| 1. |
- Capezza, Antonio Jose
(författare)
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Sustainable Biobased Protein Superabsorbents from Agricultural Co-Products
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The preparation of sustainable protein superabsorbents from agricultural industry side-streams is reported. Wheat gluten (WG), a co-product from the ethanol/starch industry, was processed into foams with sponge-like behavior and high liquid uptake. The materials were obtained by phase-separation of aqueous WG dispersions followed by ambient drying, or by lyophilization. The use of a natural and non-toxic cross-linker (genipin) resulted in foams with high water swelling properties (~18 g/g in 10 min). The rapid swelling may be of use in bio-based foams in e.g., sanitary pads.As an alternative, potato protein concentrate (PPC, side-stream from the starch industry), was functionalized and prepared as particles. The liquid swelling capacity was compared after acylation with five different agents. It is shown that the PPC can be acylated to replicate the chemistry of synthetic superabsorbent polymers (SAP), showing water swelling capacity >10 g/g. The acylation (using EDTAD) of WG suspensions resulted in protein particles with water and saline uptake of 22 and 5 g/g, respectively. Limited network stability was however observed when acylating WG in low-protein suspensions. This was addressed by mixing the acylated protein with genipin, which provided a stable protein network. The process gave functionalized particles with swelling capacity ~40 g/g and ~80 % retention of swelling in centrifuge retention tests.The extrusion of WG showed that porous WG with water uptake of 500 % can be produced. Further, the scalability of PPC production was pilot-tested by functionalizing potato fruit juice (PFJ), containing the potato protein in its soluble state before the industrial drying used to obtain PPC. This resulted in water swelling capacities >10 g/g, which was comparable to the PPC-functionalized materials. The results pave the way for future optimization of high-throughput production techniques using protein sources in mass production of sustainable protein-based SAPs.
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| 2. |
- Hoogendoorn, Billy W.
(författare)
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Exploring cellulose as a biomacromolecule for enhanced battery metal ion recovery/recycling
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The research focused on the effects of integrating nanocellulose in the solidification of metal ions into metal oxide particles or metallic electrodeposits. Firstly, the cellulose was isolated as highly crystalline ca. 15-25 nm thick and 500 nm long fibers from bacterial cellulose using acid hydrolysis and had a negative surface charge. Positively charged nanocellulose was also explored using cationic functional groups substituted onto the nanofiber surface. The effect of the isolated nanocellulose when preparing metal oxides via enforced precipitation of zinc metal ions into zinc oxide particles was investigated at ultra-low nanocellulose content ≤0.01 %. The result indicated that increased reaction yields of ~15 % and a reduction of particle sizes by up to 50 % could occur at nanocellulose concentrations of 0.01 %. The kinetics was studied and showed that the presence of cellulose consistently increased the consumption rates of zinc ions. If the reaction consumed a large fraction of the zinc-ions (>80%) within the first 15 min, continued growth of ZnO was also suppressed by the presence of nanocellulose. This was observed during the synthesis of sheet-like ZnO-particles, where an increase in reaction yield from 81 to 95 % hindered the growth of additional nanorods, which otherwise had formed after 15 min of the reaction. Further, nanocellulose was then evaluated for metal recovery reactions of Zn, Cd, and Ni using electrodeposition. Zinc and cadmium, which generally form separate, faceted metal particles during electrodeposition, grew large dendrites when nanocellulose was present in the electrolyte. In the case of cadmium, the formation of dendrites was correlated with increases in yield by up to 15 %. For nickel, which always deposited as uniform and non-faceted layers, the presence of nanocellulose did not result in dendritic deposits. While the presence of 0.05 % of nanocellulose did not affect the yield for negatively charged nanocellulose, positively charged nanocellulose decreased the deposited amount by up to ca. 20 %. The temperature was also used to tune the dendritic formation during the zinc deposition. The major finding was that while the zinc electrodeposition in the presence of nanocellulose at 20 or 40°C induced dendritic growth, a similar deposition at 60 °C did not, reverting the deposition towards promoting dense and faceted zinc particles. The research on integrating nanocellulose in metal oxide particle solidification and metal recovery using electrodeposition aligns with the United Nations' Sustainable Development Goals (SDGs), particularly Goal 12: Responsible Consumption and Production, and Goal 1: End poverty in all its forms everywhere, but also Goal 13: Climate Action. The use of nanocellulose as an additive can contribute to sustainable consumption and production practices, reducing waste and conserving natural resources. This approach can help to address the challenge of meeting growing demands for metals used in various industrial applications, particularly those associated with battery manufacturing. Recycling valuable metals using nanocellulose can reduce the environmental impact of mining and processing ores, contributing to sustainable resource management and contribute to poverty reduction for creating job opportunities. Furthermore, the use of nanocellulose in electrodeposition reactions will help to combat climate change by promoting more efficient and environmentally friendly metal recovery methods, potentially reducing the carbon footprint associated with traditional metal recovery and mitigate the environmental impacts of metal extraction and mining. Overall, the research on integrating nanocellulose in metal oxide particle solidification and metal recovery using electrodeposition demonstrates innovative and sustainable solutions for resource management, contributing to the UN's SDGs.
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| 3. |
- Pushp, Mohit
(författare)
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Microcalorimetry and Infrared Spectroscopy : Thermal processes related to solid waste, ageing rubber, phase change materials, and biomass gasification
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Microcalorimetry (MC) is a unique technique for an online measurement of heat production. It can be applied to solids, liquids, or gases. MC can be used to measure the heat involved in either exothermic or endothermic processes. The heat signal obtained from MC is a lumped parameter so chemical, biological, and physical changes involving heat are measured simultaneously. In this study MC has been used to study the thermal processes in municipal solid waste, phase change materials and polymeric materials. A self-heating phenomenon, which may lead to significant heat production in piles of stored municipal solid waste, was studied with MC. This enabled us to understand the propensity of self-heating in municipal solid waste in storage conditions closer to real-life. The results showed that the self-heating in the solid waste was due to the aerobic metabolism of microorganisms. With the development of a third generation MC and better temperature control mechanisms, MC can be operated in non-isothermal mode as a differential scanning calorimeter (DSC). However, MC is capable of measuring heat flow using significantly larger sample masses than DSC. The larger sample mass is more representative of complex/heterogeneous materials, like cementitious blocks. Hence, MC was applied here to determine if it could be a useful tool in characterizing the thermal properties (latent heat and specific heat) of cementitious grout containing phase change materials (PCMs). It was observed that the phase changes (melting and crystallization) due to the PCM could be accurately characterized with MC. Performance of PCM can be investigated using thermal cycling tests that mimic real-life temperature scans. The high sensitivity of MC (μW/10000 mg) means that chemical changes can be measured at least 100 K lower than DSC (μW/~30 mg). The increased sensitivity opens up the possibility of measuring the ageing/degradation of polymers at closer to real-life temperatures and conditions. This is advantageous, since the normally used accelerated testing at significantly higher temperatures leads to degradation conditions that do not resemble service conditions. It is shown here, with the MC technique on a highly filled ethylene propylene diene monomer (EPDM) material, that the ageing processes, as well as the activation energy of the ageing processes, at close to real-life temperature are different from those at high temperature. With the high sensitivity of the MC, local thermal processes on a small scale could be readily observed, such as the melting of the antioxidant and further reactions in the peroxide cross-linking system. Hence, the results indicate that MC is a promising technique for measuring chemical changes and reaction parameters closer to the real-life temperatures in complex systems like highly filled EPDM rubber. To relate heat flow data to chemical mechanisms, post analysis of polymeric materials should be carried out with alternate techniques, for example, infrared spectroscopy (FTIR), gas chromatography and scanning electron microscopy coupled to energy dispersive X-ray. In principle, the signature of hydrocarbons can be detected using FTIR. However, subjecting the instrument to the raw gas from biomass gasification runs the risk of condensation of tars on optical components and subsequent malfunction. As a solution, an external cell that can be heated to at least 400 °C was designed to ensure that tars remain in the gas phase. The on-line measurements for permanent gases, water and tars were made using a lab-scale downdraft gasifier. Concentrations of permanent gases are in good agreement with Micro-GC and spectral signatures of tars are comparable with measurements using the solid phase adsorption (SPA) technique.
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| 4. |
- Ullsten, Henrik, 1977-
(författare)
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Processing and Development of Wheat Gluten Plastics
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Renewable packaging materials are of interest for a more sustainable environment. Wheat gluten is one of the most interesting candidates to replace petroleum-based oxygen-barrier polymers for packaging applications. The high amount of hydrogen bonds makes wheat gluten interesting as oxygen barrier films with sufficient elastomeric mechanical properties. Wheat gluten based materials are homogeneous, mechanically strong and relatively water insoluble compared with other biological materials. Several studies of wheat gluten films have been performed on solution cast films and a few studies have been executed on compression molding. Extrusion, without solvents, is the most common and fastest processing method for the production of packaging films. In order to develop wheat gluten films to commercially competitive material it is crucial to make the material extrudable.The temperature window for extrusion of glycerol-plasticized wheat gluten was increased by the use of salicylic acid, a known scorch retarder and radical scavenger. Small effects of shear-induced heating during extrusion at the higher temperatures suggested that the acid acted as a lubricant and viscosity reducer. The latter was suggested to originate primarily from the salicylic-acid-induced reduction in the degree of protein aggregation/crosslinking, as indicated by size-exclusion high-performance liquid chromatography and chemiluminescence. Electron paramagnetic resonance spectroscopy on extruded films indicated that the beneficial effect of salicylic acid was due to its radical scavenging effect. The complex shear modulus increased more slowly with increasing salicylic acid content above 110-120°C, indicating that the aggregation/crosslinking rate was slower with salicylic acid, i.e. that it did have a scorch-retarding effect, besides yielding a lower final degree/complexity of aggregation.Sodium hydroxide was used as an additive to be able to extrude gluten at alkaline conditions. The oxygen barrier, at dry conditions, was improved significantly with the addition of sodium hydroxide. Oxygen transmission rate measurements, tensile tests, protein solubility, glycerol migration, infrared spectroscopy and electrophoresis were used to assess the properties of the extrudate. It was observed that the extrudate with 3 wt.% sodium hydroxide had the most suitable combination of properties, low oxygen permeability, large strain at break and relatively small aging-induced changes in mechanical properties, the reason probably due to high protein aggregation and low plasticizer migration.As an alternative method to get alkaline conditions ammonium hydroxide was added. It resulted in a three times stronger film compared to the pure gluten glycerol material and had an oxygen barrier that can favorably be compared with these of oriented polyethylene terephtalat or Nylon 66.Several plasticizers were examined in a screening test where the extrusion properties were predicted in a plasticorder. The temperature and melt viscosity were recorded during the kneading. The most promising plasticizers were chosen to further studies with tensile tests. Glycerol was shown to be the most efficient plasticizer for thermoformed gluten films.In order to use wheat gluten as a packaging material, it is important to be able to seal it. Wheat gluten films, molded at 100–130°C, were sealed by impulse sealing at 120– 175°C. The lap-shear and peel strength of the sealed films were evaluated. The lapshear strength was greater than or similar to that of polyethylene film, although the peel strength was poorer.
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| 5. |
- Wei, Xin-Feng, 1990-
(författare)
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Ageing behavior of plastics used in automotive fuel systems
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The increase in service temperature and the use of biobased fuels, such as biodiesel, have raised concerns on the short/long-term performance of plastic components used in automotive fuel systems.In this work the ageing behavior of unreinforced and glass-fibre reinforced polyamide 12 (PA12), exposed to three different fuels (petroleum diesel, biodiesel, and a mixture of these (80/20)) at high temperature, was investigated. The interactions between the polymer and the fuel, and the associated polymer ageing mechanisms (fuel uptake, extraction of monomer and oligomers, annealing and oxidation), were found to be “generic” in the sense that they occurred, although to various extent, for all fuels. In the glass-fibre reinforced polyamides, the ageing occurred mainly in the polyamide matrix and not in the matrix-fibre interface. The semi-aromatic polyamide showed better performance when exposed to fuels than the aliphatic PA12. At a component level, multilayer polyamide-based pipes, with polyamide or fluoropolymer as inner layer, were aged under “in-vehicle” conditions where the pipes were exposed to fuel on the inside and to the air on the outside. All pipes stiffened during ageing but embrittlement occurred only for the pipes with polyamide being the inner layer. Compared to polyamide, the fluoropolymer inner layer showed significantly better barrier properties towards the fuel and no material was extracted into the fuel. The plasticizer loss from the PA12 outer layers into air was diffusion controlled and its diffusivity followed a linear Arrhenius behavior in the high temperature region. Relationships between plasticizer loss and the changes in mechanical properties were established.The polyamides experienced diffusion-limited oxidation when exposed to air and/or fuel, involving the formation of a thin oxidized surface layer which was responsible for a significant decrease in strain-at-break. The fracture behavior of PA 6 in air at high temperature, found to involve three distinct stages, were systematically studied and linked to underlying mechanisms responsible for the reduction in strain-at-break.
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| 6. |
- Wennman, Maria, 1985-
(författare)
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Biobased and biodegradable binders for paper and nonwoven
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nonwovens are textile-like materials with similarities close to paper. One significant sector where nonwovens are used is for single-use products such as wet wipes and hygiene products. With an increasing global population, the manufacturing and use of nonwovens have grown significantly. With a higher standard of living worldwide, the demand for nonwoven products is expected to continue its growth in the foreseeable future. Several nonwoven materials are composed of cellulosic fibers and binder.This can be referred to as chemically bonded nonwovens. The binders are typically fossil-based and non-degradable. In this thesis, it is demonstrated that a binder composed of two polyelectrolytes (carboxymethyl cellulose and chitosan) along with citric acid, can serve as an excellent replacement for synthetic binders. Since the polyelectrolytes have opposite charges, they combine to form a polyelectrolyte complex (PEC).The PEC binder can be used both in the wet-end of a papermaking process and for treating already formed webs. Mechanical tests showed that the dry tensile strength increased significantly compared to untreated materials, as did the important wet tensile strength. It was found from Fourier-Transform Infrared Spectroscopy and Dynamic Nuclear Polarization enhanced NMR that newly established ester bonds and amide bonds, along with electrostatic interactions, were the key factors for the enhanced mechanical properties. PEC combined with sunflower oil resulted in fine emulsions that provided higher dry and wet tensile strength. Hydrophobicity in terms of high contact angles (>125°) for treated materials were also attained. Furthermore, combining PEC with two vegetable protein sources, pea protein and wheat gluten, demonstrated how the scope for PEC binders can be broadened. Together with the proteins, cellulosic materials acquired properties such as hydrophobicity and high tensile strength.
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| 7. |
- Özeren, Hüsamettin Deniz
(författare)
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Plasticization of Biobased Polymers: A Combined Experimental and Simulation Approach
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The field of bio-based plastics has developed significantly in recent decades and there is an increasing demand for industries to shift from petrochemical to biobased polymers. Biobased polymers offer competitive properties, and in many cases have advantages in terms of cost. Thermoplastic starch is already commercially available, while wheat-gluten protein-based materials are considered to be promising candidates for commercial use.Biobased materials can, however, have several drawbacks that have to be handled. Starch-based materials are, in general, brittle due to the stiff glucose-based molecular chain and hydrogen bond network. This is the case also for proteins (due to the stiff peptide bond, bulky side groups and hydrogen bond network), like for example gluten. These issues can, however, be resolved with effective compatible plasticizers. But in order to be able to optimize the choice of the right plasticizer for a specific polymer, there is a need for an increased understanding of the plasticizer mechanisms. Besides, a methodology for prediction of the plasticizer amount needed, as well as to be able to rank possible plasticizer candidates, based on their effectiveness. As a part of the development of a methodology (based on the combination of experimental and molecular-dynamics simulations) for prediction of plasticization and to investigate and understand plasticizer mechanisms, the main material investigated was starch, but also wheat gluten, both plasticized with glycerol. The main plasticizer used to date for biobased polymer materials is glycerol, because of its effectiveness, stability and low cost. In addition, it is also a large byproduct of biodiesel production. A number of other plasticizer candidates were also studied for the starch system to see if the developed methodology could be used to rank plasticizers. Diols were tested in the starch system as plasticizers, but they had no or little plasticization effect. Nevertheless, they gave rise to unexpected structures and properties. Several techniques were used to determine the experimental properties of the bio-based films, including calorimetry, gravimetry, dynamic mechanical analysis, and tensile testing.The results (based on mechanical and thermal properties) showed that the methodology could be used to rank plasticizers in terms of their effectiveness. It was also possible to predict the amount of plasticizer needed for effective softening. With the help of the simulations, the emollient effect could be studied in detail and largely explained by hydrogen bonding effects. The methodology was also developed to be able to predict from simulation not only trends in mechanical properties but also absolute values in stiffness and strength at elongation rates corresponding to experimental measurements.
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| 8. |
- Alipour, Nazanin
(författare)
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Interactions between polymers and the environment
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation addresses the structure and properties of a number of polymer-based materials when they come into contact with specific environments. The first part describes the migration and depletion of active substances from insecticide-impregnated polyethylene sheets in water and air at different humidity levels and higher temperatures. In the second part, the structure, crystallization kinetics, and mechanical and transport properties of multilayer polymer films, consisting of metallocene (mPE) and low-density (LDPE) polyethylene layers, and in some cases also with layers of poly(ethylene-co-vinyl alcohol) and a polyethylene compatibilizer were investigated. Furthermore, inhomogeneous swelling was observed in the 2-layer films containing mPE and LDPE due to differences in the uptake of n-hexane (and limonene) in the respective film layers. These differences caused a bending/curvature of the film upon exposure to the vapour. This effect was further evaluated to determine whether solvent-induced bending could be used as a passive sensor to detect the presence and content of volatile organic compounds in air (VOC). The third part of this thesis describes the possibility of producing biopolymer materials based on larvae from the black soldier fly. After adding a plasticizer to the degreased larval material, protein-based biopolymer films were prepared via compression-moulding. The lipid extracted from the degreasing operation could potentially be used in various applications, such as those involving lubricants. In the last part of this work the release of micro- and nano-particles were determined from a polypropylene nanoclay-composite in a commonly occurring environment for plastics (air at elevated temperature). A prototype exposure chamber was built, and a method was developed to allow aging (degradation) of the sample in this chamber and analyze the effects of aging on the sample.
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| 9. |
- Asem, Heba, 1987-, et al.
(författare)
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Functional nano-carriers for drug delivery by surface engineering of polymeric nanoparticles post-PISA
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Engineered polymeric nanoparticles (NPs) have been comprehensively explored as potential platforms for diagnosis and targeted therapy for several diseases including cancer. Herein, we designed functional poly(acrylic acid)-b-poly(butyl acrylate) (PAA-b-PBA) NPs using reversible addition-fragmentation chain-transfer (RAFT)-mediated emulsion polymerization via polymerization-induced self-assembly (PISA). The hydrophilic PAA-macroRAFT, forming a stabilizing shell (i.e. corona), was chain-extended using the hydrophobic monomer n-butyl acrylate (n-BA), resulting in stable, monodisperse and reproducible PAA-b-PBA NPs, typically having a diameter of 130 nm. Two approaches of surface engineering of the PAA-b-PBA NPs post-PISA were explored; a two-step and a one-step approach. In the two-step approach, the hydrophilic NP-shell corona was modified with allyl-groups under mild conditions using allylamine in water which resulted in stable allyl-functional NPs (allyl-NPs) suitable for further bio-conjugation. Their versatility was investigated by the subsequent conjugation of a thiol-functional fluorescent dye (BODIPY-SH) to the allyl-groups using click chemistry, in order to mimic the attachment of a thiol-functional target ligand. The average size and size distribution of the corresponding NPs did not change after BODIPY-conjugation. Neither the NPs nor allyl-NPs showed significant cytotoxicity towards RAW264.7 or MCF-7 cell lines, which indicates their desirable safety profile. A one-step approach to concurrently conjugate allyl-groups and a fluorescent dye (FITC) to the preformed PAA-b-PBA NPs was investigated. The cellular uptake of the FITC-NPs using J774A cells in vitro was found to be time- and concentration-dependent. The anti-cancer drug, doxorubicin, was efficiently (90%) encapsulated into the PAA-b-PBA NPs during NP formation. After a small burst release during the first two hours, a controlled release pattern over 7 days was observed. The present investigation demonstrates a potential method to functionalize polymeric NPs post-PISA to produce targeted drug delivery carriers.
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| 10. |
- Eliasson, Adrian, et al.
(författare)
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Highly Ductile Cellulose-Rich Papers Obtained by Ultrasonication-Assisted Incorporation of Low Molecular Weight Plasticizers
- 2023
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 11:24, s. 8836-8846
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Tidskriftsartikel (refereegranskat)abstract
- Ultrasonication was used as a mean toincorporate glycerolor urea, yielding paper films with a ductility of up to 35%. Fiber-based materials are attractive sustainable alternativestofossil-based plastics, however, the lack of ductility (i.e., brittleness)limits their applicability in complex shapes as are often utilizedfor plastics. In this study, we hypothesize that it is possible toenhance the ductility of a cellulose-rich material by the incorporationof low molecular weight plasticizers (glycerol, urea, citric acid,and tannic acid). However, no significant effects could be observedafter swelling in the presence of plasticizers. To enhance any potentialeffect, it was decided to employ ultrasonication to mechanically disintegratethe fiber and aid the sorption of plasticizer prior to formation ofsheets from the treated fibers. Glycerol or urea in combination withultrasonication resulted in both internal and external fibrillationof the fibers, and it could be observed that the resulting fines createa film at the surface of the fibers in the formed sheets. Tensiletesting shows that this gives rise to a 100% increase in ductilitycompared to sheets from untreated fibers. The use of citric or tannicacid has the opposite effect, reducing ductility to a third of thatof the reference sheet. This is suggested to be due to the formationof covalent cross-links in the treated fibers, which also leads todifferent internal and external fibrillation mechanisms, as observedby scanning electron microscopy. The exceptionally high improvementof the strain-at-break for sheets from the glycerol- and urea-treatedfibers suggests that low molecular weight plasticizers affect theinternal properties of the fiber wall as well as the interactionsbetween the fine material forming in-between the fibers. The findingsfrom the current study suggest that the proposed approach to obtainductile cellulose-rich materials holds promise for the future, butit is also clear that more in-depth research is required to obtaina mechanistic understanding and release the full potential.
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