Browsing by Author "Rojas, Orlando"

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  • Bioactive nanocellulose films with spatial definition
    (2018-07-31) Solin, Katariina
     Kemian tekniikan korkeakoulu | Master's thesis
    In this thesis, fluidic channels were prepared on films made from cellulose nanofibers (CNF) and their potential use in biosensor applications was studied. The main goal was to develop hydrophilic-hydrophobic patterns to controllably produce CNF substrates for microfluidic applications. The work included a detailed investigation, to prevent non-specific adsorption of a type of human serum protein, hIgG, on CNF. A suitable antifouling agent for the CNF films was tested. CNF is a cellulosic material that has at least one dimension in the nanometer range and it is mainly produced mechanically from wood fibers. It can be used to make strong, translucent and smooth films. Two different approaches were tested to prepare 2D-channels on the CNF films: photolithography and inkjet printing of hydrophobic materials. The photolithographic method utilized simultaneously thiol-ene and thiol-yne click chemistries. In the inkjet studies, it was observed that polystyrene dissolved in p-xylene worked successfully. The prepared microfluidic CNF materials were characterized with SEM, AFM, contact angle measurements and liquid flow tests. Additionally, the non-specific protein adsorption was studied by using model CNF films with QCM-D, SPR and AFM techniques. Furthermore, the adsorption of fluorescent hIgG was performed on real CNF films and channels with CLSM method. The molecules used for protein blocking included BSA, fibrinogen and PDMAEMA-block-POEGMA copolymers. The results indicated that the best fluid flow was obtained by inkjet printing channels with polystyrene edges on CNF films. In addition, the PDMAEMA-block-POEGMA copolymer was the best antifouling agent for CNF and it reduced the hIgG adsorption up to 95 %. The successful blocking of the channels point out that these systems could be developed further and possibly be used in future biosensing applications.
  • Biohybrid pickering foams: Early stage development of scaffolds for bone tissue engineering
    (2023-12-12) Paganelli, Zoe
     Kemian tekniikan korkeakoulu | Master's thesis
    The present study focuses on the early stage development of biohybrid Pickering foams composed of partially deacetylated chitin nanofibres (cht), chitosan (chs), and bioactive glass (BAG) for bone tissue engineering applications. The investigation involved the test of formulations containing different concentrations of cht, chs, crosslinkers, and BAG, ultimately leading to the selection of a base formulation with 0.6wt% cht and 0.6wt% chs in combination with 0.6wt% BAG or 0.06wt% BAG. Gas bubbles (N2O and CO2) were added to these formulations through the use of a foam dispenser. Mechanical tests of the developed foams showed promising results, with formulations displaying characteristics properties relatable to bone tissue support. Scanning Electron Microscopy (SEM) imaging of the foams reveals highly porous structures, demonstrating the potential for efficient nutrient diffusion and cell proliferation. Ion leaching from the foams, as determined by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), is comparable to existing literature, ensuring biocompatibility. Additionally, immersion of the scaffolds in simulated body fluid results in the growth of hydroxyapatite (HA) on the surface, further affirming their potential for bone tissue engineering. Differential Scanning Calorimetry-Thermogravimetric Analysis (DSC-TGA) provides valuable insights into the thermal stability of different scaffold compositions. Preliminary rheology tests are promising, indicating the potential use of these formulations as inks for 3D printing, facilitating precise scaffold fabrication. In conclusion, this study presents a significant step towards the development of biohybrid Pickering foams as potential scaffolds for bone tissue engineering. The successful incorporation of chitin, chitosan, and bioactive glass, along with the advantageous mechanical, morphological, and biocompatible properties, makes these foams promising candidates for further research and applications in tissue engineering.
  • Biosynthetic production of bacterial cellulose-chitosan composite by modifying Hestrin-Schramm broth sugar composition
    (2019-12-17) Laine, Mikko
     Kemian tekniikan korkeakoulu | Master's thesis
    Some microorganisms provide an ecological way to produce pure cellulose without costly, energy-intensive purification steps. However, while bacterial cellulose (BC) holds desirable properties, such as biodegradability and high mechanical strength, human body lacks cellulose-hydrolyzing enzymes, which restricts the use of BC in different biomedical applications. To overcome this limitation, amine-incorporated BC composites, exhibiting chitosan-like properties are introduced. Reactive amine groups incorporated in BC provide an excellent basis for enzyme immobilization and biocompatibility, required for medical applications ranging from drug delivery to artificial skins. In this thesis, BC-chitosan composites are produced biosynthetically by modifying Hestrin-Schramm broth sugar composition. It has been previously shown, that Komagataeibacter xylinus is able to in situ incorporate chitosan and chitin groups from the culture medium to the BC. The results of this study suggest that compared to K. xylinus, K. medellinensis is a more suitable strain for amine-incorporated BC production. The highest chitosan content, 2.3 % (w/w), was achieved with K. medellinensis in HS culture including 2.0 % (w/v) N-acetyl-glucosamine. In addition, amine-incorporated BC was produced with culture including glucose and ammonium chloride, with 0.2 % (w/v) determined as the optimal NH4Cl concentration for BC-composite production. The produced BC composites were analyzed with FTIR, MALDI-TOF, HPAEC-PAD and SEM, with ζ-potential and water holding capacity also determined.
  • Black Bioinks from Superstructured Carbonized Lignin Particles
    (2023-11-02) Dufau Mattos, Bruno; Jäntti, Noora; Khakalo, Sergei; Zhu, Ya; Miettinen, Arttu; Parkkonen, Joni; Khakalo, Alexey; Rojas, Orlando; Ago, Mariko
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A renewable source of carbon black is introduced by the processing of lignin from agro-forestry residues. Lignin side streams are converted into spherical particles by direct aerosolization followed by carbonization. The obtained submicron black carbon is combined with cellulose nanofibers, which act as a binder and rheology modifier, resulting in a new type of colloidal bioink. The bioinks are tested in handwriting and direct ink writing. After consolidation, the black bioinks display total light reflectance (%R) at least three times lower than commercial black inks (reduction from 12 to 4%R). A loading of up to 20% of nanofibers positively affects the cohesion of the dried bioink (1 to 16 MPa), with no significant reduction in light reflectance. This is a result of the superstructuring of the ink components, which disrupts particle packing, intensifies colloidal interactions, introduces light absorption, and non-reflective multiple scattering.
  • Cellulose based conductive polymers
    (2015-06-11) Lin, Haishu
     Kemian tekniikan korkeakoulu | Master's thesis
    Conductive fibers show potential applications in different areas. In this thesis, cellulose and its derivatives, including carboxymethyl cellulose, cellulose acetate as well as methyl cellulose were used to produce fibers via wet spinning. Different conductive materials were also introduced in an attempt to obtain cellulose-derived conductive fibers. Different conductive fillers (Zelec, carbon black, conductive polymers) were evaluated. Among them, PEDOT and PPy conductive polymers showed promising performance. In the future, the production of core/shell fibers should be studied, as well as the optimization of fiber processing conditions (such as viscosity of solution, spinning speed, coagulation bath.)
  • Cellulose Nanofibers as Functional Biomaterial from Pineapple Stubbles via TEMPO Oxidation and Mechanical Process
    (2022-03) Araya-Chavarría, Kenly; Rojas, Ruth; Ramírez-Amador, Karla; Sulbarán-Rangel, Belkis; Rojas, Orlando; Esquivel-Alfaro, Marianelly
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The pineapple fruit when harvested generates a large amount of residual biomass; this biomass can be used to generate value-added products such as cellulose nanofibers. This study was focused on the isolation of CNF from pineapple leaves after oxidation pretreatment with 2,2,6,6-tetramethylpireridine-1-oxyl, followed by mechanical deconstruction of the fibers via combination of grinding and microfluidization process. One and two microfluidization passes were applied to bleached and unbleached fibers, respectively. The implications of these findings are that during the production process it is possible to reduce the amount of chemicals needed for bleaching and the energy involved in the mechanical microfluidization process. Such process yielded corresponding fibril lengths and widths in the range of 481–746 nm and 16–48 nm. The respective electrostatic charges, as measured by zeta potentials, were −41 mV and −31 mV. As expected, the CNF crystallinity was higher than that of the starting material, especially for the cellulose. However, the thermal stability was reduced, showing two degradative processes due to the chemical modification of the fibers. The CNF produced from pineapple leaves has a potential to be used like biomaterial in diverse applications while representing a viable alternative to producers, which face serious environmental and health challenges given the large volume of biomass that is otherwise left in the fields as waste.
  • Colloidal structures of phospholipids in vegetable oil and their potential usage in surface treatment of nanocellulose for food applications
    (2019) Lehtinen, Olli-Pekka
     School of Chemical Engineering | Licentiate thesis
    The aim of the licentiate’s thesis was to understand the colloidal behaviour of phospholipids in vegetable oils and to study the adsorption of phospholipid nanostructures onto the surface of cellulose nanofibrils. Water concentration, temperature and free fatty acid had an effect on the formation of reverse micelles of phospholipids in vegetable oil. At low water concentration, phospholipids formed solubilized reverse cylindrical micelles above critical micelle concentration (cmc) in the oil. Increasing temperature decreased the cmc of phospholipids in oil. Addition of moderate amount of water into oil caused solubilized phospholipids to form lamellar liquid crystal structures that were precipitated from the oil and formed separate phase. Oleic acid in rapeseed oil increased the solubility of lecithin and suppressed the formation of phospholipid reverse micelles at low water content. In presence of more water, the oleic acid stabilized the reverse micelles and consequently more water was needed to induce the phase separation. Thus it could be concluded that moderate amounts of oleic acid (5 wt.-%, 10 wt.-% and 20 wt.-%) in the oil delayed the removal of phospholipid reverse micelles upon addition of water, and the formation of lamellar structures required more water. This was caused by the increased solubility of lecithin into oil due to the co-solvent effect of oleic acid. Nanocellulose has shown many potential applications in foods, such as emulsifiers, fillers, structuring agents and cholesterol binders. An interesting application for nanocellulose would be the replacement of saturated fats in foods to decrease the fat content and the energy content of the products. To increase the compatibility of nanocellulose with the vegetable oil, the adsorption of phospholipid nanostructures was studied by immersing cellulose nanofibril film into the oily liquid containing phospholipid lamellar structures. The contact angle measurement seemed not to be an optimal way to measure the adsorption of phospholipids onto the surface of nanocellulose due to the variation in the results. Some of the contact angle measurement results indicated that the addition of the oily liquid containing phospholipid lamellar structures onto the surface of nanocellulose decreased the hydrophilicity of the surface after rinsing it with chloroform. In addition, two measurements indicated that the addition of oily liquid containing phospholipid lamellar structures decreased the hydrophilicity of the surface.
  • Comparison of the surface activity of hemicelluloses extracted from spruce and birch sawdust
    (2018-12-11) Ishfaq, Amal
     Kemian tekniikan korkeakoulu | Master's thesis
    This thesis investigated the surface activity of four extracted, unmodified hemicelluloses, namely, galactoglucomannan, GGM, phenolic galactoglucomannan, pGGM, glucuronoxylan, GX, and phenolic glucuronoxylan, pGX. It was determined that the relative amount of sugars was almost the same for GGM and pGGM as well as GX and pGX. With the increased concentration, the lowest surface tension was determined for pGX while the highest foamability and foam stability was observed for GX. The acetylation degree and the presence of residual lignin greatly affected the foam properties. The bubble size (optical microscopy) increased over time at increased concentration, owing to the combination of different foam destabilisation mechanisms. Hemicellulose aggregation was investigated via dynamic light scattering. In contrast to the aggregates formed by GGM and GX, which remained stable as the concentration was increased, those from pGGM and pGX became smaller. This is likely due to the presence of free and bound lignin. Overall, the better foamability and foam stability over time for GX suggest this extracted hemicellulose as an alternative to synthetic amphiphilic molecules.
  • The effect of chemical additives on the strength, stiffness and elongation potential of paper
    (2017) Strand, Anders; Khakalo, Alexey; Kouko, Jarmo; Oksanen, Antti; Ketola, Annika; Salminen, Kristian; Rojas, Orlando; Retulainen, Elias; Sundberg, Anna
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The effects of wet-end additions of cationic starches and/or carboxymethyl cellulose (CMC) on paper properties was determined by papermaking trials. The aim of this study was to mitigate the distinctive decrease in strength and stiffness due to unrestrained drying by addition of wet-end additives, while maintaining the extraordinarily high stretch potential of papers after unrestrained drying. Addition of the different polysaccharides increased the tensile index and density of the paper. The largest incgtreases in tensile index and stiffness were seen when combining cationic starches with CMC. With certain combinations of cationic starch and CMC, it was possible to increase the tensile index and stiffness of the paper, while maintaining the high elongation at break after unrestrained drying. To complement the results from the papermaking trials, adsorption of cationic starches and CMC onto cellulose nanofibril model surfaces was studied by QCM-D and SPR techniques. The additives adsorbed onto cellulose surfaces as soft gels, containing a large amount of coupled water. Adsorption of soft and malleable polysaccharide layers in the fiber-fiber joints enhanced the paper properties significantly on a macroscopic level. The softest and most swollen polysaccharide layers resulted in the largest increases in tensile index and stiffness of paper
  • End-functionalization of biosynthetic oligocellulose and polyisoprene for Click chemistry derived block copolymer
    (2020-08-18) Elomaa, Nina
     Kemian tekniikan korkeakoulu | Master's thesis
    This master thesis dealt with the use of biosynthetic oligocellulose (OC) and commercial polyisoprene (PI) to synthesize a new sustainable carbohydrate-based block copolymer (BCP). The BCP would have been derived by the coupling of OC and PI by copper(I) catalyzed alkyne/azide cycloaddition (CuAAC). Block copolymer (BCP) self-assembly is a versatile concept for designing functional nanostructures in materials science, nanomedicine, and nanotechnology. By using carbohydrate-based BCPs, sugar moiety brings high hydrophilicity, increasing the interaction parameter for BCP self-assembly with a small number of repeating units. The nanostructure domain sizes can approach the sub 10 nm range. The experimental part of the work spins from a theoretical basis presented in the first part of the thesis. The OC block is end-functionalized with alkyne functionality to the reducing end carbonyl moiety. 6-azidohexanoic acid (linker) is synthesized for PI end-functionalization, and afterward, PI is reacted with linker molecule from one or both ends of the chain. The PI azide end-functionalization enables the future BCP synthesis with the end-functionalized OC by CuAAC. OC, PI, and their derivates were characterized by Nuclear Magnetic Resonance spectroscopy (NMR), Fourier-Transform Infrared Spectroscopy (FT-IR), Matrix-assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometer (MALDI ToF-MS), Thermogravimetric Analyzer (TGA), and Differential Scanning Calorimetry (DSC). According to analysis, the synthesis of end-functionalized OC, the linker, and end-functionalized PI with the linker were all successfully conducted.
  • Evaporation-induced self-assembly of cellulose nanocrystals from aqueous suspensions into chiral nematic solid structures
    (2018-06-05) Klockars, Konrad
     Kemian tekniikan korkeakoulu | Master's thesis
    Biobased and renewable cellulose nanocrystals (CNC) can form hierarchically structured assemblies with impressive optical and mechanical properties. These rod-shaped nanoparticles, produced through acid hydrolysis of biomass, self-assemble in aqueous suspensions and form a liquid crystalline anisotropic volume fraction (AVF), the extent of which depends on the concentration. The anisotropic chiral nematic liquid crystalline phase can be preserved in the dry state through evaporation-induced self-assembly (EISA). This transition is not fully understood and requires more thorough inspection, in order to create large-scale defect-free structures for demanding applications, such as impact resistant materials. This work addresses this by studying the conditions during EISA for producing highly ordered CNC films. Solid CNC films display structural colour, whose intensity and uniformity reveal how well the chiral nematic order is preserved and defined within the film. UV-Vis spectroscopy, optical microscopy and scanning electron microscopy (SEM) provide information on the formation and distribution of the structural colour. In the first part of this work, the EISA drying temperature was varied (23, 28, 36, 41, 51 and 61°C). The results showed deteriorated helical order within solid films produced at higher drying temperatures. This conclusion was deduced from UV-Vis spectroscopy data that implied a larger distribution of structural colours in the films dried at elevated temperatures. In the second part, five different concentrations of the suspensions (3-7% w/w), and thereby AVFs, were used, while keeping the drying conditions the same. One set of samples was dried immediately after casting, while another set was equilibrated prior to drying. The characterization of the dry films by microscopy, UV-Vis and SEM showed that suspensions dried from a high AVF and an equilibrated state produced films with more homogeneous, long-range order, having larger chiral nematic domains. In contrast, films dried from AVF=0 lacked long-range order and did not benefit from equilibration.
  • Fiber-based superabsorbents
    (2017-08-29) Ajdary, Rubina
     Kemian tekniikan korkeakoulu | Master's thesis
  • Functionalized nanocellulose supported phase change materials for thermal energy storage
    (2019-10-22) Shi, Xuetong
     Kemian tekniikan korkeakoulu | Master's thesis
  • Lignin effect in castor oil-based elastomers: Reaching new limits in rheological and cushioning behaviors
    (2021-02-08) Borrero Lopez, Antonio M.; Wang, Ling; Valencia, Concepción; Franco, José M.; Rojas, Orlando
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Lignin is demonstrated as an unprecedented reinforcing material that tailors the rheological and cushioning properties of castor oil-based polyurethane elastomers, expanding their viscoelastic moduli by four orders of magnitude. The tensile strain at break was triplicated in the presence of lignin while the Young modulus and the stress at break were enhanced 17- and 7-fold, respectively. Remarkably, in compression tests, lignin addition increased the stresses at break by more than 88-fold, whereas the strain at failure shifted from 50 to 93%. Dynamic mechanical compression tests indicated outstanding cushioning and resistance performance. Overall, the results demonstrate a performance not reached before for biosourced elastomeric materials, fitting the demands of a wide range of applications.
  • Lignin films – production and characterization
    (2018-08-28) Päärnilä, Sonja
     Kemian tekniikan korkeakoulu | Master's thesis
    Due to the increased awareness of the negative effects of petroleum-based products, biobased alternatives have been considered for their suitability and environmental friendliness. Among these, lignin macromolecules have several interesting properties, related to their role in mass transport (barrier), as well as antioxidative, antimicrobial and UV-blocking activity. Moreover, lignin is less hydrophilic compared to most biobased polymers. However, to facilitate lignin`s use in applications, its chemical heterogeneity should be reduced, which can be accomplished via fractionation. Thus, the aim of this thesis was to study the relationship between the structure and properties of lignin by preparing supported films from kraft lignin and its fractions. Further, to provide preliminary information about which fractions would function better in given applications, particularly in food packaging and edible films, was targeted. The physicochemical properties of the lignins were studied by using spin-coated films. Atomic force microscopy, contact angle measurement and X-ray photoelectron spectroscopy were used to investigate the topography, wettability and surface chemical composition of the films. More heterogeneous, globular structured films were obtained from the unfractionated kraft lignin and its soluble fractions when polystyrene was used as a prime layer on the silica wafer substrates. The critical surface energy was quantified based on results from contact angle measurements with different liquids. Small differences in surface energy were determined. The higher critical surface tension obtained for unfractionated kraft lignin was partly related to its larger carbohydrate content. Heat treatments applied on the films showed that their hydrophobicity increased to the same level regardless of the differences in the lignin structures between the fractions. Moreover, the polystyrene pre-layer had an increasing effect on the hydrophobicity which was attributed to lignin and polystyrene fusing together during the thermal treatment. XPS measurement revealed that during heating the oxygen content increased. Hence, the degradation of carbohydrates was responsible for the increased hydrophobicity. No significant differences between lignin fractions in wetting or hydrophobicity after heating were observed. Thus, based on this study, all the fractions have similar potential for utilization that require given surface chemical behaviours, such as in food products. Basic research on the film properties, such as water interaction and viscoelasticity, should be carried out next in order to gain more knowledge on lignin`s behaviour.
  • Modified cellulose nanofibrils in co-stabilized Pickering foams and supraparticles
    (2020-12-15) Abidnejad, Roozbeh
     Kemian tekniikan korkeakoulu | Master's thesis
    Two-phase dispersions, such as foams, are thermodynamically unstable structures and the phases tend to separate eventually. Considering that these systems have a wide variety of applications, improving their stability is essential. Traditionally, surfactants have been used to increase the stability of multiphase systems; however, the surfactant effect is reversible. As a result, an alternative way to enhance these systems' stability was established by using particles. This method is called the Pickering stabilization. This thesis's main objective was to fabricate foams and fiber-particle composites stabilized by particles and reinforced with cellulose nanofibers (CNF), as well as to investigate the characteristics of the formed systems, including volume, stability, morphology, and mechanical properties. Regarding the fabrication, hydrophobic particles (silica and polytetrafluoroethylene), CNF (isobutyrilated, acetylated and nonmodified) and a suspension of water-ethanol as the foaming media were used. The results showed that the presence of hydrophobic CNFs improved the volume and stability of wet foams significantly. Also, the presence of CNFs improved the cohesion of hydrophobic particulate materials, where a balance between interfiber and fiber-particle can be tuned based on the fiber's surface chemistry.
  • Nano-cellulose based insulation biomaterials for thermal regulation purposes
    (2021-10-19) Le, Wendy
     Perustieteiden korkeakoulu | Master's thesis
    There is a growing urgency to develop more sustainable solutions to address climate change impacts. Energy consumption from building thermal regulation is a large contributor to CO2 emissions from heating and cooling units. Phase change materials (PCM), such as polyethylene glycol (PEG), can thermoregulate and alleviate the intensive use of heating and cooling of buildings. Commercial PCMs used for thermo-regulation in buildings still have the problem of leakage from the transformation of solid-liquid phase. Nanocellulose (CNF) is successful in providing physical encapsulation with PEG, referred to as a phase change nanohybrid. In this study, a novel phase change nanocellulose hybrid (PCN) is introduced and characterized. Modified CNF (TEMPO-oxidized, acetylated and lignin, and TiO2 additive containing CNFs) and different processing techniques (3D printing, freeze templating and casting) are explored to observe their effects on the insulating qualities of the PCN. The PCNs exhibited very low bulk densities (0.022-0.043〖g /cm〗^3) and high porosity (95.8-98.1%). Scanning electron microscope (SEM) and porosity analysis measured with BJH methods revealed structural properties. Differential scanning calorimetry (DSC) measured latent energy storage (100-160 J/g) and specific heat capacity (up to 2.10 J/gK). The PCN demonstrated stable PEG encapsulation of up to 80 ℃ and 200 ℃ surface temperatures without leakage; imaged with a thermal IR camera. Thermocouple sensors revealed heat transfer behavior and low thermal conductivity (0.035-0.039 W/mK) was determined. Surprisingly, impedance testing revealed sound absorption capability, and compressive dynamic mechanical analysis (DMA) indicated the PCN’s structural reformation ability.
  • Nanocellulose as barrier coating deposited using a laboratory rod coater
    (2017-04-24) Matikainen, Lauri
     Kemian tekniikan korkeakoulu | Master's thesis
    Both nanocellulose and barrier coatings are topical subjects, as evidenced by the accelerated number of recent reports related to nanocellulose and packaging. This thesis aims to understand the flow behaviour of nanocellulose as a coating layer deposited on paper by using a laboratory rod coater. The experimental efforts cover tests related to the rod-coating parameters and the properties of the deposited nanocellulose. Associated properties were explored with respect to nanocellulose pretreatment, substrate type, heat treatment, as well as the effect of added soy proteins. The latter relied on the effect of this inexpensive biomolecule to facilitate layer cohesion. The main target was to investigate the response of the end-use properties on both the device parameters and the properties of the coated material. In terms of liquid packaging, the main properties studied included barrier effects, which in this thesis were assessed by measurements of air permeability, water and oil absorption. In addition, the tensile strength and fracture toughness were determined. Moreover, the relation between the rod coater parameters, the properties of the coating layer, coat weight and coating thickness were investigated. Heat treatment and binding with soy protein were identified as suitable strategies to reduce water absorption by nanocellulose. In addition, a connection between rod metering speed, air permeability and oil absorption was found. The effect was also based on rod gap size which regulated the amount of coating. Water transfer from the coating layer to the substrate and reduced coat weight were possible causes of a relatively high air permeability and oil absorption. However, the rheology of the layer and fibril agglomeration also played a role. Finally, nanocellulose percolation was found to decrease the fracture toughness as a function of coating solids.
  • Nanocellulose, pectin and lignin biomimetic composite filaments by wet spinning
    (2016-02-02) Wang, Ling
     Kemian tekniikan korkeakoulu | Master's thesis
    Bio-based materials are central components for the success of the future bio-economy and to fulfil product demands, for example, those derived from wood components, including cellulose, hemicellulose, lignin, extractives, etc. In turn, they can potentially address many current societal needs. An effort within the field of biomimetics of wood fibres, as presented in this thesis, is the use of TEMPO-oxidized nanocellulose (TOCNF), pectin and alkaline lignin to synthesize composite filaments. Such effort is aimed to the development of high performance products with low environmental impact. The composite water-based dope, containing the cell wall components along with calcium salts, displayed shear thinning properties and their spinnability was in some ways related to the apparent viscosity that need to be further proved. It was shown that pectin gelation was necessary for producing filaments by the wet spinning technology. In order to gellify pectin, two types of calcium salts (CaCO3 and CaCl2) were applied. It was found that acetone as coagulation medium afforded better spinnability compared to ethanol. In addition, the mechanical properties of the obtained filaments were compromised if excess calcium carbonate was used. It turned out that filaments obtained by using CaCO3 for in-situ gelation showed similar mechanical properties as those from TOCNF. In contrast, CaCl2 applied for ex-situ gelation made the filaments to become elastic. Remarkably, regardless the type of pectin gelation used, lignin improved the mechanical properties of TOCNF-based filament, in both the dry and wet state. SEM imaging was used to determine the surface morphology of the filaments. Filaments from in-situ gelation had similar surface features as those from neat TOCNF while those from ex-situ gelation were different. Polyhedral particles from CaCl2 salts were identified on the surface of filaments obtained from ex-situ gelation. Finally, quartz crystal microgravimetry was applied to understand the interaction mechanism between TOCNF, pectin and lignin.