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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.
71

Kinetics and Modeling of the Radical Polymerization of Acrylic Acid and of Methacrylic Acid in Aqueous Solution

Wittenberg, Nils Friedrich Gunter 24 October 2013 (has links)
No description available.
72

Membranas de quitosana-graft-acrilato de sódio incorporadas com nanopartículas de prata para o desenvolvimento de curativos / Membranes chitosan-graft-sodium acrylate embedded with silver nanoparticles for the development of curative

Nascimento, Joyce Kelly Melo January 2012 (has links)
NASCIMENTO, Joyce Kelly Melo. Membranas de quitosana-graft-acrilato de sódio incorporadas com nanopartículas de prata para o desenvolvimento de curativos. 2012. 77 f. Dissertação (Mestrado em química)- Universidade Federal do Ceará, Fortaleza-CE, 2012. / Submitted by Elineudson Ribeiro (elineudsonr@gmail.com) on 2016-06-02T18:19:16Z No. of bitstreams: 1 2012_dis_jkmnascimento.pdf: 1875159 bytes, checksum: 3b7fcf890b841321d324440bd2b45087 (MD5) / Approved for entry into archive by José Jairo Viana de Sousa (jairo@ufc.br) on 2016-06-21T23:21:39Z (GMT) No. of bitstreams: 1 2012_dis_jkmnascimento.pdf: 1875159 bytes, checksum: 3b7fcf890b841321d324440bd2b45087 (MD5) / Made available in DSpace on 2016-06-21T23:21:39Z (GMT). No. of bitstreams: 1 2012_dis_jkmnascimento.pdf: 1875159 bytes, checksum: 3b7fcf890b841321d324440bd2b45087 (MD5) Previous issue date: 2012 / Silver nanoparticles (NPsAg) can be obtained by chemical, physical and biological methods. One of the most used methods is based on chemical reduction with sodium borohydride in the presence of stabilizers. Chitosan can act as NPsAg stabilizer. The grafting of acrylic monomers in the side chain of chitosan gives copolymers with improved physical roperties. Type graft copolymer based on chitosan and sodium acrylate was obtained by copolymerizing a system solution using free radical initiation, and from this membrane were prepared. NPsAg membranes were synthesized by the method of reduction with borohydride. The copolymer was characterized by proton absorption in the infrared (FTIR), thermogravimetric analysis, differential scanning calorimetry, elemental analysis, absorption capacity in water and scanning electron microscopy. The reason monomer / polysaccharide used in the reaction was 1/2. The grafting percentage was 49%. FTIR and elemental analysis confirmed the formation of the copolymer. Observed absorption capacity water membrane of the copolymer 13% higher compared to chitosan membrane, confirming the efficiency of grafting of the sodium acrylate in increasing hydrophilicity of the material. Nanocomposite chitosan-graft-sodium acrylate / Ag were obtained by varying the concentrations of silver nitrate (2, 5 and 10 mmol.L-1) and sodium borohydride (40, 100 and 200 mmol.L-1) added to the membranes. The nanocomposites were characterized by spectrophotometry in the UV-Vis region. The Color changes in the membranes from light yellow to dark brown shows the formation of silver nanoparticles. The analysis showed UV-Vis absorption bands in the region of 430 nm, confirming the formation of silver nanoparticles in the membranes of the copolymer. The displacement of the plasmon band of the samples 2/40, 5/100 and 10/200 mmol.L-1, respectively, for shorter wavelengths demonstrate that decreased particle diameter with increasing concentration of silver ions. The bacteriological test showed that the nanocomposite membranes exhibit antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa species. studies Preliminary indicate that the nanocomposite has potential for the study with potential application as dermatological dressing. / Nanopartículas de prata (NPsAg) podem ser obtidas por métodos químicos, físicos e biológicos. Um dos métodos mais utilizados baseia-se na redução química com boroidreto de sódio, na presença de estabilizantes. Quitosana pode agir como estabilizante de NPsAg. A enxertia de monômeros acrílicos na cadeia lateral da quitosana origina copolímeros com ropriedades físicas melhoradas. Copolímero do tipo enxertado à base de quitosana e acrilato de sódio foi obtido por copolimerização em solução utilizando um sistema de iniciação via radical livre e a partir deste foram preparadas membranas. NPsAg foram sintetizadas nas membranas por método de redução com boroidreto. O copolímero foi caracterizado por espectroscopia de absorção na região do infravermelho (FTIR), análise termogravimétrica, calorimetria exploratória diferencial, análise elementar, capacidade de absorção em água e microscopia eletrônica de varredura. A razão monômero/polissacarídeo utilizada na reação foi de 1/2. A porcentagem de enxertia foi de 49%. FTIR e análise elementar confirmaram a formação do copolímero. Observou-se uma capacidade de absorção de água da membrana do copolímero 13% maior em relação à membrana de quitosana, confirmando a eficiência da enxertia do acrilato de sódio no aumento da hidrofilicidade do material. Nanocompósitos quitosana-graft-acrilato de sódio/Ag foram obtidos variando-se as concentrações de nitrato de prata (2, 5 e 10 mmol.L-1) e boroidreto de sódio (40, 100 e 200 mmol.L-1) adicionados às membranas. Os nanocompósitos foram caracterizados por espectrofotometria na região do UV-Vis. A mudança nas cores das membranas de amarelo claro para marrom escuro evidencia a formação das nanopartículas de prata. A análise por UV-Vis mostrou bandas de absorção na região de 430 nm, confirmando a formação das nanopartículas de prata nas membranas do copolímero. O deslocamento da banda plasmônica das amostras 2/40, 5/100 e 10/200 mmol.L-1, respectivamente, para menores comprimentos de onda demonstra que houve diminuição do diâmetro das partículas à medida que aumenta a concentração do íons prata. O teste bacteriológico mostrou que as membranas dos nanocompósitos apresentam atividade antibacteriana contra as espécies Staphylococcus aureus e Pseudomonas aeruginosa. Os estudos preliminares indicam que o nanocompósito apresenta potencial para o estudo com potencial aplicação como curativo dermatológico.
73

Um micro flow-batch para determinação fotométrica e turbidimétrica de taninos em amostras de chás / A micro flow-batch for photometric and turbidimetric determination of tannins in tea samples

Lima, Marcelo Batista de 10 September 2010 (has links)
Made available in DSpace on 2015-05-14T13:21:51Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 3041446 bytes, checksum: ababcafc4806728e34bf8d0bd8ea021e (MD5) Previous issue date: 2010-09-10 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This study proposed a miniaturized flow-batch system for chemical analysis. The technique used microfabricated urethane-acrylate, a commercial polymer. The microsystem was evaluated and optimized by analysis of synthetic dye samples. Afterwards, it was employed for the determination of tannins in tea samples. The tannins are a group of polyphenols of significant relevance in the food industry and pharmaceuticals. The samples used were green and black tea, obtained from the local market. The determinations were performed by turbidimetric methods using copper (II) in an acetate medium, with photometric methods and ferrous tartrate as a reference. Miniaturization in urethane-acrylate implies low cost and low maintenance, rapid prototyping and includes the satisfactory physicochemical properties of polymer. These characteristics combined with the general advantages of miniaturization in analytical devices, such as high frequency analysis and low waste generation, make the system a great source in academic research. For analysis of tannins in tea samples, the system had precise and accurate results, and high speeds. This flow-batch microsystem was able to perform up to 300 tests per hour, for the photometric method of reference and up to 200 tests per hour for the turbidimetric method. Each analysis performed generated waste volumes lower than 70 μL. Data validation of statistical models obtained have proved very satisfactory and promising for new optical applications. / Neste trabalho de pesquisa foi proposto o uso da técnica de microfabricação em polímero comercial uretana-acrilato para a miniaturização de um sistema automático de análises químicas em fluxobatelada, o flow-batch. O microssistema desenvolvido foi avaliado e otimizado pela análise de amostras sintéticas de corantes. Posteriormente, o microssistema, foi empregado para a determinação de taninos, grupo de polifenóis de expressiva relevância industrial, em amostras de chá verde e preto, por dois métodos ópticos distintos, fotométrico e turbidimétrico. A técnica de microfabricação em uretana-acrilato se caracteriza pelos baixos custos de implementação e manutenção, satisfatórias propriedades físicoquímicas do polímero e a rápida prototipagem de sistemas microfluídicos. Tais características aliadas às vantagens inerentes da miniaturização de dispositivos analíticos, como a elevada frequência de análise e a baixa geração de resíduos, conferem a esse sistema de análise uma ótima fonte de pesquisa acadêmica. Para análise dos taninos em amostras de chá, o sistema apresentou resultados precisos e exatos, além de uma alta velocidade analítica para ambos os métodos ópticos, sendo capaz de executar até 300 análises por hora, no método fotométrico e 200 análises por hora pelo método turbidimétrico. Cada análise efetuada gerou resíduos cujos volumes foram inferiores a 70 μL. Os dados de validação estatística dos modelos obtidos se mostraram bastante satisfatórios e promissores para novas aplicações ópticas.
74

Membranas de quitosana-graft-acrilato de sÃdio incorporadas com nanopartÃculas de prata para o desenvolvimento de curativos / Membranes chitosan-graft-sodium acrylate embedded with silver nanoparticles for the development of curative

Joyce Kelly Melo Nascimento 20 December 2012 (has links)
NanopartÃculas de prata (NPsAg) podem ser obtidas por mÃtodos quÃmicos, fÃsicos e biolÃgicos. Um dos mÃtodos mais utilizados baseia-se na reduÃÃo quÃmica com boroidreto de sÃdio, na presenÃa de estabilizantes. Quitosana pode agir como estabilizante de NPsAg. A enxertia de monÃmeros acrÃlicos na cadeia lateral da quitosana origina copolÃmeros com ropriedades fÃsicas melhoradas. CopolÃmero do tipo enxertado à base de quitosana e acrilato de sÃdio foi obtido por copolimerizaÃÃo em soluÃÃo utilizando um sistema de iniciaÃÃo via radical livre e a partir deste foram preparadas membranas. NPsAg foram sintetizadas nas membranas por mÃtodo de reduÃÃo com boroidreto. O copolÃmero foi caracterizado por espectroscopia de absorÃÃo na regiÃo do infravermelho (FTIR), anÃlise termogravimÃtrica, calorimetria exploratÃria diferencial, anÃlise elementar, capacidade de absorÃÃo em Ãgua e microscopia eletrÃnica de varredura. A razÃo monÃmero/polissacarÃdeo utilizada na reaÃÃo foi de 1/2. A porcentagem de enxertia foi de 49%. FTIR e anÃlise elementar confirmaram a formaÃÃo do copolÃmero. Observou-se uma capacidade de absorÃÃo de Ãgua da membrana do copolÃmero 13% maior em relaÃÃo à membrana de quitosana, confirmando a eficiÃncia da enxertia do acrilato de sÃdio no aumento da hidrofilicidade do material. NanocompÃsitos quitosana-graft-acrilato de sÃdio/Ag foram obtidos variando-se as concentraÃÃes de nitrato de prata (2, 5 e 10 mmol.L-1) e boroidreto de sÃdio (40, 100 e 200 mmol.L-1) adicionados Ãs membranas. Os nanocompÃsitos foram caracterizados por espectrofotometria na regiÃo do UV-Vis. A mudanÃa nas cores das membranas de amarelo claro para marrom escuro evidencia a formaÃÃo das nanopartÃculas de prata. A anÃlise por UV-Vis mostrou bandas de absorÃÃo na regiÃo de 430 nm, confirmando a formaÃÃo das nanopartÃculas de prata nas membranas do copolÃmero. O deslocamento da banda plasmÃnica das amostras 2/40, 5/100 e 10/200 mmol.L-1, respectivamente, para menores comprimentos de onda demonstra que houve diminuiÃÃo do diÃmetro das partÃculas à medida que aumenta a concentraÃÃo do Ãons prata. O teste bacteriolÃgico mostrou que as membranas dos nanocompÃsitos apresentam atividade antibacteriana contra as espÃcies Staphylococcus aureus e Pseudomonas aeruginosa. Os estudos preliminares indicam que o nanocompÃsito apresenta potencial para o estudo com potencial aplicaÃÃo como curativo dermatolÃgico. / Silver nanoparticles (NPsAg) can be obtained by chemical, physical and biological methods. One of the most used methods is based on chemical reduction with sodium borohydride in the presence of stabilizers. Chitosan can act as NPsAg stabilizer. The grafting of acrylic monomers in the side chain of chitosan gives copolymers with improved physical roperties. Type graft copolymer based on chitosan and sodium acrylate was obtained by copolymerizing a system solution using free radical initiation, and from this membrane were prepared. NPsAg membranes were synthesized by the method of reduction with borohydride. The copolymer was characterized by proton absorption in the infrared (FTIR), thermogravimetric analysis, differential scanning calorimetry, elemental analysis, absorption capacity in water and scanning electron microscopy. The reason monomer / polysaccharide used in the reaction was 1/2. The grafting percentage was 49%. FTIR and elemental analysis confirmed the formation of the copolymer. Observed absorption capacity water membrane of the copolymer 13% higher compared to chitosan membrane, confirming the efficiency of grafting of the sodium acrylate in increasing hydrophilicity of the material. Nanocomposite chitosan-graft-sodium acrylate / Ag were obtained by varying the concentrations of silver nitrate (2, 5 and 10 mmol.L-1) and sodium borohydride (40, 100 and 200 mmol.L-1) added to the membranes. The nanocomposites were characterized by spectrophotometry in the UV-Vis region. The Color changes in the membranes from light yellow to dark brown shows the formation of silver nanoparticles. The analysis showed UV-Vis absorption bands in the region of 430 nm, confirming the formation of silver nanoparticles in the membranes of the copolymer. The displacement of the plasmon band of the samples 2/40, 5/100 and 10/200 mmol.L-1, respectively, for shorter wavelengths demonstrate that decreased particle diameter with increasing concentration of silver ions. The bacteriological test showed that the nanocomposite membranes exhibit antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa species. studies Preliminary indicate that the nanocomposite has potential for the study with potential application as dermatological dressing.
75

New scaffolding materials for the regeneration of infarcted myocardium

Arnal Pastor, María Pilar 16 January 2015 (has links)
There is growing interest in the development of biomimetic matrices that are simultaneously cell-friendly, allow rapid vascularization, exhibit enough mechanical integrity to be comfortably handled and resist mechanical stresses when implanted in the site of interest. Meeting all these requirements with a single component material has proved to be very challenging. The hypothesis underlying this work was that hybrid materials obtained by combining scaffolds with bioactive hydrogels would result in a synergy of their best properties: a construct with good mechanical properties, easily handled and stable thanks to the scaffold; but also, because of the gel, cell-friendly and with enhanced oxygen and nutrients diffusion, and promoter of cell colonization. Moreover, such a composite material would also be useful as a controlled release system because of the gel’s incorporation. Poly (ethyl acrylate) (PEA) scaffolds prepared with two different morphologies were envisaged to provide the mechanical integrity to the system. Both types of scaffolds were physicochemically characterized and the effect of the scaffolds production process on the PEA properties was examined. The scaffolds preparation methods affected the PEA properties; nevertheless, the modifications induced were not detrimental for the PEA biological performance. Two different bioactive gels were studied as fillers of the scaffolds’ pores: hyaluronan (HA), which is a natural polysaccharide, and a synthetic self-assembling peptide, RAD16-I. HA is ubiquitously present in the body and its degradation products have been reported to be angiogenic. RAD16-I is a synthetic polypeptide that mimics the extracellular matrix providing a favourable substrate for cell growth and proliferation. Given the hydrophobic nature of poly(ethyl acrylate), the combination of PEA scaffolds with aqueous gels raised a number of problems regarding the methods to combine such different elements, the ways to gel them inside the pores, and the procedures to seed cells in the new composite materials. Different alternatives to solve these questions were thoroughly studied and yielded protocols to reliably obtain these complex structures and their biohybrids. An extensive physico-chemical characterization of the components’ interaction and the combined systems was undertaken. As these materials were intended for cardiac tissue engineering applications, the mechanical properties and the effect of the fatigue on them were studied. The different composite systems here developed were homogeneously filled or coated with the hydrogels, were easy to manipulate, and displayed appropriate mechanical properties. Interestingly, these materials exhibited a very good performance under fatigue. The use of the composite systems as a controlled release device was based on the possibility of incorporating active soluble molecules in the hydrogel within the pores. A release study of bovine serum albumin (BSA), intended as a model protein, was performed, which served as a proof of concept. The biological performance of the hybrid scaffolds was first evaluated with fibroblasts to discard the materials cytotoxicity and to optimize the cell seeding procedure. Subsequently, human umbilical vein endothelial cells (HUVECs) cultures were performed for their interest in angiogenic and vascularization processes. Finally, co-cultures of HUVECs with adipose-tissue derived mesenchymal cells (MSCs) were carried out. These last cells are believed to play an important role for clinical regenerative medicine, and their cross-talk with the endothelial cells enhances the viability and phenotypic development of HUVECs. Through the different experiments undertaken, hybrid scaffolds exceeded the outcome achieved by bare PEA scaffolds. / Arnal Pastor, MP. (2014). New scaffolding materials for the regeneration of infarcted myocardium [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/46129 / TESIS / Premios Extraordinarios de tesis doctorales
76

Short wavelength UV–LED photoinitiated radical polymerization of acrylate–based coating systems—A comparison with conventional UV curing.

Torfgård, Olof January 2021 (has links)
The present work was performed at Sherwin–Williams Sweden group AB with the objective of comparing short-wavelength light emitting diodes (UVB/UVC) with the conventional mercury arc lamp as a curing method of acrylate-based, UV-paint undergoing free-radical polymerization when exposed to UV-radiation. Due to environmental and health risks, mercury-doped radiation sources will be phased out in the near future, according to the United Nations Minamata convention, hence new alternatives are needed. Light-emitting diodes differ from the mercury arc lamp as they provide semi-discrete output intensity lines within the UV spectrum instead of a broad output distribution with several main intensity lines. The power output is also considerably lower compared to the conventional method which limits the irradiance and dose that are key parameters in activating and propagating free-radical polymerization of UV-paint. Seven different light-emitting diodes between 260–320 nm was examinedand compared to the conventional mercury arc lamp. Cured coatings were evaluated by measuring the relative extent of acrylate conversion with ATR-FTIR and micro-hardness indentation test. Both methods correlate to the relative cross-linking density and qualitatively describe the curing process for each radiant source at a specific irradiance and dose. Three different paint formulations with widely different properties were used in the experiments. All three paints were able to cure with one or several light emitting diodes at comparable doses and 10 to 20 times lower irradiance to the conventional mercury arc lamp, resulting in similar acrylate conversion and hardness.
77

Inside the Cycle: Understanding and Overcoming Decomposition of Key Intermediates in Olefin Metathesis

Bailey, Gwendolyn Anne 19 April 2018 (has links)
Ru-catalyzed olefin metathesis is an exceptionally powerful, versatile methodology for the assembly of carbon–carbon bonds. The N-heterocyclic carbene (NHC)-stabilized, “second-generation” Ru catalysts have enabled groundbreaking recent advances, ranging from the RCM assembly of cyclic peptides as hepatitis C virus therapeutics, to the elaboration of renewable seed oils and phenylpropanoids into value-added products and chemicals. However, key limitations arise from facile catalyst decomposition. Despite a plethora of studies on the synthesis of new catalysts, and on the decomposition processes accessible to the precatalyst and resting-state species, the underlying principles that govern decomposition of the active intermediates have been surprisingly little examined. One important reason for this is their incredible reactivity: the four-coordinate methylidene intermediate RuCl2(H2IMes)(=CH2) is too short-lived to be observed, while the metallacyclobutane (MCB) intermediate RuCl2(H2IMes)(2-C3H6) can only be observed below –40 °C. This makes them extremely challenging, but also fascinating targets for study. Understanding the underlying chemistry that dictates their reactivity and decomposition is essential for informed catalyst and process redesign, and is thus of fundamental interest, but also considerable practical importance. This thesis work thus aims at understanding the decomposition of active intermediates relevant to the highly-active, second-generation class of catalysts. Emphasis is placed on examining a variety of metathesis contexts, as well as providing solutions. Treated first are the decomposition pathways that arise during metathesis of electron-deficient olefins, a frontier area in organic synthesis, and in the utilization of renewable resources. An unexpected correlation is revealed between rapid catalyst decomposition, and the presence of a stabilizing PCy3 ligand in the standard catalyst for this reaction. The nucleophilic phosphine ligand is shown to attack an acrylate olefin, forming enolates that function as potent Brønsted bases. Literature evidence suggests that such strong bases are innocuous towards the precatalyst, pointing towards a key role for the active intermediates in Brønsted base-induced catalyst decomposition. Precisely which intermediate is involved, as well as the site of deprotonation, is elucidated next. Prior to this work, the NHC ligand was widely believed to be the target for attack. However, through labelling experiments, analysis of the Ru and organic byproducts, and computational studies, deprotonation is shown to occur at the MCB ring. Moreover, MCB deprotonation is revealed to be unexpectedly general, and not contingent on the presence of either an exceptionally strong base, or an electron-deficient substrate. This understanding is key, given recent reports from pharma highlighting the adverse impact of base contaminants, as well as current interest in metathesis of amine-containing substrates. Next examined are the intrinsic decomposition pathways operative for the MCB and four-coordinate methylidene. Prior to this work, the only reported pathway for decomposition of these two species involved beta-elimination of the MCB ring as propene. However, beta-elimination is shown to play an unexpectedly minor role in catalyst decomposition: less than 40% propenes are observed, even under conditions expected to favour MCB elimination. Bimolecular coupling of the methylidene, with loss of the methylidene moiety as ethylene, is proposed to account for the difference. Thus, transiently-stabilized adducts RuCl2(H2IMes)(=CH2)(L)n (L = o-dianiline or pyridine) are synthesized at temperatures down to –120 °C. On warming, these adducts lose Ln and rapidly decompose via bimolecular coupling, with loss of the methylidene moiety as ethylene. These experiments provide the first unambiguous evidence for bimolecular coupling in the important "second-generation" Ru systems, nearly two decades after which this pathway was dismissed in leading papers and reviews. The last two sections focus on solutions. First, a powerful, straightforward solution to the “enolate problem” is developed, whereby the acrylate enolates are quenched and sequestered via reaction with a polyphenol resin. Then, methods for preventing catalyst decomposition during matrix-assisted laser desorption / ionization mass spectrometry (MALDI-MS) are developed, via elucidation of the instrumental and experimental factors that promote successful analysis. As one of the only MS methods capable of affording insight into neutral metal complexes and catalysts, MALDI has unique potential to enable routine analysis of catalyst speciation and decomposition in situ, under real catalytic conditions, for a wide range of catalytic reactions. Collectively, the findings in this thesis offer a much more complete understanding of the fundamental pathways accessible to the important, highly-active metathesis intermediates, and offer strategies likely to inform practice in both academic and industrial settings. This understanding is key to harnessing the full potential of metathesis methodologies.
78

Life Cycle Assessment within Arkema’s portfolio: Carbon Footprint of Acrylics / Livscykelanalys inom Arkemas portfölj: Akrylers koldioxidavtryck

Faye, Alizé January 2023 (has links)
Livscykelanalys är en metod som utformades och utvecklades för att kvantifiera miljöpåverkan från produkter och tjänster för mer än trettio år sedan. Sedan dess har den kontinuerligt förbättrats och blivit mer och mer robust. Som tillverkare av kemiska produkter och monomerer använder Arkema livscykelanalys för att mäta sina produkters miljöpåverkan. Detta görs för att förstå enskilda produkters fotavtryck samt företagets övergripande miljöpåverkan. För att göra detta används ISO-normerna 14040 och 14044. Dessa normer anger generiska ramar för LCA-beräkningar men är inte specifika för den kemiska industrin. Med tanke på att metodologiska svårigheter kan uppstå inom den kemiska sektorn har många riktlinjer och rekommendationer publicerats på senare tid. I denna uppsats studeras och jämförs några av dessa riktlinjer. Tillämpningen av dessa metoder utförs på två produkter inom Arkemas portfölj: akrylsyra och etylakrylat, som är byggstenar för många polymerer. Resultaten av utvärderingen visar på områden där förbättringar kan göras. För de studerade produkterna är råvarorna de största bidragande orsakerna. Därför kan det vara fördelaktigt att övergå från petroleumbaserade material till biobaserade. Att välja den minst miljöpåverkande produktionsvägen är också ett sätt att aktivt minska produkternas koldioxidavtryck. / Life Cycle Assessment is a methodology that has been designed and developed to quantify the environmental impacts of products and services more than thirty years ago. Since then, it has been in continuous improvement and becomes more and more robust. As a producer of chemical products and monomers, Arkema uses Life Cycle Assessment to measure the environmental impact of its products. This is done to understand the footprints of individual products as well as the company's overall environmental impact. To do so, the ISO norms 14040 and 14044 are used. These norms set generic frames for LCA calculation but are not specific to the chemical industry. Considering that methodological difficulties can arise in the chemical sector, many guidelines and recommendations are being published recently. In this thesis, some of those guidelines are studied and compared. The application of these methodologies is performed on two products within Arkema’s portfolio: acrylic acid and ethyl acrylate, which are building blocks for many polymers. The results of the assessment reveal areas where improvements can be made. For the products studied, the main contributors are the raw materials. Therefore, transitioning from petroleum-based materials to biobased ones could be beneficial. Additionally, selecting the least impactful production route is also a way to actively reduce the carbon footprint of the products.
79

PREPARATION AND CHARACTERIZATION OF SOME UNUSUAL ELASTOMERIC AND PLASTIC COMPOSITES

RAJAN, GURU SANKAR 11 June 2002 (has links)
No description available.
80

Assessment of a Light-Activated Adhesive for Hernia Mesh Repair / Utvärdering av ett ljusaktiverat klister för bråcknätreparation

Amathieu, Ludivine January 2021 (has links)
Background and objectives: TISSIUM light-activated adhesive was investigated as an alternative to tissue-penetrating products to fix meshes in intraperitoneal laparoscopic ventral hernia repair. The objective of this study was to ensure efficient polymer light activation through commercial meshes and to assess the acute and chronic fixation strength of the light-activated adhesive in a porcine model in comparison to commercial fixation products. Methods: A spectroscopic analysis was conducted on the light-activated adhesive through three different meshes (1, 2, and 3) to quantify the acrylate conversion associated with the level of polymer cross-linking. Two setups were implemented: a static (light source fixed over a drop of polymer) and a dynamic (light source rotated around a pattern of polymer to mimic the surgical procedure). Hernia defects were created in porcine models and repaired either using the light-activated adhesive or a commercial product (A, B, C, and D) to fix a mesh. For each tested condition, the acute and chronic (3 months) fixation strength performances were assessed using burst ball and t-peel mechanical tests. Results: The light activation proved to be effective (more than 90% of the acrylates converted) in static in 7 seconds through the three meshes and in dynamic between 3 min and 5 min 32 sdepending on the considered mesh. In a burst ball test, the light-activated adhesive reached between 42 and 84% of the commercial products’ acute performance with the three meshes (between 75,9 and 95,9 N) and reached 88% of the commercial product A’s chronic performance with mesh 1 (610,1 N). A t-peel test demonstrated similar strength of ingrowth for the repairs using the light-activated adhesive or the commercial product A at the 3-month timepoint with mesh 1 (2,55 and 2,37 N/cm respectively). Conclusions: Data suggest the light-activated adhesive has the potential to be used in intraperitoneal laparoscopic ventral hernia repair. In a reasonable time, the adhesive is efficiently light-activated through commercial meshes. The light-activated adhesive’s performances to fix commercial meshes, both acute and chronic, are similar to commercial products, but with a strong advantage of not being tissue penetrating.

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