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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.
11

Controlled Formation of New Si-Based Polymeric Materials

Roth, Michael J. 09 1900 (has links)
<p> This thesis provides examples of new Si-based polymeric materials in three parts. The rapid evolution of hydrogen gas was observed after the combination of an α- or β-hydroxy carboxylic acid with an alkoxyhydrosilane. This unusual reactivity is interpreted to arise from the cooperative nucleophilic attack of the hydroxy group at silicon and the electrophilic attack of the acid proton at the Si-H bond. These systems further react to produce modified sol-gel materials in which the acid units were incorporated into the matrix.</p> <p> The reactions of tetraethoxysilane, (TEOS) and α-hydroxy acids similarly produced modified sol-gels (in solution, DMSO) and solids (precipitated from THF). The reaction kinetics were followed in these systems using 29Si NMR. Extensive characterisation of our sol-gels was carried out by the use of various NMR techniques, FT-IR, elemental analysis and thermal methods of solids characterisation (TGA, DTA, and DSC).</p> <p> Silicones containing vinylsilane units were prepared in order to examine the silicon β-effect in a polymeric system for the first time. The addition of bromine to these systems unexpectedly resulted in no reaction unless vigorous conditions were used. Steric factors as shown by molecular modeling are attributed to this lack of reactivity. Although many silicone systems were studied where more sterically "open" vinylsilanes were present these steric problems could not be overcome.</p> / Thesis / Master of Science (MSc)
12

Artificial Spider Web : Selection of Polymeric Materials for Special Effects Applications

Huas, Hugo, Jérome, Titouan January 2021 (has links)
Artificial  spider  webs  are  a  challenge  for  the  special  effects  companies.   The natural  spider webs  are  displaying  incredible  mechanical  properties  combined with  a  low  density  and  a  high stickiness making them hard to reproduce. Throughout this project the aim is to produce artificial spider  webs  using  a specific  manufacturing  method,  pouring  a  mix  of  polymer  and  Naphtha  oil into  water  to  form  the  webs.   This  method  was  used  in  previous  cinematic applications  giving outstanding results for the artificial spider webs.  Unfortunately, due to the loss of it, the specific parameters,  tools and raw materials have to be found.  A material selection is given leading to a specific choice of thermoplastic polymers.  The selected material are then tested manually so they can be listed depending on the results obtained.  Finally, the most promising material seems to be TPU, thermoplastic polyurethane;  thanks to its excellent mechanical properties and good visual aspect. / Konstgjord  spindelväv  är  en  utmaning  för  specialeffektföretag.   De  naturliga spindelnäten visar  otroliga  mekaniska  egenskaper  i  kombination  med  låg densitet  och  hög  klibbighet  vilket gör  dem  svåra  att  reproducera.    Under hela  detta  projekt  är  målet  att  producera  konstgjord spindelväv med hjälp av en specifik tillverkningsmetod, hälla en blandning av polymer och naftaolja i vatten för att bilda näten.  Denna metod användes i tidigare filmiska applikationer och gav enastående resultat för de konstgjorda spindelnäten.  Tyvärr, på grund av förlusten av det, måste de specifika parametrarna, verktygen och råvarorna hittas. Ett materialval ges vilket leder till ett specifikt val av termoplastiska polymerer. Det valda materialet testas sedan manuellt så att de kan listas beroende på de erhållna resultaten.  Slutligen verkar det mest lovande materialet vara TPU, termoplastisk polyuretan; på grund av dess utmärkta mekaniska egenskaper och bra visuella aspekt.
13

Hide and seek : Ett utforskande av nya materialupplevelser i ull

Edqvist, Helena January 2019 (has links)
Informationen om att det bränns ull i mängder samtidigt som vi importerar ull talar sitt tydligaspråk att något behöver göras. Ull som är ett hållbart och 100% förnybart material med bådehistoriska och fantastiska egenskaper, vilket gör att det är ett enormt resursslöseri att brännaull som om det vore skräp. Det finns många eldsjälar inom fårbranchen som arbetar för atthitta lösningar för dessa problem. Ullklassificering, att ta fram en nationell agenda överullhantering och försök att öka intresset för ull i allmänhet står på agendan. Utifrån ett hållbarhetsperspektiv såväl som ett personligt intresse och utifrån mina år somstylist har jag undersökt ullens sinnliga egenskaper för att hitta nya materialupplevelser i ettav världens äldsta textila material. Klimatfrågan som är högst aktuell, vilket vi alla på ett ellerannat sätt måste förhålla oss till, samt mitt mål att göra min forskning tillgänglig för alla, göratt mitt arbete har relevans utifrån ett hållbart, samhällsmässigt och kunskapsmässigtperspektiv. Utifrån en materialdriven design, där materialets mening står för att väva in denkänslomässiga kopplingen svensk ull, vill jag med konstnärlig ansats ta mig an arbetet i attutforska, utvärdera och ifrågasätta mig själv. Basen i hela mitt arbete är den materialdrivnaprocessen där jag varvar material och användartester för att bidra med nyamaterialupplevelser av ull. Jag hoppas att mitt arbete gör att vi ser med nya ögon på ull ochatt våra associationer till svensk ull inte enbart ses som en stickad tjocktröja eller ett parlovikkavantar från en gången tid. Jag vill vidga perspektiv och inspirera till att se möjligheter iden materialskatt vi har runt hörnet. / The information that wool is burned in quantities while we are importing wool speaks its clearlanguage, something needs to be done. Wool, which is a durable and 100% renewablematerial with both historical connections as well as fantastic properties, is a huge waste ofresources to burn as if it were rubbish. From a sustainability perspective as well as a personal interest, based on my years as astylist, I have investigated the sensual properties of the wool to find new materialexperiences in one of the world's oldest textile materials. The climate issue that is mostup-to-date, which we all have to relate to in one way or another, and that I want to make myresearch available to everyone, means that my work is relevant from a sustainabilityperspective. I have worked from a material-driven design, where the meaning of the material has beenimportant in order to weave the emotional connection to a material. With an artisticapproach, I wanted to take on my work in exploring, evaluating and questioning myself andmy work in a material-driven process, in which I turn materials and user tests to contributewith new material experiences of wool. I hope that my work contributes to seeing Swedishwool with new eyes. With new associations and perspectives. To see opportunities insteadof impossibilities.
14

Mechanoresponsive drug delivery materials

Kaplan, Jonah Andrew 28 October 2015 (has links)
Stimuli-responsive drug delivery materials release their payloads in response to physiological or external cues and are widely reported for stimuli such as pH, temperature, ionic strength, electrical potential, or applied magnetic field. While a handful of reports exist on materials responsive to mechanical stimuli, this area receives considerably less attention. This dissertation therefore explores three-dimensional networks and polymer-metal composites as mechanoresponsive biomaterials by using mechanical force to either trigger the release of entrapped agents or change the conformation of implants. At the nanoscale, shear is demonstrated as a mechanical stimulus for the release of a monoclonal antibody from nanofibrous, low molecular weight hydrogels formed from bio-inspired small molecule gelators. Using their self-healing, shear-thinning properties, mechanoresponsive neutralization of tumor necrosis factor alpha (TNFα) in a cell culture bioassay is achieved, suggesting utility for treating rheumatoid arthritis. Reaching the microscale, mechanical considerations are incorporated within the design of cisplatin-loaded meshes for sustained local drug delivery, which are fabricated through electrospinning a blend of polycaprolactone and poly(caprolactone-co-glycerol monostearate). These meshes are compliant, amenable to stapling/suturing, and they exhibit bulk superhydrophobicity (i.e., extraordinary resistance to wetting), which sustains release of cisplatin >90 days in vitro and significantly delays tumor recurrence in an in vivo murine lung cancer resection model. This polymer chemistry/processing strategy is then generalized by applying it to the poly(lactide-co-glycolide) family of biomedical polymers. As a macroscopic approach, a tunable, tension-responsive multilayered drug delivery device is developed, which consists of a water-absorbent core flanked by two superhydrophobic microparticle coatings. Applied strain initiates coating fracture to cause core hydration and subsequent drug release, with rates dependent on strain magnitude. Finally, macroscopic, shape-changing polymer-composite materials are developed to improve the current functionality of breast biopsy markers. This shape change provides a means to prevent marker migration from its intended site—a current clinical problem. In summary, mechanoresponsive systems are described, ranging from the nano- to macroscopic scale, for applications in drug delivery and biomedical devices. These studies add to the nascent field of mechanoresponsive biomedical materials and the arsenal of drug delivery techniques required to combat cancer and other medical ailments. / 2017-10-27T00:00:00Z
15

Prevention of waste from textile in Sweden

Shenxun, Yuan January 2012 (has links)
With the population growing gradually and economy booming in the world, the need of textile product accordingly increases rapidly, which results in the big generation of textile waste. The disposal of textile waste brings in many adverse effects on environment, such as the landfill occupation. The production of textile product itself also causes much environmental concerning. In order to cope with the increasing textile waste and reduce the pressure of waste management, waste prevention is primary, as well as effective choice. The prevention of waste from textile can return ideal revenue from economic, social and environmental aspects. So many countries have conducted some researches and practices on the prevention of waste from textile. Sweden also has some existed prevention measures. But these prevention measures mainly focus on two stakeholders: consumer and charitable organization.  Associated with the practical situation in Sweden, some existed prevention measures are transferred to the Swedish circumstance and then suggest a new prevention scheme about textile waste in Sweden. The suggested prevention scheme is based on four stakeholders’ (designer, retailer, consumer, charitable organization) point of view.
16

Shiboriteknik på möbeltyg. En studie i slumpens tecken.

Mörtberg, Ann-Christine January 2021 (has links)
The Shibori technique on modern furniture fabrics. A study in the name of chance. / <p>Presentation-framläggning via zoom-länk.</p>
17

Unified Model of Charge Transport in Insulating Polymeric Materials

Sim, Alec 01 December 2013 (has links)
Charge transport, charging, and subsequent electrostatic discharge due to interactions with the space environment are primary concerns of spacecraft designers. Developing a physical understanding of the interactions of charge with the multitude of materials that spacecraft are composed of is a critical step in understanding and mitigating both short-term and long-term spacecraft degradation. In particular, the study of charge transport in highly insulating materials is critical as they store charge longer, with higher capacity, and with greater destructive capability than other materials.The Utah State University Materials Physics Group, with the funding of the NASA James Webb Space Telescope project and Rocky Mountain Space Consortium, have developed a complete and consistent theoretical model that predicts short-term and long-term storage capabilities based on physical material parameters. This model is applicable across a wide range of experimental systems designed to test specific behaviors that characterize charging phenomena.Modeling and understanding the complex relationships between the spacecraft and its surroundings are fundamentally based on detailed knowledge of how individual materials store and transport charge. The ability to better understand these effects will help make exploring the edges of the universe more stable, reliable, and economic.
18

Bioflavonoid coated materials

Thomas, Howard, Dowling, D.P., Katsikogianni, Maria G. January 2014 (has links)
No / Polymeric materials are described which have a bioflavonoid coating, the bioflavonoid content of the coating comprising at least naringin and neohesperidin. The use of such coated polymeric materials is also described as well as the process for making the coated polymeric materials.
19

Manifestation och implementering av CSR : En studie om hur ett mindre företag kan använda CSR som instrumentför att stärka varumärket

Lindblad, Angelica, Chu, Anny January 2015 (has links)
Syfte: Syftet är att undersöka och analysera hur arbete med CSR (Corporate SocialResponsibility) och hållbarhet kan manifesteras och implementeras i ett mindre företag för attstärka företagets varumärke. Metod: Uppsatsen grundas i en kvalitativ metod för att eftersträva en holistisk- ochövergripande bild. Metoden är explorativ och utforskande och ger en djupare insikt ochförståelse för företagets tillvägagångssätt. Som utgångspunkt för sekundära källor harelektroniska och tryckta källor samt akademiska artiklar använts. Slutsats: Efter avslutade studier kan konstateras att genom företagets ståndpunkt i etik, moraloch värderingar i kombination med de praktiska handlingar de utför, manifesteras ochimplementeras CSR- och hållbarhetsarbete i verksamheten. Kundens medvetande ger styrkanoch det värdefulla i varumärket vilket leder till att dessa aktiviteter på ett omsorgsfullt ochgenuint sätt bör planeras och genomföras för att behålla och stärka företagetsvarumärkesimage.
20

Migração de carga espacial em copolímeros P(VDF/TrFE) / Space charge migration in P(VDF/TrFE) copolymer

Nagashima, Haroldo Naoyuki 22 April 1992 (has links)
Este trabalho apresenta um modelo teórico que procura explicar a origem de um pico anômalo de corrente, observado na fase faraeletrica do copolímero P(VDF/TrFE), nos processos de descarga. Quando uma voltagem tipo V(t) = Vo S(t) é aplicado em materiais isolantes, correntes elétricas observadas em medidas, de carga-descarga decaem aproximadamente com T-n e obedecem ao principio da superposição linear (PSL). Esse comportamento e também observado em polímeros dielétricos. Entretanto, nos processos de descarga, acima da temperatura de Curie do copolímero p (VDF/TrFE), surge um pico anomalo de corrente que viola, aparentemente, o (PSL). Apresentamos um modelo de migração de cargas de espaço em presença de armadilhas, que pode ser responsável pelo pico de corrente e que estaria superposta a corrente de descarga da absorção dielétrica, conforme o modelo, durante os processos de carga, impurezas extrínsecas seriam varridas, pelo campo, do volume da amostra e ficariam, preferencialmente, presas em armadilhas de superfície. Nos processos de descarga, essas cargas se deslocariam em direção ao interior da amostra, devido a repulsão Coulombiana. Esse mecanismo de condução gera um pico de corrente. A aplicação do modelo, permitiu-nos inferir valores de parâmetros como a mobilidade dos portadores de carga e o tempo de transito. / A model based on space charge migration to explain an anomalous electric current peak on films of P (VDF/TrFE) copolymer in its paraelectric phase is presented. In general step-voltage current measurements of insulating polymeric materials obey the Principle of Linear Super-position. However, an unexpected anomalous peak was observed in discharge currents in measurements performed with P (VDF/TrFE) above the Curie temperature. We have assumed that space charges were dragged from the bulk of the sample by the external field during the charge measurement, and trapped close to the surface of the sample in a region where the concentration of traps would be very high. Two methods were developed to calculate the magnitude of the current peak: I) assuming a given space charge distribution during the discharge measurement, and II) considering the movement of thin discrete layers of charge under the influence of the internal field.

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