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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.
1

Production And Structure/Properties Of Nylon-6 Core / Isotactic Polypropylene Sheath Bicomponent Fibers Suitable For Use In Carpeting Applications

Godshall, David Leonard 28 May 1999 (has links)
Bicomponent fibers consisting of nylon-6 and isotactic polypropylene were produced. In-situ, reactive compatibilization was achieved using a maleic anhydride functionalized polypropylene between the materials at the interface. The overall goal of the research was to produce a bicomponent fiber of these materials that would be suitable for use in commercial carpet applications. Carpet samples produced using nylon-6 core / polypropylene sheath bicomponent fibers displayed stain resistance comparable to a wholly polypropylene carpet. The wear characteristics of these fibers were found to be strongly dependent upon the maleic anhydride content and the molecular weight of the maleic anhydride functionalized polypropylene. Adhesion between the nylon-6 and polypropylene phases, and the mechanical properties of the polypropylene phase were affected by the addition of the functionalized polypropylene. Additional information regarding the processing conditions necessary to produce fibers of the desired cross-section from these materials was obtained using capillary rheometry. A number of analytical techniques including DSC, TGA, and SEM were used to better understand the structure of the maleated materials. / Master of Science
2

Avaliação do uso de adsorventes preparados a partir de resíduo agroindustrial na adsorção de fenol e Cd+2

GAMA, Brígida Maria Villar da 14 July 2016 (has links)
Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2017-03-27T18:47:41Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação Brígida Maria Villar da Gama_final.pdf: 2712176 bytes, checksum: 3f4942f50259e73bb4ef1389562092a5 (MD5) / Made available in DSpace on 2017-03-27T18:47:41Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação Brígida Maria Villar da Gama_final.pdf: 2712176 bytes, checksum: 3f4942f50259e73bb4ef1389562092a5 (MD5) Previous issue date: 2016-07-14 / PRH-28 / O fenol e Cd+2 são contaminantes presentes nos efluentes das etapas de processamento da indústria do petróleo. Esses contaminantes são prejudiciais à saúde humana e ao meio ambiente. Dessa forma é necessária a remoção de fenol e Cd+2 antes do descarte dos efluentes em corpos hídricos. Nesse contexto, a adsorção desempenha um papel de destaque em função de sua eficiência na remoção de contaminantes em efluentes. O presente trabalho teve como objetivo avaliar a eficiência da casca de amendoim como adsorvente (RS) e como precursor de carvão carbonizado (CC) e carvões ativados com ar sintético (CA) para remoção de fenol e/ou Cd+2 em soluções. O CC foi preparado a partir de pirólise e CA preparado a partir da pirólise seguida de ativação física com ar sintético. Foi realizada a caracterização dos adsorventes pelos métodos de determinação da área superficial (BET), difração de raios-X (DRX), análise termogravimétrica (TGA), espectroscopia na região do infravermelho (FT-IR) e ponto de carga zero (pHpcz). Todos os experimentos foram realizados em pH natural das soluções. O efeito da massa de adsorvente em solução, estudos cinético e de equilíbrio para sistemas monocomponente, e competição entre fenol e Cd+2 em sistema bicomponente foram avaliados. Foi observado um aumento na área superficial e volume dos poros após a ativação. Na TGA foram observadas três perdas de massa, devido à perda de umidade e degradação da biomassa. Na análise de DRX foi possível identificar que ambos os materiais possuem estrutura predominantemente amorfa. Pela análise de FT-IR identificou-se picos referentes a grupos hidroxilas, carboxílicos e carbonilas em RS, CC e CA com diferentes intensidades para antes e após o contato com adsorvato. Os pHpcz foram de 6,9 para RS, 7,9 para CC e 10,0 para CA, apresentando carga superficial favorável a adsorção de fenol. O estudo do efeito da massa do adsorvente indicou melhor relação massa/volume de 0,1 g em 50 mL de solução. Através desse estudo foram selecionados os adsorventes com maior capacidade adsortiva (q em mg.g-1), utilizados nos estudos cinéticos e de equilíbrio. A evolução cinética foi rápida atingindo o equilíbrio em torno de 180 minutos. Não ocorreu diferença significativa entre os modelos cinéticos avaliados, exceto para o Cd+2 o modelo pseudo primeira ordem apresentou diferença significativa. Com base no modelo de Weber-Morris, o processo adsortivo é controlado por dois ou mais mecanismos. Para o equilíbrio de adsorção do fenol os modelos de Langmuir, Freundlich e Langmuir-Freundlich não apresentaram diferença significativa para o CC quando comparado, pelo Teste F. Para o CA foi observado diferença entre o modelo de Langmuir-Freundlich em relação aos demais modelos, já para o estudo do equilíbrio do Cd+2 o comportamento foi inverso. A capacidade adsortiva máxima do CC foi de 16,32 ± 4,30 mg.g-1 e 34,73 ± 4,93 mg.g-1 para adsorção de fenol e Cd+2, respectivamente. Para CA foi de 21,00 ± 2,11 mg.g-1 para fenol e 75,43 ± 6,82 mg.g-1 para Cd+2. Para o sistema bicomponente foi constatado o efeito de sinergismo da mistura para fenol e antagônico para Cd+2. Os resultados demonstraram o potencial técnico carvões para remoção de fenol e Cd+2 em soluções aquosas compatibilizando as questões ambientais. / Phenol and Cd+2 are contaminants found in effluents from the oil industry processing stages. These contaminants are harmful to human health and the environment. Therefore, the removal of phenol and Cd+2 before effluent disposal into water bodies is required. In this context, the adsorption plays an important role due to its efficiency in removing contaminants in wastewater. This study aimed to evaluate the efficiency of peanut shell as adsorbent (RS), carbonized coal precursor (CC), and activated coals with synthetic air (CA) in removing phenol and/or Cd+2 in solution. The CC was prepared from pyrolysis and the CA was prepared from the pyrolysis followed by physical activation with synthetic air. The adsorbents characterization was performed by the following methods: determination of the surface area (BET), X-Ray diffraction (XRD), thermogravimetric analysis (TGA), infrared spectroscopy (FT-IR), and point of zero charge (pHpzc). All experiments were performed in the natural pH of the solutions. The effect of the adsorbent mass in solution, kinetic and equilibrium studies for one-component systems, and the competition between phenol and Cd+2 in two-component systems were evaluated. An increase was observed in the surface area and in the pores volume after activation. Three mass losses were observed in the TGA, loss of moisture and degradation of biomass. In the XRD analysis, it was possible to identify that both materials have a predominantly amorphous structure. By the FT-IR analysis, peaks related to hydroxyl groups, carboxylic acids and carbonyls in RS, CC and CA with different intensities before and after the contact with adsorbate were identified. The pHpzc values were 6,9 for RS, 7,9 for CC and 10,0 for CA, with surface charge favorable to the adsorption of phenol. The study of the adsorbent mass effect indicated better mass/volume ratio of 0,1 g in 50 mL of solution. Through this study, adsorbents with higher adsorption capacity (q in mg.g-1) used in kinetic and equilibrium studies were selected. The kinetic evolution was quick, reaching the equilibrium around 180 minutes. There was no significant difference between the kinetic models evaluated, except for the Cd+2 in which the pseudo first-order model showed a significant difference. Based on the Weber-Morris model, the adsorptive process is controlled by two or more mechanisms. For the phenol adsorption equilibrium, the Langmuir, Freundlich and Langmuir-Freundlich models showed no significant difference to the CC when compared by the F-test. Also, there was observed difference for the CA between the Langmuir-Freundlich model compared to other models; however, for the Cd+2 equilibrium study, the behavior was reverse. The maximum adsorption capacity of CC was 16,32 ± 4,30 mg.g-1 and 34,73 ± 4,93 mg.g-1 for the phenol and Cd+2 adsorption, respectively. For the CA was 21,00 ± 2,11 mg.g-1 for phenol and 75,43 ± 6,82 mg.g-1 for Cd+2. For the two-component system, it was observed the synergistic effect of the mixture for phenol and antagonistic for Cd+2. The results demonstrated the technical potential of coals for phenol and Cd+2 removal in aqueous solutions conciliating environmental issues.
3

Coupling agent effects on the interfacial adhesion in a sheath/core type bicomponent fiber

Li, Jian-xing January 1989 (has links)
No description available.
4

Mechanical behaviour of thermally bonded bicomponent fibre nonwovens : experimental analysis and numerical modelling

Demirci, Emrah January 2011 (has links)
In contrast to composites and woven fabrics, nonwoven materials have a unique web structure, which is composed of randomly oriented fibres bonded in a pattern by mechanical, thermal or chemical techniques. The type of nonwovens studied in this research is a thermally bonded one with polymer-based bicomponent fibres. Such fibres have a core/sheath structure with outer layer (sheath) having a lower melting temperature than that of the core. In thermal bonding of such fibres, as the hot calender with an engraved pattern contacts the fibrous web, bond points are formed thanks to melting of the sheath material. Molten sheath material acts as an adhesive while core parts of the fibres remain fully intact in the bond points. On the other hand, web regions, which are not in contact with the hot engraved pattern, remain unaffected and form the fibre matrix that acts as a link between bond points. With two distinct regions, namely, bond points and fibre matrix, with different structures, nonwovens exhibit a unique deformation behaviour. This research aims to analyse the complex mechanical behaviour of thermally bonded bicomponent fibre nonwoven materials using a combination of experimental and numerical methods. A novel approach is introduced in the thesis to predict the complex mechanical behaviour of thermally bonded bicomponent fibre nonwovens under various threedimensional time-dependent loading conditions. Development of the approach starts with experimental studies on thermally bonded bicomponent fibre nonwovens to achieve a better understating of their complex deformation characteristics. Mechanical performance of single bicomponent fibres is investigated with tensile and relaxation tests since they are the basic constituents of nonwoven fabrics. The fabric microstructure, which is one of the most important factors affecting its mechanical behaviour, is examined with scanning electron microscopy and X-ray micro computed tomography techniques. At the final part of experimental studies, mechanical response of thermally bonded bicomponent fibre nonwovens is characterised with several mechanical tests. (Continues...).
5

Piezoelectric behaviour of woven constructions based on poly(vinylidene fluoride) bicomponent fibres

RUNDQVIST, KARIN January 2013 (has links)
During this project it was investigated how the newly developed piezoelectric PVDF bicomponent fibre behaved when integrated in different weave constructions. The possibility to integrate conductive yarns as outer electrode was studied in order to see if it was possible to create a fully textile piezoelectric sensors. The piezoelectric properties of the bicomponent fibre is given by the sheath material, which is a polymeric material known as poly(vinylidene fluoride) (PVDF). Today only piezoelectric film made by PVDF is commercially available, but with a flexible PVDF bicomponent fibre it improves the possibility to integrate piezoelectric material into a textile construction. In this study the PVDF bicomponent fibre was integrated in the warp direction into weave constructions, such as plain weave, twill and weft rib. All the woven bands included 60 PVDF bicomponent yarns, with 24 filaments in each bundle and the average width of the bands produced was 30 mm. Different conductive materials and fibres, acting as outer electrode, were coated or integrated together with the PVDF fibre and the behaviour of the PVDF fibres was analysed. All the woven samples went through corona poling with a voltage of 7 kV in 70 ⁰C for 3 min. The weave construction that gave highest piezoelectric output signal was twill with weft that has low tex. The twill construction gave a range amplitude of 1.5- 3.3 V when subjected to a dynamic strain of about 0.25% at 4 Hz. It was shown that different conductive materials influenced the PVDF fibre in different ways, due to the resistance of the material. It was also shown that it was possible to integrate piezoelectric bicomponent fibre into a textile construction and that a fully textile piezoelectric sensor could be produced by using conductive yarns as outer electrode. / Program: Masterutbildning i textilteknik,
6

Bicomponent Fiber in Sound Absorbent Production : Investigation of using bicomponent fiber as adhesive between woven and nonwoven textile and how it affects the sound absorption

LINDSTRÖM, KATARINA January 2014 (has links)
A new way of adhering woven textile to a nonwoven backing was explored, the end product in mind being a sound absorbent panel. Today a hot melt adhesive is sprayed on the nonwoven with woven decorating textile put on top before compression molding. This method results in an uneven layer of adhesive with the consequence of decorating textile detaching from the nonwoven and thereby a high number of discarded products. The report investigates the possibility of using a bicomponent fiber as the adhesive. This would guarantee an even layer of adhesive and make the manufacturing process one step shorter. A bicomponent fiber of core/sheath construction with a low melting polymer in the sheath was incorporated in the nonwoven upon fabrication. In the main bulk of the nonwoven a smaller ratio of bicomponent to normal polyester fiber was used, enough to stabilize the nonwoven. For the top layer of the nonwoven a higher ratio was chosen. As the nonwoven is then compression molded under heat together with the decorating textile, the low melting sheath of the bicomponent fiber will melt and create bonds within the nonwoven as well as to the textile. The ratio in the top layer was varied as well as the pressure in compression molding. The adhesion strength between nonwoven and decorating textile was tested, and the sound absorbing properties of the different manufactured samples were compared. The sound absorbing parameter of air flow resistance was tested and sound absorption was tested using impedance tube with transfer function method. Further, a way of testing transmission loss was developed by the manufacturing of a custom built impedance tube, which was then compared to the transfer function method. The results showed that a higher bicomponent percentage gave higher sound absorption in lower frequencies, but a lower sound absorption in higher frequencies. The thickness of the samples gave a positive effect on the sound absorption in all frequencies. The conclusion is to recommend a thicker material, and choose bicomponent according to which frequencies that should be absorbed and what adhesion strength is needed for end product. / Program: Textilteknik
7

On the structure and assembly of staphylococcal leukocidin: a study of the molecular architecture of beta-barrel pore-forming toxins

Miles, Jr., George Emmett 16 August 2006 (has links)
Staphylococcal leukocidin pores are formed by the obligatory interaction of two distinct polypeptides, one of class F and one of class S, making them unique in the family of β-barrel pore-forming toxins (β-PFTs). By contrast, other β-PFTs form homooligomeric pores. For example, the staphylococcal α- hemolysin is a homoheptamer. Limited and controversial data exist on the assembly and molecular architecture of the leukocidin pore. In this work, biochemical and biophysical methods were used to characterize the leukocidin pore produced by the LukF (HlgB) and LukS (HlgC) components encoded by Staphylococcus aureus. I demonstrate that LukF and LukS assemble to form an SDS-stable pore on rabbit erythrocyte membranes. In addition, the pore-forming properties of recombinant leukocidin were investigated with planar lipid bilayers. Although leukocidins and staphylococcal α-hemolysin share partial sequence identity and related folds, LukF and LukS produce a pore with a unitary conductance of 2.5 nS (1 M KCl, 5 mM HEPES, pH 7.4), which is over three times greater than that of α-hemolysin measured under the same conditions. The subunit composition and stoichiometry of a leukocidin pore were determined by two independent methods, gel shift electrophoresis and sitespecific chemical modification during single channel recording. Four LukF and four LukS subunits were shown to co-assemble into an octameric transmembrane structure. The existence of an additional subunit in part explains properties of the leukocidin pore, such as its high conductance. Additionally, this is the first time that either technique has been applied successfully to assess the composition of a heteromeric membrane protein. It is also relevant to understanding the mechanism of assembly of β-PFT pores, and suggests new possibilities for engineering these proteins. In additional studies, the HlyII pore encoded by Bacillus cereus was found to form a homoheptameric transmembrane pore with properties conforming in general with those of other members of the class of β-PFTs. HlyII possesses additional properties which make it an attractive candidate for applications in biotechnology, such as an oligomer with a high thermal stability in the presence of SDS and the ability of the pore to remain open at high transmembrane potentials.
8

Fabrication of Inorganic Oxide Nanofibers Using Gas Jet Fiber Spinning Process and Their Applications in Photocatalytic Oxidation

GHOSH, MONOJ 16 October 2017 (has links)
No description available.

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