Browsing by Author "Maloney, Thaddeus"

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  • Acid dissociation of surface bound water on cellulose nanofibrils in aqueous micro nanofibrillated cellulose (MNFC) gel revealed by adsorption of calcium carbonate nanoparticles under the application of ultralow shear
    (2017-08) Liu, Guodong; Maloney, Thaddeus; Dimic-Misic, Katarina; Gane, Patrick
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    At ultralow shear rate (similar to 0.01 s(-1)), acting below the yield stress of the aqueous gel, adsorption of calcium carbonate nanoparticles (<~100 nm) onto cellulose nanofibrils is induced without pigment–pigment preflocculation. Dispersant-free and polyacrylate treated dispersed carbonate particles are compared. Initially, it is seen that the polyacrylate dispersed material does not adsorb, whereas the dispersant-free carbonate adsorbs readily under the controlled ultralow shear conditions. However, repeated cycles of ultralow shear with intermittent periods in the rest state eventually induce the effect as initially seen with the dispersant-free calcium carbonate. The fibril suspension in the bulk is slightly acidic. The addition of buffer to a controlled pH in the case of the dispersant treated particles maintained a similar delay in the onset of adsorption, but adsorption occurred eventually after repeated cycles. During this cycling process, in parallel, the pH gradually drops under repeated cycles of ultralow shear, opposite to expectation, given the buffering capacity of calcium carbonate. The conductivity, in turn, progressively increases slightly at first and then significantly. The action of surface bound water on the nanofibril is considered key to the action of adsorption, and the condition of ultralow shear suggests that the residence time of the particle in contact with the nanofibril, acting under controlled strain against diffusion in the gel, is critical. It is proposed that under these specific conditions the calcium carbonate nanoparticles act as a probe of the nanofibril surface chemistry. The hydrogen bonded water, known to reside at the nanofibril surface, is thus considered the agent in the carbonate-surface interaction, effectively expressing an acid dissociation, and the calcium carbonate nanoparticles act as the probe to reveal it. An important phenomenon associated with this acid dissociation behaviour is that the adsorbed calcium carbonate particles subsequently act to flocculate the otherwise stable cellulose material, leading to release of water held in the aqueous gel matrix structure. This latter effect has major implications for the industrial ease of use of micro and nanofibrillar cellulose at increased solids content. This novel mechanism is also proposed for use to enhance the dewatering capability in general of complex cellulose-containing gel-like water-holding suspensions.
  • Activation of softwood Kraft pulp at high solids content by endoglucanase and lytic polysaccharide monooxygenase
    (2021-08) Ceccherini, Sara; Rahikainen, Jenni; Marjamaa, Kaisa; Sawada, Daisuke; Grönqvist, Stina; Maloney, Thaddeus
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The manufacturing of man-made cellulose fibers starts with the dissolution of wood pulp fibers. Pulps can dissolve at different rates and leave different amounts of undissolved particles. Thus, their properties can be modified to achieve better dissolution. Enzymatic treatments are an effective means of enhancing pulp dissolution, and this study compares the effect of endoglucanase (TrCel45A) and lytic polysaccharide monooxygenase (LPMO, TrAA9A) on bleached softwood Kraft pulp at 20 % solids content. The enzymes were applied individually and in combination. Both enzymes increased fibrillation, fines content, porosity, water retention value, crystallinity index and crystallite size, but the largest changes were achieved with the enzyme mixture. For example, fiber saturation point and water retention value increased by 64 and 37 % with TrCel45A, by 27 and 25 % with TrAA9A, and by 73 and 52 % with both TrCel45A and TrAA9A. Pulp reactivity was indirectly assessed by measuring the dissolution time in cupriethylenediamine. The average dissolution time of the reference pulp measured 642 s, while those of the pulps treated with TrCel45A, TrAA9A and their mixture were 399, 473 and 298 s, respectively. The decrease in dissolution time correlated with the increase in fines, fibrillation, porosity, and water retention value.
  • Additives to optimize kraft-lignin pelletizing and pellet performance
    (2022-03-25) Laukkanen, Sanna
     Kemian tekniikan korkeakoulu | Master's thesis
    Lignin is a highly abundant natural polymer found in lignocellulosic plants and extracted from wood in various pulping processes. Kraft-lignin is a by-product of kraft-pulping process and is mainly used as a fuel for energy production but its application potential as an alternative for fossil-based polymers in production of chemicals and materials has become increasingly recognized. Currently kraft-lignin is often transported and used in a fine powder form which creates challenges of material loss, dust hazards, flowability and handling problems as well as lower cost-efficiency of the shipping. Aim of this thesis was to investigate potential binding additives, added in dosages of 0,5 and 2w%, to improve kraft-lignin pellet formation, their physical characteristics and ability to resist wear, and ultimately improve kraft-lignin feasibility through material efficiency. Moisture content, pelleting pressure and temperature were found to have a significant effect on the quality of the lignin pellets and optimizing these parameters was essential to achieve stable quality during production. Binder effectiveness was evaluated based on pellet fines content, bulk density, mechanical durability in ambient and elevated temperature / relative humidity (RH) conditions, solubility in water and sodium hydroxide, glass transition temperature and visual appearance. The pellets released ~5w% of fines with majority under 1,4mm in size and their bulk density stayed rather stable at around 0,5g/cm3. The results of mechanical durability showed the highest increase and consistency of performance with 2% of carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA) and Bentonite, although variability between individual products was considerable. Pellet solubility was mildly affected by the binder content whereas glass transition temperature was mostly related to the lignin moisture content. Physical appearance and thickness of the pellets varied depending on the binder type and its dosage but visually the best quality was achieved with 2% of CMC A, CMC C, guar gum, PVA B and Bentonite.
  • Barriers in Food Packaging
    (2016-09-09) Somerpalo, Veera
     Kemiantekniikan korkeakoulu | Bachelor's thesis
  • Biological activity of multicomponent bio-hydrogels loaded with tragacanth gum
    (2022-08-31) Teixeira Polez, Roberta; Morits, Maria; Jonkergouw, Christopher; Phiri, Josphat; Valle-Delgado, Juan José; Seppälä, Jukka; Linder, Markus B.; Maloney, Thaddeus; Rojas Gaona, Orlando; Österberg, Monika
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Producing hydrogels capable of mimicking the biomechanics of soft tissue remains a challenge. We explore the potential of plant-based hydrogels as polysaccharide tragacanth gum and antioxidant lignin nanoparticles in bioactive multicomponent hydrogels for tissue engineering. These natural components are combined with TEMPO-oxidized cellulose nanofibrils, a material with known shear thinning behavior. Hydrogels presented tragacanth gum (TG) concentration-dependent rheological properties suitable for extrusion 3D printing. TG enhanced the swelling capacity up to 645% and the degradation rate up to 1.3%/day for hydrogels containing 75% of TG. Young's moduli of the hydrogels varied from 5.0 to 11.6 kPa and were comparable to soft tissues like skin and muscle. In vitro cell viability assays revealed that the scaffolds were non-toxic and promoted proliferation of hepatocellular carcinoma HepG2 cells. Therefore, the plant-based hydrogels designed in this work have a significant potential for tissue engineering.
  • Birch wood pre-hydrolysis vs pulp post-hydrolysis for the production of xylan-based compounds and cellulose for viscose application
    (2018-06-15) Borrega, Marc; Larsson, Per Tomas; Ahvenainen, Patrik; Ceccherini, Sara; Maloney, Thaddeus; Rautkari, Lauri; Sixta, Herbert
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Hydrothermal treatments of birch wood and kraft pulp were compared for their ability to extract the xylan and produce viscose-grade pulp. Water post-hydrolysis of kraft pulp produced a high-purity cellulosic pulp with lower viscosity but higher cellulose yield than traditional pre-hydrolysis kraft pulping of wood. Post-hydrolysis of pulp also increased the crystallite dimensions and degree of crystallinity in cellulose, and promoted a higher extent of fibril aggregation. The lower specific surface area in post-hydrolyzed pulps, derived from their larger fibril aggregates, decreased the accessibility of –OH groups. However, this lower accessibility did not seem to decrease the pulp reactivity to derivatizing chemicals. In the aqueous side-stream, the xylose yield was similar in both pre- and post-hydrolysates, although conducting post-hydrolysis of pulp in a flow-through system enabled the recovery of high purity and molar mass (∼10 kDa) xylan for high-value applications.
  • Broke and waste coating color as a source of detrimental substances on a special paper machine
    (2014-06-23) Hoikkala, Eerika
     Kemian tekniikan korkeakoulu | Master's thesis
    The purpose of this work was to investigate the chemical stability of wet-end and impact of broke and wet waste coating color on final quality and machine runnability. Main target was to find out the correlation of broke and waste coating color with defect amounts and runnability problems. For this the most common wet-end measurements and additionally flow cytometer was used as analysis method. One idea of the work was also to define actions to prevent or decrease the negative impact of broke compounds on final quality. The focus of theoretical part was mainly in defining broke components and their characters as possible detrimental substances. Also the impact of different dry broke slushing parameters on broke quality was dealt. Main part of the theoretical part focused on defining the measurements and most common parameters affecting to wet-end stability, which were used in the experimental part. Introduction of different hydrophobic particles and ways to control them was as well studied. The experimental part composes four different parts and the first displays the overall chemical state of the wet-end and stock preparation system. The second and third part focuses on impact of broke and wet waste coating color on wet-end stability and defect amounts. The last part is a laboratory study for finding the optimal fixing agent to control the hydrophobic particles. Clear and biggest negative effect on wet-end stability was seen with coated broke and also some correlation to defect amount and runnability problems were detected. From waste coating color addition and broke slushing tests latex seemed to cause the highest disturbance to the process. Positive effect on decreasing the amount of hydrophobic particles was observed with highly cationic chemicals in production and fixing agents in laboratory study.
  • Characterization of milk of lime
    (2012) Heino, Juhana
     School of Chemical Engineering | Master's thesis
  • Chirality and bound water in the hierarchical cellulose structure
    (2019-07-15) Paajanen, Antti; Ceccherini, Sara; Maloney, Thaddeus; Ketoja, Jukka A.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Abstract: The origins of the unique properties of natural fibres have remained largely unresolved because of the complex interrelations between structural hierarchy, chirality and bound water. In this paper, analysis of the melting endotherms for bleached hardwood pulps indicates that the amount of non-freezing bound water (0.21 g/g) is roughly half of the amount of freezing bound water (0.42 g/g). We link this result to the two smallest constitutive units, microfibrils and their bundles, using molecular dynamics simulations at both hierarchical levels. The molecular water layers found in the simulations correspond quite accurately to the measured amount of non-freezing and freezing bound water. Disorder that results from the microfibril twist and amphiphilicity prevents co-crystallisation, leaving routes for water molecules to diffuse inside the microfibril bundle. Moreover, the simulations predict correctly the magnitude of the right-handed twist at different hierarchical levels. Significant changes in hydroxymethyl group conformations are seen during twisting that compare well with existing experimental data. Our findings go beyond earlier modelling studies in predicting the twist and structure of the microfibril bundle.
  • Comparative analysis of silane and maleic anhydride coupling agents in wood polymer composites: Adhesion mechanisms and impact on mechanical properties
    (2023-08-22) Legesse, Netsanet
     Kemian tekniikan korkeakoulu | Master's thesis
    Wood polymer composites (WPC) have emerged as versatile and sustainable materials with diverse applications. However, achieving optimal interfacial adhesion between hydrophilic wood fibers and hydrophobic polymer matrices remains a key challenge, impacting the overall mechanical performance of WPC. This thesis aimed to address this challenge by investigating the effectiveness of different coupling agents in improving interfacial adhesion and mechanical properties of WPC. Wood fiber polypropylene (PP) composites were produced using two different approaches: by modifying the fiber surface before compounding or through an in-situ compatibilization method in a hot/cold mixer and extruder. Interfacial adhesion between wood fiber and PP was enhanced by the addition of 3-(trimethoxysilyl) propyl methacrylate (MPTMS) and vinyltrimethoxysilane (VTMS) with or without initiator, and the results were compared to those obtained using the commonly used maleic anhydride grafted polypropylene (MAPP), as well as WPC without any coupling agents. Injection-moulded specimens were prepared for mechanical testing, and the fractured surface from tensile testing was characterized by SEM. Water up-take of WPC was measured by immersing the specimens in water. All results showed that the interfacial adhesion between wood fiber and PP matrix is crucial in determining the properties of WPC. SEM images confirmed that the interfacial interaction between wood fiber and PP matrix determines the overall mechanical properties of the composite. Silanes with an initiator resulted in higher tensile strength compared to WPC without coupling agents, confirming the enhanced interfacial adhesion of WPC. Moreover, the incorporation of silane coupling agents with an initiator resulted in decreased water absorption, fulfilling the requirement for water resistance in outdoor applications. Among all the combinations, WPC with MAPP exhibited the highest tensile and flexural strength by improving the fiber-matrix adhesion and changing the failure mode from fiber/matrix debonding to fiber fracture. However, there was no significant difference observed in the modulus among all the samples.
  • Composition and application potential of fibre-rich side streams from the forest industry
    (2023-06-13) Sandberg, Mia
     Kemian tekniikan korkeakoulu | Master's thesis
    Circular economy and material efficiency are strong influencers in the forest industry. Nevertheless, the forest industry generates substantial quantities of waste and side streams that are mainly incinerated or disposed in landfills. Fibre-rich side streams are generated in different stages of pulp, paper, board, and tissue paper production. Significant amounts of valuable components such as fibres and minerals are lost in form of fibre-rich side streams as their complex compositions are not fully known and the current uses are limited. In this master’s thesis, a selection of fibre-rich side streams from pulp, board and tissue paper mills are characterized in order to outline their suitability as raw material sources for side products in terms of chemical composition and physical properties. Two knot rejects, a fibre sludge, a fibre clay, and a deinking sludge were selected for this study. The chemical composition analyses determined the carbohydrate, lignin, extractives, ash, metal, and elemental contents. The fibre characteristics and fine material species within these side streams were analysed using both laboratory analyses and microscopy. Additionally, the feasibility of analysing these side streams using these methods was evaluated. As a result, this master’s thesis provides a rough overview of the chemical composition and physical properties of the studied side streams, guidance on how to perform the analyses more reliably and conclusions on the most potential new uses. The studied fibre-rich side streams are heterogenous materials containing 47-85% carbohydrates, 0.2-2.4% extractives, 0.5-2.0% acid soluble lignin, 1.7-50% ash and 13-32% acid insoluble material. In terms of chemical composition, the fibre sludge showed highest potential as feedstock in sugar platform or in agricultural uses, the fibre clay as a reinforcement material in composites and the deinking sludge as a source of fillers and pigments. In case of the knot reject, it was estimated that the most profitable use would be to recycle the side stream back into the digester and use it for pulp production. Further research on the applicability of fibre-rich side streams is still required to assess the viability of these materials for specific applications.
  • Consolidation and dewatering of a microfibrillated cellulose fiber composite paper in wet pressing
    (2015) Rantanen, Juuso; Maloney, Thaddeus
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • Corrected Gibbs-Thomson coefficient for the cellulose-cyclohexane system
    (2017-10-03) Moriam, Most
     Kemian tekniikan korkeakoulu | Master's thesis
    Thermoporosimetry is a calorimetric method that allows the measurement of the pore size distribution (PSD). The method measures the melting or freezing point depression of a liquid trapped in a pore. Then, this melting/freezing point depression is correlated to the pore size by the Gibbs-Thomson coefficient. Thermoporosimetry has several advantages. For example, it does not require toxic chemicals. Compared to other methods, the sample preparation is relatively simple. Moreover, samples analysis occurs in wet-state. However, the application of thermoporosimetry to cellulosic materials presents some critical limitations. Instead of using pulp fibers, the Gibbs-Thomson coefficients are calculated from materials with a different porosity, such as, silica or controlled porous glass material. This might provide misleading pore information. Thus, the primary aim of this work was to overcome this limitation. By combining cyclohexane thermoporosimetry and Hg-porosimetry, a system for determining an alternative Gibbs- Thomson coefficient was presented for a set of five types of pulps. These included bleached/unbleached, hardwood/softwood, and dried/never dried fibers. Additionally, by combining thermoporosimetry and centrifugation method, a novel platform was developed to estimate the amount of true macropores in fiber cell wall. In conclusion, a framework for calculating ‘corrected’ Gibbs-Thomson coefficient for thermoporosimetry-based PSD determination in cellulose-cyclohexane system was demonstrated in this study. Furthermore, thermoporosimetry was applied to quantify fiber cell wall macropores.
  • Cost-benefit analysis of chemi-thermomechanical pulp use in board production
    (2018-08-28) Parkkonen, Ville
     Kemian tekniikan korkeakoulu | Master's thesis
  • Cyclic Pressing as a Viable Approach for Dewatering and Controlling Shrinkage of Micro-Nanofabricated Cellulose Films
    (2024-06-27) Zamani, Elaheh Sharifi; Ahadian, Hamidreza; Maloney, Thaddeus
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Cellulose films, predominantly consisting of micro-nanocelluloses, are a new type of product with interesting properties for functional packaging applications. However, the potentially scalable production methodology has not yet been elucidated. Poor dewatering and high web shrinkage are issues that need solutions beyond what is available in conventional paper production. This research investigates a cyclic pressing method that shows potential in cellulose film consolidation. Cyclic pressing allows the MNFC films to be dewatered to about 90% solids while yielding a smooth, flat product. The results show no inherent physical limits for mechanical dewatering these high swelling webs, even at very high solids. Cyclic pressing allows controlled restraint during consolidation, which could be adjusted in an industrial setup to produce even films with desirable product characteristics.
  • Deaggregation of cellulose macrofibrils and its effect on bound water
    (2023-11-01) Maloney, Thaddeus; Phiri, Josphat; Zitting, Aleksi; Paajanen, Antti; Penttilä, Paavo; Ceccherini, Sara
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The purpose of this study was to determine how to control and measure the hierarchical swelling in pulp fibers via electrostatic interactions and localized osmotic pressure. A eutectic solvent system was used to systematically increase phosphate groups in the cell wall. Increase in fiber charge led to an increase in swelling properties, as expected. At a charge value around 180–200 μmol/g the macrofibrils were found to deaggregate. This led to a large jump in mesoscale swelling, from 0.9 to 2.5 mL/g, and surface area, from 400 to 1000 m2/g. This deaggregation was confirmed with X-ray scattering and solute exclusion. A novel thermoporosimetry method was used in the study. This involved splitting the nonfreezing water into two subfractions, thus allowing a more complete analysis of pore structure and surface area. The hydrated surface area for the samples was in the range 1200–1400 m2/g, which agreed well with simulations of aggregated microfibrils. Adding charge to the pulp fibers had a nonlinear effect on handsheet strength properties. This suggests that hierarchical control of fiber swelling may be a useful approach to improve important property pairs such as strength/density in packaging and other commercially important fiber products.
  • Determination of the flow properties of microfibrillated suspensions
    (2012) Henriksson, Antti
     School of Chemical Engineering | Master's thesis
  • Development of a novel rheology-based method to estimate pulp reactivity
    (2016-08-23) Ceccherini, Sara
     Kemian tekniikan korkeakoulu | Master's thesis
    The recent expansion and diversification of cellulose-based products market has created the need for a more accurate pulp characterization, and new parameters have been developed, including cellulose and pulp reactivity. Cellulose reactivity has been often described as the ability degree of the reactive hydroxyl groups within the polysaccharide to react with chemicals, and it has been estimated by means of complex, time-consuming methods. Many studies have utilized these estimations as representative values of pulp reactivity. However, this approach is questionable, because the latter depends not only upon cellulose reactivity, but also on other parameters. Thus, the aim of this work was to develop an alternative fast user-friendly procedure to estimate pulp reactivity as such. This novel evaluation method was based on the monitoring of pulp dissolution in a bis (ethylenediamine) copper (II) hydroxide solution (CED) at constant measurement conditions using a rheometer equipped with a bob-and-vane geometry. Torque values were first measured throughout the reaction and then plotted as function of time. The resulting torque profile was found to consist of four phases: torque decrement, linear increment, non-linear increment, and the plateau. The dissolution began with the linear phase and ended with the plateau value. Based on the analysis of the profile, three parameters were identified as best representing pulp reactivity: pre-dissolution time (PDT), initial dissolution rate (IDR), and optimal dissolution time (ODT). The first estimated the accessibility of CED to the pulp, while the second and the third evaluated pulp reactivity as such. In particular, high IDRs and low ODTs were found to correspond to high pulp reactivities, though these two parameters were not directly proportional. In order to optimize the method, the experiments were organized in two parts. The first evaluated the measurement conditions affecting the results and allowed the standardization of the procedure. Differently, the second part verified the applicability of the procedure on a wide range of pulps, evaluating the reactivity of dissolving, kraft and mechanical pulps exposed to different physical and chemical treatments. Although the IDRs showed higher repeatability than the ODTs, all the measurements resulted consistent. Moreover, the optimal dissolution times allowed the comparison among pulps obtained by different manufacturing processes. Finally, the rheological estimations were accompanied by further analyses in order to better understand the factors influencing pulp reactivity. The here proposed rheology-based pulp reactivity estimation method was proved to be sensitive, reliable, fast, and relatively simple. Thus, the procedure was confirmed as an efficient alternative to the other methods based on cellulose reactivity. Nevertheless, the results reported also the necessity of further studies, especially to better interpret the dynamics regulating torque plateau.
  • Effect of cellulase family and structure on modification of wood fibres at high consistency
    (2019-05) Rahikainen, Jenni; Ceccherini, Sara; Molinier, Matthieu; Holopainen-Mantila, Ulla; Reza, Mehedi; Väisänen, Saija; Puranen, Terhi; Kruus, Kristiina; Vuorinen, Tapani; Maloney, Thaddeus; Suurnäkki, Anna; Grönqvist, Stina
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Abstract: Enzymatic modification of bleached softwood kraft fibres for improved fibre reactivity was studied at high (20% w/w) and low (1% w/w) dry matter content. The role of enzyme family and structure in fibre modification was assessed using endoglucanases from three structurally different glycoside hydrolase (GH) families (5, 7 and 45) with and without a carbohydrate binding module (CBM). Based on the amount of dissolved sugars, enzyme action at high consistency was about sixfold higher compared to a fibre treatment at low consistency. The GH45 endoglucanase was found to be most specific in acting on pulp cellulose whereas the family 5 and 7 endoglucanases had activity also on pulp hemicelluloses. The GH45 endoglucanase was found to be most efficient in reducing molecular weight and viscosity of the pulp. In addition, treatment with the GH45 endoglucanase resulted in the highest micropore volume in fibres and thus an increase in cellulose accessibility. The increased accessibility could be seen as decreased dissolution time in cupriethylenediamine using recently developed analytical techniques: viscometric analysis and microscopic video analysis. At high consistency, CBM was not promoting enzyme action, although CBMs are known to be beneficial at low dry matter conditions. Graphical abstract: [Figure not available: see fulltext.].
  • Effect of Compression Refining on Fiber Properties
    (2020-11-01) Käyhkö, Jari; Hiltunen, Eero; Hiltunen, Yrjö; Nikolskaya, Ekaterina; Kulmala, Lauri; Maloney, Thaddeus
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This article shows how fiber properties obtained by the compression refining of bleached softwood pulp refined using a KID 300 refiner differs from traditional bar refining. A KID refiner is a stone crusher that has been modified to refine fiber, and it offers a refining method that could be used at the mill scale. This study showed that compression refining caused more internal fibrillation compared with blade refining and improved the pulp’s ability to be beaten. Net energy consumption in compression refining was less than that of bar refining. Compression refining yielded pulp with shorter fibers and a higher number of fines, kinks, and curves. Still, the strength properties of the paper were the same level as bar-refined pulp, probably due to the higher internal fibrillation and flexibility of the fibers. It was also shown that the low field time-domain nuclear magnetic resonance (TD-NMR) method was capable of measuring the porosity and internal fibrillation of the fiber.