structure of TEMPO-mediated oxidized CNF hydrogels, chemically cross-linked with water-soluble diamines, is studied. Solute exclusion method and pulsed-field-gradient NMR are used to estimate the mesh size distribution in the gel network in its hydrated state. Dextran fractions with the nominal molecular weights in the range 10-2000 kDa are used as probes. The results show a non-uniform network structure, consisting of a group of large openings that contain about 50% of the water, and regions with a more compact structure and smaller mesh units that restrict the diffusivity of the dextran molecules. A biexponential model is proposed for the NMR echo amplitude decay due to the probe diffusion into the gel network. Typical single exponential model does not fit the experimental data when the probe molecular size is comparable to the network mesh size. The results obtained with NMR, using the proposed biexponential model, are in very good agreement with those determined with solute exclusion. Precise mesh size estimation with solute exclusion using pore models is subject to restrictions, and varies with the assumed pore geometry. The average mesh size obtained using spherical pore model, 35 nm, in the compact regions of the hydrogel, is in good agreement with the theoretical value in a network of rodlike particles. Neglecting the wall effects leads to underestimation of the mesh size with both techniques.
Key words: Cellulose nanofibril, Hydrogel, Mesh size, Solute exclusion, Self-diffusion, NMR
- Sugar production from lignocellulosic materials – A study of enzyme characteristics contributing to unproductive enzyme adsorption onto lignin
Author(s): Miriam Kellock, Jenni Rahikainen, Kaisa Marjamaa, Kristiina Kruus
Corresponding author: Miriam Kellock
Affiliation: VTT Technical Research Centre of Finland Ltd
Biorefineries aim at complete utilization of lignocellulosic biomass for high value speciality products and low value bulk products with minimal waste production. Lignocellulose from forestry and agricultural waste streams are potential raw materials for the production of fuels and chemicals through enzymatic hydrolysis and further conversions of the released sugars. The use of lignocellulosic biomass for chemical and fuel production will reduce our dependency on non-renewable resources and bring us towards a carbon neutral bio-economy. Enzymatic hydrolysis is still a major bottleneck in the utilization of lignocellulosic materials. Lignin is a major inhibitor that prevents enzyme action by unproductively binding enzymes and consequently limiting their action on carbohydrates. In addition, the soluble lignin-derived compounds can affect the enzyme activity. Enzyme properties such as the presence of a cellulose binding module (CBM) and surface hydrophobicity have been reported to affect enzyme adsorption onto lignin. Our study of the common enzymes involved in cellulose degradation show that the different enzymes have distinctive binding patterns onto lignin. Insight into the causes of unproductive enzyme adsorption onto lignin can provide guidelines for selecting or modifying enzymes to be less prone to the presence of lignin in hydrolysis conditions.
Key words: Lignocellulose, lignin, enzymatic hydrolysis, non-productive enzyme adsorption
- Pressurized hot water flow-through extraction of birch wood
Author(s): Petri Kilpeläinen, Sanna Hautala, Johanna Tanner, Veikko Kitunen, Andrey Pranovich, Hannu Ilvesniemi, Stefan Willför
Corresponding author: Petri Kilpeläinen
Affiliation: Natural Resources Institute Finland
Effective processes to fractionate the main compounds in biomass, such as wood, are a prerequisite for an effective biorefinery. Water is environmentally friendly and widely used in industry, which makes it a potential solvent also for forest biomass. At elevated temperatures over 100 °C, water can readily hydrolyse and dissolve hemicelluloses from biomass. Birch sawdust was extracted using pressurized hot water (PHWE) flow-through systems. The aim was to obtain polymeric, water-soluble hemicelluloses from birch sawdust using flow-through PHW extractions at both laboratory and pilot scale. Different extraction temperatures in the range 140 – 200 °C were evaluated to see the effect of temperature to the xylan yield.
The performance of the PHWE flow-through system was evaluated in the laboratory and the pilot scale using vessels with the same shape but different volumes, with the same relative water flow through the sawdust bed, and in the same extraction temperature. The PHWE system was successfully scaled up by a factor of 6000 from the laboratory to pilot scale and extractions performed equally well in both scales. The results show that a flow-through system can be further scaled up and used to extract water-soluble xylans from birch sawdust.
Key words: Pressurized hot water, Flow-through, Birch, Sawdust, Xylan
- Spruce wood fractionation process
Author(s): Ekaterina Korotkova, Andrey Pranovich, Stefan Willför
Corresponding author: Ekaterina Korotkova
Affiliation: Åbo Akademi University
The focus of this study was on the biorefinery process where first hemicelluloses are removed from spruce wood with pressurized hot water in polymeric form, after that lignin isolation is done as a next step, and at the same time cellulose is preserved from degradation as much as possible. First isolation of lignin with an Accelerated Solvent Extractor (Dionex ASE 350) and low concentration aqueous NaOH as a solvent was studied. Extraction was performed at 170°C for 4 hours total time, but different extraction sequences were studied: 1 cycle per 240 minutes static time (1×240 min), 2 cycles per 120 minutes static time (2×120 min), 4 cycles per 60 minutes static time (4×60 min), 6 cycles per 40 minutes static time (6×40 min), and 12 cycles per 20 minutes static time (12×20 min). It was found that higher alkali concentration allows extracting more lignin from spruce wood. The extraction sequence has great influence on the process – shorter extraction cycles extracted up to 10 times more lignin compared to longer ones. It was possible to extract up to 22.5% of the wood as lignin, which corresponds to 75% of the total lignin content in the wood. Effect of preliminary hot-water extraction of hemicelluloses on lignin isolation with alkali was investigated.
Key words: Lignin, Hemicelluloses, Spruce, Extraction, Accelerated Solvent Extractor
- Towards complete raw material utilisation
Author(s): Risto Korpinen and Pekka Saranpää
Corresponding author: Risto Korpinen
Affiliation: Natural Resources Institute Finland (Luke)
The aim of our work is to use renewable forest based biomasses which are harvested from sustainable sources. We develop green extraction, separation and purification techniques in order to obtain extractives, hemicellulose, lignin and cellulose from woody biomass and residues including process side streams. These constituents can be further processed into new products such as chemicals, biomaterials and fuels. One of the major aims is to achieve complete raw material utilisation and generation of zero waste. The fractionation and purification processes we are applying do not contain any toxic chemicals. Thus the products are free of harmful substances. The same raw material can also be used for converting into fractionation solvents such as water, supercritical CO2, ethanol and acetic acid which can be recycled.
Today forest industry is mainly producing timber, pulp, paper, tissue and board. Especially the global market for printing paper is decreasing significantly. Several paper machines have been shut down and consequently severe job cuts have taken place. To increase the profitability and to meet the growing demand of commodities made from renewable sources, forest industry should consider biorefining to be one of the most promising options. A complete new spectrum of forest based chemicals, materials and fuels could penetrate the market. This would eventually create completely new businesses, services and jobs benefiting the whole society.
Key words: Biomass, extraction, forest, renewable, sustainable
- Which genes allow a tree “to grow as a tree”? – Molecular regulation of vascular cambium
Author(s): Melis Kucukoglu, Jeanette Nilsson, Salma Chaabouni, Bo Zheng, Göran Sandberg and Ove Nilsson
Corresponding author: Melis Kucukoglu
Affiliation: Swedish University of Agricultural Sciences / Umeå Plant Science Centre
Wood is one of the most important natural resources serving mankind. It can be utilized as a source of energy, as raw material for paper and pulp production, or for construction purposes. Moreover, the polymers within the secondary cell walls of the woody biomass, such as cellulose, hemicelluloses and lignin, offer a massive pool of molecules to produce biofuels or other valuable chemicals in biorefinery applications.
Wood is generated through the activity of the vascular cambium, a secondary meristem that contains the vascular stem cells. The purpose of my graduate studies is to understand how the vascular cambium stem cell identity and activity is controlled on the molecular level. A deep understanding of the vascular cambium regulation holds a great significance because it determines the amount and type of wood that is produced within a plant. Consequently, this knowledge has the potential to be used as a tool to breed and genetically engineer trees with increased biomass production.
Our research strategy throughout this project is to employ RNAi-mediated down-regulation or ectopic over-expression of candidate regulatory genes in trees, mainly in Populus. Results indicate that manipulation of these genes affect a diversity of traits such as plant height, stem width, and leaf size/shape in trees.
Key words: Secondary development, vascular cambium, Populus, genetic engineering
- Innovative Timber Connections; The shear plate dowel connection
Author(s): Gustaf Larsson, Per-Johan Gustafsson, Erik Serrano, Roberto Crocetti
Corresponding author: Gustaf Larsson
Affiliation: Lund University, Division of Structural Mechanics
Despite the environmental friendliness of large timber structures compared to steel and concrete, the economic competitiveness is to a great extent governed by the properties and cost of the structural connections. The objective of this project is to develop an innovative connector design for large timber structures suitable for industrialized construction methods.
The shear plate dowel connection is a new design concept developed to achieve a high connection strength while maintaining easy on site assemblage. In comparison to connections commonly used today, the shear plate dowel connection can easily be designed to match the strength of the joined members and thus enabling more slender structures. The shear plate dowel connection is a type of adhesive lap joint with an intermediate rubber foil.
Full scale tests have been conducted together with Chinese researchers. The tests and analytical work suggests an ultimate load capacity increase by 150% by adding the rubber foil, while larger increase in service state. The flexible design allows the concept to be used in a variety of connection types in timber engineering, e.g. truss nodes or hinges at arch springing points.
Key words: large timber structures, shear plate dowel connection, numerical model
- Environmentally-friendly surface modification of TEMPO-oxidized cellulose nanofibrils by an amine-terminated compound: A model study
Author(s): Nathalie Lavoine, Julien Bras, Tsuguyuki Saito, and Akira Isogai
Corresponding author: Nathalie Lavoine
Affiliation: The University of Tokyo
This study focuses on the surface modification of TEMPO-oxidized cellulose nanofibrils (TOCNs) by an amine-terminated model compound, 3-Amino-1-Propanol (3AP), using two environmentally-friendly strategies.
The first strategy lies in the grafting of 3AP onto TOCNs using an amide coupling reaction, i.e. by formation of amide bonds. The second strategy consists in the coupling of 3AP onto TOCNs through ionic bonds. Both these reactions were performed in aqueous medium at room temperature.
Formation of either ionic or covalent bonds was investigated and compared using characterization techniques such as infra-red spectroscopy, elemental analysis, and thermogravimetric analysis.
Covalently-bound samples showed a better thermal stability than samples linked through ionic bonds, whereas a grafting yield of only 60 % was achieved for the first strategy against 100 % for the second one. Despite a low degradation temperature of 3AP (< 100 °C), the presence of amide bonds prevented it from being degraded below 200 °C, and led thus to a better thermal stability of the modified-TOCN samples.
These preliminary, but promising results pave the way for the development of new functional materials with good thermal stability.
Key words: TEMPO-oxidized cellulose nanofibrils, TOCNs, amine coupling reaction, ionic bonds, 3-Amino-1-Propanol, thermal stability
- Novel wood biorefinery concept based on ?-valerolactone (GVL)/water fractionation
Author(s): Huy Quang Le, Yibo Ma, Marc Borrega, Herbert Sixta
Corresponding author: Huy Quang Le
Affiliation: Aalto University
The production of materials, chemicals and energy is currently almost exclusively dependent on the refining of oil. Global warming and limited availability of fossil resources has stimulated the research for alternative processes employing renewable resources. In this context, biorefinery emerges as basis for a sustainable bio-economy. We hereby introduce an organosolv fractionation process where wood is treated at elevated temperature in a binary mixture of ?-valerolactone (GVL) and water for effective and selective deconstruction into its principal components: cellulose, hemicellulose and lignin. The pulp fraction is characterized by high-purity cellulose, which allows the manufacture of a viscose-grade dissolving pulp without any further refinement. The pulp has been successfully converted to high-tenacity regenerated cellulose fibers of the Lyocell-type. The hemicelluloses fraction is targeted for catalytic conversion to furanic platform chemicals or to GVL. The sulfur-free lignin fraction, readily separable from the spent liquor, can be used as fuel or further upgraded to chemicals or can be employed as a matrix polymer for biocomposites production. The suggested process enables the full conversion of wood biopolymers into valuable products in an environmentally friendly manner: the process is sulfur-free and the high pulp bleachability allows an effective Total-Chlorine-Free (TCF) bleaching sequence.
Key words: Biorefinery, gamma-valerolactone, organosolv fractionation, dissolving pulp
- Multifunctional materials for environmental applications based on TEMPO-oxidized cellulose nanofibers (TOCNF)
Author(s): Peng Liu, Aji P. Mathew and Kristiina Oksman
Corresponding author: Peng Liu
Affiliation: Luleå University of Technology
Cellulose nanocrystals and fibers isolated from bioresources or residues are being used as functional additives in many applications during the past decades, recently these nanocrystals and fibers in its native form or modified form have been used as functional component in water purification processes. TEMPO oxidization applied to cellulose nanofibers can dramatically improve the Cu(II) adsorption capacity (around 10-fold) by introduction of carboxylate groups on the surface. Its Cu(II) adsorption behavior is more competitive compared to other popular adsorbents in the market, such as activated carbon, carbon nanotubes and nanoclay.
Meanwhile, evaluation of the TOCNF after Cu(II) adsorption revealed interesting nanostructured clusters that were attributable to Cu(II) ions first being adsorbed by carboxylate groups on the TOCNF and subsequently being reduced and self-assembled to Cu(0) nanoparticles (NPs) or copper oxide NPs by microprecipitation. Therefore, TOCNF after Cu(II) removal from aqueous medium are likely to be equipped with copper NPs or their oxides with antibacterial property and be reused as biocides or a variety of value-added products.
Key words: TEMPO, cellulose nanofibers, copper removal, nanoparticles, adsorption, antibacterial property, water purification
- Making trees sustainable packaging materials
Author(s): Veronica Lopez Duran, Per Larsson, Lars Wågberg
Corresponding author: Veronica Lopez Duran
Affiliation: Royal Institute of Technology KTH
Packaging materials help us protect most of our goods for storage and transport. Problem with most of the current packaging materials is that they are made of oil-based components, making them among other things non-renewable. Furthermore, Swedish forest industry has faced significantly decreased demand of paper for the first time in years, which creates a need for the development of new materials that can be mass produced. In other words, development of cellulose-based materials, not only allow a more sustainable society, it also creates new valuable products for the forest industry. However, in order to make cellulose competitive against oil-based materials its properties (e.g. ductility) must be improved.
We have shown that it is possible to produce ductile wood fibres through a two-step chemical reaction. First, periodate oxidation is performed to open the C2-C3 bond of the glucopyranose units and produce dialdehyde cellulose. The second step consists of reduction of the formed aldehydes with sodium borohydride to produce dialcohol cellulose. To this date, the reason behind the ductility in dialcohol cellulose is not fully understood. In an attempt to unveil the relationship between the flexibility and the chemical structure of cellulose, we have produced cellulose derivatives by using in different combinations TEMPO-mediated oxidation, periodate oxidation, chlorite oxidation and borohydride reduction.
Key words: Chemical modification, TEMPO-mediated oxidation, Periodate oxidation, Chlorite oxidation, Borohydride reduction, Tensile strength, Strain-at-break
- Flexible 3D Energy Storage Devices from Wood-Based Templates
Author(s): Andrew Marais, Gustav Nyström, Erdem Karabulut, Lars Wågberg, Yi Cui, Mahiar Hamedi
Corresponding author: Andrew Marais
Affiliation: KTH Royal Institute of Technology
Traditional cellulose based materials like paper have been produced for decades and are ubiquitous in our everyday life. However, the growing environmental awareness associated with the economic restrictions and the increasing use of electronic technologies has pushed cellulose-related industries towards the development of a new generation of materials.
The overall objective of my research has been to develop new functional nanomaterials from cellulose. A new class of porous cellulosic materials was developed by freeze-drying and crosslinking a cellulose nanofibrils (CNF) gel into a wet-stable and shape-recovery aerogel. The porous material can be functionalized by Layer-by-Layer self-assembly (LbL), a versatile method in which multilayer thin films are deposited on a surface in order to provide specific properties to the material. The CNF aerogel can therefore be envisioned as a platform for functional materials, with applications in construction, flame-retardant, or biomedical materials to mention a few. To demonstrate one of the numerous possibilities, three dimensional energy storage devices were designed and built by LbL deposition of active materials into the aerogel, used as a template. The devices are flexible, compressible, and bendable, opening up numerous possibilities in future flexible electronics applications, where cellulose could therefore be used as a template.
Key words: Cellulose Nanofibrils, Aerogels, Layer-by-Layer, Carbon Nanotubes, Energy Storage Devices
- Lightweight Structural Composites from Fibre-based Materials
Author(s): Amanda Mattsson
Corresponding author: Amanda Mattsson
Affiliation: Mid Sweden University
A grand challenge for the forest products industry is to create a new product platform that will enable the industry’s true transformation. Our project aims at developing lightweight, structural composites from fibre-based materials. Lightweight composites are an emerging field, particularly crucial for energy-efficient, environmentally friendly transportation systems (automobiles, trains, boats, wheel chairs, bicycles). Fibre is an ideal material for this purpose in terms of its high specific strength (strength/weight), bio-renewability, convertibility, and outstanding production efficiency.
However, the biggest challenge is that product designers don’t consider the material as “reliable” or “durable” for serious structural applications. The reliability and durability are difficult properties to evaluate, unlike strength properties, but most important in real end-use.
We have recently developed systematic methods for evaluating these performance parameters by using time-dependent, stochastic failure theories.
We performed Monte Carlo simulations of fibre network failures to understand how the fibre properties and network structures control reliability and durability, experimentally determined these properties, and benchmarked with data for carbon fibres, graphite fibres, and Kevlar. The preliminary results are encouraging: Our materials are comparable to those fibres used for advanced composites.
The above results indicate that fibre networks are actually one of the most promising materials for lightweight composites, such as corrugated and honeycomb sandwich. Our target is to explore even lighter structures, e.g., truss sandwich, made from our fibres.
Key words: Lightweight composites, fibre-based materials, time-dependency, stochastic failure, truss sandwich
- Interpenetrating Polymer Networks (IPN) hydrogels based on nanocellulose for soft tissue engineering
Author(s): Narges Naseri, Aji P. Mathew, Kristiina Oksman
Corresponding author: Narges Naseri
Affiliation: Luleå University of Technology
Currently, the use of bio-based nanomaterials as reinforcements has attracted much interest especially in medical applications due to their cytocompatibility, good mechanical performance, good moisture stability, hydrophilicity and ability to form porous structure. In tissue engineering, development of materials, which positively interact with tissues, is very important. In this regard, hydrogels composed of three-dimensional polymeric networks, have become more attractive materials due to their ability to absorb high water content and swell without losing their structural integrity. Moreover, hydrogels need to provide physico-mechanical support for cell growth, proliferation and new tissue formation. However, their low mechanical properties have found one drawback. We attempted a novel technology to design double crosslinked interpenetrating polymer networks (IPN) of nanocellulose-based hydrogels of sodium alginate and gelatin with potential use in soft tissue engineering. Advanced, innovative fully bio-based porous IPN scaffolds have been prepared via freeze-drying and crosslinked using calcium chloride and genipin. Highly porous structure, which is considered beneficial for cells attachment and extracellular matrix (ECM) production was obtained. The addition of nanocellulose and crosslinking decreased the moisture uptake while increased the compression modulus. The study showed the potential use of these hydrogels based on nanocellulose in cartilage application.
Key words: IPN hydrogel, nanocellulose, porous structure, mechanical performances, cytocompatibility, soft tissue engineering
- Characterizing Influence of Laminate Characteristics on Elastic Properties of Cross Laminated Timber
Author(s): Jan Niederwestberg & Dr. Ying-Hei Chui
Corresponding author: Jan Niederwestberg
Affiliation: University of New Brunswick
Cross laminated timber (CLT) is an engineered wood product made from layers of lumber. The layers are glued together at 90 degrees to adjacent layers, and form a stiff and strong panel structure. The stiffness properties of CLT are dependent on its build-up and the properties of its layers. Layer properties are related to their laminates’ stiffness properties. Parameters such as lumber growth ring orientation and laminate aspect-ratio (width to thickness), and the presence of edge-gluing affect the mechanical performance of single layers, but their influence is rather unknown.
Stiffness properties of wooden laminates were evaluated. The laminates were grouped based on stiffness properties and growth ring orientation. “Homogeneous” single-layer panels with different aspect-ratios and edge-gluing type were formed. Stiffness properties of the panels were evaluated in laboratory tests. The results of the single-layer tests were compared with the properties of the corresponding laminates and with finite element calculations. CLT panels were formed from the single-layers and were evaluated in laboratory tests. The results of the CLT panel tests were compared with results from finite element calculations using the corresponding single-layer properties.
It can be seen that a selection of certain laminate characteristics has a beneficial influence on the stiffness performance of single-layers and overall CLT.
Key words: Cross Laminated Timber (CLT), Modal Testing, Elastic Properties, Laminate Characteristics
- Silver birch (Betula pendula): a novel model for forest tree genetics
Author(s): Kaisa Nieminen 1), Juan Alonso Serra 2), Juha Immanen 2), Omid Mohammadi 2), Pezhman Safdari 2), Jarkko Salojärvi2 and Ykä Helariutta 2,3)
Corresponding author: Kaisa Nieminen
1) Natural Resources Institute Finland (Luke)
2) University of Helsinki
3 ) University of Cambridge
The aim of our research is to understand molecular mechanisms controlling tree development. We explore natural variation in forest trees to identify novel genetic regulators of wood production and composition. Our model is an important forestry tree, silver birch, whose small diploid genome is being sequenced. Birch has both male and female flowers at the same tree, and already young seedlings can be induced to flower. This brings the power of inbreeding and short generation times into tree genetics, enabling exploitation of advanced crossing schemes for genetic analyses. With birch as our model, our project represents a novel approach in tree genetics with potential for groundbreaking insights into tree development. Besides its fascinating basic science aspect (what makes a tree a tree?), this knowledge has immense applied value for forest industry. Detailed knowledge about the regulatory mechanisms controlling tree traits will provide us tools for the domestication of forest trees. As wood represents a renewable source of lignocellulosic biomass, with potential for conversion into timber, pulp, fuels, energy, and value-added chemicals, improving its composition and boosting its efficient production in commercial forests is essential for sustainable management of natural resources.
Key words: Tree development, wood production, forest tree genetics
- Colloidal Interactions in Nanocellulose Systems
Author(s): Malin Nordenström and Lars Wågberg
Corresponding author: Malin Nordenström
Affiliation: KTH Royal Institute of Technology
Cellulose nanofibrils (CNF) possess properties that are highly desirable in many material applications. They are produced from renewable resources, have high aspect ratio, nm size and high stiffness and strength, just to name a few. However, nanocellulose materials are commonly formed from dilute aqueous dispersions and as the concentration is increased the nanofibrils have a strong tendency to form transparent gels at very low solids concentration and to irreversibly aggregate as the concentration is increased even further. The final mechanical properties of the materials made from CNF are strongly dependent on the distribution of the nanoparticles within the materials and therefore, aggregation must be prevented in order to maximize the benefits of the excellent properties of nanofibrils.
To achieve control of the aggregation in nanofibrils systems it is crucial to have an understanding of its colloidal behaviour. In this project we study the colloidal stability of nanocellulose dispersions, and how the stability is influenced by factors such as chemical environment, particle concentration and charge, and choice of counterion to the charges of the CNF. The goal is to use the results collected from the experiments to formulate new models that can describe the colloidal behaviour of cellulose nanofibrils.
Key words: Nanocellulose, colloidal interactions, dispersion, aggregation, counterion
- Added value materials from glycolic acid via sugar platform
Author(s): Leena Nurmi, Thomas Gädda, Minni Pirttimaa, Ali Harlin, Peter Richard, Outi Koivistoinen, Joosu Kuivanen
Corresponding author: Leena Nurmi
Affiliation: VTT Technical Research Centre of Finland
Poly(glycolic acid) (PGA) is a strong, biodegradable material with exceptionally high barrier against oxygen, and is therefore a potential material to be applied e.g. in packaging as barrier layer. However, the very high cost of the material has currently limited its use to marginal, mainly biomedical applications. The value chain to economically viable, bio-based PGA can potentially start from lignocellulosic carbohydrates, which after hydrolysis are converted to glycolic acid by fermentation, and further polymerized to PGA – thus providing a high-value product concept for future forest biorefineries. Several steps in such value chain have been evaluated in our studies, both experimentally and with techno-economic calculations.
Currently, glycolic acid is produced industrially only from petroleum based resources. Recently, biotechnological routes for glycolic acid production have emerged, including method developed at VTT based on genetically modified eukaryotic microbes. The engineered microorganisms have shown potential for utilization of both hexose and pentose sugars as well as the C2 substrates acetate and ethanol as possible carbon sources.
Furthermore, industrial scale polymerization of glycolic acid is currently conducted by ring-opening polymerization of glycolide, which first needs to be produced from glycolic acid in a rather complicated process. We have investigated an alternative process involving direct glycolic acid polycondensation followed by chain-extension in the preparation of high molecular weight PGA polymer. Significant cost reduction potential was calculated for this alternative process. The molecular weight, mechanical strength, thermal properties, and barrier properties were tested for polymers produced both in laboratory and pilot scale, and were in many aspects found to be on a comparable level to current commercial PGA. The bio-based value chain starting from sugar was estimated to allow PGA production at <4€/kg, which would allow application as a barrier layer in packaging.
Key words: Biopolymers, sugar platform, glycolic acid, poly(glycolic acid), barrier materials
- Solubility and Precipitation of Lignin in Aqueous Media
Author(s): Tor Sewring, Weizhen Zhu, Maria Sedin, Hans Theliander
Corresponding author: Tor Sewring
Affiliation: Chalmers University of Technology
The knowledge regarding the fundamental mechanisms governing the solubility and precipitation of lignin in aqueous solutions is currently scares. The importance of understanding those mechanisms is, however, undoubtedly high; in particular in process steps in a conventional pulp mill. The solubility is important for the yield of delignification during cooking; the extraction of lignin in the washing-stage of the pulp; and the efficiency of pulp bleaching-stages. However, the relevance of understanding the solubility and precipitation of lignin on a fundamental basis does not end at the conventional pulp mill, but will also be crucial in future integrated pulp production and forest-based biorefineries. Fundamental knowledge regarding the solubility and precipitation will play a key-role in efficient extraction of lignin from wood tissue and in separation technologies based on precipitation of lignin from process streams. In the literature some few works can be found on the solubility/stability of lignin macromolecules in aqueous solutions. However, the detailed mechanisms are far from well understood. One important mechanism is the balance between attractive and repulsive forces between lignin macromolecules, however forces between lignin molecules and other macro-components present in a liquid such as wood tissue, xylan and glucomannans, could also be of importance. The protonation/deprotonation equilibrium of phenolic groups on kraft lignin at alkaline conditions has been targeted as a key-mechanism related to the electrostatic repulsive forces. Due to this, the first study in this research project was focused on the deprotonation degree of phenolic groups on kraft lignin in black liquor; which has been theoretically investigated and compared with previous experimental precipitation data at various industrially relevant conditions.
Key words: kraft lignin, solubility/precipitation, phenolic groups, deprotonation degree
- Transparent Films Prepared from Functionalized Cellulose Macrofibers
Author(s): Goeun Sim, Yanqing Liu and Theo van de Ven
Corresponding author: Theo van de Ven
Affiliation: McGill University
E-mail: Goeun.firstname.lastname@example.org , Theo.email@example.com
Novel, transparent, cellulose films were made from macrofibers that are treated by a single step chemistry without applying any mechanical treatments. Partially carboxymethylated pulp fibers (CMF) exhibit a wide range of properties depending on the degree of substitution (DS), pH, and drying conditions. With an increase in the DS, films prepared from CMF show increased strength, toughness, transparency, water absorbency, and gas barrier properties. As highly swollen CMF create intrinsic water pockets within the fiber walls, they can function as superabsorbent materials by absorbing water up to 300 times their own weight. Tensile strength and Young’s modulus of CMF films at DS 0.45 are comparable to those prepared from TEMPO-oxidized cellulose nanofibers (TOCN) which require multiple chemical and mechanical processing steps. The oxygen transmission rates of CMF films are in between those of cellophane and TOCN films. When the CMF counter ions (Na-CMF) are replaced by hydrogen (H-CMF), H-CMF films no longer display superabsorbency but show significantly increased wet strength. No obvious changes in transparency nor tensile strength were observed between H-CMF and Na-CMF films. Drying conditions mainly affect the physical appearance of CMF, where highly transparent CMF films can only be prepared by effectively and completely collapsing their swollen structures. CMF films can be potentially used in many fields of applications including disappearing packaging, wound dressing, and moisture sensing.
Key words: Carboxymethylcellulose, superabsorbent fibers, transparent films
- Influence of the flexibility and dimensions of nanocelluloses on flow properties of their aqueous dispersions
Author(s): Reina Tanaka, Tsuguyuki Saito, Hiromasa Hondo, Akira Isogai
Corresponding author: Reina Tanaka
Affiliation: The University of Tokyo
The influence of the flexibility and dimensions of nanocelluloses on flow properties of their dispersions was investigated by experimental and theoretical approaches. Three types of rod-like nanocrystalline celluloses (NCCs) with the aspect ratios p of 23‒77 and four types of spaghetti-like nanofibrillated celluloses (NFCs) with those of 103‒376 were used as nanocellulose samples. Both of the NCCs and NFCs were prepared as dispersions in water. The experimental intrinsic viscosity [η] of the nanocellulose dispersions was determined by shear viscosity measurement. The theoretical [η] was calculated using an equation for rotational motions of rigid rods and then compared with the experimental [η]. As the aspect ratios of the nanocelluloses increased, they became more flexible and their dispersions had higher viscosity. Regardless of the flexibility and dimensions of the nanocelluloses, the [η] values of their dispersions were expressed as a function of solely their p values. The relationship was shown as ρ[η] = 0.15 × p1.9, where ρ is the density of the nanocellulose.
Key words: nanocellulose, flexibility, viscosity, aspect ratio
- Fibre Yarns from Pulp Dispersed in Deep Eutectic Solvent Dope
Author(s): Tiia-Maria Tenhunen, Minna Hakalahti, Arto Salminen, Jarmo Kouko, Jaakko Pere, Tiina Härkäsalmi, Ali Harlin, Tuomas Hänninen
Corresponding author: Tiia-Maria Tenhunen
Affiliation: VTT Technical Research Centre of Finland Ltd.
Recent trend in the field of bioeconomy has been an increased interest in renewable wood-based materials to be used in novel application areas. Ability to use native cellulose without dissolution in yarns would decrease the amount of processing needed and intrinsic properties of cellulose I could be utilized in a new way.
In this study, a novel method for fibre yarn manufacturing from pulp fibres is presented. Deep eutectic solvent (DES) composed of choline chloride and urea is used as a swelling agent and rheological modifier in order to produce water-stable fibre yarns from wood pulps. Gel-like suspension is formed by applying heat and mixing, but no dissolution of cellulose occurs in the process. Polyacrylic acid has been used as an additive for enable heat initiated crosslinking and water stability. The fibre yarns produced are stable in water, porous and have relatively good mechanical properties. The materials used in the process are all recyclable and reusable. The process shows also great potential for up-scaled production. Fabrics, geo- and agrotextiles, composite reinforcements, disposable textiles, and all-cellulose multicomponent structures can be identified as potential applications for the fibre yarns.
Key words: Fibre yarn, pulp, deep eutectic solvent, polyacrylic acid