Dissertations / Theses on the topic 'Melt strength'
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張顯基 and Hin-kei Cheung. "Study on the strength of polymer melt." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31215087.
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Cheung, Hin-kei. "Study on the strength of polymer melt /." Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19471415.
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Doody, Paul David. "The rheology and strength of hot melt adhesives." Thesis, Coventry University, 1997. http://curve.coventry.ac.uk/open/items/aee7101d-7aef-41a0-a6a1-32d9877f92d1/1.
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Various properties of the components and adhesives were modelled. The compatibility of the components were successfully incorporated into an extended Fox equation to predict the glass transition temperature. The peel strength of the adhesive was modelled in terms of the rheological properties of elastic moduli and loss tangent values at different temperatures. A second model based upon the value of the loss tangent at room temperature was also broadly successful but deviations from predicted behaviour were observed which were attributable to failure of the adhesive joints by a mode not included in the model. The modulus of the adhesive was modelled on the basis of an extended mixture rule in which the extent of compatibility was identified by a parameter n. The value of n varied as a function of adhesive composition and temperature, indicating that the behaviour of the adhesives changed subtly as the compatibility of the phases changed. The value of the parameter could not be directly related to the morphology of the adhesive phases. Fourteen commercially available poly(ethylene-co-vinyl acetate) (EVA) copolymer samples were selected in which there was a systematic change in the melt index, amount of vinyl acetate, and degree of crystallinity. Various hot melt adhesives were made using these copolymers and a standard amount of wax and resin. The materials were examined using differential scanning calorimetry (DSC), oscillatory rheometry (both controlled strain and controlled stress), and transient (creep) rheometry. The adhesives were also investigated using a variety of industrial tests which included peel adhesion and tensile testing at four different rates, open and setting time, shear and peel stress resistance at elevated temperatures, and viscosity determination over a wide range of temperatures. Detailed thermal analysis and characterisation have provided a range of accurate and systematic data on all of the materials and in particular showed that the components of the adhesive did not merely act as a mechanical mixture but had a distinct compatibility. The controlled stress technique was found to more discriminatory than the controlled strain, due to the more precisely controlled heating and cooling of the sample during loading and evaluation. Other key differences between the techniques are attributable to the different thermal histories imposed upon the semi-crystalline adhesive components. Detailed analysis of the complex rheological curves showed several key factors. One of the most important was the modulus crossover temperature Tx which was shown to correlate well with the softening point of the adhesive, its open time, and the heat resistance under shear as determined by the shear adhesion failure temperature (SAFT). It was possible to construct a linear relationship between Tx and SAFT which allowed prediction of this key adhesive parameter. There was no significant relationship established between the softening point of an adhesive and its heat resistance, open time, or critical thermal characteristics, and the use of the softening point as a useful indicator of adhesive performance is contested. The open time was shown to be clearly influenced by the properties of the copolymer. The relationship between open time and melt index is complex and two competing mechanisms are thought responsible. These are the inability to fully wet the substrate for high molecular weights and resistance to complete substrate penetration by capillary effects for adhesives formulated with low molecular weight polymers. Both of these effects cause a reduction in open time. The cloud points of the adhesives were independent of the molecular weight but strongly affected by composition. Degree of crystallinity was also an influence at higher molecular weights. Cloud point correlated slightly with the onset of crystallisation as determined by DSC however differences are extremely small and the method was not deemed robust enough for widespread industrial application. Various properties of the components and adhesives were modelled. The compatibility of the components were successfully incorporated into an extended Fox equation to predict the glass transition temperature. The peel strength of the adhesive was modelled in terms of the rheological properties of elastic moduli and loss tangent values at different temperatures. A second model based upon the value of the loss tangent at room temperature was also broadly successful but deviations from predicted behaviour were observed which were attributable to failure of the adhesive joints by a mode not included in the model. The modulus of the adhesive was modelled on the basis of an extended mixture rule in which the extent of compatibility was identified by a parameter n. The value of n varied as a function of adhesive composition and temperature, indicating that the behaviour of the adhesives changed subtly as the compatibility of the phases changed. The value of the parameter could not be directly related to the morphology of the adhesive phases.
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Githuku, David N. "Melt strength of polyolefins and its role in plastics processing." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65328.
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He, Chunxia 1968. "Shear flow behavior and molecular structure of high melt strength polypropylenes." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84208.
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Linear shear flow behavior and molecular structure studies were carried out on linear polypropylenes produced using Ziegler-Natta catalysts and sets of branched polypropylenes produced from these linear precursors.A method combining dynamic and creep measurements was employed to obtain a complete picture of the linear viscoelastic behavior of these polypropylenes. It was found that all samples in a set of polypropylenes have the same linear viscoelastic behavior in the high-frequency range, but display dramatic differences at low frequencies. Increasing branching level results in a steep increase of the zero-shear viscosity, an increase of the steady-state compliance, and a broadening of the relaxation spectrum whose shape changes dramatically and peaks shift to longer times.
Molecular models were tested and applied to the linear polypropylenes to predict linear viscoelastic properties from the molecular weight distribution (MWD). The parameters obtained from the best fit of predicted and experimental data of linear polypropylenes were used to calculate a fictive relaxation spectrum for branched polymers from their MWDs as if they were linear. The comparison between this predicted result and the experimental spectrum showed the separate effects of polydispersity and branching on rheology.
To obtain detailed structural information, the branching process of polypropylenes was simulated using a Monte-Carlo approach, which provides detailed information such as MWD and branching distribution. The simulated MWD was adjusted to the measured GPC curve using a single parameter simply related to the branching density lambda (LCB/1000C). Relations between branching parameters and moments of the MWD were determined, which offer the possibility to calculate branching parameters directly from GPC results. The branching efficiency was estimated and correlations between engineering properties of polypropylenes and the structural information were obtained, which is of valuable industrial interest for polymer design.
A determination of the weight fractions of branches and segments between branch points from the relaxation spectrum is proposed. Due to the complexity of molecular relaxation mechanisms, only approximate correlations between molecular architecture and rheology were observed.*
*This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Microsoft Office.
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La-Orchan, Wittaya. "Melt treatment effects on porosity and impact strength in hypoeutectic aluminum silicon alloy." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22446.
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The effects of the three factors (modification, grain refinement, and hydrogen level) on the amount of porosity, impact strength, and performance of the reduced pressure test in A356 alloy have been studied. It was found that grain refinement, acting singly and in combination with modification, reduces the porosity by inducing mass feeding. However, this beneficial effect may not be found at all cooling rates and casting sizes. There is less total shrinkage in Sr-alloyed samples than in those which are non Sr-alloyed. The reason for this is supposed to be a difference in the liquid density which may be higher in Sr-alloyed samples. Modification has the strongest effect on improving the impact strength of A356 alloy. Hydrogen reduces it slightly. On the other hand, grain refinement, acting singly or in combination with modification, was not found to improve the impact strength of the alloy. To obtain optimum impact strength, it is recommended that a combination of modification and degassing to about 0.1 ml.H$ sb2$/100 g. Al. be used. An excellent linear relatiosnhip between density and hydrogen level exists for all combinations of melt treatment processes when the redued pressure test is used. Three methods of predicting the true hydrogen level are proposed and calculated hydrogen levels agree reasonably well with measured melt hydrogen within the error range of $ pm$0.05-0.1 ml./100 g. Al.
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Parmar, Harisinh, and h_arzoo@yahoo com. "Rheology Of Peroxide Modified Recycled High Density Polyethylene." RMIT University. Civil, Environmental and Chemical Engineering, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080724.164249.
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Consumption of plastics has increased exponentially, in line with the world's population. Not surprisingly this is reflected in enormous growth of the plastic industry especially during the last five decades. Commensurate with this, waste produced from plastics consumption has created a major environmental problem. Many types of waste disposal methods have been used all over the world so far, but all of them have disadvantages. Furthermore, some methods are responsible for the generation of green house gases and further contribution to global warming. Recently, reduction of green house gas emission has become a target of most industries. Plastic recycling and reuse breaks the cycle of endless production of virgin polymer and thus contributes to a net reduction of green house gas emission. Recycling of plastics should produce materials with improved properties to replace virgin plastics for a variety of applications. Improvement in the properties of recycled plastics can be achieved by blending with other plastics, by filler addition and by modification using free radical initiators. Introduction of the free radical initiator (organic peroxide) during reprocessing of the recycled plastics has been found to offer significant property improvements to the recycled materials. Extremely small amounts of a free radical initiator (typically ranging between 0.01 wt% to 0.2 wt%) is capable of enhancing the properties of the recycled plastics to a great extent. This project investigates the use of free radical initiators in the recycling of post consumer recycled high density polyethylene using reactive extrusion. Both molecular and rheological characterisation of recycled and reprocessed materials was carried out and this was followed by tensile testing of the modified materials to satisfy end use applications such as packaging and drainage piping. Post consumer recycled high density polyethylene (R-HDPE) resin and virgin high density polyethylene (V-HDPE) were reactively extruded with low concentrations of dicumyl peroxide (DCP) and 1, 3 1, 4 Bis (tert- butylperoxyisopropyl) Benzene (OP2) respectively in a twin screw extruder in order to produce modified materials with varying composition (0.0 wt%, 0.02 wt%, 0.05 wt%, 0.07 wt%, 0.10 wt% and 0.15 wt%) of both organic peroxides. Morphological characterisation using modulated differential scanning calorimetry (MDSC) demonstrated that there is a decrease in the crystallinity level for all the modified samples. Shear rheological tests were carried out to study the structure of the modified materials within the linear viscoelastic region. Viscoelastic parameters, such as storage modulus (G'), loss modulus (G
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Faust, Karsten, André Bergmann, and Jens Sumpf. "Influence of the Melt Flow Rate on the Mechanical Properties of Polyoxymethylene (POM)." Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-231703.
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In this article the correlation between the average molar mass and the melt flow rate (MFR) is achieved. Based on the example of Polyoxymethylene (POM) it is shown that a high average molar mass is associated with a low MFR (high viscosity). On the basis of this dependency, the mechanical properties of static and dynamic tensile strength, elastic modulus, hardness and notched impact strength are investigated. It was found that the characteristic values of static tensile strength, elastic modulus and hard-ness increase with increasing MFR (decreasing viscosity). On the other hand the dynamic long-term properties and notched impact strengths decrease with increasing MFRIm Beitrag wird der Zusammenhang zwischen der mittleren molaren Masse und des Schmelzfließindex (MFR) hergestellt. Dabei wird am Beispiel von Polyoxymethylen (POM) ersichtlich, dass eine hohe mittlere molare Masse mit einem geringen MFR (hochviskos) einhergeht. Basierend auf dieser Abhängigkeit werden die mechanischen Eigenschaften statische und dynamische Zugfestigkeit, E-Modul, Härte sowie Kerbschlagzähigkeit untersucht. Dabei konnte festgestellt werden, dass die Kenngrößen statische Zugfestigkeit, E-Modul und Härte mit steigendem MFR (abnehmende Viskosität) zunehmen. Die dynamischen Langzeiteigenschaften und Kerbschlagzähigkeiten sinken hingegen mit zunehmendem MFR
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ZHOU, HONG. "KINETICS, PROCESSING, AND PROPERTIES OF Si/SiC COMPOSITES FABRICATED BY REACTIVE-MELT INFILTRATION." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin994941745.
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Korin, Christer. "Mechanical Behaviour of Adhesive Joints in Cartonboard for Packaging." Doctoral thesis, Karlstads universitet, Avdelningen för kemiteknik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-4731.
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A cartonboard package is often sealed and closed with an adhesive – either a hot-melt adhesive (adhesives that are applied in a molten state on the cartonboard) or a dispersion adhesive (adhesives that are applied as water-based dispersions). This thesis focuses on the process of hot-melt gluing, and how material properties and process conditions affect the performance of the adhesive joint. Requirements vary depending on how the package is to be used. A package that is only supposed to protect the product during transport differs from one that is supposed to attract consumers and facilitate their use of the product. If a package has been opened, due to external or internal forces that cause a fracture in the adhesive joint, the consumer may choose another package instead. A fracture of the adhesive joint may occur in several different ways; for example, a cohesive fracture in the adhesive, an interfacial fracture between the adhesive and one of the cartonboard surfaces, and a cohesive fracture in the cartonboard. The traditional way of testing the adhesive joint is to subjectively evaluate the fibre tear after manually tearing the joint apart. The primary interest of this study has been to find an objective method that can characterise the adhesive joint – that is, its strength and joint characteristics. The work has principally concentrated on physical experiments where the Y-peel method has been evaluated and further developed, including the construction of a laboratory adhesive applicator. Adhesive joint failure is analysed and correlated to the force-elongation curve during Y-peel testing in order to explore various mechanisms of the failure. The force versus elongation curves are transformed into a force versus inelastic deformation curve for the adhesive joint. The inelastic deformation of the adhesive joint is defined as the inelastic opening of the adhesive joint perpendicular to the cartonboard surface. The dissipative descending energy has been used to characterise the adhesive joint. High descending dissipative energy showed high resistance against final failure of the joint. This correlates very well with the manual fibre-tear test. Characteristic force-elongation curves in Y-peel testing – that is, the shape of the curve – have been analysed, and four main failure modes have been identified. The finite element method has been used to predict mechanical behaviour in the ascending part of the force-elongation curve. When it comes to local behaviour, a high stiffness adhesive results in bending behaviour while a low results in shearing, but on a global scale, no big difference was detected on the ascending part of the force-elongation curve. The new laboratory adhesive applicator and finite element method can be used to objectively design the interaction between the adhesive and the cartonboard for a specific application. This can be achieved by modifying the cartonboard, the adhesive or the process parameters.
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Thiele, Marc. "Die Schichtbildung beim Feuerverzinken und die Eigenschaften der Zinküberzüge." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2010. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-39726.
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Es wurde das Verzinkungsverhalten von Baustahl beim Stückverzinken im technisch nutzbaren Bereich untersucht. Dazu wurde das Schichtwachstum der Zinküberzüge bei Verwendung konventioneller ZnPb-Schmelze anhand von Schichtdicken und Gefügeausbildungen in Ab-hängigkeit von den relevanten Parametern ermittelt. Weiterhin wurde der Einfluss des Was-serstoffs im Stahl auf die Schichtbildung beim Feuerverzinken eingeschätzt. Das Resultat ist eine umfassende Modellvorstellung der Schichtbildungsvorgänge beim Feuerverzinken von 435°C bis 620°C. Sie erklärt das Verzinkungsverhalten von Baustahl und trägt zum Verständnis vieler Phänomene beim Feuerverzinken bei. Weiterhin wurden Überzüge aus legierten Zinkschmelzen untersucht. Die Ergebnisse wurden hinsichtlich der Wirkung der einzelnen Legierungselemente in der Zinkschmelze interpretiert. Dem Anwender wird ein Leitfaden zur Verfügung gestellt, der Vor- und Nachteile der in der Praxis verfügbaren Zinkschmelzen beschreibt.
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Zuanetti, Bryan. "Plate Impact Experiments for Studying the Dynamic Response of Commercial-Purity Aluminum at Temperatures Approaching Melt." Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1557132337419911.
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Ouvrard, Blanche. "Matériaux conducteurs à haute limite d’élasticité dans le système Cu-Mg : élaboration, caractérisation et modélisation." Thesis, Bordeaux 1, 2013. http://www.theses.fr/2013BOR14860/document.
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Les alliages conducteurs à haute tenue mécanique sont utilisés dans de nombreux domaines tels que le transport, l’énergie et l’industrie électronique. La demande en ces matériaux est croissante. Les alliages Cu-Be constituent à l’heure actuelle les matériaux conducteurs les plus résistants mais posent un problème de toxicité et de coût. Pour proposer une alternative à ces derniers, nous avons étudié des alliages Cu-Mg hypo-eutectiques. Deux voies de synthèse ont été utilisées afin d’obtenir des composites endogènes possédant une combinaison originale de propriétés structurelles et fonctionnelles : le refroidissement conventionnel et la solidification rapide par melt-spinning. Les microstructures obtenues ont en commun la présence d’agrégats eutectiques et diffèrent principalement par la dimension des paramètres métallurgiques tels que la taille de grains et la distance interlamellaire. Les systèmes présentent des forces motrices de transformation de phases importantes conduisant à une précipitation au cours d’un maintien thermique. L’investigation des propriétés mécaniques et électriques des alliages Cu-Mg montre que ces dernières égalent celles des alliages Cu-Be. En complément de l’approche expérimentale, nous avons adapté deux modèles : un modèle thermocinétique pour décrire l’évolution temporelle de la microstructure qui a lieu à haute température et un modèle mécanique permettant de rationaliser l'influence des paramètres microstructuraux sur les propriétés mécaniques et électriquesCopper-based high strength conductive alloys are used in a myriad of applications such as transport, energy and electronic industries. The demand for these materials is booming. The strongest conductive alloy is based on the Cu-Be system which has the disadvantage of toxicity and cost. In an attempt to find an alternative to these, we have developed hypoeutectic Cu-Mg alloys. Two synthesis routes were applied to produce endogenous compounds with a unique combination of structural and functional properties: the conventional cooling and the rapid solidification by melt-spinning. The obtained microstructures share the presence of eutectic aggregates and differ mainly by the size of the metallurgical parameters such as grain size and interlamellar distance. The two systems provide high driving forces for phase transformations leading to precipitation during aging. The investigation of the mechanical and electrical properties of Cu-Mg alloys shows that they are equal to those of the Cu-Be alloys. In addition to experimental approach, we have adapted two models: a thermo-kinetic one to describe time evolution of the microstructure which takes place at high temperature and a mechanical one to rationalize the influence of microstructural parameters on mechanical and electrical properties
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Hooper, David A. "The basic underwater demolition/SEAL accession model determining the optimal number of junior officer accessions to meet end-strength goals." Thesis, Monterey, California. Naval Postgraduate School, 2011. http://hdl.handle.net/10945/5760.
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Approved for public release; distribution is unlimited.The mission of the Naval Special (NSW) community is to provide a versatile, responsive, and offensively focused force with continuous overseas presence in order to have strategic impact in missions that include special reconnaissance, direct action, unconventional warfare, and combating terrorism. Currently, the NSW community has large manpower gaps within the officer corps especially, at the Lieutenant Commander rank. This gap threatens the operational readiness of the NSW community, which in turn affects our national security. This thesis presents the development of the Basic Underwater Demolition/SEAL (BUD/S) Accession Calculator (BAC) which uses goal programming and Markov chain analysis to determine the optimal number of new accessions needed to enter the BUD/S training program to meet target end-strength goals for company grade ranks. By properly manning the junior ranks the Lieutenant Commander rank can be properly manned. The results demonstrate that the NSW community can closely meet target end-strength goals of 127 and 285 for Lieutenant Junior Grades and Lieutenants, respectively, with the 100 accessions to BUD/S every year. However, as the attrition rate fluctuates the number of accessions change. The most dramatic impact to BUD/S accession requirements is observed when attrition rate increases. Decrease in attrition rate show that small changes to accession requirements occur.
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Geyer, Lourens Stephanus. "Evaluering van 'n maatskaplike groepwerk-bemagtigingsprogram met alkoholafhanklike bejaardes : 'n sterkteperspektief / Lourens Stephanus Geyer." Thesis, North-West University, 2006. http://hdl.handle.net/10394/1351.
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Nkukwana, Tobela T. "The effect of moringa oleifera leaf meal on growth perfomance, gut integrity, bone strenght, quality and oxidative stability of meat from broiler chickens." Thesis, University of Fort Hare, 2012. http://hdl.handle.net/10353/d1006835.
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This study was designed was to determine the effects of additive supplementation of Moringa oleifera leaf meal on growth performance, digestibility, digestive organ size, intestinal integrity, bone ash content and bone breaking strength, as well as meat yield and quality of broiler chickens. A total of 2400 day-old unsexed Cobb-500 broiler chicks were randomly allocated to 5 treatment groups: T1, positive control, 668 g/ton Salinomycin and 500 g/ton Albac; T2, T3 and T4 contained graded levels of MOLM at 1 percent, 3 percent and 5 percent of dry matter (DM) intake, respectively; and T5, a negative control (0 percent additives) in a complete randomized design experiment. Except for week one, FI and FCR was highest (P < 0.05) in T4 birds; while T1 birds had the highest FI in the period of 22 to 27d (P < 0.05). Throughout the production period, birds supplemented with MOLM had the highest BW (P < 0.05) than the birds fed the control diets. Feed intake (FI) and feed conversion ratio (FCR) among treatments was highest (P < 0.05) in T4 birds during the period of 8 to 14 d; and was highest (P < 0.05) for T1 birds in the period of 22 to 27d. Protein efficiency ratio (PER) and energy utilization efficiency (EEU) ratios were statistically significant among treatments (P < 0.05). However, dietary treatments had no effect (P > 0.05) on the weights of the heart, liver, spleen, or the gizzard, although the bursa for T2 birds was the lightest (P < 0.05); while gizzard erosion score was highest in T2 birds. All of the nutrients measured, except for fat, had negative intercepts that were significantly different (P < 0.05) from zero, indicating the presence of endogenous fecal losses. Tibiae length (TL) was highest in T2. The dried defatted weight (DW) was heaviest (P < 0.05) for T3 (11.20 ± 0.347) and T5 (11.08 ± 0.328). A positive correlation (r = 0.667; P < 0.01) between TW and DW was observed. There were no dietary effects on bone breaking strength (BBS), but T1 tibiae had highest resistance to breaking force (T1 > T4 > T3 > T2 > T5). Calcium was highest (P < 0.05) in T1; and lowest inT2 and T5. Phosphorus levels were lowest (P < 0.05) in T1; and highest (P < 0.05) in T5 compared. The highest Ca: P ratio was obtained in T4 (P < 0.05); while the ash percent was highest (P < 0.05) in T1. Drip loss increased as L* values increased; and a negative correlation was observed between L* and pH. On D1, C18: 0 and C22 in T2, while C15:0 was highest in T4. On D1, C20:2, C20:3n6 and C22:6n3 were highest in T2 (P < 0.05); T4 had the highest C18:3n6 (P < 0.05), while C20:2 was highest in T5 (P < 0.05). The P/S ratio on D1 was highest in T4; while n-6/n-3 was highest in T1; and n-3 was highest in T3. On D8, the n-3 was highest in T1 (P < 0.05). Results of the current study show that supplementation of M. oleifera leaf at additive levels of up to 5 percent of the bird’s DMI does have the potential to influence the bird performance without any detrimental effects on nutrient utilization, bird health, bone strength and/or meat quality, which can be concluded that MOLM enhanced the bird’s genetic potential for optimal productivity.
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Boiago, Marcel Manente [UNESP]. "Microminerais complexados a moléculas orgânicas sobre aspectos produtivos e qualitativos da carne de frangos de corte criados sob condições de estresse térmico." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/104963.
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boiago_mm_dr_jabo.pdf: 456558 bytes, checksum: 5fedc7f36c4c91c58db0f60b0bc4ccb5 (MD5)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Avaliou-se o desempenho, qualidade e composição química da carne, resistência óssea e empenamento de frangos de corte arraçoados com dietas contendo selênio, zinco e manganês complexados ou não a moléculas orgânicas e criados sob condições de estresse térmico. Foram utilizados 980 pintos machos Cobb de um dia de idade, criados até 42 dias de idade em três câmaras climáticas, que proporcionaram temperaturas alta, termoneutra e baixa. Foi utilizado o delineamento inteiramente casualizado, em esquema fatorial 3 X 2 + 1, sendo três temperaturas de criação, duas fontes de selênio, zinco e manganês: inorgânica e “orgânica”, mais o tratamento testemunha (criação em câmara termoneutra sem adição de Se, Zn e Mn na ração). As aves criadas em condições de estresse térmico apresentam desempenho inferior e ossos com densidade óssea e resistência à quebra menores. A fonte orgânica proporcionou melhor desempenho, principalmente em condições de temperaturas elevadas. Selênio e zinco foram melhor absorvidos na forma orgânica, já o manganês teve absorção similar nas duas formas. As aves criadas em temperaturas baixas apresentaram carne menos macia. O empenamento das aves não foi influenciado pelos fatores testados
It were evaluated performance, meat quality and composition, bone strength and feathering of broilers fed supplemented diets with different selenium, zinc and manganese sources (organic and inorganic) and raised under different environmental temperatures. Nine hundred and eighty one d. old Cobb male broilers were used during 42 days. It were used three climatic chambers (high, neutral and low temperatures) and twenty chickens per pen. It was used a 3x2 + 1 factorial arrangement (three breeding temperatures, two mineral sources and a control treatment that provided neutral temperature without mineral supplementation) with seven replicates. The means were compared by Tykey's test (5%).The thermal stressed broilers showed lower performance, bone density and strength. The organic source took to a better performance, mainly under high temperatures. Organic sources of selenium, zinc and manganese were highly absorbed, however, the absorption of both sources of manganese was similar. Chickens raised under low temperatures presented lower values of tenderness. The factors didn't influence the feathering of the chickens
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Boiago, Marcel Manente. "Microminerais complexados a moléculas orgânicas sobre aspectos produtivos e qualitativos da carne de frangos de corte criados sob condições de estresse térmico /." Jaboticabal : [s.n.], 2010. http://hdl.handle.net/11449/104963.
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Resumo: Avaliou-se o desempenho, qualidade e composição química da carne, resistência óssea e empenamento de frangos de corte arraçoados com dietas contendo selênio, zinco e manganês complexados ou não a moléculas orgânicas e criados sob condições de estresse térmico. Foram utilizados 980 pintos machos Cobb de um dia de idade, criados até 42 dias de idade em três câmaras climáticas, que proporcionaram temperaturas alta, termoneutra e baixa. Foi utilizado o delineamento inteiramente casualizado, em esquema fatorial 3 X 2 + 1, sendo três temperaturas de criação, duas fontes de selênio, zinco e manganês: inorgânica e "orgânica", mais o tratamento testemunha (criação em câmara termoneutra sem adição de Se, Zn e Mn na ração). As aves criadas em condições de estresse térmico apresentam desempenho inferior e ossos com densidade óssea e resistência à quebra menores. A fonte orgânica proporcionou melhor desempenho, principalmente em condições de temperaturas elevadas. Selênio e zinco foram melhor absorvidos na forma orgânica, já o manganês teve absorção similar nas duas formas. As aves criadas em temperaturas baixas apresentaram carne menos macia. O empenamento das aves não foi influenciado pelos fatores testadosAbstract: It were evaluated performance, meat quality and composition, bone strength and feathering of broilers fed supplemented diets with different selenium, zinc and manganese sources (organic and inorganic) and raised under different environmental temperatures. Nine hundred and eighty one d. old Cobb male broilers were used during 42 days. It were used three climatic chambers (high, neutral and low temperatures) and twenty chickens per pen. It was used a 3x2 + 1 factorial arrangement (three breeding temperatures, two mineral sources and a control treatment that provided neutral temperature without mineral supplementation) with seven replicates. The means were compared by Tykey's test (5%).The thermal stressed broilers showed lower performance, bone density and strength. The organic source took to a better performance, mainly under high temperatures. Organic sources of selenium, zinc and manganese were highly absorbed, however, the absorption of both sources of manganese was similar. Chickens raised under low temperatures presented lower values of tenderness. The factors didn't influence the feathering of the chickens
Orientadora: Hirasilva Borba
Coorientador: Pedro Alves de Souza
Banca: Alexandre Oba
Banca: Antônio Carlos de Laurentiz
Banca: Otto Mack Junqueira
Banca: Maria Regina Barbieri de Carvalho
Doutor
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Leger, Pierre-Emmanuel. "Rôle de la microstructure sur les mécanismes de corrosion marine d’un dépôt à base d’aluminium élaboré par projection dynamique par gaz froid (« cold spray »)." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEM005.
Full textAbstract:
Le principe de la projection dynamique par gaz froid ou « cold spray » repose sur la projection de particules de poudres convoyées par un gaz à des vitesses supersoniques vers un substrat. La déformation des particules à l’impact avec ce dernier permet la construction d’un dépôt. Ce procédé permet de conserver la microstructure des particules de poudre et de produire des dépôts peu poreux. Cette dernière caractéristique est essentielle dans le cadre d’applications anticorrosion. L’ambition de la thèse est de comprendre le rôle de la microstructure sur les mécanismes de corrosion marine d’un dépôt à base d’aluminium élaboré par cold spray. Pour atteindre cet objectif sont projetées des poudres à base d’aluminium (aluminium pur, alliages d’aluminium et mélanges avec ajout d’alumine) sur un substrat en acier. Les microstructures des dépôts sont étudiées jusqu’à l’échelle nanométrique (MET). L’adhérence des dépôts est mesurée par l’essai de plot collé. A partir des microstructures sont proposés plusieurs mécanismes de formation de la porosité dans un dépôt cold spray à différentes échelles. Une étude numérique par éléments finis complète cette analyse microstructurale. Grâce aux mesures de la vitesse (DPV-2000) et de la température (caméra thermique) d’impact des particules, les paramètres de nouveaux modèles matériau sont optimisés pour simuler le comportement de l’aluminium et de l’alumine à l’impact. De plus, plusieurs essais de corrosion marine (immersion et brouillard salin) sont conduits. L’étude des microstructures corrodées permettent d’établir différents mécanismes de corrosion du dépôt cold spray. Un lien entre la porosité du dépôt et son comportement en corrosion est notamment montré. Enfin, une première approche du transfert de technologie du procédé à l’échelle industrielle est décriteCold spray process is based on spraying particles carried by a gas at a supersonic speed onto a substrate. Particle deformation during impact with the substrate creates a coating. This spraying process can retain particle microstructure and produce very dense coating. This property is crucial for anticorrosion applications. The aim of this work is to understand the effect of cold spray aluminum coating microstructure on marine corrosion mechanisms. To achieve this goal, several aluminum powders (including pure aluminum, aluminum alloys and mixtures with alumina) are sprayed onto a steel substrate. Coating microstructure is studied down to a nanoscale (TEM). The coating-substrate bond strength is determined using pull-off testing. From a thorough microstructure study, various mechanisms are proposed to explain multiscale porosity formation in coatings. A numerical study using finite elements modeling complements this microstructure analysis. From particle speed (DPV-2000) and temperature (thermal camera) measurements during impact, new material models are optimized to model aluminum and alumina behavior at particle impact. Moreover, corrosion tests are conducted (including immersion and salt spray tests). The study of corroded coating microstructures is used to identify corrosion mechanisms which occur in the coating. A relationship between coating porosity and its corrosion behavior is particularly brought into light. Finally, a first approach to a technological transfer of this process to an industrial application is proposed
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Ghosal, Anindya Kumar. "Crystallization of isotactic poly(propylenes) with enhanced melt strength." 2008. http://etd.lib.fsu.edu/theses/available/etd-02142008-134818/.
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Thesis (Ph. D.)--Florida State University, 2008.Advisor: Rufina G. Alamo, Florida State University, FAMU-FSU College of Engineering, Dept. of Chemical Engineering. Title and description from dissertation home page (viewed July 8, 2008). Document formatted into pages; contains xix, 250 pages. Includes bibliographical references.
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Paradkar, Anant R., Adrian L. Kelly, Philip D. Coates, and Peter York. "Shear and extensional rheology of hydroxypropyl cellulose melt using capillary rheometry." 2009. http://hdl.handle.net/10454/6121.
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NoWith increasing interest in hot melt extrusion for preparing polymer-drug systems, knowledge of the shear and extensional rheology of polymers is required for the formulation and process design. Shear and extensional rheology of three commercial grades of hydroxypropyl cellulose (HPC) was examined at 140, 145 and 150 degrees C using twin bore capillary rheometry at range of processing rates. The power law model fitted for shear flow behaviour up to shear strain rates of approximately 1000s(-1), above which measured shear viscosities deviated from the power law and surface instabilities were observed in the extrudate, particularly for higher molecular weight grades. Shear thinning index was found to be relatively independent of temperature and molecular weight, whilst the consistency index, indicative of zero shear viscosity increased exponentially with increase in molecular weight. Extensional viscosity of all grades studied was found to decrease with increasing temperature and increasing processing rate. Foaming of the extrudate occurred especially at low temperatures and with the high molecular weight grade. An understanding of the relationships between shear and extensional flows with temperature, processing rate and molecular weight is a useful tool for process design; optimisation and troubleshooting of Hot melt extrusion (HME) of pharmaceutical formulations.
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Kitching, V. R., Nejat Rahmanian, N. H. Jamaluddin, and Adrian L. Kelly. "Influence of type of granulators on formation of seeded granules." 2020. http://hdl.handle.net/10454/17907.
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YesIt has been shown that seeded granules of calcium carbonate can be produced in commercial batch high shear granulators such as the Cyclomix high-shear impact mixer. Seeded granules are attractive to the pharmaceutical industry due to their high uniformity and good mechanical properties which can assist efficient tablet manufacture. In the current study, attempts to produce seeded granules of Durcal 65 and PEG 4000 binder using hot melt granulation are reported, in response to the recent shift towards continuous pharmaceutical manufacturing. Various screw configurations and rotation speeds were investigated in a series of experiments to determine the relationship between process conditions and granule properties. Particle size analysis, strength measurement and structural characterisation were used to quantify granule properties. It was found that using a series of kneading elements arranged at a 60° staggering angle located near to the feed section of the extruder screw generated strong, spherical granules. From structural characterisation approximately 5–15% of extruded granules were found to be seeded. Twin screw melt granulation is therefore considered to be a promising technique for continuous production of seeded granules, although a more detailed investigation is required to optimise yield and quality.
The full-text of this article will be released for public view at the end of the publisher embargo on 27 May 2022.
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Fang, Yi-Wen, and 方以文. "The study of melting enthalpy and mechanical strength of EVA influenced by the molecular weight of low temperature EVA hot melt adhesive." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/q42agx.
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碩士國立臺北科技大學
有機高分子研究所
96
The paper is concerned about Ethylene Vinyl Acetate Copolymer(abbr. EVA) base hot melt adhesives (HMA), which is applied at high temperature between 180 to 200℃. Regarding to the short of energy, this study ‘s main goal is to develop a new hot melt adhesives applied by lower temperature (i.e. 140~150℃) and which can hold the similar prosperities as the traditional high-temperature-applicative HMA. This study presents that the higher melt index (MI) of the EVA, the lower of melting enthalpy and total strength. The strength is similar while we adjust the relative percent of the low melting enthalpy and tackifier; when we fix the ration of low-temperature-applicative HMA, introducing the crystalline wax and change the ratio of tackifier and wax. The maximum strength is obtained by adding10% crystalline wax, which has the lowest MI value of all low-temperature-applicative HMA products.
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Guettler, Barbara Elisabeth. "Soy-Polypropylene Biocomposites for Automotive Applications." Thesis, 2009. http://hdl.handle.net/10012/4427.
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For the automotive sector, plastics play the most important role when designing interior and exterior parts for cars. Currently, most parts are made from petroleum-based plastics but alternatives are needed to replace environmentally harmful materials while providing the appropriate mechanical performance and preferably reduce the cost for the final product.
The objective of this work was to explore the use of soy flakes as natural filler in a composite with polypropylene and to investigate the mechanical properties, water absorption and thermal behaviour. For a better understanding of the filler, the soy flakes were characterized extensively with analytical and microscopic methods.
Two types of soy fillers were investigated, soy flakes, provided by Bunge Inc., with a 48 wt-% protein content and an industrial soy based filler with 44 wt-% protein content and provided by Ford.
The size of the soy flakes after milling was mainly between 50 and 200 µm and below 50 µm for the industrial filler. The aspect ratio for all filler was below 5. The soy flakes were used after milling and subjected to two pre-treatment methods: (1) one hour in a 50 °C pH 9 water solution in a 1 : 9 solid-liquid ratio; (2) one hour in a 50 °C pH 9 1M NaCl solution in a 1 : 9 solid-liquid ratio. A control filler, without pre-treatment was considered. The soy flakes were also compared to an industrial soy based filler provided by Ford (soy flour (Ford)). The thermogravimetric analysis showed an onset of degradation at 170 °C for the treated filler (ISH2O and ISNaCl) and 160 °C for the untreated filler.
The biocomposites formulation consisted of 30 wt-% filler, and polypropylene with/without 0.35 wt-% anti-oxidant Irganox 1010 and with/without the addition of MA-PP as coupling agent. All biocomposites were compounded in a mini-extruder, pressed into bars by injection moulding and tested subsequently.
The mechanical properties of the biocomposites are promising. An increase of the E-modulus was observed when compared to pure polypropylene. The addition of MA-PP as coupling agent increased the yield strength of the biocomposites. When pure polypropylene and the biocomposites were compared no difference could be seen for their yield strength.
The thermal behaviour deduced from differential scanning calorimetry, revealed a similar behaviour for the biocomposites and the pure polypropylene. Only the samples treated in the presence of NaCl and without a coupling agent, appear to have a slightly higher degree of crystallinity. The melt flow index was slightly increased for the biocomposites containing soy flakes pre-treated with NaCl and decreased for biocomposites containing the soy flour.
The water absorption behaviour of the biocomposites was quite similar at the beginning with a slightly lower absorption for the materials with coupling agent. After three months, all samples except the ones treated with water showed a weight loss that can be due to the leaching of the water soluble components in the untreated filler and the NaCl treated filler.
In conclusion, soy flakes represent an attractive filler when used in a polypropylene matrix if an aqueous alkaline pre-treatment is performed. The aqueous alkaline extraction also leads to the recovery of the proteins that can be used in food products while the remaining insoluble material is used for the biocomposites, avoiding the competition with the use of soy for food products...
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Hilyard, Mark D. "Partitioning of rare earth and high field strength elements between pargasitic amphibole and silicate melts." Thesis, 1997. http://hdl.handle.net/1957/34001.
Full text
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Wiser, Cathy. "Stability and gel strength of meat emulsions made with prerigor, preblended beef and reduced salt levels." Thesis, 1989. http://hdl.handle.net/1957/27054.
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The purpose of this study was to investigate the use
of preblended, prerigor beef in reduced salt meat batters.
The functional properties of water-holding capacity, fat
binding and gel strength were evaluated. Proximate
analyses (protein, moisture and fat contents) of all
cooked samples were performed, in duplicate.
The sternomandibularis muscle (SM) was removed from
the right side of each of fifteen steers within 1 hr after
death. The control samples remained on the left side of
each carcass for 48 hr at 2°C before removal.
The muscles removed prerigor were preblended with
four different levels of salt: 1.5, 2.25, 2.5, and 3.0%.
The preblends and the postrigor SM were used to formulate batters with 1.5 or 2.5% salt. During preparation, the
batters were chopped until a temperature of 16.0 +/- 0.5°C
was reached, and the batter pH was adjusted to 5.8 with
NaOH.
Aliquots of batter were weighed into centrifuge tubes
and cooked in a 70 - 75°C water bath for 30 min. Water-holding
capacity was determined by weighing the amount of
fluid lost during cooking. After the cooked batters had
cooled, gel strength was evaluated with an Instron
Universal Testing Machine using the penetration method
with a cylindrical punch.
The mean pH of the prerigor muscles (6.70) was
significantly higher (p<0.01) than that of the control
muscles (5.66). The proximate analysis results indicated
no significant differences between treatments for the
moisture and fat contents. The mean protein content of
the 2.5% salt batter control treatment was significantly
lower (p<0.05) at 11.13%, than the four prerigor,
preblended treatments which ranged from 11.88 to 12.21%.
The 1.5% salt batter control treatment had a mean
cook loss of 9.75% and was significantly higher (p<0.05)
than the other treatments which ranged from 4.55 to 6.93%.
A red-colored cook loss fluid was observed in the
prerigor, preblended 1.5% salt final batter treatments.
This loss seemed to have no significant (p<0.05) effect on
the functional properties of the batters studied. Fat release was negligible amounting to only a few droplets
per treatment.
The four preblended treatments had significantly
stronger (p<0.05) gel strengths (0.88 - 0.97 lbs) than the
two postrigor control treatments (0.67, 0.69 lbs). Gel
strength seemed to be more dependent on the state of rigor
when salt was added than on the amount of salt added. The
evidence indicates that it is possible to make an
acceptable reduced salt product using prerigor, preblended
beef.Graduation date: 1990
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Lian, Huey-Ruey, and 連慧瑞. "Effects of sink strength on photosynthetic rate and sucrose metabolism of the muskmelon leaves(Cucumis melo L.)." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/13411815757132274094.
Full textAbstract:
碩士國立中興大學
植物學系
85
To change the ratio of the source(leaf) and sink(fruit), muskmelon in greenhouse were taken non-fruiting(Fu0), one fruit remained(Fu1), and two fruit remained(Fu2) treatments during the pollination stage. The influences of photosynthetic rate and sucrose metabolism were investigated in terms of above treatments. The study results were stated below.The results showed that photosynthetic rate and stomatal conductance of Fu1 and Fu2 were higher than Fu0 and the contents of sucrose and starch were accumulated. The activity of sucrose synthase was increased during the fruiting stage. However, the photosynthetic rate、Rubisco activity、sucrose phosphate synthase activity、 starch content、and chlorophyll content were decreased during the fruiting stage. There were no significant difference between Fu1 and Fu2. The total fruit weight of Fu2 was higher than that of Fu1 during the fruiting stage. However, fruit sweetness was lower than that of Fu1.The photosynthetic rate and stomatal conductance of Fu0 were slightly decreased after taking non- fruit treatment than those of Fu1 and Fu2. The activities of Rubisco and sucrose synthase and contents of starch and chlorophyll were not different after taking non-fruiting treatment. The content of sucrose and activities of sucrose phosphate synthase were not significantly different among Fu0、 Fu1 and Fu2.The results also found that photosynthetic rate was positively correlated with stomatal conductance and negatively correlated with starch content, however, it was not correlated with Rubisco activity. The export of assimilates was not correlated with the activity of sucrose phosphate synthase and the content of sucrose.
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Aseri, Abdullah. "Effects of fluorine on the solubilities of Nb, Ta, Zr and Hf minerals in highly fluxed water-saturated haplogranitic melts." Thesis, 2012. http://hdl.handle.net/10012/7129.
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The effect of fluorine on the solubilities of Mn-columbite (MnNb2O6), Mn-tantalite (MnTa2O6), zircon (ZrSiO4) and hafnon (HfSiO4) were determined in highly fluxed, water-saturated haplogranitic melts at 800 to 1000 °C and 2000 bars. The melt corresponds to the intersection of the granite minimum with the albite-orthoclase tieline (Ab72Or28) in the quartz-albite-orthoclase system (Q-Ab-Or) due to the addition of P2O5 to the melt. The melt content of P2O5 is 1.7 wt. %, and also contains 1.1 and 2.02 wt. % of Li2O and B2O3, respectively. The composition of the starting glass represents the composition of melts from which rare-elements pegmatites crystallized. Up to 6 wt. % fluorine was added as AgF in order to keep the aluminum saturation index (ASI) of the melt constant. In an additional experiment F was added as AlF3 to make the glass peraluminous. The nominal ASI (molar Al/[Na+K]) of the melts is close to 1 and approximately 1.32 in peraluminous glasses, but if Li considered as an alkali, the ASI of the melts are alkaline (0.85) and subaluminous (1.04), respectively.
The solubility products [MnO]*[Nb2O5] and [MnO]*[Ta2O5] are nearly independent of the F content of the melt, approximately 18.19 ± 1.2 and 43.65 ± 2.5 x10-4 KSP (mol2/kg2), respectively. By contrast, there is a positive dependence of zircon and hafnon solubilities on the fluorine content, which increases from 2.03 ± 0.03 x10-4 (mol/kg) ZrO2 and 4.04 ± 0.2 x10-4 (mol/kg) HfO2 for melts with 0 wt. % F to 3.81 ± 0.3 x10-4 (mol/kg) ZrO2 and 6.18 ± 0.04 x10-4 (mol/kg) HfO2 for melts with 8 wt. % F. Comparison of the data from this work and previous studies indicates that ASI of the melt seems to have a stronger effect than the contents of fluxing elements in the melt and the overall conclusion is that fluorine is less important (relative to melt compositions) than previously thought for the control on the behavior of high field strength elements in highly evolved granitic melts. Moreover, this study confirms that although Nb, Ta, Zr and Hf are all high field strength elements, Nb-Ta and Zr-Hf are complexed differently.
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Sardashti, Amirpouyan. "Wheat Straw-Clay-Polypropylene Hybrid Composites." Thesis, 2009. http://hdl.handle.net/10012/4712.
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The preparation of polymeric hybrid composite consisting of organic and inorganic fillers is of interest for industries like automotive, construction and packaging. In order to understand and predict the physical and chemical properties of these hybrid composites, it is necessary to fully understand the nature and properties of the employed fillers. In this study, the preparation of polypropylene hybrid composite consisting of wheat straw and clay was investigated. A detailed study was performed on wheat straw from South Western Ontario region. The effect of grinding the straw and compounding it with polypropylene was investigated. Experiments were carried out to identify the thermal stability of the ground wheat straw with respect to their size and composition. It was important to identify a correlation between these properties in order to minimize the straw degradation by processing and also to improve the final properties of the hybrid composite. The composite samples were prepared through melt blending method using a co-rotating twin-screw extruder. Sample test bars were prepared by injection moulding. The composition of the constituents of the hybrid composite; percentages of wheat straw, clay and coupling agent, were varied in order to investigate their influence on thermal stability, water resistance and mechanical properties.
The results of the study indicated that grinding the wheat straw with a hammer mill produced particles with different sizes and shapes. It was found that through the grinding system all particles, regardless of their size, had a multi-layered structure similar to the plant structure. Further hammer milling did not produce plant particles with long aspect ratios that would be expected in a defibrillation process. Analysis of the chemical composition of wheat straw particles of different sizes and shapes was used to measure the ratio of hemicelluloses: lignin and the ash content. It was found that the large particles contained more amount of lignin whereas smaller particles had larger amount of ash content. The thermal stability of the particles was found to be a function of particle size rather than the lignin content. Particle size analysis on the wheat straw particles after the extrusion process indicated a reduction in the particle length and aspect ratio.
The thermal stability of the composites was found to be enhanced by the addition of clay particles at higher temperature and the addition of coupling agent at lower temperatures. Increasing the amount of wheat straw and clay content increased the flexural modulus and reduced the resistance for water absorption. Increasing the amount of coupling agent also increased the flexural modulus and resistance for water absorption. The morphological study by scanning electron microscopy revealed that coupling agent increased the interfacial interaction between the particles and the polymer matrix.
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Stone, Maria Magdalena. "Benutting van Gestaltspelterapie met die fokus op selfondersteuning by die kind in die middelkinderjare." Thesis, 2007. http://hdl.handle.net/10500/1938.
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Text in AfrikaansIn this study the researcher explored and described the use of Gestalt play therapy with specific focus on self-support with the child in middle childhood years. A literature study was undertaken to examine the concepts of child, Gestalt play therapy, self-support and the play therapy process. This literature study forms the theoretical frame in which this study was done. After the completion of the literature study, the empirical study was conducted. The researcher made use of unstructured interviews within a intrinsic single case study in order to compile research data. During the empirical study ten therapy sessions were conducted with the participant which was explored within the framework of qualitative research methodology. The researcher was able to use ample Gestalt play therapy concepts and principles during the description of the case study in order to explore self-support within the child during middle childhood. These concepts and principles will be discussed in depth within this study.
Social Work
M.Diac. (Spelterapie-rigting)