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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

Fundamental Modeling of Solid-State Polymerization Process Systems for Polyesters and Polyamides

Lucas, Bruce 22 November 2005 (has links)
The dissertation describes and assembles the building blocks for sound and accurate models for solid-state polymerization process systems of condensation polymers, particularly poly(ethylene terephthalate) and nylon-6. The work centers on an approach for modeling commercial-scale, as opposed to laboratory-scale, systems. The focus is not solely on coupled polymerization and diffusion, but extends to crystallization, physical properties, and phase equilibrium, which all enhance the robustness of the complete model. There are three applications demonstrating the utility of the model for a variety of real, industrial plant operations. One of the validated simulation models is for commercial production of three different grades of solid-state PET. There are also validated simulation models for the industrial leaching and solid-state polymerization of nylon-6 covering a range of operating conditions. The results of these studies justify our mixing-cell modeling approach as well as the inclusion of all relevant fundamental concepts. The first several chapters discuss in detail the engineering fundamentals that we must consider for modeling these polymerization process systems. These include physical properties, phase equilibrium, crystallization, diffusion, polymerization, and additional modeling considerations. The last two chapters cover the modeling applications. / Ph. D.
22

Multiscale Modeling of an Industrial Nylon-6 Leacher

Gaglione, Anthony 28 February 2007 (has links)
This thesis presents a multiscale model of an industrial nylon-6 leacher. We develop several models at various spatial scales and implement them together in a simplistic, efficient way to develop an overall leacher model. We solve dynamic transport differential equations using the finite-volume method and method of lines in an in-house-developed FORTRAN program. We use the ODEPACK package of ordinary differential equation (ODE) solvers to solve our system of coupled ODEs. Our multiscale model performs transport, thermodynamic, physical property, and mass-transfer calculations at a finite-volume scale. We introduce two additional scales: a mesoscale, in which we perform computational fluid dynamic (CFD) simulations, and a molecular scale. Our CFD simulations solve for turbulent properties of fluid flowing over a packed bed. We incorporate the turbulent diffusivity of the fluid into our finite-volume leacher model. We perform molecular simulations and use the conductor-like screening model-segment activity coefficient (COSMO-SAC) model to generate solubility predictions of small, cyclic oligomers in water and ε-caprolactam. Additionally, we develop an extension of COSMO-SAC to model polymer species, which we refer to as Polymer-COSMO-SAC, and apply it to solve liquid-liquid equilibrium equations. We present a unique methodology to apply COSMO-based models to polymer species, which shows reasonable results for nylon-6. Because of the computational intensity of our Polymer-COSMO-SAC liquid-liquid equilibrium algorithm, we generate pre-computed tables of equilibrium predictions that we may import into our leacher model. Our integration of multiscale models maximizes efficiency and feasibility with accuracy. We are able to use our multiscale models to estimate necessary parameters, but we need to fit two mass-transfer related parameters to industrial data. We validate our model against the plant data and find average-absolute errors in the final mass percent of ε-caprolactam and cyclic dimer in polymer chips of 25.0% and 54.7%, respectively. Several plant data sets are suspected outliers and we believe an unforeseen equilibrium limitation may cause this discrepancy. If we remove these outlying data sets, we then find average-absolute errors of 7.5% and 19.3% for ε-caprolactam and cyclic dimer, respectively. We then use our validated model to perform application and sensitivity studies to gain critical insight into the leacher's operating conditions. / Master of Science
23

Gecko-Inspired Electrospun Flexible Fiber Arrays for Adhesion

Najem, Johnny F. 19 July 2012 (has links)
No description available.
24

Avaliação da tensão superficial do PVB e da PA-6. / Evaluation of surface tension of poly(vinyl butyral) and nylon-6.

Morais, Douglas 02 September 2008 (has links)
No laboratório de Análise, Processamento e Reologia de Materiais Poliméricos da Escola Politécnica da USP tem sido estudadas blendas de Poliamida-6 (PA-6) e filme de poli(vinil butiral) (PVB), como uma alternativa para reciclagem do filme de PVB oriundo do processo de separação dos componentes do vidro laminado pós-consumo. As propriedades mecânicas de uma blenda polimérica dependem da sua morfologia e, por sua vez, a morfologia depende das propriedades reológicas e da tensão interfacial entre os polímeros formadores da blenda, que para o caso de blendas envolvendo filme de PVB podem mudar em função da concentração de plastificante presente na composição do filme. Apesar da importância do seu conhecimento, a tensão interfacial entre PA-6 e filme de PVB não é conhecida. O presente trabalho teve como objetivo avaliar a tensão superficial do filme de PVB e da PA-6. O método utilizado foi o da gota pendente. Também estudou-se a influência da adição de plastificante na tensão superficial do filme de PVB. Os resultados mostraram que a tensão superficial dos polímeros estudados decresce com o aumento da temperatura (temperatura variando entre 240 e 260ºC). Em particular, para o filme de PVB a entropia de superfície ( (d/dT) ) apresentou um valor acima dos normalmente encontrados para polímeros fundidos. Este comportamento foi atribuído à estabilidade térmica do filme. O filme de PVB utilizado nos ensaios de tensão superficial foi caracterizado por Espectroscopia no Infravermelho (FTIR), Espectroscopia no Ultravioleta/Visível (UV-VIS), Espectroscopia Eletrônica para Análise Química (ESCA) e Análise Termogravimétrica (TG). Os resultados obtidos comprovaram que há mudanças na estrutura do PVB durante sua exposição a temperaturas elevadas, por longo período de tempo (condições do ensaio de tensão superficial). Foi observado, primeiramente, a evaporação do plastificante, seguida por perda de grupos polares (-OH, C=O e C-O-C) presentes na estrutura do PVB. A tensão superficial da Poliamida-6 foi determinada para temperaturas de 250 e 260ºC. Os resultados mostraram que a PA-6 manteve-se estável durante os ensaios. / In the Rheology and Polymer Processing Laboratory of Escola Politécnica of the University of São Paulo, Polyamide-6 / poly(vinyl butiral) film blends have been studied as an alternative for the recycling of post-consumption laminated glasses. The mechanical properties of these blends were studied and explained in light of their morphology. The morphology of polymer blends strongly depends on the rheological behavior of the blend and on the interfacial tension between the polymers forming the blend. In the case of Poliamide-6 (PA-6)/poly(vinyl butiral) (PVB) film blends, the interfacial tension depends on the plasticizer concentration present in PVB film. However, to our knowledge neither the PA-6/PVB film interfacial tension nor the surface tension of PVB film at temperatures above softening temperatures have been evaluated. In this work, the surface tension of poly(vinyl butyral) and polyamide was evaluated using the pendant drop method. Also it was tried to evaluate the surface tension of PVB film as a function of plasticizer content. The surface tension values obtained were in the same range as the ones obtained for other molten polymers: the surface tension decreases with increasing temperature (for temperatures ranging from 240 to 260°C). However, the value of PVB film surface entropy ((d/dT) where is the surface tension and T is the temperature) was much larger than values reported for other molten polymers. This result was attributed to thermal stability of PVB film during the surface tension measurement. The drops of PVB film after surface tension analysis were examined for any change in their functional groups using infrared spectroscopy (FITIR), ultraviolet-visible spectroscopy (UV/VIS), electron spectroscopy for chemical analysis (XPS/ESCA) and thermogravimetric analysis (TG). The results showed that changes in the chemical structure of PVB film occur during surface tension measurement. First, the plasticizer within the PVB film evaporates and, then, the PVB suffers reduction of polar units and creation of C=C bonds. The surface tension of PA-6 was evaluated for temperatures of 250 and 260°C. The PA-6 remained stable during tests.
25

Production And Characterization Of Nanofibers From Polycaprolactam And Ethylene-butyl Acrylate-maleic Anhydride Terpolymer Mixture

Biber, Erkan 01 April 2010 (has links) (PDF)
The impact strength of Nylon 6 was improved by adding Ethylene- n-Butyl acrylate- maleic anhydride (E-nBA-MAH) terpolymer with various concentrations from 0% (w/w) to 15% (w/w). The bare interaction energy between two polymers was investigated by using melting point depression approach utilizing both the Flory-Huggins (FH) theory and the Sanchez-Lacombe Equation of State (SL EOS). The solution of the mixture was electrospun, and the effects of process parameters on the expected radii of nanofibers were investigated. The effects of process parameters such as polymer concentration in solution, electrical field, diameter of syringe needle, feed rate, and collector geometry on nanofibers were studied. The statistical analysis to relate these parameters on the diameter of nanofibers was carried out by using Johnson SB distribution. The ratio of elastic modulus to viscosity coefficient of nanofibers was worked out by using AFM and combined viscoelastic models. The experiments were carried out on single fiber. The ratio came out to be a function of nanofiber diameter and terpolymer concentration. Isothermal crystallization kinetics and WAXS diffraction patterns of blends revealed and also SEM images supported that after 5% addition of elastomeric terpolymer, the interaction between the components of the blend gets weaker. The elastic modulus of the blend with 5% of terpoymer was greater than that of the neat Nylon 6, but the elastic modulus decreased for the blends containing more than 5% terpolymer.
26

Propriedades mecânicas de compósitos de PVC reciclado reforçados com fibras de sisal e de nylon 6

Medeiros, Marco Antônio Rocha January 2006 (has links)
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27

Avaliação da tensão superficial do PVB e da PA-6. / Evaluation of surface tension of poly(vinyl butyral) and nylon-6.

Douglas Morais 02 September 2008 (has links)
No laboratório de Análise, Processamento e Reologia de Materiais Poliméricos da Escola Politécnica da USP tem sido estudadas blendas de Poliamida-6 (PA-6) e filme de poli(vinil butiral) (PVB), como uma alternativa para reciclagem do filme de PVB oriundo do processo de separação dos componentes do vidro laminado pós-consumo. As propriedades mecânicas de uma blenda polimérica dependem da sua morfologia e, por sua vez, a morfologia depende das propriedades reológicas e da tensão interfacial entre os polímeros formadores da blenda, que para o caso de blendas envolvendo filme de PVB podem mudar em função da concentração de plastificante presente na composição do filme. Apesar da importância do seu conhecimento, a tensão interfacial entre PA-6 e filme de PVB não é conhecida. O presente trabalho teve como objetivo avaliar a tensão superficial do filme de PVB e da PA-6. O método utilizado foi o da gota pendente. Também estudou-se a influência da adição de plastificante na tensão superficial do filme de PVB. Os resultados mostraram que a tensão superficial dos polímeros estudados decresce com o aumento da temperatura (temperatura variando entre 240 e 260ºC). Em particular, para o filme de PVB a entropia de superfície ( (d/dT) ) apresentou um valor acima dos normalmente encontrados para polímeros fundidos. Este comportamento foi atribuído à estabilidade térmica do filme. O filme de PVB utilizado nos ensaios de tensão superficial foi caracterizado por Espectroscopia no Infravermelho (FTIR), Espectroscopia no Ultravioleta/Visível (UV-VIS), Espectroscopia Eletrônica para Análise Química (ESCA) e Análise Termogravimétrica (TG). Os resultados obtidos comprovaram que há mudanças na estrutura do PVB durante sua exposição a temperaturas elevadas, por longo período de tempo (condições do ensaio de tensão superficial). Foi observado, primeiramente, a evaporação do plastificante, seguida por perda de grupos polares (-OH, C=O e C-O-C) presentes na estrutura do PVB. A tensão superficial da Poliamida-6 foi determinada para temperaturas de 250 e 260ºC. Os resultados mostraram que a PA-6 manteve-se estável durante os ensaios. / In the Rheology and Polymer Processing Laboratory of Escola Politécnica of the University of São Paulo, Polyamide-6 / poly(vinyl butiral) film blends have been studied as an alternative for the recycling of post-consumption laminated glasses. The mechanical properties of these blends were studied and explained in light of their morphology. The morphology of polymer blends strongly depends on the rheological behavior of the blend and on the interfacial tension between the polymers forming the blend. In the case of Poliamide-6 (PA-6)/poly(vinyl butiral) (PVB) film blends, the interfacial tension depends on the plasticizer concentration present in PVB film. However, to our knowledge neither the PA-6/PVB film interfacial tension nor the surface tension of PVB film at temperatures above softening temperatures have been evaluated. In this work, the surface tension of poly(vinyl butyral) and polyamide was evaluated using the pendant drop method. Also it was tried to evaluate the surface tension of PVB film as a function of plasticizer content. The surface tension values obtained were in the same range as the ones obtained for other molten polymers: the surface tension decreases with increasing temperature (for temperatures ranging from 240 to 260°C). However, the value of PVB film surface entropy ((d/dT) where is the surface tension and T is the temperature) was much larger than values reported for other molten polymers. This result was attributed to thermal stability of PVB film during the surface tension measurement. The drops of PVB film after surface tension analysis were examined for any change in their functional groups using infrared spectroscopy (FITIR), ultraviolet-visible spectroscopy (UV/VIS), electron spectroscopy for chemical analysis (XPS/ESCA) and thermogravimetric analysis (TG). The results showed that changes in the chemical structure of PVB film occur during surface tension measurement. First, the plasticizer within the PVB film evaporates and, then, the PVB suffers reduction of polar units and creation of C=C bonds. The surface tension of PA-6 was evaluated for temperatures of 250 and 260°C. The PA-6 remained stable during tests.
28

Study of Take-Up Velocity in Enhancing Tensile Properties of Aligned Electrospun Nylon 6 Fibers

Najem, Johnny Fares January 2009 (has links)
No description available.
29

Properties of nylon-6-based composite reinforced with coconut shell particles and empty fruit bunch fibres

Savetlana, S., Mulvaney-Johnson, Leigh, Gough, Timothy D., Kelly, Adrian L. 28 December 2017 (has links)
yes / Novel natural fibre composites of nylon-6 reinforced with coconut shell (CS) particles and empty fruit bunch (EFB) fibres have been investigated. Fillers were alkali treated before melt compounding with nylon-6. Mechanical, thermal and rheological properties of composites were measured. Tensile modulus was found to improve with both fillers up to 16% for nylon-6/CS composite and 10% for nylon-6/EFB composite, whereas a moderate increase in tensile strength was observed only with CS composites. Differences in the strengthening mechanisms were explained by the morphology of the two fillers, empty fruit bunch fibres having a weaker cellular internal structure. Observation of composite morphology using SEM showed that both fillers were highly compatible with nylon-6 due to its hydrophilic nature. Both fillers were found to cause a slight drop in crystallinity of the nylon matrix and to lower melt viscosity at typical injection moulding strain rates. Moisture absorption increased with addition of both fillers.
30

Monomer recovery from nylon carpets via reactive extrusion

Bryson, Latoya G. 28 March 2008 (has links)
The catalytic depolymerization/pyrolysis of nylon 6 and 66 were investigated with the prospect of helping to curb the amount of carpet landfilled. Thermogravimetric analysis was used to determine which catalysts (and their nylon/catalyst ratio) were most suited for the depolymerization. By adding bases, the onset of degradation for some bases was 100 aC lower than that of the pure nylons. Potassium hydroxide and sodium hydroxide were found to be the most effective catalysts at a catalyst ratio of 100:1 of nylon 6 and nylon 66 to catalyst, respectively. After determining the most efficient catalyst, kinetic models/parameters from the TGA data were determined. These parameters were used in a reactive extrusion model for depolymerizing nylon 6 in carpet. Data from the model was then used to do cost analysis for the process. It was found that to get a Present Value Ratio greater than 1, the flow rate has to be greater than or equal to 500 lb/hr. At even higher flow rates up to the model¡¦s limit (1500 lb/hr), the Net Present Value shows that this process is economically viable. Extrusion of a 100:1 ratio of pure N6 and KOH was done in a 30 mm counter-rotating non-intermeshing twin screw extruder. The material collected from the vents of the extruder was tested with a gas chromatograph- mass spectrum (GC-MS) in tandem. There was only one significant peak from the GC and the primary molecular weight on the MS was 113, the molecular weight of caprolactam. This shows that the process could be profitable and require little purification if done industrially.

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