[diss] Kemian tekniikan korkeakoulu / CHEM

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2-Dimensional Assembly of Cellulose-Based Materials
(2016) Niinivaara, Elina
School of Chemical Technology | Doctoral dissertation (article-based)
The objective of this thesis was to systematically investigate the two dimensional assembly of cellulose-based materials and the two dimensional response to various external stimuli. The motivation of studying such materials is the ever increasing trend in materials science to substitute synthetic polymers for greener materials. Studies such as the one presented here are essential to understand the fundamental behaviours and characteristics of bio-based polymers and to be able to utilize them in new functional materials. Trimethylsilyl cellulose (TMSC), cellulose triacetate (CTA), cellulose acetate propionate (CAP) and cellulose acetate butyrate (CAB) were extensively studied by means of Langmuir-Schaefer deposition. The formation of nanostructures on the surface of solid substrates as a result of monolayer transfer from the air/water interface was investigated using substrates of varying total surface free energy. It was established that for TMSC, a decrease in substrate surface energy resulted in progressive dewetting of the transferred film, which eventually led to the formation of dendritic fractals. A similar pattern was not detected in the films of CTA, CAP and CAB however, it was found that the acetate and residual hydroxyl group content of the cellulose esters played a key role in the morphologies of the ultrathin films. The morphology of the cellulose derivative films could be tuned by regeneration, exposure to water or by altering film deposition surface pressure. The behaviour of the cellulose esters upon compression at the air/water interface was also thoroughly scrutinized by monitoring surface pressure-area Langmuir isotherms with a fast and slow compression. Results revealed the behavioural differences in monolayer assembly as a function of compression rate. The intricate relationship between cellulose-based materials and water was also studied using cellulose in its native form. The water vapour sorption behaviours of ultrathin films of cellulose nanocrystals (CNCs) and regenerated amorphous cellulose (from TMSC) along with films with a combination of both were studied using a quartz crystal microbalance with dissipation monitoring (QCM-D) and spectroscopic ellipsometry (SE). Quantitative analysis of the results showed that hydration of CNC networks occurs through the envelopment of the individual crystals by three monolayers of water. The water vapour response of the cellulose films became unexpectedly complex when CNCs were mixed with amorphous cellulose. Relative humidity studies showed that the crystalline/amorphous ratio of films containing both types of cellulose played a critical role in water vapour adsorption. Adsorption in films with a similar ratio to that prevalent in the woody plant cell wall (~50/50) was promoted by the addition of CNCs, whereas in predominantly amorphous films it was inhibited.
Abatement of industrial greenhouse gas emissions
(2021) Kajaste-Rudnitskaja, Raili
School of Chemical Technology | Doctoral dissertation (article-based)
Reducing anthropogenic greenhouse gas (GHG) emissions is increasingly proposed as one of the key components in achieving global sustainable development goals. The GHG emissions are continuing to rise annually at a rate of 1.5%. The total GHG emissions reached a record high of 55GtCO2eq in 2018. The direct industry contribution accounts for 21% and indirect GHG emissionsfor 11% of the global electricity and heat production emissions in the sector. The key sectors dominating the generation of global industrial GHG emissions are the iron and steel, cement andchemical industries. The growing global demand, especially for cement and plastics, is increasing the GHG emissions from these sectors.The fundamental objective of this study was to explore the possibilities to manage GHG emissions in industrial production chains. The speciﬁc objective was to ﬁnd solutions for the reduction of GHG emissions in the production chains of cement, plastics and methanol. In addition, one aim was to highlight the possibilities of future bioreﬁneries to reduce GHG emissions by replacing fossil resources in the production of chemicals and fuels. In this dissertation the research approach and process was multidisciplinary including attributional life cycle assessment (LCA), the capital recovery factor (CRF) and regression analysis of contributors to further develop incomplete datasets of the GHG emissions from the global cement sector. The key results of this dissertation are: (1) the total emission reduction potential identiﬁed in the global cement and chemical industry amount to 1112 Mt/a, corresponding to 17% of the GHG emissions from these two sectors. For comparison, the GHG emissions from the whole European Union area in 2017 were 4483 Mt, excluding land use change and land use change forestry (LUCLUCF); (2) the emissions from the plastics production chain are responsible for 51% of the GHG emissions from the chemical industry. Improved resource efﬁciency and increased additional recycling would reduce the emissions by 673 Mt/a in the value chain of plastics; (3) despite the large volumes of available biomass resources, the fuels and chemicals produced from fossil resources will continue to dominate until the market pull and cost-efﬁciency of renewable replacements make them attractive enough to compete. Lignocellulosic biomass, residuals, organic waste and algae were assessed as more sustainable resources for bioreﬁneries than food and feed crops. Methanol production from biomass adjacent to a pulp and paper mill was evaluated to becommercially viable; (4) the production of methane and methanol will probably be the ﬁrst to beneﬁt from the emerging carbon capture and utilization technologies, and (5) this study proposed a method for the assessment of greenhouse gas emissions in production chains by introducing a climate impact management matrix together with a capital recovery factor. To conclude, many of the GHG mitigation measures identiﬁed in this study are readily available for implementation provided the ﬁnancial gains and political willingness lower the threshold to investment.
Accessibility and enzymatic degradation of native and model cellulose substrates
(2011) Suchy, Miro
Kemian tekniikan korkeakoulu | Doctoral dissertation (article-based)
This thesis investigated two issues relevant to the bioconversion of lignocellulosic biomass. The first part relates to the accessibility of cellulose in wood, more specifically, the impact of initial drying on wood ultrastructure. The second part of this thesis pertains to the enzymatic hydrolysis of cellulose, including a characterization of a model film of amorphous cellulose and its subsequent utilization in a fundamental evaluation of the mechanism of cellulase action. In addition, the impact of cellulase treatment on the properties and the morphology of wood pulp fibers was evaluated. The impact of drying on the ultrastructure of fresh wood was studied by deuterium exchange coupled with FT-IR analysis. Initially, the experimental concept and its reliability were evaluated using fresh wood samples. The same experimental concept was then applied to study the impact of initial drying on wood pulps of different characteristics and composition. The objective was to correlate the trends in drying-induced alterations observed for wood and for pulps, bleached chemical pulp in particular. Drying-induced alterations of a native wood sample exhibited a remarkable similarity to those observed for wood pulp samples. The results suggest that the supramolecular rearrangements in the native wood matrix upon dehydration are qualitatively identical to the well-known changes occurring in pulp fibers after drying, although the changes are considerably different in quantity. Quantitative studies of cellulose degradation by cellulase enzymes were carried out using an amorphous cellulose model film with well-defined characteristics. First, the films were extensively characterized, particularly their crystalline nature and swelling behavior. The film swelled excessively in water, doubling its thickness, but returned to the original thickness upon water removal, while retaining its amorphous nature. This film was then used as a substrate in studying the action of monocomponent endoglucanase (EG) that acts on amorphous cellulose. The study was carried out using a quartz crystal microbalance with dissipation monitoring (QCMD). The main objectives were to study the impact of film thickness on the rate of hydrolysis and to directly quantify the extent of hydrolysis (decrease in thickness of films after hydrolysis). It was demonstrated that the amount of substrate available for hydrolysis did not have an impact on the rate of hydrolysis. The investigation also demonstrated impacts of various factors on the kinetic evaluation of the cellulase action. The investigation of the action of a commercial celobiohydrolase on wood pulp fibers showed that the treatment had no significant impact on the strength properties of the pulp. Changes of fiber morphology and of fracture type in the treated fibers during zero span evaluation,
Adhesion of reactive sizes and paper machine fouling
(2007-11-23) Lindfors, Juha
Doctoral dissertation (article-based)
The use of reactive sizes, alkyl ketene dimer (AKD) and alkenyl succinic anhydride (ASA), in papermaking has increased during the last decades and today they are commonly used in the manufacture of various paper and board products. The contribution of AKD and ASA to the fouling of paper machines has been shown to be considerable, and fouling has a major influence on the performance and economy of paper production. Adhesion unquestionably plays a major part in fouling phenomena. The aim of this work was to clarify how fouling could be minimized or avoided by control of adhesion; therefore different methods were used to study factors that have an influence on adhesion. Spreading kinetics and adhesion of reactive sizes on different surfaces were examined using contact angle measurements. Also, contact mechanics measurements of adhesion were performed. Surface hydrophilicity/hydrophobicity, pH and Ca2+-ion concentration were the key factors whose contribution to adhesion of AKD and ASA were studied. Model surfaces of AKD and ASA were also developed. In addition to fundamental laboratory experiments, applied fouling tests were carried out. According to the results, the spreading and adhesion of both AKD and ASA on hydrophilic materials in aqueous environment – excluding the high pH, high ion concentration conditions – is almost negligible compared to the adhesion on hydrophobic materials. The hydrolysis of ASA molecules at the liquid-liquid interface is very fast. Ca2+-ions had a markedly larger influence on the spreading and adhesion of ASA than pH. Furthermore, the outcome of combining high pH and calcium is even more remarkable; under such conditions significant changes occur in the spreading of ASA on both hydrophilic and hydrophobic surfaces and the nature of the surface does no longer have any effect on the spreading of ASA. This suggests that surface contamination can not be avoided in these conditions by just choosing the right surface chemistry. The composition of ASA or the formulation of ASA emulsions should be changed. The correlation between contact angle and contact mechanics methods used to measure adhesion was found to be adequate, and thus the choice of preferred method can be made depending on the system to be investigated. Both methods will be very useful in studying interactions that are of great interest in different phenomena related to papermaking. The results from the contamination testing showed similar features to those observed in fundamental laboratory experiments; the formation of deposits seems to be particularly troublesome when ASA is used concomitantly with precipitated calcium carbonate (PCC) or calcium chloride (CaCl2) at neutral or slightly alkaline pH.
Adsorption of lignin and lignin/cationic polymer complexes on cellulose fibres and their effect on sheet properties
(2004-12-17) Maximova, Natalia
Doctoral dissertation (article-based)
The objective of this dissertation was to deepen the understanding of lignin uptake by cellulose fibres by systematic studies under well-controlled conditions, and to clarify its effect on the papermaking properties of the fibres. It was possible to gain some direct insight into lignin sorption mechanisms by a comprehensive approach including studies of lignin behaviour in the solution, adsorption measurements and surface chemistry examination, studies of lignin distribution in the fibres, as well as analysis of sheet technical properties. It was found that van der Waals' interactions between lignin and fibres in aqueous dispersion are very weak and do not overcome the mutual electrostatic repulsion. No lignin is adsorbed from aqueous lignin solutions onto pure cellulose fibres: lignin loosely attaches to bleached fibres by imbibition with solution and filtration effect, and can be washed away with water. However, in sheets lignin binds to the fibres: some lignin is distributed throughout the cell wall, but the major part is located in the layers formed between the fibres. Restrained drying is responsible for binding of trapped lignin to the fibrous mat. Irreversible adsorption may occur in the presence of cationic polymers. The course of adsorption depended on the sequence of polymer addition. Kraft lignin is adsorbed as a monolayer onto cationised surfaces. In the aqueous solutions lignin and cationic polymers (PDADMAC and cationic starch (CS)) form both soluble and insoluble complexes, which are cationic or anionic, depending on the lignin/cationic polymer charge ratio. The complexes adsorb on kraft pulp fibres (and mica), especially at low lignin/polyelectrolyte ratios, when the complexes are cationic, covering the surface with patches, films or blobs. The driving force for adsorption of lignin/cationic polymer complexes on chemical pulp fibres is primarily electrostatic: adsorption takes place as long as the fibre surface and the lignin are oppositely charged. Adsorption of complexes is highly dependent on the sequence of addition of lignin and cationic polymer. If the complexes are formed in solution prior to adsorption on the fibres there is a relatively sharp maximum in adsorption at cationic polymer/lignin ratios below the isoelectric point. If complexes are formed directly on the fibre surface (adsorption of lignin on fibres treated with cationic polymer) the isotherm reaches a plateau value. Adsorbed complexes are located on the outermost surface of the fibres, which leads to brightness losses. Papers made from fibers with adsorbed lignin complexes exhibit improved strength and water resistance. This could be utilized in the manufacture of packaging grades of paper. Lignin particles in the solution are elongated and are about 1 nm thick and 2.5 nm wide. They adsorb onto cationised substrates in the form of individual granules, consisting of about 1200 primary lignin particles that are held together by strong cohesive forces.
Adsorption studies of polyelectrolytes and enzymes on lignocellulosic model surfaces
(2008) Saarinen, Terhi
Doctoral dissertation (article-based)
This thesis presents fundamental studies on the adsorption of polyelectrolytes and enzymes on solid surfaces. The overall objective of the research was to clarify the adsorption phenomena of polyelectrolytes and enzymes taking place in papermaking. The adsorption experiments were made with a quartz crystal microbalance with dissipation, QCM-D, and the enzyme-modified surfaces were characterised by atomic force microscopy, AFM. In order to study the interactions taking place at a molecular level, model surfaces of different pulp components are needed. Therefore, at first the preparation and characterisation of cellulose and lignin model films for QCM-D studies were evaluated. The adsorption of single cationic polyelectrolytes and of the polyelectrolyte multilayers and complexes on silica and cellulose surfaces was studied. The low-charge cationic polyelectrolytes adsorbed more on silica while the adsorption of high-charge polyelectrolytes was higher on cellulose. At the beginning of the adsorption the polyelectrolyte layers were viscous and more dissipative on cellulose and when the adsorption proceeded the layers became more rigid, in contrast to the behaviour on silica. The low-charge complexes (PECs) were more dissipative and viscous than those of high-charge PECs. The multilayers and complexes formed by low-charge polyacrylamides formed rather thick layers on both surfaces, unlike the high-charge polyelectrolytes which formed flat and thin layers with both addition techniques. By using polyelectrolyte complexes instead of the multilayering technique, thick and dissipative layers with a lower amount of polyelectrolyte can be formed. The modification of lignocellulosic model surfaces with laccases and further the adsorption of anionic ferulic acid on laccase-activated lignin were also examined by QCM-D. Both enzymes, Trametes hirsuta and Melanocarpus albomyces laccases adsorbed on cellulose and lignin surfaces. The adsorbed amount of M. albomyces laccase was higher than that of T. hirsuta laccase and the adsorption of M. albomyces laccase was strongly dependent on pH on the lignin surface. Stable ferulic acid adsorption was found on laccase-activated lignin but the mode of action of laccases was different when laccase and ferulic acid were added simultaneously on lignin.
Adsorption studies on cellulose surfaces by combinations of interfacial techniques
(2011) Eronen, Paula
Kemian tekniikan korkeakoulu | Doctoral dissertation (article-based)
In this work, the adsorption of various polymers on cellulose surfaces was studied in detail at molecular level. Special attention was paid on the interactions between renewable polysaccharides and different nanofibrillated cellulose (NFC) grades. Polymer or nanoparticle adsorption in aqueous medium was explored as a strategy to functionalize NFC. The role of pulp raw material and chemical pre-treatment on the NFC properties was clarified via indirect adsorption studies with ultrathin NFC films. Atomic force microscopy (AFM) -in different imaging and force detection modes-, quartz crystal microbalance with dissipation (QCM-D), Raman spectroscopy and surface plasmon resonance (SPR) were combined to carry out this research. The similar backbone having polysaccharides had natural affinity on NFC substrates. Comparison between NFC from different origin (hardwood vs. softwood), although of similar morphology, revealed differences in the conformation of adsorbed polysaccharide layer. The polysaccharide structure rather than NFC origin had more notable effect on adsorbed polysaccharide amount and layer properties. The attachment of the very thin (only few nm thick) polysaccharide layer was uniform without aggregates. They nevertheless were able to change the surface properties of cellulosic materials. One example was the lowered friction co-efficient with one polysaccharide (chitosan) determined for regenerated cellulose spheres in low pH aqueous solution. In addition, NFCs prepared after chemical pre-treatments were compared to unmodified NFC. Increasing the anionicity prevented the interfibril association by electrostatic repulsion. As a consequence the fibrillation efficiency was enhanced and very thin nanofibrils were achieved. The surface interactions were systematically probed and compared with different cationic counterparts using layer-by-layer (LbL)-technique. The high charged, chemically modified NFC behaved differently compared to low charged, unmodified NFC: they bound more water and the layer formation and stabilization was faster; and the adsorbed amount increased as the function of layer number. Nevertheless, multilayers could also be formed with the lower charged NFCs to some extent. Non-electrostatic interactions were significant between oppositely charged all-cellulosic materials. A considerable increase in adhesive forces during multilayer build-up due to high compressibility of the high charged NFC was also detected. The information obtained in this study for the interactions of emerging, renewable, bio-based materials can be used to create more sustainable material applications in the future.
Adsorption-based deep syngas purification
(2022) Frilund, Christian
School of Chemical Technology | Doctoral dissertation (article-based)
In order to limit our dependence on fossil carbon, gasification emerges as a versatile conversion platform of various organic feedstocks to syngas for subsequent sustainable fuels and chemicals production. One of the challenges, especially for biomass-to-liquids (BTL) concepts, however, is the economic smaller-scale production of high-purity syngas in proximity to the feedstock origin. Conventional deep contaminant removal often comprises absorption technologies, originally developed for large-scale plants. A simplified final gas cleaning process is therefore proposed, primarily based on adsorption, and applied to smaller BTL processes. Sulfur species are some of the most challenging syngas impurities, and therefore this dissertation experimentally investigated several H2S adsorption materials for the proposed process. Zinc oxide exhibited in long-term packed-bed breakthrough experiments deep H2S removal capabilities even in tar-rich syngas. Breakthrough tests using electric arc furnace (EAF) dust, a zinc-containing steel making side stream, demonstrated excellent high-temperature desulfurization capabilities, even exceeding primary ZnO performance, with up to 240 mg g-1 H2S capture capacity. Low temperature activated carbon (AC) tests revealed that cheaper non-impregnated AC had poor desulfurization performance compared to impregnated- or doped AC, which exhibited capture rates comparable to metal oxides. However, introducing ammonia to the syngas improved non-impregnated AC performance to over 270 mg g-1. The beneficial effect of ammonia was validated in real syngas from biomass, and consequently this method was evaluated as the most compelling low-cost H2S removal method of the tested materials. To determine the final gas cleaning concept's feasibility as a realistic alternative to conventional solutions, comprehensive gas cleaning experiments in real syngas were performed. A bench-scale final gas cleaning process, "UC5", was operated in a full BTL plant configuration in multiple week-long campaigns in residual biomass syngas with downstream coupling to FT synthesis. Complete and sustained impurities removal was achieved in syngas in varying impurities concentrations and compositions, hence proving the practical feasibility of the cleaning concept. Furthermore, in the subsequent campaigns in dirtier syngas, the contribution of each unit in the process was determined. Additionally, it was demonstrated that activated carbons had affinity for removal of other syngas contaminants such as COS and HCN. Based on the experimental results, this dissertation proposes optimized final gas cleaning process configurations that for H2S removal use either ammonia-enhanced AC or EAF-based adsorbent.
Advanced Structures and Compositions for 3D Forming of Cellulosic Fibers
(2017) Khakalo, Alexey
School of Chemical Technology | Doctoral dissertation (article-based)
The objective of this thesis was to systematically investigate strategies to endow fiber-based materials with toughness and formability. Bio-based polymers and green treatments were applied to develop 3D packaging structures. Formability, the material's ability for three-dimensional shaping, was achieved by plastic deformations in paper structures that were defect-free in terms of appearance and functionality. A set of methods to improve paper toughness was explored, including: (a) combined mechanical treatment of fibers in aqueous dispersions of high- and low-solids content, (b) in-plane compression of paper webs followed by unrestrained drying and (c) chemical modification of fiber joints by protein spraying. The mechanical treatment of fiber suspensions at elevated temperature and high solids content induced permanent fiber deformations, including kinks and curls, which are associated with the formation of microcompressions and dislocations. In turn, they increased the extensibility but compromised the axial stiffness of single fibers. Simultaneously, shrinkage of fibers and paper webs were promoted. In contrast, the low-consistency treatment straightened the fibers while their deformations were partly preserved. Fiber bonding was promoted by fibrillation. The application of gelatin affected the strength of fiber joints and improved their deformation ability, making strong fiber webs. The drying shrinkage was also increased. The fiber network was subjected to in-plane compressive treatment and drying shrinkage, which led to fiber buckling and network compression. The role of proteins as compatibilizers and eco-friendly dispersants in composites comprising cellulose nanofibrils (CNF) and thermoformable polylactide (PLA) was also investigated. The combination of mechanical and protein treatment of fibers and their structures improved paper extensibility, from 5% to 29%. Moreover, tray-like shapes were possible with a level of out-of-plane deformation that has not been recorded before for thermoforming with a fixed blank. Overall, this thesis provides fundamental and practical knowledge about the role of several factors contributing to paper toughness and formability. The suggested modification strategies to improve paper toughness are compatible with modern papermaking and conversion processes and can be implemented easily and economically.
Advances in amine catalysis : Brønsted acids in iminium and enamine activation
(2007-10-26) Erkkilä, Anniina
Doctoral dissertation (article-based)
Condensation of aldehydes and ketones with primary and secondary amines results in the formation of reactive imines and iminium salts. Additionally, a loss of a proton form an iminium species leads to the formation another active intermediate: enamine. Iminium salts and enamines are more reactive than their parent compounds and thus their formation can be exploited in amine catalysis. In fact, activation of carbonyl compounds by iminium and enamine catalysis has attracted wide attention in the last decade and become a practical tool for the synthetic organic chemists. In the summary part of this thesis reactions activated via iminium ion or enamine formation are reviewed focusing on the role of the Brønsted acid co-catalyst. The described catalysts consist of a primary or secondary amine iminium or enamine catalyst and an acid co-catalyst and can often be derived from nature's chiral pool. The Brønsted acid co-catalysis plays a central role in the iminium and enamine catalysis. In the iminium catalysis the co-catalyst functions as a general acid catalyst in the iminium formation and as a general base catalyst in the some times required removal of hydrogen from the nucleophile when it has reacted to form the initial iminium intermediate. In enamine catalysis these modes are already combined in the formation of the reactive enamine species. Thereafter the co-catalyst may be used to activate and orient the approaching electrophile. In this thesis enamine catalysis was utilized in the synthesis of polypropionate building blocks by asymmetric aldol reactions. Also, combined enamine-iminium catalysis was employed in the synthesis of alpha-substituted enals, which in turn were utilized as substrates in iminium catalyzed transformations. For the iminium catalyzed transformation of alpha-substituted enals a novel aniline catalyst was developed.
Advancing Sustainability in Mining - Studies on managerial perspective on strategic environmental management
(2022) Ruokonen, Eeva
School of Chemical Technology | Doctoral dissertation (article-based)
Demand for metals and minerals is boosted by global population growth, rising living standards, urbanization and energy transition. Society is increasingly committed to mitigating climate change with carbon reduction measures, and therefore the energy transition to low-carbon technology is the main driver for the current elevated demand for metals. In order to achieve the climate goal of a low-carbon society, our society is moving towards mineral-intensive production of energy. Together with stakeholders' rising environmental expectations regarding sustainably produced metals and minerals, this provides opportunities for those mining companies that can meet these expectations. Therefore it is justified to argue that mining companies can benefit from a strategic approach to their environmental management practices. Moreover, the Finnish State has set the national target of becoming a leader in the sustainable extractive industry, which places even greater importance on mining companies' strategic approach to this matter. This study extends the current understanding on the measures that senior managers at mining companies in the Finnish context employ to manage environmental considerations. The objective is to understand the key aspects of the strategic environmental management of sustainable mining by answering the following three research questions: Which approaches do mining companies take towards strategic environmental management? Which drivers and strategies advance environmental considerations? Which implementation practices do companies adopt to improve environmental performance and how is the use of voluntary sustainability initiatives perceived? Based on the findings, mining companies are clearly committed to improving their environmental and social performance, and work to gain stakeholder approval and acceptance. For mining companies, the most important external drivers are environmental legislation and societal expectations, and management expects to gain "a social license to operate" with an emphasis on minimizing emissions. Voluntary sustainability initiatives provide leading practices for improved environmental performance when the mining companies invest in their implementation and incorporate sustainability into their business strategies and practices. The results also indicate that the maturity of individual companies varies greatly. Some companies demonstrate a strategic approach to their environmental management, maintaining a balance between top management commitments, their implementation and results. For some, there is room to be more proactive in taking ownership of the environmental agenda and setting challenging goals to search for strategic opportunities. To conclude, there is a positive tailwind for the shift to adopt – to a greater extent – sustainable mining practices. The speed of adoption depends on not only how the companies meet the challenges they are facing, but also how the governmental sector facilitates the change.
All carbon hybrid multi-functional composite thin films
(2017) Iyer, Ajai
School of Chemical Technology | Doctoral dissertation (article-based)
The use of nanoscale materials has become common practice in a variety of industries such as electronics, medicine, cosmetics, construction and automobile to name a few. Whether used as dispersed nanoparticles or in the form of coatings and thin films, these nanomaterials open up a world of possibilities for new emerging technologies. Carbon nanomaterials in particular have great potential with a dynamic range of interesting properties in different dimensional structures. Under most application conditions the nanomaterials need to be protected from mechanical and/or chemical disruption by a protective matrix. In this thesis the feasibility and viability of fabricating thin composite films by embedding carbon nanomaterials in a protective matrix is explored. Tetrahedral amorphous carbon (ta-C) containing high sp3 bonded carbon fraction has been selected as the protective matrix due to its high hardness, chemical inertness, optical transparency and ability to be deposited as a thin film. Carbon nanomaterials in the form of single wall carbon nanotubes (SWCNTs) and detonation nanodiamonds (DNDs) were tested in this thesis, due to their increasing usage in applications related to conductive films, thin film transistors, sensing elements and photonic components. SWCNT networks were coated by ta-C using a pulsed filtered cathodic arc process (p-FCVA) and tested to ascertain the electrical and mechanical properties. Experimental results supported by simulations show that ta-C coating with high sp3 carbon fraction of 75% could be deposited onto the SWCNT networks. The ta-C coating encapsulates the SWCNT bundles providing superior mechanical and chemical protection with 60% reduction in wear and limited immunity to oxygen plasma in comparison to uncoated network. The increase of electrical resistance by around 4500% for the SWCNT network post deposition of ta-C coating, has been investigated. The predominant cause of this resistance increase is attributed to the intrinsic compressive stress of the ta-C coating which moves the SWCNT bundle junctions apart, thus increasing the contact resistance leading to drastic increase in the network resistance. It has been shown that use of an intermediate coating between the SWCNT network and ta-C coating limits the resistance increase to manageable proportions. A 9 nm thick evaporated carbon coating as intermediate layer, limited the network resistance increase to 90% and improved the mechanical wear by 50% in comparison to ta-C coated network without intermediate coating. Furthermore, a novel method to deposit DND embedded ta-C composite films in a single step using p-FCVA process has been demonstrated here. The DND-ta-C composite film, with DND concentration of the order of 0.1 vol% has 15% increase of hardness and 40% lower wear in comparison to ta-C film. Even under high load and multiple wear test conditions the DND-ta-C composite film has mechanical performance superior to ta-C films making them an ideal candidate for tribological applications.
Amphiphilic cationic polymethacrylates: synthesis, characterization and interactions with cellulose
(2011) Vesterinen, Arja-Helena
Kemian tekniikan korkeakoulu | Doctoral dissertation (article-based)
Amphiphilic cationic co-polymers, containing poly([2-(methacryloyloxy)ethyl] trimethyl ammonium iodide) (polyMETAI) or poly[2-(dimethylamino) ethyl methacrylate] (PDM) segment, were synthesized through two different main routes. Block co-polymers containing poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) were synthesized with oxyanionic polymerization, whereas radical polymerization was used to obtain statistical co-polymers with stearyl methacrylate (SMA) and fluorodecyl methacrylate (FMA). The melt and thermal transition properties of the polymers were studied with dynamic scanning calorimetry and rheometry. PDM decreased crystallinity of the polymer and increased the melt strength of the polymers. The solution properties were studied with a surface tension measurement, with dynamic light scattering equipment, and with rheometry. Polymers containing highly hydrophobic segments, such as stearyl, formed charge stabilized aggregates in a water solution, whereas polymers with a less hydrophobic block, such as PEO, formed a micellar structure. The suitability of the prepared polymers, as well as a set of commercial polymers, on cellulose fiber systems was studied. The polymers containing a cationic segment formed permanent adhesion on the anionic surface, and strong bonding with the cellulose fibers. The mechanical strength of the cellulose fiber sheets was increased more with polymers containing cationic segments than the ones with corresponding nonionic segments. Strain hardening behaviour was introduced into the fiber-polymer sheets that did not contain cationic segments and the bonding between the fiber and the polymer was weak enough. A mechanically strong cellulose fiber network could also be prepared with a hydrophobic cationic polymer, but the strength was decreased with the high density of the hydrophobic side group in the polymer. The polymers containing a highly hydrophobic segment formed a thin layer coating on the paper surface and a small amount of polymer was enough for a complete thin layer coverage of the surface. Additionally, the higher amount of the polymer did not change the chemical or physical properties of the surface, which supported the assumption of a nanolayer formation.
Analysing sawnwood supply distribution in Finnish sawmilling industry with database approach
(2005-09-20) Virtanen, Jussi
Doctoral dissertation (monograph)
The thesis analyses sawnwood supply in the Finnish sawmilling industry using the database approach. The analyses help to understand the supply and demand of sawnwood between customers and sawmills. In the analyses two databases were used to examine the supply of sawnwood. In addition, the following three criteria were used: 1) quantity, 2) price and 3) quality. The study focused on a sample of 63,774 sales of over 19 million m3 sawnwood from 1995 to 2000. Quality in the thesis is defined in terms of dimensions, quality classes, end moisture contents and user segments. The coniferous species in the sample were Scots pine (Pinus sylvestris) and Norway spruce (Picea abies). Additionally, time series data about the consumption of coniferous sawnwood from the years between 1961 and 2002 was used in the study. The most essential new result of the thesis was that the features of sawnwood as a commodity product were clear in the sample from 1995 to 2000. Nevertheless, the marketing and the operations of the Finnish sawmilling industry at the time emphasised the features related to special and customer products. In 2002, the global consumption of coniferous sawnwood (CSW) was 283 million m3. The same year in Finland, the consumption of sawnwood increased to 1.02 m3 per capita, the highest in the world. Finland experienced a structural change in the sawnwood consumption between the periods of 1961-1996 and 1997-2002. From 1995 to 2000, sawnwood supply and sales from Finnish sawmills were largely limited to only a few volume dimensions. For pine, 20% of the number of dimensions encompassed 91% of volume and 90% of value. For spruce, 20% of the number of dimensions covered 82% of volume and 83% of value. The Pareto principle assumption applied to the distribution of sawnwood dimensions from the quantity (m3) and value (€) perspectives. There was a sawnwood market trend towards smaller batch sizes. It was observed that the end moisture content class MC 18% has a dominant position – over 90% – in the end moisture content distribution. The results supported the view that sawnwood supply consists mainly of a limited number standard products. Dimensions had big differences specific to country and species of timber. The basis price system worked by dimension, quality class and species with a defined basis of pine 50 × 150 mm U/S or similar. This system was used in the pricing of sawnwood in the Finnish sawmilling industry in 2000. In the analyses, the supply of sawnwood was divided according to end moisture content classes, countries, dimensions and segments. In the supply analyses, standard dimensions and qualities were linked with the standard moisture content classes as MC 18%. The results showed that the supply was greatest for standardised sawnwood. The supply and demand for special qualities increased particularly for pine. There was a correlation between sawnwood export countries, moisture content classes and end-user segments. The results showed that sawnwood user segmentation was still unfinished. The thesis seeks to present such methods that give relevant information to sawmills and other segments of the forest cluster. These useful methods include logistic regressions and other statistical tools. Applying these tools can give new insight into business management as well as the dynamics of the demand for sawnwood and other wood products.
Analytical ultracentrifugation as a tool to understand interactions in biomolecular materials
(2024) Fedorov, Dmitrii
School of Chemical Technology | Doctoral dissertation (article-based)
The modern world dictates new rules and requirements for materials used in various applications. The development of human society has reached a point where, in addition to the requirements for good functional properties, the requirements for safety and sustainability of the materials are also increasing. Bio-based materials satisfy all these criteria. They are functional, sustainable, renewable and have a good mechanical properties. One of the most promising representatives is spider silk, the fibers of which are formed on the basis of triblock proteins. Spider silk stands out for its excellent mechanical properties. However, to achieve the properties similar to native spider silk using artificial analogues, a deep understanding of processes and interactions at the molecular level is required. In overall this is the true for any materials. The lack of the knowledge about molecular interactions is critical and significantly complicates the material development. It can be compared to forging a sword when one knows nothing about metal processing. Theoretically, it is possible to forge a sword that looks like a sword. Applying a lot of efforts, one even can make it beautiful. But most likely it will be either fragile or too soft, since the person does not know how to process it correctly. Applying even more efforts, after many attempts, one can find the conditions under which the sword would have the desired properties, but what if after sword it is needed to forge a horseshoe, for example. There could be different requirements for properties and all the process of searching the best conditions will be repeated all over again. However, knowing the rules of hardening and alloying of iron, everything would be much simpler. Absolutely the same situation occurs with biomaterials and intermolecular interactions. This work devoted to certain gaps in the understanding of protein interactions at the molecular level, how they affect intermediate states such as liquid-liquid phase separation (LLPS), shows the importance of understanding the interactions, and also demonstrates the capabilities of Analytical Ultracentrifugation (AUC) in combination with other techniques for material science application. Publication 1 demonstrates the effect of terminal domains on LLPS of engineered three-block spider silk proteins. The discovered patterns will serve for creation of coacervates with controlled properties. Publication 2 is devoted to the stability of NT-2Rep-CT, studying the component composition of NT-2Rep-CT solution and demonstrating the influence of the history of the sample on its properties and the observed state. Publication 3 investigated the dimerization of the CBM molecule and tested various methods for AUC data analysis. In publication 4, the shape of molecule of the CBM-AQ12-CBM protein was investigated using a combination of AUC and MD simulation. A similar approach was used in publication 5, where the polypeptides PLL and PGA were the objects of study. Solution composition, molecular weights and shape were determined.
Antibacterial properties of Scots pine and Norway spruce
(2017) Vainio-Kaila, Tiina
School of Chemical Technology | Doctoral dissertation (article-based)
Wooden surfaces in interior use hold potential for improving human health and wellbeing. The antibacterial properties of wood might reduce the possibility of cross-contamination from surfaces. In order to be able to control the hygienic quality of the wooden surface, the antibacterial effect should be better understood. The main aim of this thesis was to identify and evaluate the antibacterial properties of wood and its components. Different methods were developed and used to study the antibacterial properties of Scots pine and Norway spruce, heartwood and sapwood. The solid wood surface showed clear antibacterial properties, even when the extractives had been removed with acetone. Studies with the extracts showed several human pathogens, including methicillin-resistant Staphylococcus aureus, to be susceptible to pine heartwood and sapwood in particular, and also, to some extent, spruce. Besides extractives, lignin was the only separate wood component showing antibacterial properties. Wood volatile organic compounds (VOCs), which were studied in gaseous form, showed an antibacterial effect against various human pathogens. Several antibacterial compounds were found in all the extracts, however, they did not always explain the order of antibacterial activity between wood species. No single compound could alone explain the effect, hence the antibacterial effect derives either from different mechanisms in different species or from a synergistic effect. α-pinene and limonene could partly explain the antibacterial effect of the VOCs, but other components were also found to have an influence. Wood was found to have various antibacterial parts and a diverse range of bacterial pathogens that were sensitive to it. These results offer a good ground for the exploitation of the hygienic properties of wood and a good starting point for enhancing them further. Additionally, the extracts showed promising qualities and they should be studied further in regard to resistant pathogens.
Antilipogenic mechanism of conjugated linoleic acid in yeast
(2017) Hokkanen, Sanna
School of Chemical Technology | Doctoral dissertation (article-based)
Conjugated linoleic acid (CLA) is a mixture of linoleic acid isomers having two double bonds in conjugated position. Beneficial health effects of CLA are unique: inhibition of fat accumulation and atherosclerosis, prevention of carcinogenesis, exhibition of anti-inflammatory properties and protection from diabetes. Synthetic CLA supplements are marketed for weight-loss purposes. However, concerns of safety of CLA have emerged, because the exact antilipogenic mechanism could not been clarified despite the active research with mammalian cells in vivo and in vitro. In this thesis the potential of yeast Saccharomyces cerevisiae as a model organism for elucidating the mechanism was examined. The trans-10,cis-12 isomer, which is recognized to be responsible of the antilipogenic effect in mammals, reduced yeast triacylglycerol content when supplemented in the cultivation medium. In contrast, the cis-9,trans-11 isomer induced high triacylglycerol accumulation. Both isomers were incorporated in the yeast phospholipids and triacylglycerols and were present in minor amounts also as free fatty acids. In triacylglycerols the CLA isomers were enriched in sn-1 and sn-3 positions. In yeast, two important mechanisms for the reduced triacylglycerol content by the trans-10,cis-12 CLA emerged. After the diauxic shift the CLA treated cells used efficiently the fatty acids from the cultivation medium and triacylglycerols as carbon source to produce more biomass resulting in the lowered triacylglycerol content. Also cis-9,trans-11 CLA induced this effect. Another mechanism specific for the trans-10,cis-12 CLA was the significant inhibition of monounsaturated fatty acid accumulation. The isomer was suspected to have direct effect on the membrane bound Δ9 desaturase, because the transcription of the enzyme was not affected by the trans-10,cis-12 CLA supplementation. In contrast, the cis-9,trans-11 isomer reduced the transcription of the enzyme, but its effect on monounsaturated fatty acid content was not that remarkable and rather typical for cis-9 unsaturated fatty acids. The transcriptional inhibition of the enzymes catalyzing DAG esterification was not induced by CLA in yeast. Are2p, the enzyme catalyzing sterol ester synthesis in yeast, showed elevated transcription by the trans-10,cis-12 CLA supplementation. On the basis of these results, yeast was proven to serve as an excellent model for CLA research. Especially the impact of CLA on membrane associated processes are encouraged to study further by using yeast as a tool.
Antimicrobial Polysaccharides for Biomedical Applications
(2024) Laurén, Isabella
School of Chemical Technology | Doctoral dissertation (article-based)
Polysaccharides are widely used across various fields owing to their biological properties, biodegradability, and availability. Through various modification techniques, their properties can be tailored for specific applications. Chitosan, derived from deacetylated chitin, is particularly appealing in the biomedical sector due to its antimicrobial properties in acidic conditions. The polymer's amino groups become protonated in acidic environments, imparting a positive charge. This cationic charge is a crucial factor for antimicrobial activity, as most pathogens possess a net-negative surface charge and are thus susceptible to the positive charge of protonated chitosan. Introducing quaternary ammonium groups to the polysaccharide backbone establishes a permanent positive charge. In this thesis, two distinct quaternary ammonium moieties, [2-(acryloyloxy)ethyl]trimethylammonium chloride (AETMAC) and glycidyl trimethylammonium chloride (GTMAC), were incorporated into chitosan to investigate the potential of these derivatives as antiviral and antibacterial agents. These chitosan derivatives demonstrated significant promise as antimicrobial agents, particularly in biomedical applications, where there is an urgent need for new biobased solutions to combat infections and antibiotic resistance. This study evaluated and optimized the physiochemical and biological properties of the AETMAC and GTMAC derivatives. Due to differences in chemical structure and polymerization processes, the derivatives exhibited vastly different properties. Here, AETMAC functionalization is based on radical polymerization, while GTMAC is directly grafted onto the chitosan structure as a result of a nucleophilic ring-opening reaction of the epoxide moiety. AETMAC-functionalized derivatives showed superior antimicrobial properties and were further used to develop biocompatible chitosan-based composite materials. Quaternary chitosan was combined with other polysaccharides and synthetic polymers to develop biocompatible hydrogels for medical purposes, especially wound healing applications. By optimizing the constituents of the composite, 3D printable and injectable hydrogels were obtained, featuring cross-linked polymeric networks based on physical and chemical cross-linking. In vitro biocompatibility assays of the hydrogels showed no acute cytotoxicity, addressing a common issue associated with higher degrees of quaternization. These findings underscore the potential of quaternary chitosan in developing biocompatible and effective antimicrobial materials for biomedical applications.
Applicability of fractionation of softwood and hardwood kraft pulp and utilisation of the fractions
(2015) Asikainen, Sari
School of Chemical Technology | Doctoral dissertation (article-based)
Fractionation of final or semi-finished fibres gives more advanced possibilities to design pulps with unique fibre characteristics. The objectives of this thesis were to clarify the applicability of fractionation of softwood and hardwood kraft pulp and utilisation of the fractions. Fractionation of softwood, birch and eucalyptus pulps gave fractions with substantially different physical and chemical properties. The contents of lignin, extractives and some metals were higher in the birch and softwood accept fraction because of the primary fines. Removal of primary fines from the oxygen-delignified birch kraft pulp gave a higher final brightness at slightly lower active chlorine consumption in DEDeD bleaching and improved brightness stability. When the birch fines were bleached using a ZeQP sequence, the extractives content of the fines fraction was reduced by 40%. The hydrocyclone- and pressure screen-fractionated softwood pulps were blended with thermomechanical (TMP) and groundwood (GW) pulp. The softwood long fibre fraction and the thick-walled fibre fraction gave in the mixture with mechanical pulp higher freeness values than the unfractionated pulp. The thick-walled fibre fraction gave clearly higher tear index values than the feed pulp in the mixture both with GW and TMP. Also, the long fibre fraction gave somewhat higher tear index values, especially when mixed with GW. Softwood thin- and thick-walled fibre fractions were refined separately. Fractions that were separately refined and after refining re-combined were then blended with GW. Separately refined fibre fractions in all cases gave higher freeness and higher fibre length of the chemical pulp-GW mixture than the unfractionated pulp-GW mixture. It was possible to increase the tear index by up to 16% and the fracture toughness index by up to 23% of the GW blend sheets by separate refining of the softwood kraft pulp fractions. Through hydrocyclone fractionation of birch pulp, a coarse fraction was obtained with a high tensile stiffness. The fine fraction had a high bonding ability. The coarse fraction could be used in the top layer of board or in fine paper. The fine fraction obtained by hydrocyclone and screen fractionation could be used for bonding in the middle layer of board making it possible to use coarser mechanical pulp. The vessel-picking tendency of eucalyptus pulp was significantly reduced by removing vessel elements from the pulp using hydrocyclone, and also by refining the vessel-rich fraction.
Application and wear durability of hybrid thin films on dental steel instruments
(2018) Leppäniemi, Jarmo
School of Chemical Technology | Doctoral dissertation (article-based)
Dentistry is one of the few fields today where use of steel instruments operated by hand is acommon practice. These instruments need to possess mechanical properties necessary for theiroperation, good corrosion resistance due to daily autoclaving, and surface related properties, suchas non-stick performance, to shape restorative composite materials. This work investigated howwear resistance, corrosion protection and non-stick properties of dental steel instruments couldbe improved by choosing suitable base steel material, optimal surface treatment and a combinationof thin films. The investigation focused on Gracey curettes and restorative instruments – these aretools for removal of dental calculus and for constructing dental filling, respectively. Change of base steel material to a highly alloyed high-speed steel (HSS) was shown more effectiveto improve the wear resistance than use of physical vapor deposition (PVD) coatings. Limitedcorrosion resistance of this HSS imposed a need for corrosion protection. Three types of corrosionprotective coatings were investigated: a commercial PVD CrN coating, an in-house depositedatomic layer deposition (ALD) nanolaminate coating consisting of Al2O3/TiO2, and a hybrid coatingconsisting of both of these. Use of plasma pre-treatment was shown critical for the adhesion of theALD film, and its success in corrosion protection. Superior corrosion protection was shown with the hybrid PVD/ALD coating, with corrosion currentdensities two orders of magnitude lower than with the PVD coating alone. As the corrosionprotection in these hybrid coatings is based on ALD film sealing the pinholes in the PVD coating,the hypotesis in this work was that the corrosion protection should be mostly unaffected even ifthe ALD film is completely worn away from the top of the PVD surface. In this work, it wasshown that the corrosion protection mostly remains after such surface wear, but some of protectionis lost due to new defects opening and thus creating new pathways for the corrosion to attack thesubstrate. These hybrid coatings could be used in applications with heavy abrasive wear, such asGracey curettes. ALD films were also utilized in multistep fabrication process of omniphboic coatings onrestorative instruments. These coatings consisted of surface structuring by etching in HF:H2O2,surface stabilization by a 7 nm ALD film, and chemical surface functionalization by a self-assembled monolayer of fluorinated organosilicon. This coating greatly reduced the amount ofrestorative materials sticking to the instrument, as shown by contact angle measurements and acustomized dipping procedure developed to simulate dental restorative operation. Some of theperformance with these omniphobic coatings was lost when the surface was worn and autoclaved.

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