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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.
551

Synthèse et modification d'un polyester biodégradable pour application agro-textile : le poly(butylène succinate) / Synthesis and modifications of a biodegradable polyester for agro-textiles : poly(butylene succinate)

Vandesteen, Marie 27 March 2015 (has links)
Au cours des dernières décennies, l’utilisation de polymères biodégradables a connu un regain d’intérêt pour des applications agricoles. Dans cette étude, nous nous concentrons sur le développement de textiles biodégradables destinés à la protection anti-insecte des cultures. Actuellement, ces textiles doivent être collectés par des entreprises après la saison agricole et entraîne un coût non négligeable pour l’utilisateur. Une alternative serait d’avoir des agro-textiles qui pourraient être collectés par l’utilisateur et minéralisés après quelques mois. Les polymères biodégradables pourraient répondre à ces objectifs. Dans cette étude, nous nous sommes concentrés sur le poly(butylene succinate) un polymère biodégradable et biosourcé. Le PBS a été synthétisé sur un pilote de polycondensation. Néanmoins, le PBS issu de cette synthèse présente de faibles propriétés rhéologiques. La structure du PBS a donc été modifiée par l’incorporation de branchements ou d’allongeurs de chaines. Les propriétés mécaniques ont également été optimisées via la synthèse de systèmes PBS/PLA transréagits et de PBS nanocomposites. Ces PBS modifiés ont été testés au filage. Finalement un fil de PBS avec 0,5% de silice sphérique a été produit à plus grande échelle et un textile a été fabriqué. Le vieillissement de ces fils PBS a été étudié et la conservation des propriétés mécaniques durant l’utilisation du fil en extérieur a été validée. Enfin, une dernière approche plus exploratoire a été testée. Elle consiste en la modification du PBS par des interactions supramoléculaires réversibles en température. / In the last decade, biodegradable polymers have gained significant interest for agricultural applications. Here we focus on the development of biodegradable textiles for insect-proof nets. Currently these textiles must be collected by specialized companies after the growing season and generate disposal cost. An ideal agrotextile would be collected by the user at the end of the growing season, and undergo full mineralization within few months. These requirements can be achieved by using biodegradable polymers. In this study, poly(butylene succinate) (PBS), a biobased and biodegradable polymer was studied. PBS was synthesized by polycondensation on a pilot plant reactor. Because of low rheological properties of the synthesized polyester, the chemical structure of PBS was modified by several approaches like chain extension or branching. The mechanical properties were tuned with the synthesis of PBS/PLA transreacted systems and PBS nanocomposites. These modified PBS were tested upon fiber spinning. Finally a PBS yarn with 0,5% spherical silica was produced at higher scale and a textile was done. Ageing of the PBS yarns was also studied and the conservation of the mechanical properties during use of the textile was validated. Lastly a more exploratory approach was tested. It is synthesis of modified PBS by supramolecular interactions, which are reversible upon temperature.
552

SALUFFA – esponjas para el cuidado de la piel

Anaya Medina, Fiorella, Coral Sartori, Pamela Sandy, Cruzado Hernandez, Bryan Kevin, Pizarro Sayán, Fiorela Milagros, Vivas Cubas, Diana María 02 February 2021 (has links)
Nuestro proyecto se genera a partir de una preocupación que afecta a muchas personas en el mundo, el uso de plásticos para la elaboración de artículos de cuidado personal y la escasa ayuda a las organizaciones comunitarias a partir de un modelo de negocio. Es por ello, que la idea de negocio se genera a partir de esas dos necesidades. Este proyecto se divide en dos etapas fundamentales; la validación del problema y la solución propuesta. Hoy en día las personas no tienen conciencia en el impacto del uso de artículos de cuidado personal que son hechos a base de plásticos, ya que no cuentan con un conocimiento de los productos biodegradables que existen en el mercado. Sin embargo, cuando se deciden a comprar productos biodegradables no suelen ser constantes en sus compras; ya que no saben del todo sus beneficios que tienen y el valor agregado que podría tener su contribución mediante la compra. Es aquí donde Saluffa decide apostar por las esponjas biodegradables que son producidas en la región de Ancash por la Organización Matto Grosso para presentarlas en un kit de esponjas que cuentan con tres presentaciones y ser comercializadas en Lima Metropolitana. En la primera etapa, se realizaron entrevistas a nuestro público objetivo y expertos con la finalidad de obtener información relevante para nuestro problema. En la segunda etapa, se realizó nuestro modelo de negocio para determinar si es que nuestro proyecto resultaría viable. Nuestro diferencial de producto son los múltiples beneficios que tiene y el valor agregado que es la contribución monetaria a la OMG, mediante el contrato de exclusividad para la comercialización de las luffas. Las proyecciones indican que bajo una tasa de descuento de %, lograremos un VAN de S/.41,162 soles con una tasa interna de retorno (TIR) de % en un periodo de recupero de la inversión de años por lo cual nuestro proyecto sería viable en cuanto a inversión. / Our project is generated from a concern that affects many people in the world, the use of plastic to produce personal care items and a little help to community organizations based on a business model. That is why the business idea is generated from these two needs. This project is divided into two fundamental stages: the validation of the problem and the proposed solution. Today people are not aware of the impact of the use of personal care items that are made from plastic, since they do not have a knowledge of the biodegradable products that exist in the market. However, when they decide to buy biodegradable products, they are not usually constant in their buying; since they do not fully know their benefits and the added value that their contribution and could have through the purchase. It is here where Saluffa decides to invest in the biodegradable sponges that are produced in the Ancash region by Matto Grosso Organization to present them in a sponge kit that have three presentations and be marketed in modern Lima. In the first stage, interviews were conducted with our target audience and expert to obtain relevant information for our problem. In the first stage, interviews were conducted with our target audience and expert to obtain relevant information for our problem. In the second stage, our business model was carried out to determine if our project would be viable. Our product differential is the multiple benefits it has and the added value that is the monetary contribution to the OMG, through the exclusive contract for the commercialization of the luffas. The projections indicate that under a discount rate of %, we will achieve a VAN of S/.41,162 soles with an internal rate of return (IRR) of % in a period of recovery of investment of years for which our project would be viable as investment. / Trabajo de investigación
553

Temporally Programmed Stretching of Polymer Films: Influence of Nanoparticles

Seif, Sylvain S. 03 September 2009 (has links)
No description available.
554

Phytochemical Modification of Biodegradable/Biocompatible Polymer Blends with Improved Immunological Responses

Buddhiranon, Sasiwimon 06 December 2012 (has links)
No description available.
555

Förnybara fibrer i textila produkter : en väg mot hållbar utveckling / Renewable fibers in textile products : a path to a sustainable development?

Stenström, Mathilda, Johnsson, Elin January 2022 (has links)
Den globala efterfrågan på textila produkter ökar ständigt, samtidigt som branschen står inför stora utmaningar gällande dess höga klimat- och miljöpåverkan. Omkring 65 miljoner ton syntetiskt material framställs årligen, där polyester står för 82% och dominerar marknaden. Polyester (PET) tillverkas från fossila råvaror, det vill säga icke-förnybara källor, vilket bidrar till en ökad andel CO2 i atmosfären, vilket i sin tur leder till en förhöjd medeltemperatur. För att lyckas minska koldioxidavtrycket med 30% fram till år 2030 behövs flera åtgärder genomföras. Bioplaster kan komma att bidra till en mer hållbar livscykel, då de jungfruliga polymererna tillverkas av förnyelsebara eller återvunna råvaror. Denna rapport söker svar på effekten av att ersätta konventionell polyester med biobaserade polymera material i textila produkter. Studien ger en inblick i fibervalets klimatpåverkan under framställning, användarfasen och hantering vid end-of-life som en del av vägen mot en cirkulär ekonomi. Arbetet utgår ifrån en produkt tilldelad från uppdragsgivaren BRAV Norway, Lundhags. Med hjälp av en litteraturstudie och Higg MSI, som mäter klimatpåverkan cradle-to-gate, utvärderas och jämförs återvunnen polyester (rPET), polytrimetylenteftalat (Bio-PTT), polyetenfuranoat (PEF), polyetentereftalat (Bio- PET), polymjölksyra (PLA), polybutensuccinat (PBS) och polyhydroxialkanoater (PHA). I teorin kan samtliga biobaserade material som undersökts spinnas till textila fibrer, vissa finns redan på marknaden och andra är under utvecklingsfasen. Resultatet i Higg MSI visar att råvarans ursprung har en inverkan, men att de biobaserade råvaror inte alltid leder till en lägre klimatpåverkan, här kan återvunna fossilbaserade material uppvisa bättre resultat. Biobaserade material är fördelaktiga ur den synpunkt att de utvinns från förnybara källor, vilket bidrar till lägre koldioxidutsläpp längs hela värdekedjan. Konceptet kring bioekonomi stärker tillämpningen av biopolymerer, då materialet kan övergå från den tekniska till biologiska cykeln enligt Ellen MacArthus fjärilsdiagram. Hanteringen när produkten når end-of-life avgör om man kan närma sig ett cirkulärt kretslopp. Bionedbrytningsbara polymerer ingår i en open-loop- För en cirkulär ekonomi eftersträvar man att material skall ingå i en closed-loop samt uppnå så lång livslängd som möjlig för att minska den totala klimatpåverkan, vilket kan var kritiskt för de bionedbrytningsbara material. I detta område krävs mer efterforskning. Bio-PET och PEF är fördelaktiga då de går att framställa och återvinna i samma strömmar som PET. Det är även avgörande hur stor tillgängligheten är, möjlighet för återvinning och materialets egenskaper när det kommer till val av fibrer för en minskad klimatpåverkan. Bland de bionedbrytningbara materialen är PLA den mest lämpade. Polyester är i dagsläget svårt att ersätta med ett annat polymert material som avsevärt förbättrar produkten under användarfasen. Forskningen som bedrivs leder till ökad tillgång av de biobaserade materialen samt förbättrade egenskaper under användarfasen. Biobaserade material är ett bra komplement till återvunna material för att fasa ut tillverkningen av jungfruliga material. / The global demand for textiles is constantly increasing, and at the same time the textile industry is facing major challenges regarding its significant impact on the climate and the environment. Approximately 65 million tons of synthetic materials are produced annually, with polyester accounting for 82% and dominating the market. Polyester (PET) is produced from non-renewable resources, increasing the share of CO2 in the atmosphere and contributing to higher average temperatures. Several measures need to be implemented to reduce CO2 emissions by 30% until 2030. Bioplastics have the potential to contribute to a more sustainable life cycle because they are made from renewable or recycled raw materials. The purpose with this report is to investigate the impact of replacing conventional polyester with bio-based polymeric materials in textile products. The study will provide insight into the climate impacts of fiber choices production, usephases, and waste management as part of the transition to a circular economy. The study is based on products provided by the Norwegian company BRAV (Lundhags). The information is based on a literature review and the Higg MSI, and is based on cradle-to-gate. Recycled polyester (rPET), polytrimethylenephthalate (bio-PTT), polyethylenefuranoate (PEF), polyethyleneterephthalate (bio-PET), polylactic acid (PLA), and polybutenesuccinate (PBS) and polyhydroxyalkanoate(PHA) were evaluated and compared in terms of their impact on the climate, recycled PET and polytrimethylene (BPET) shows the best result. Theoretically, all of the biobased materials considered can be spun into fiber, some are already on the market, and others are still under development. The result from HiggMSI shows that the source of the raw material has an impact, but biobased raw materials doesn't necessarily have a lower impact on climate and conversely, fossil-based recycled feedstock may show better results. Bio-based feedstocks are advantageous in that they are extracted from renewable resources and contribute to lower carbon emissions throughout the value chain. The concept of bioeconomics enhances the application of biopolymers because it allows materials to move from the technological cycle to the biological cycle according to the Ellen MacArthus butterfly diagram. Waste management determines whether a material can be moved closer to a circular cycle or not. Biodegradable polymers are part of an open-loop, and in a circular economy, the goal is for materials to be part of this system. It is also desirable to achieve the longest possible lifetime to reduce the impact on climate, which is critical for biodegradable materials and requires further research in this area. Bio-PET and PEF have the advantage that they can be produced and recycled in the same stream as PET. In addition, availability, recyclability, and properties are important to consider when choosing fibers to reduce climate impact. Among biodegradable materials, PLA is the most suitable. Polyester is currently difficult to replace with other polymeric materialsals can significantly improve products during the usephase. As research continues, access to biobased materials will increase and their properties will improve. Biobased materials are an effective complement to recycled materials and can help phase out the production of virgin materials.
556

The blue-end of the spectrum of plastics : A step toward understanding the role of blue biopolymers in phasing out fossil plastics / Den blå delen av plastspektrumet : Ett steg mot att förstå blåa biopolymerers roll i utfasningen av fossila plaster

Rudberg, Alice January 2021 (has links)
For more than a century, plastics have become an increasingly important part of the human society. Thanks to the durability and the many varieties of plastic it has a wide range of applications, but unfortunately the traditional plastic made from fossil oil has its drawbacks. Neither the fact that fossil oil is used, nor that these plastics won’t degrade in nature, are in any way sustainable for the environment in the long run. But out of the shadow of these problems, new technologies for the manufacturing of bioplastics are born. This thesis aims towards mapping out properties of different plastics, fossil based as well as bio-based, and investigating the possibilities to manufacture plastic material from algae, so called blue plastics. Additionally, the thesis shed light on terms related to plastic production and bioplastics.  The result shows that there are multiple approaches to the manufacturing of blue plastics; several divergent polymers (e.g. starch, protein and alginate) can be extracted from algae for the production of plastic material, and there is a large number of algae strains and methods to use. Blue plastics are still not produced in large scale, and therefore suffer from high production costs, which makes it challenging to replace traditional plastics. Another obstacle is bad durability and mechanical properties of some algae-based materials. But the blue side of the spectrum of plastics is still a young field of study and new innovations are yet to be discovered. / I över ett sekel har plast blivit en allt viktigare del i det mänskliga samhället. Tack vare sin tålighet och mångsidighet har plast en mängd olika användningsområden, men tyvärr har den traditionella plasten även sina nackdelar. Varken det faktum att fossil olja används, eller det faktum att dessa plaster inte bryts ned i naturen, kan anses hållbart i längden. Men ur skuggan av dessa problem träder nya tekniker fram, som möjliggör tillverkning av bioplaster. Detta projekt syftar till att kartlägga egenskaperna hos olika plaster, fossilbaserade såväl som biobaserade, samt möjligheterna att tillverka plast med alger som råvara. Dessutom läggs fokus på att förklara vissa termer relaterade till plaster, bioplaster och dess livscykel.  Resultatet visar att det finns ett flertal tillvägagångssätt för tillverkningen av algbaserade plaster. Flera olika polymerer (t.ex. stärkelse, protein och alginat) kan extraheras från alger för vidare produktion av plastmaterial, och dessutom finns ett stort antal olika algarter och tillverkningsmetoder som kan användas. Idag produceras algplaster ännu inte i stor skala, något som innebär att produktionskostnaderna fortfarande är höga och att det således är svårt att konkurrera ekonomiskt med traditionella plaster. Ett annat hinder för algbaserade plaster är i vissa fall låg resistans och sämre mekaniska egenskaper jämfört med traditionella plaster. Men den algbaserade delen av plastspektrumet är fortfarande ung och outforskad, fortfarande finns nya upptäckter och möjligheter som väntar på att bli funna.
557

Fabrication, Characterisation and Optimisation of Biodegradable Scaffolds for Vascular Tissue Engineering Application of PCL and PLGA Electrospun Polymers for Vascular Tissue Engineering

Bazgir, Morteza January 2021 (has links)
Annually, about 80,000 people die in the United Kingdom due to myocardial infarction, congestive heart failure, stroke, or from other diseases related to blood vessels. The current gold standard treatment for replacing the damaged blood vessel is by autograft procedure, during which the internal mammary artery (IMA) graft or saphenous vein graft (SVG) are usually employed. However, some limitations are associated with this type of treatment, such as lack of donor site and post-surgery problems that could negatively affect the patient’s health. Therefore, this present work aims to fabricate a synthetic blood vessel that mimics the natural arteries and to be used as an alternative method for blood vessel replacement. Polymeric materials intended to be used for this purpose must possess several characteristics including: (1) Polymers must be biocompatible; (2) Biodegradable with adequate degradation rate; (3) Must maintain its structural integrity throughout intended use; (4) Must have ideal mechanical properties; and (5) Must encourage and enhance the proliferation of the cells. The feasibility of using synthetic biodegradable polymers such as poly (ε- caprolactone) (PCL) and poly (lactide-co-glycolic acid) (PLGA) for fabricating tubular vascular grafts was extensively investigated in this work. Many fundamental experiments were performed to develop porous tissue- engineered polymeric membranes for vascular graft purposes through electrospinning technique to achieve the main aim. Electrospinning was selected since the scaffolds produced by this method usually resemble structural morphology similar to the extracellular matrix (ECM). Hence, four 6mm in diameter tubular shape vascular grafts PCL only, PLGA only, coaxial (core-PCL and shell-PLGA), and bilayer (inner layer-PCL and outer layer-PLGA) was designed and fabricated successfully. The structure and properties of each scaffold membrane were observed by scanning electron microscopy (SEM), and these scaffolds were fully characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), water contact angle measurements, mechanical tensile test, as well as cell culture studies were carried out by seeding human umbilical vein cells (HUVEC) and human vascular Fibroblast cells (HVF). Moreover, all polymeric grafts underwent degradation process, and the change in their morphological structure properties was studied over 12 weeks at room temperature. All scaffolds were also exposed to a controlled temperature of 37°C for four weeks, in phosphate-buffered saline solution (pH, 7.3). It was found that all scaffolds displayed exceptional fibre structure and excellent degradability with adequate steady weight-loss confirming the suitability of the fabricated scaffolds for tissue engineering applications. The coaxial and bilayer scaffolds degraded at a much slower (and steadier) rate than the singular PCL and PLGA tubular scaffolds. Coaxial grafts fabricated via coaxial needle showed an increase in their fibre diameter and pore size volume than other membranes, but also showed to have significant tensile strength, elongation at fracture, and Young’s modulus. To conclude, all scaffolds have demonstrated to be reliable to adhere and proliferate HUVEC, and HVF cells, but these cells were attracted to the PLGA membrane more than other fabricated membranes.
558

Green Polymer Chemistry: Synthesis of Poly(disulfide) Polymers and Networks

Rosenthal-Kim, Emily Quinn January 2013 (has links)
No description available.
559

Engineered carbon-based scaffolds for hard and soft tissue repair, reconstruction or regeneration

Czarnecki, Jarema S. January 2013 (has links)
No description available.
560

Tunable Biodegradable Polymers for Regenerative Medicine

Yu, Jiayi 23 May 2018 (has links)
No description available.

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