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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Bestämning av dynamiska moduler hos fluorgummi FKM 70–1. : En motodbeskrivning för dynamiska modulvärden.

Johnsson, Emil, Hellgren, Elvira January 2020 (has links)
In order to quality assure and investigate material compositions in materials for components, safe methods need to be used to obtain correct results. When starting up a new analysis tool, a basic investigation is needed of how the tool is prepared, operated and how analysis data is interpreted. This is to maneuver the analysis tool correctly in the future work. Misuse of the analysis tool could potentially lead to the wrong material being selected for components and failure to respond to accident investigations. This thesis has been written at Husqvarna AB and its department Specialist Lab´s Material Laboratory. This study would lay the groundwork for how their new dynamic mechanical analysis tool should be used and operated to obtain correct material data for future analyzed materials. Dynamic mechanical analysis is a tool that has a wide range of application and Husqvarna's main purpose is to be able to analyze the dynamic mechanical properties of different polymers and rubber types. This study will primarily address an analysis of the dynamic properties of polyethylene FKM 70-1 in a DMA instrument. This is to carry out a successful analysis that can be used as a basis for future work in Husqvarna's DMA instrument.
22

Washing and drying reusable sanitary pads

Sundberg, Fanny, Anderhell, Max January 2019 (has links)
Period poverty is a problem mainly found in places characterized by poverty. The lack of means for women and girls to properly handle their menstruation is the essence of the problem. With a lack of both quantity and quality regarding water often being an issue in such places, the hygiene is a constant challenge. Two different kinds of sanitary products are used globally, disposable and reusable. The reusable ones are often being made of cotton or other absorbent materials. Regardless the material, reusable products need cleaning between the times of use, which could be a challenge when water is not always accessible. To have a reusable sanitary pad that efficiently can be cleaned with low amounts of resources is important, especially in impoverished places. Spacerpad is a reusable sanitary pad and a part of a project at the University of Borås. The aim for the project is to reduce period poverty and to educate women and girls in menstrual hygiene management. The pad is made of polyester which does not absorb blood or water, instead the pad merely contains the fluids. This thesis was conducted as a field study in Nairobi, Kenya. The study aimed to simulate a menstruation, in order to analyze the microbial activity in two different reusable sanitary pads, during as well as after menstruation. With the influences from interviews and resources found in Kibera (a slum in Nairobi) a simulation of five days was executed, with nutrient solution instead of menstrual blood. The Spacerpad and a cotton pad were exposed to the same procedures and the effects of washing and drying were studied. The microbial activity was measured with the help of dipslides, a growth medium. The results of this study show that both Spacerpad and the cotton pad could be carriers of heavy growth of bacteria. Increasing microbial activity throughout the simulation as the days went by, ended with a dividing result after a soap wash as the final washing procedure. The pad made of cotton still carried above slight growth, compared to Spacerpad that showed almost no activity after the final cleanse. Even though the microbial activity reached high levels during the simulation, the fact that the Spacerpad can be cleaned with limited resources could be reason enough to consider the Spacerpad as a sufficiently sanitary product in an impoverished place like Kibera. / Mensfattigdom är något som vanligtvis återfinns på platser präglade av fattigdom. Bristen på medel för kvinnor och flickor att kunna hantera sin menstruation är kärnan av problemet. Med en brist i kvantitet och kvalitet på vatten som ett vanligt problem på sådana platser är det en konstant utmaning att upprätthålla sin hygien. Menstruationsskydd delas in i två olika typer, engångs- och återanvändningsbara produkter. De återanvändningsbara produkterna består ofta av bomull eller andra absorberande material. Oavsett material måste produkterna rengöras mellan användningarna, vilket kan vara en utmaning på platser där vatten inte alltid är tillgängligt. Tillgång till en återanvändningsbar binda som kan rengöras med små resurser är viktigt, speciellt på platser som kännetecknas av fattigdom. Spacerpad är en återanvändningsbar binda, framtagen som del av ett projekt vid Högskolan Borås, vars syfte är att reducera mensfattigdom och samtidigt utbilda kvinnor och flickor om menstruation och hygien. Bindan är tillverkad av polyester som inte absorberar blod eller vatten, vilket gör att bindan snarare håller vätskorna på plats. Denna uppsats gjordes som en fältstudie på plats i Nairobi, Kenya och hade som mål att simulera en menstruation. Detta för att se hur den mikrobiella aktiviteten skulle kunna se ut, under och efter en menstruation. Med influenser ur intervjuer och tillgångar från Kibera (ett slumområde i Nairobi) genomfördes simulationen med näringslösning som substitut till mensblod. I simulationen studerades effekten av tvätt och tork på den mikrobiella aktiviteten. Spacerpad och en bomullsbinda genomgick samma processer där aktiviteten mättes med hjälp av dipslides, ett växtmedium. Resultaten från denna studie visar att både Spacerpad och bomullsbindan kan vara bärare av hög tillväxt av bakterier. En ökande bakteriell aktivitet genom testdagarna, slutade med ett tudelat resultat efter en tvåltvätt som sista procedur. Bindan av bomull hade lätt tillväxt, medan Spacerpad knappt visade någon tillväxt alls efter den sista rengöringen. Den mikrobiella aktiviteten hos Spacerpad nådde höga nivåer under simulationen. Trots det så gör förmågan att kunna rengöras med låg åtgång av resurser, att den kan anses vara sanitär nog för att användas på platser präglade av fattigdom, som i Kibera.
23

Viskostygs inverkan på plagg efter tvätt. : Hur krympning av viskos påverkar plaggets passform, mått och konstruktion för en klänning

Asres, Bersabeh Zemedagegnehu January 2020 (has links)
Denna studie tas fram i samband med ett mindre modeföretag inom damkonfektion. Företaget har haft återkommande problem med passformen av deras viskosklänning. Syftet med studien är att undersöka viskosmaterialets påverkan efter tvätt på passform så som balans, rörelsevidd, längd och plaggs mått. Viskos är ett av de finaste textilmaterialet för sömnad av klänningar på grund av sin fina glans, snyggt fall och höga absorberande egenskaper. Däremot har viskosmaterial tendensen att förlora styrkan när det är vått, vilket händer att plagget krymper efter tvätt. Studien utförs genom att jämföra tre framtagningsprocessen av en klänning för att få den bästa passformen och önskade plaggmått. För prototyperna A och B används samma mönsterkonstruktion, förutom för prototyp B tvättas viskos tyget i förhand. Medans för prototyp C tvättades med tygprov och krympningen beräknades i cm, mönsterkonstruktioner justerades med att addera resultatet av krympningen. Klänningarna syddes av samma viskostyg, provades på en person i storlek Medium och tog mått på klänningarna både före och efter tvättning. Prototyp C resultatet visades att klänningen har krympt till den bästa passformen och uppfyller önskade plaggmåtten i jämförelse med prototyperna A och B. I Studien visades att plagg som är sytt i viskosmaterial förändas både i passform och mått efter tvätt. Före tvätt av viskosmaterial innan tillskärning kommer inte att garantera att det uppsydda plagget inte krympa eller att plaggen behåller sitt mått efter tvättning. Ändringen i mönsterkonstruktion ger bättre resultat. / This study is developed in collaboration with a small company that works with women's clothing. The company has had recurring problems with the fit of their viscose dress. The purpose of the study is to analyze the effect of the viscose material shrinkage after laundering on the fit of the garment such as balance, ease, length and the garment dimension. Viscose is one of the finest textile materials for dresses sewing because of its properties such as it’s fine shine, drapes well and it have high absorbent. In contrast, viscose material tends to lose strength when wet, which affects garment fit due to viscoses shrinkage after laundering. The study is performed through comparing of three production processes of a dress to get the best fit and dimensions. For sample A and B, the same pattern construction is used, except for sample B, the viscose fabric was pre-washed in advance. While for sample C fabric samples was washed and the number of shrinkage is calculated . Pattern construction was adjusted by adding the results of shrinkage . The three sample dresses were sewn with the same viscose fabric, and the fit were tasted by one person in size Medium .The dress samples were measured both before and after laundering. The result of prototype C showed that the dress has shrunk to the best fit and meets the desired garment sizes in comparison with prototypes A and B. The study showed that garments that are sewn in viscose material change both in fit and size after washing. Washing viscose material before cutting will not ensure that the sewn garment will not shrink or that the garments will retain its dimension after washing. The change in pattern design gives better results.
24

Strain rate-dependent mechanical properties of high-density polyethylene(HDPE)

Andersson, Oscar, Wiklund, Alexander January 2022 (has links)
In today’s packaging industry HDPE is widely used and correct understanding of itsproperties and how to model them is of vital importance. HDPE is a semi-crystallinepolymer with a known strain rate dependence, that is a higher yield and lower strainto failure at higher strain rates. HDPE does also exhibit the phenomena of cold-drawing, together with other polymers. Cold-drawing is where after the specimenhas necked, the necking stabilizes and starts to pull material above and below intothe neck, effectively elongating the neck while maintaining its width. The objective of the study is to look at the local strain rates as the specimen necksand if a simple Abaqus model can capture those effects. The effect of strain rate onthe shape of the neck was also studied. The work was to test HDPE in uniaxial tension with different strain rates (∼10-3 s-1to ∼10-1 s-1) and measure the local strain rates with 2D-DIC. A decent amount oftime was used to make sure the camera setup gave the best quality possible for theequipment available. The videos produced was used for the DIC analysis as well asfor the image analysis to measure the width of the neck. After the tests a calibrationscheme was used to create a material model that matched the force-displacementfrom the physical 100 mm/min test data. Studying the force displacement the strain rate effects noted in previous researchare present. The results from the DIC show a very high local strain rate as the spec-imen necks, between 11-65 times higher than the global (grip-to-grip) strain rate.From the measurement of the width there are some rate effects as well. The slowerspeeds (5 and 10 mm/min) shows a continually reducing width while the 50 and 100mm/min shows a more stable neck and the 500 mm/min test does not have any sig-nificant neck propagation. The simple elastic-plastic model show similar local strainrates as the experiment however does show a noticeable thinner neck. / I dagens förpackningsindustri används HDPE ofta och korrekt förståelse av dess egenskaper och hur man modellerar dem är av avgörande betydelse. HDPE är ensemikristallin polymer med ett känt töjningshastighetsberoende, det vill säga en hö-gre sträckgräns och lägre töjning till brott vid högre töjningshastigheter. HDPEuppvisar också fenomenet kalldragning, tillsammans med andra polymerer. Kall-dragning är det fenomen som uppstår efter att provet har påbörjat midjebilding ochmaterial börjar dras in i midjan, vilket leder till en förlängd midja. Syftet med studien var att titta på de lokala töjningshastigheterna under midje-bildning och om en enkel Abaqus-modell kan fånga dessa effekter. Effekten av töjn-ingshastighet på midjan form studerades också. Arbetet började att testa HDPE i enaxlig spänning med olika töjningshastigheter(∼10-3 s-1 till ∼10-1 s-1) och mäta de lokala töjningshastigheterna med 2D-DIC. Endel tid lades ner på att se till att kamerauppsättningen gav högsta möjliga kvaliteti förhållande till den utrustning som användes. Filmen från testerna användes bådeför DIC och en bildanalys för att mäta bredden på midjan. Efter testerna använ-des ett kalibreringsschema för att skapa en materialmodell för att matcha kraft-förskjutningskurvan från det fysiska 100 mm/min-testet. Genom att studera kraft-förskjutning är effekterna av töjningshastigheten som noter-ats i tidigare forskning närvarande. Resultaten från DIC visar en mycket hög lokaltöjningshastighet under midjebildning, mellan 11-65 gånger högre än den globala(grepp-till-grepp) töjningshastigheten. Från mätningen av bredden finns det ocksåvissa hastighetseffekter. De lägre hastigheterna (5 och 10 mm/min) visar en kon-tinuerligt minskande bredd, 50 och 100 mm/min visar en stabilare midja och 500mm/min-testet har ingen signifikant kalldragning. Den enkla elasto-plastmodellenvisar liknande lokala töjningshastigheter som experimentet men de visar en märk-bart tunnare midja.
25

Reinforced Biodegradable Polymer Composite Material based on Japanese Washi Paper

Rova, Lovisa January 2022 (has links)
In this study, traditional Japanese washi paper was sandwiched with poly(butylene succinate)(PBS) in order to produce a paper-based composite material that can be biologically degraded. Specimens were prepared using a hot press, and the mechanical properties of the washi paperand the new composite material were investigated by tensile tests. The cross-sections of specimens were then observed with a digital microscope as well as by scanning electron microscope (SEM) analysis. The microscope images indicated that therelatively hollow washi provides a structure for the polymer to settle into, which could contribute to the improved strength of the composite material. Specimens made from three layers of washipaper and combined with two layers of PBS film had remarkable mechanical propertiesincluding a UTS of 95 MPa.The composite material was incubated in compost and a MODA C-S (Microbial Oxidative Degradation Analyzer) was used to evaluate its biodegradability. The material showed good biodegradability with significant losses of mass (-32 %) as well as major loss of mechanical strength after four weeks of incubation. The biodegradability of the material will be further investigated.
26

Conditioned 3D-printed polyamides for structural optimization : Establishing the material data to advance in AM utilization

Olsson, Philip January 2022 (has links)
Polyamides are commonly used in additive manufacturing for final part production, but the material performance can be affected by environmental conditions. The purpose of this project was to evaluate the effects of moisture and temperature on 3D printed polyamides and how structural optimization can benefit from condition-specific data. Conditioned and unconditioned specimens were tensile tested in regions of -20 °C, 23 °C and 60 °C. Two techniques were evaluated; multi jet fusion and selective laser sintering, and mainly two polyamides; polyamide 11 and polyamide 12. Simulations with the obtained data were performed as well as conceptual structural optimization with the intent of optimizing for the intended end-use environment. Infrared thermography provided specimen temperatures as well as temperature and strain relations present during testing. The stress-strain curves obtained showed generally decreasing stiffness and strength with increasing moisture and temperature, albeit moisture in certain cases increased the tensile modulus at freezing temperatures. Temperature affected stiffness and strength more so than moisture. Polyamide 11 absorbed moisture at a higher rate than polyamide 12. The mechanical performance of laser-sintered polyamide 12 was superior, while laser-sintered polyamide 11 showed great elongation before breakage. Further investigation of polymer crystallinity could explain the behaviour of the 3D printed polyamides.
27

Studies on the thermal degradation of thermosetting polyimides and their composites / Studier av termisk degradering i härdplastpolyimider och dess kompositer

Petkov, Valeri January 2022 (has links)
The thesis contains a background and reflections section, an introduction, and three appended articles. The first section is reserved for some of the background and basics on polymers and polymer composites and a discussion on their effect on our everyday lives. The introduction gives a brief recap of the project. The articles contain the research that was performed on the thermal oxidation of thermosetting polyimides and their composites during the project. The first article covered the thermal oxidative degradation of satin weave and thin-ply composites made by resin transfer molding with carbon fibers and thermosetting polyimide. The degradation was studied by weight loss measurements and X-ray computed microtomography. The weight loss measurements showed that the initial desorption stage during ageing followed Fickian behavior and the proposed model. It was also observed that the satin weave composites formed crack clusters that grew into a network of cracks, voids and delaminations throughout the specimens as the ageing time progressed, while the thin-ply composites only formed delaminations at the free edges. The second manuscript studied the behavior of the neat polyimide resin when aged for up to 1500 hours in ambient air, and compared it with a newly developed polyimide formulation, with slightly altered chemical composition. The reduced amount of internal crosslinkers in the newer formulation was expected to enhance the fracture toughness of the material. Three-point bending, differential scanning calorimetry, dilatometry, weight loss, light optical microscopy and nanoindentation experiments were performed and highlighted the differences in the thermal and mechanical properties of the two formulations. A slight increase in the fracture toughness was observed, while the glass transition of the new formulation had decreased. The third manuscript was aimed at continuing the discussion from the second article on the differences between the two thermosetting polyimides. Thermogravimetric scans showed that the polyimide formulations behaved very similarly under thermal oxidative tests. The initial analysis gave indications that the model could capture well the degradation at high temperatures, but is not adequate in predicting long-term degradation at temperatures around 288–400 °C.
28

Synthetic Functionalization of Colloidal Lignin Particles for Wood Adhesive Applications / Syntetisk funktionalisering av kolloidala Lignin-partiklar förvedhäftande applikationer

Alexander Deen, Fusi January 2020 (has links)
Functionalizable spherical colloidal lignin particles (CLPs) represent a valuable asset for the valorization of lignin side-streams from the pulp industry. The spherical structure allows for the circumvention of the heterogeneous and poorly dispersible structure of the biopolymer. However, organic solvents and alkaline media degrade the particle structure and dissolve the polymers due to their chemical nature and solubility. The solvents will alter the aggregated polymers into irregular shapes that would correspond to inconsistent physicochemical properties. Then, the material will become unusable for advanced material applications, namely wood adhesives. In this study, a replicable process to yield pH ca. 12 stable CLPs for wood adhesives or further functionalization for other advanced material applications was developed and optimized. Lignin was functionalized with cross-linkers, glyoxal or formaldehyde, and selfassembled into spherical structures in the micro emulsification of the organic solution. The formed colloids were partially rotary evaporated to retain organic solvents within the colloidal structures, and then be cured at 73-76 °C until pH stable and further functionalized for advanced material applications. The functionalization with glyoxal was pursued further for its possibly increased reactivity and the health concerns associated with formaldehyde. The process requires the addition of glyoxal to lignin in an acidic organi cmedia at ambient temperature, and the solution to react at 64 °C. Glyoxal is likely added to the polymer structure in its hydrated and dimerized form, and its attachment to lignin should be analyzed through the behavior of glyoxal in different media. The formed colloids were rotary evaporated to an organic solvent content of 60 wt. % of the spheres to allow the occurrence of the curing reaction. These materials were finally cured by thermosetting them at 73-76 °C until pH stable. The particles can be cured with base-catalysis through the controlled addition of the base NaOH(aq). However, the mode and rate of addition of the catalyst are critically important for a nondegradative infusion of a base into solvent present ot removed particles without morphological changes. Further procedural improvement and larger batches are necessary to conduct CLP adhesive experiments. / Funktionaliserbara sfäriska kolloidala ligninpartiklar (CLP) är en värdefull tillgång för valorisering av ligninsidoströmmar från massaindustrin. Den sfäriska strukturen reducerar effekten av den heterogena och dåligt dispergerbara biopolymeren. Organiska lösningsmedel och alkaliska medier försämrar emellertid partikelstrukturen och löser upp polymererna på grund av deras kemiska natur och löslighet. Lösningsmedel kommer att resultera i att de aggregerade polymererna antar oregelbundna former vilket skulle resultera i inkonsistenta fysikalisk-kemiska egenskaper. Därigenom blir materialet oanvändbart för avancerade materialapplikationer, såsom t ex trälim. I denna studie, utvecklades och optimerades en reproducerbar process för att ge pH ca. 12 stabila CLP för trälim eller ytterligare funktionalisering för andra avancerade materialapplikationer. Lignin funktionaliserades med tvärbindare, glyoxal eller formaldehyd och självorganiserades till sfäriskas trukturer genom mikroemulgering av organfasen. De bildade kolloiderna indunstades delvis roterande för att bibehålla det organiska lösningsmedlet i de kolloidala strukturerna och härdades sedan vid 73-76 ° C tills pH-stabilitet och funktionaliserades ytterligare för avancerade materialapplikationer. Funktionaliseringen med glyoxal utfördes också för att reaktiviteteten och begränsa de hälsoproblem som är förknippade med formaldehyd. Förfarandet kräver tillsats av glyoxal till lignin i ett surt organiskt medium vid rumstemperatur för att sedan reageras vid 64 ° C. Glyoxal i dess hydratiserade och dimeriserade form adderas sannolikt till polymeren, och dess kemiska inbindning till lignin kan analyseras genom att undersöka glyoxal uppförande i olika medier. De bildade kolloiderna indunstades till ett organiskt lösningsmedelsinnehåll av 60 viktprocent för att möjliggöra härdning. Dessa material härdades slutligen genom värmehärdning vid 73-76 ° C tills pH var stabilt. Partiklarna kan härdas med baskatalys genom kontrollerad tillsats av basen NaOH (aq). Emellerti där sättet och tillsatshastigheten för katalysatorn kritiskt viktigt. Ytterligare processförbättringar och större satser är nödvändiga för att genomföra CLP-limexperiment.
29

Vertical charge transport in conjugated polymers

Skrypnychuk, Vasyl January 2017 (has links)
Conjugated polymers are novel organic electronic materials highly important for organic photovoltaic applications. Charge transport is one of the key properties which defines the performance of conjugated polymers in electronic devices. This work aims to explore the charge transport anisotropy in thin films of P3HT, one of the most common conjugated polymers. Using X-ray diffraction techniques and charge transport measurements, the relation between vertical charge transport through thin P3HT films and structure of the films was established. It was shown that particular orientations of crystalline domains of P3HT, namely face-on and chain-on, are beneficial for vertical charge transport. These orientations provide the efficient pathways for the charges to be transported vertically, either via π-π stacking interaction between the adjacent conjugated chains, or via the conjugated chain backbones. It was also demonstrated that particular orientations of crystallites are favourable for the formation of interconnected percolated pathways providing enhanced vertical charge transport across the film. Deposition of P3HT on most commonly used silicon substrates typically results in the formation of mostly edge-on orientation of crystallites which is unfavourable for vertical charge transport. Nanoimprint lithography was demonstrated as a powerful processing method for reorienting the edge-on crystalline domains of P3HT into chain-on (vertical) orientation. It is also shown that thin P3HT films with preferentially face-on orientations of crystallites can be deposited on graphene surface by spin coating. Using patterning of thin P3HT films by nanoimprint lithography, unprecedentedly high average vertical mobilities in the range of 3.1-10.6 cm2 V-1 s-1 were achieved in undoped P3HT. These results demonstrate that charge transport in thin films of a relatively simple and well-known conjugated polymer P3HT can be significantly improved using optimization of crystallinity,orientation of crystallites, polymer chain orientation and alignment in the films.
30

Increasing the Writing Resolution for Electro-hydrodynamic 3D-Printing : by Active Steering of e-jet / Förbättring av skrivupplösning vid additiv tillverkning på mikroskala genom elektrostatisk styrning av skrivmaterial

Bergman, Henrik Dan January 2019 (has links)
Additive manufacturing has grown considerably during the last couple of decades, whether it comes to the printing of metal structure or living cells. Additive manufacturing techniques relays on the successive addition of material to create the wanted structure. Among the diversity of these many printing techniques, electrohydrodynamic 3D-printing is of particular interest, as the technique has a promising outlook for high-resolution printing on the microscale. The technique is compatible with a myriad of thermoplastics, but its writing resolution is limited due to the inherent affect the manufacturing process has on the material. Electrostatic forces between already deposited fibres and the fibre in light affect the final position of printed fibre. This thesis evaluates the possibility to increase the writing resolution in melt electrohydrodynamic 3D printing by a closed-loop feedback system. Components were built and added to an already existing printing setup to implement in-situ measurements of the fibres position as well as active electrostatic guiding of the fibre. The setup consisted of a camera that determined the position of the fibre; the position was then used in a PID controller to calculate an appropriate potential. The potential was forwarded to a high voltage amplifier, connected to a steering electrode, mounted in the vicinity of the jet. The setup built for one-dimensional steering of the fibre improved the printing accuracy by ten times through suppressing the repulsive/attractive forces, where the process variable of the PID controller was measured. However, the precision decreased roughly four times as it was deposited on the substrate. The limitations of the system have been evaluated, and possible improvements for the two-dimensional control of the fibre are further discussed.

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