Browsing by Author "Virtanen, Tommi"

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  • Combining Rigid Cellulose Nanocrystals and Soft Silk Proteins: Revealing Interactions and Alignment in Shear
    (2023-07-17) Leppänen, Ilona; Arola, Suvi; King, Alistair W.T.; Unger, Miriam; Stadler, Hartmut; Nissen, Gry Sofie; Zborowski, Charlotte; Virtanen, Tommi; Salmela, Juha; Setälä, Harri; Lésage, Stephanie; Österberg, Monika; Tammelin, Tekla
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Natural materials, such as silk and cellulose, have an inspiring set of properties, which have evolved over hundreds of millions of years. In this study, cellulose nanocrystals (CNCs) and regenerated silk fibroin (RSF) are combined to evaluate their suitability for filament formation. This is assessed by tuning and characterizing the interactions between these two materials and finally by studying the alignment of the mixtures under shear. To modify the interactions between CNCs and silk, CNCs with varying surface functionalities (sulfate and/or aminosilane groups) are used. The interactions and compatibility of the two components are investigated using quartz crystal microbalance with dissipation monitoring (QCM-D) and photothermal atomic force microscopy (AFM-IR), which show that ionic interactions induce sufficient binding between the two components. Then, the alignment of the CNC and silk mixtures is evaluated by shear-induced polarized light imaging, which indicates that silk can orientate with the CNCs when not covalently bound. Finally, the potential of the materials for filament formation is tentatively demonstrated using an industrial dry-spinning environment, where CNCs are expected to bring order and alignment, whereas RSF provides soft and more mobile regions to further facilitate the alignment of the final filament structure.
  • Creaming Layers of Nanocellulose Stabilized Water-Based Polystyrene: High-Solids Emulsions for 3D Printing
    (2021-09-28) Gestranius, Marie; Kontturi, Katri S.; Mikkelson, Atte; Virtanen, Tommi; Schirp, Claudia; Cranston, Emily D.; Kontturi, Eero; Tammelin, Tekla
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Oil-in-water emulsions stabilized using cellulose nanofibrils (CNF) form extremely stable and high-volume creaming layers which do not coalesce over extended periods of time. The stability is a result of the synergistic action of Pickering stabilization and the formation of a CNF percolation network in the continuous phase. The use of methyl cellulose (MC) as a co-emulsifier together with CNF further increases the viscosity of the system and is known to affect the droplet size distribution of the formed emulsion. Here, we utilize these highly stable creaming layer systems for in situ polymerization of styrene with the aim to prepare an emulsion-based dope for additive manufacturing. We show that the approach exploiting the creaming layer enables the effortless water removal yielding a paste-like material consisting of polystyrene beads decorated with CNF and MC. Further, we report comprehensive characterization that reveals the properties and the performance of the creaming layer. Solid-state NMR measurements confirmed the successful polymerization taking place inside the nanocellulosic network, and size exclusion chromatography revealed average molecular weight (Mw) of polystyrene as approximately 700,000 Da. Moreover, the amount of the leftover monomer was found to be less than 1% as detected by gas chromatography. The dry solids content of the paste was ∼20% which is a significant increase compared to the solids content of the original CNF dispersion (1.7 wt%). The shrinkage of the CNF, MC and polystyrene structures upon drying—an often-faced challenge—was found to be acceptable for this composite containing highly hygroscopic biobased materials. At best, the two dimensional shrinkage was no more than ca. 20% which is significantly lower than the shrinkage of pure CNF being as high as 50%. The paste, which is a composite of biobased materials and a synthetic polymer, was demonstrated in direct-ink-writing to print small objects. With further optimization of the formulation, we find the emulsion templating approach as a promising route to prepare composite materials.
  • Cyclodextrin-Functionalized Fiber Yarns Spun from Deep Eutectic Cellulose Solutions for Nonspecific Hormone Capture in Aqueous Matrices
    (2018-02-12) Orelma, Hannes; Virtanen, Tommi; Spoljaric, Steven; Lehmonen, Jani; Seppälä, Jukka; Rojas, Orlando J.; Harlin, Ali
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A wood based yarn platform for capturing pharmaceutical molecules from water was developed. Cellulose fiber yarns were modified with cyclodextrins, and the capture of 17α-ethinyl estradiol (EE2), a synthetic estrogen hormone used as contraceptive, from water was tested. The yarns were prepared by spinning a deep eutectic solution (DES) of cellulose in choline chloride-urea. Despite their high porosity and water sorption capacity (5 g/g), the spun fiber yarns displayed high wet strength, up to 60% of that recorded in dry condition (128 MPa with 17% strain at break). Cyclodextrin irreversible attachment on the yarns was achieved with adsorbed chitosan and the conjugation reactions and capture of EE2 by the cyclodextrin-modified cellulose were confirmed via online detection with Surface Plasmon Resonance (SPR). The facile synthesis of the bioactive yarns and EE2 binding capacity from aqueous matrices (as high as 2.5 mg/g) indicate excellent prospects for inexpensive platforms in disposable affinity filtration. The study presents a strategy to produce a wood fiber based yarn to be used as a platform for human and veterinary pharmaceutical hormone capture.
  • The effect of the pyrolysis temperature and biomass type on the biocarbons characteristics
    (2024-04-22) Iurchenkova, Anna; Kobets, Anna; Ahaliabadeh, Zahra; Kozir, Janez; Laakso, Ekaterina; Virtanen, Tommi; Siipola, Virpi; Lahtinen, Jouko; Kallio, Tanja
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The conversion of biomass and natural wastes into carbon-based materials for various applications such as catalysts and energy-related materials is a fascinating and sustainable approach emerged during recent years. Precursor nature and characteristics are complex, hence, their effect on the properties of resulting materials is still unclear. In this work, we have investigated the effect of different precursors and pyrolysis temperature on the properties of produced carbon materials and their potential application as negative electrode materials in Li-ion batteries. Three biomasses, lignocellulosic brewery spent grain from a local brewery, catechol-rich lignin and tannins, were selected for investigations. We show that such end-product carbon characteristic as functional and elemental composition, porosity, specific surface area, defectiveness level, and morphology strictly depend on the precursor composition, chemical structure, and pyrolysis temperature. The electrochemical characteristics of produced carbon materials correlate with the characteristics of the produced materials. A higher pyrolysis temperature is shown to be favourable for production of carbon material for the Li-ion battery application in terms of both specific capacity and long-term cycling stability.
  • Kyselytutkimus laatukustannuslaskennan nykytilasta Suomessa
    (2000) Virtanen, Tommi
     School of Business | Master's thesis
  • Phenol-formaldehyde resins with suitable bonding strength synthesized from "less-reactive" hardwood lignin fractions
    (2020-02-01) Lourençon, Tainise V.; Alakurtti, Sami; Virtanen, Tommi; Jääskeläinen, Anna Stiina; Liitiä, Tiina; Hughes, Mark; Magalhães, Washington L.E.; Muniz, Graciela I.B.; Tamminen, Tarja
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The substitution of phenol by lignin in phenol-formaldehyde (PF) resins is one of the most promising end uses of lignin valorization. Lignin from grasses and softwood has been the focus of the studies in this field as they present a higher number of theoretical reactive sites for resin synthesis. Herein we examined the composition and chemical reactivity of "less-reactive" hardwood lignin fractions and their performance in PF resins, synthesized by substituting 50 wt% of the phenol with lignin. Before resin synthesis, the samples were hydroxymethylated and the maximum formaldehyde consumption was recorded. By doing so, we observed that hardwood fractions consumed formaldehyde close to the theoretical calculation, whereas the reference softwood lignin consumed only about of the theoretical value. In the resin synthesis, we added formaldehyde to the formulation according to the measured maximum formaldehyde consumption. Thus, low values of free formaldehyde in lignin-PF (LPF) resins were achieved (<0.23%). Moreover, the resin bonding strength displayed similar performance irrespective of whether the LPF resins were made with softwood or hardwood lignin (range of 3.4-4.8 N mm-2 at 150°C and 45-480 s of press time). Furthermore, we concluded that hardwood kraft lignins present no disadvantage compared to softwood lignins in PF resin applications, which have significant practical implications.
  • Understanding the interactions of cellulose fibres and deep eutectic solvent of choline chloride and urea
    (2018-01-01) Tenhunen, Tiia Maria; Lewandowska, Anna E.; Orelma, Hannes; Johansson, Leena Sisko; Virtanen, Tommi; Harlin, Ali; Österberg, Monika; Eichhorn, Stephen J.; Tammelin, Tekla
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A deep eutectic solvent composed of choline chloride (ChCl) and urea has been recently introduced as a promising cellulose compatible medium that enables e.g. fibre spinning. This paper clarifies the influence of such a solvent system on the structure and chemical composition of the cellulosic pulp fibres. Special emphasis was placed on the probable alterations of the chemical composition due to the dissolution of the fibre components and/or due to the chemical derivatisation taking place during the DES treatment. Possible changes in fibre morphology were studied with atomic force microscopy and scanning electron microscopy. Chemical compositions of pulp fibres were determined from the carbohydrate content, and by analysing the elemental content. Detailed structural characterisation of the fibres was carried out using spectroscopic methods; namely X-Ray Photoelectron Spectroscopy, solid state Nuclear Magnetic Resonance and Raman Spectroscopy. No changes with respect to fibre morphology were revealed and negligible changes in the carbohydrate composition were noted. The most significant change was related to the nitrogen content of the pulp after the DES treatment. Comprehensive examination using spectroscopic methods revealed that the nitrogen originated from strongly bound ChCl residuals that could not be removed with a mild ethanol washing procedure. According to Raman spectroscopic data and methylene blue adsorption tests, the cationic groups of ChCl seems to be attached to the anionic groups of pulp by electrostatic forces. These findings will facilitate the efficient utilisation of DES as a cellulose compatible medium without significantly affecting the native fibre structure.