Dissertations / Theses on the topic 'Polypropylene Effect of temperature on'
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Snyder, Joseph Timothy II. "The effect of compressive biaxial orientation on the low-temperature toughness and pre-fracture damage of polypropylene." Case Western Reserve University School of Graduate Studies / OhioLINK, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=case1056558280.
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Guclu, Mehmet. "Light Stability And The Effect Of Temperature On Mechanical Properties Of Polypropylene / Poly(ethylene-vinyl-acetate) Blends." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608535/index.pdf.
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The variation in properties of Polypropylene (PP) / Ethylene Vinyl Acetate (EVA) blends upon EVA content, temperature, and light stability were followed by using tensile testing, impact testing, and differential scanning calorimetry (DSC).
Young&rsquos modulus of the blends decreased with increasing drawing temperature and EVA content. The stress at break values of the blends slightly increased with EVA whereas decreased with drawing temperature. The percent strain at break values of the blends were found to increase abruptly by increasing EVA content and drawing temperature. These changes in the mechanical properties are the indication of compatibility. The impact tests were performed only at 0°
C, 25°
C and the impact strength increased with the temperature and EVA content, but none of the samples were broken at higher testing temperatures. The effect of stabilizer was very obvious because stabilizer-free samples failed after 400 hours whereas, the samples with stabilizer resisted up to 750 hours. Elongation values of the samples decreased because of increasing brittleness by UV irradiation. We also observed chain stiffening effect by crosslinking in all samples upon UV irradiation. Thermal analysis of the blends of the drawn samples showed an increasing trend of crsytallinity with increasing drawing temperature. Increasing drawing temperature made polymer chains more flexible because of the increasing chain mobility. These flexible chains were then oriented in one direction during tensile testing and therefore uniaxial crystallization occurred. The morphology of impact and tensile tests samples were also analyzed by scanning electron microscope (SEM). The fibrillation of pure PP is higher than the fibrillation of the blends.
3
Hayakawa, N., T. Kobayashi, M. Hazeyama, T. Takahashi, K. Yasuda, and H. Okubo. "Partial discharge inception characteristics of LN/sub 2//polypropylene laminated paper composite insulation system for high temperature superconducting cables." IEEE, 2005. http://hdl.handle.net/2237/6846.
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Mansour, Marwan. "Experimental tests on the effect of temperature on the short term behavior of FRC beams." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
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The effect of temperature under short term behavior on macro-synthetic polypropylene fibers reinforced concrete (MSFRC) was evaluated, to understand how this condition may affect the performance of this material. An experimental campaign of three-point bending, compressive tests and elastic modulus tests have been performed on prisms, cubes and cylinders cured at 6 temperatures, ranging from -30°C to +60°C. The results highlighted that, for the material tested, the increment of temperature causes a decrement of the peak and post-peak flexural strength. Further analysis have been done on the fibers number and failure type.
5
Magagula, Sifiso Innocent. "The effect of organic peroxides on the molecular composition of heterophasic ethylene-propylene impact copolymers." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/97850.
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Thesis (MSc)--Stellenbosch University, 2015.ENGLISH ABSTRACT: Heterophasic ethylene-propylene copolymers, also known as impact polypropylene (PP) copolymers (IPCs) or heterophasic copolymers (HECOs), are a unique group of polyolefins produced through the copolymerisation of ethylene and propylene, with the aim of improving the impact properties of the PP homopolymer at low temperatures. Therefore, this polymer comprises of a PP homopolymer matrix with a dispersed rubbery copolymer phase. Due to their unique properties, HECO polymers have become commercially important materials, with a wide range of applications. Therefore a fundamental understanding of the processes and chemistry that affects their final macroscopic properties needs to be expanded. The main focus of this investigation was to understand why specific organic peroxides influence or interact differently with the various phases of HECO polymers, in order to utilize their properties to obtain HECO polymers with optimal and desired properties. Two HECO polymers with different ethylene contents were fractionated into three fractions (30, 100 and 130 °C), using preparative temperature rising elution fractionation (P-TREF). Each individual TREF fraction was degraded with two different types of organic peroxides, and then characterised using four different analytical tools. The changes in the molecular structures of the different fractions were investigated by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The changes in comonomer sequence distributions were investigated by carbon 13 nuclear magnetic resonance spectroscopy (13C-NMR). Moreover, the degradation of the different fractions was investigated by high temperature size exclusion chromatography (HT-SEC). The investigation showed that the HECO polymers with different ethylene contents were uniquely altered. It was evident that the ethylene content influenced the degradation behaviour of the HECO polymers. The ability of the peroxide to affect certain regions of the HECO polymer more than others is highly dependent upon its miscibility with certain regions of the HECO polymers. The “visbreaking” efficiency of a specific organic peroxide appears to be primarily dependent on the number of “peroxy” groups it contains in its molecular structure. Stellenbosch University https://scholar.sun.ac.za
AFRIKAANSE OPSOMMING: Heterofase etileen-propileen ko-polimere, ook bekend as impak PP ko-polimere (IPCS) of heterofase ko-polimere (HECO), is 'n unieke groep poliolefiene geproduseer deur die ko-polimerisasie van etileen en propileen, met die doel op die verbetering in die impak eienskappe van die PP homopolimeer by lae temperature. Hierdie polimeer bestaan dus uit 'n PP homopolimeer matriks met 'n verspreide rubberagtige ko-polimeer fase. As gevolg van hul unieke eienskappe, is HECO polimere van kommersiële belang, met 'n wye verskeidenheid van toepassings. 'n Fundamentele begrip van die prosesse en chemie wat die finale makroskopiese eienskappe beïnvloed moet dus uitgebrei word. Die hooffokus van hierdie ondersoek was om te verstaan waarom spesifieke organiese peroksiede verskillende invloede en interaksies met die verskillende fases van HECO polimere het, om sodoende van hul eienskappe gebruik te maak om HECO polimere te verkry met optimale en gewenste eienskappe. Twee HECO polimere met verskillende etileen inhoud was gefraksioneer in drie fraksies (30, 100 en 130 °C), met behulp van preparatiewe temperatuur styging eluering fraksionering (P-TREF). Elke individuele TREF fraksie was gedegradeer met twee verskillende tipes organiese peroksiede en daarna gekarakteriseer deur vier verskillende analitiese metodes. Die veranderinge in molekulêre strukture van die verskillende fraksies was geondersoek met behulp van Fourier transform infrarooi spektroskopie (FTIR) en differensiële skandering kalorimetrie (DSC). Die veranderinge in ko-monomeer volgorde distribusie was bestudeer deur middel van kern magnetiese resonans spektroskopie (KMR). Verder was die degradasie van die verskillende fraksies met behulp van hoë temperatuur grootte uitsluitingschromatografie (HT-SEC) bestudeer. Die ondersoek het getoon dat die HECO polimere met verskillende etileen inhoud uniek gedegradeer was. Dus is dit duidelik genoeg dat die etileen inhoud die degradasie gedrag van die HECO polimere beïnvloed het. Die vermoë van die peroksied om sekere areas van die HECO polimeer meer as ander te beïnvloed is hoogs afhanklik van die mengbaarheid met sekere areas van die HECO polimere. Die "visbreking" doeltreffendheid van 'n spesifieke organiese peroksiede is meestal afhanklik van die aantal "peroksie" groepe in die molekulêre struktuur.
6
Nguyen, Duy Cuong. "Caractérisation de l'interface fibre/matrice : application aux composites polypropylène/chanvre." Thesis, Troyes, 2016. http://www.theses.fr/2016TROY0009/document.
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Les agro-composites font l'objet de nombreuses études et applications industrielles en raison des multiples propriétés mécaniques qu'ils présentent. Ces propriétés présentent de grandes perspectives comparées à celles des composites traditionnels. Cependant les connaissances sur le comportement mécanique de l'interface fibre/matrice restent limitées. De plus, la différence de propriété entre la fibre hydrophile et la matrice hydrophobe peut causer des défauts au niveau de l’interface. Il est donc important de caractériser finement la décohésion à l'interface au cours d'une sollicitation. Plusieurs méthodes ont été proposées dans la littérature, elles sont généralement très complexes à mettre en œuvre et sont coûteuses. Dans cette étude, nous avons développé une méthode de caractérisation en se basant sur l'essai de « pull-out ». La géométrie de la fibre a été prise en compte dans le calcul des propriétés mécaniques de l'interface par la mise à profit d'une approche inspirée de la tomographie. L'influence de la température d'élaboration sur les propriétés mécaniques de l'interface a été étudiée de manière à définir la température optimale. L'évolution des propriétés interfaciales a été suivie au cours d'un vieillissement en humidité relative. Après quatre semaines, la résistance au cisaillement et la rigidité au cisaillement de l'interface sont diminuées fortement alors que la déformation à la rupture est augmentéeAgro-composites are increasingly studied and applied to various industries over recent years due to good mechanical properties compared to conventional composites especially in terms of specific values. However, since low adhesion between the hydrophilic fiber and hydrophobic matrix, which occurs one of the main breaks modes in this kind of material, the characterization of the interface becomes a key problem. For investigation of this issue, existing methods show limitation for reasons of complexity (in preparation, in principle) and of cost. In this study, we developed a « pull-out ». In particular, the real fiber geometry of the plant fiber was taken into the calculation of mechanical properties of interface using a tomography inspired method. By checking the effective temperature of the molding then varying it, we studied the effect of this processing parameter to mechanical properties of fibre/matrix interface and determined the optimal conditions. The developed experimental protocol is applied to aged interfaces in order to clarifying the evolution of interfacial properties during the aging time to relative humidity. After four weeks, the interfacial shear strength and the shear modulus of the interface were greatly reduced while the shear deformation at the rupture was greatly increased
7
Jones, Andrew Paul. "Novel approaches to high temperature stabilisation of polypropylene." Thesis, Manchester Metropolitan University, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545931.
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Schildmeyer, Andrew Joseph. "Temperature and time dependent behaviors of a wood-polypropylene composite." Online access for everyone, 2006. http://www.dissertations.wsu.edu/Thesis/Summer2006/a%5Fschildmeyer%5F072006.pdf.
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Moeiri-Farsi, M. H. "Effects of autoclave temperatures on properties of cementitious based matrices reinforced with randomly orientated polypropylene fibres." Thesis, University of Salford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336075.
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10
Haniche, Rachid. "Contribution à l’étude des bétons portés en température / Evolution des propriétés de transfert : Etude de l’éclatement." Thesis, Lyon, INSA, 2011. http://www.theses.fr/2011ISAL0155/document.
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L’étude du comportement des bétons à hautes températures est d’une grande importance pour déterminer la stabilité et la résistance des structures en béton en situation d’incendie. Des incendies spectaculaires, ces dernières années, ont montré que le béton pouvait être très fortement sollicité. Ainsi il apparaît qu’assurer un très bon comportement du béton en température permet de sauver des vies et de diminuer les frais d'immobilisation et de réparation des structures endommagées. Le travail présenté vise, par une étude expérimentale, à apporter une meilleure compréhension des phénomènes mis en jeu lors de l’exposition aux hautes températures des bétons à hautes performances (BHP). Il s’intéresse, plus particulièrement, aux transferts des fluides dans les bétons (perméabilité) et à l’étude de l’instabilité thermique (phénomène d’éclatement) des bétons à hautes performances. Le travail de thèse a été mené sur des bétons à hautes performances (80 MPa) avec 5% de fumée de silice (matériau à faible perméabilité pour améliorer la durabilité), et différents pourcentages de fibres de polypropylène. L’utilisation des fibres de polypropylène (PP) est considérée comme une solution technique efficace pour améliorer la tenue au feu des bétons à hautes performances, notamment grâce aux phénomènes physiques apparaissant aux températures inférieures à 200°C. Notre travail concerne, dans un premier temps, la caractérisation de l’évolution des propriétés physiques (porosité, perte de masse), thermiques (conductivité et diffusivité) et mécaniques (résistance à la compression et en traction) ainsi que les isothermes de sorption. La deuxième partie de ce travail concerne l’étude de l’évolution de la perméabilité en fonction de la température (jusqu’à 200°C), principale propriété caractérisant les transferts hydriques au sein des bétons. Les paramètres étudiés sont : le type de béton (avec ou sans fibres de PP), deux types de fibre de géométries différentes, la nature du fluide (air ou vapeur d’eau) et la méthode de mesure (en résiduel et à chaud). Les résultats expérimentaux montrent que les fibres génèrent une perméabilité plus importante au-delà de 150°C et que les valeurs obtenues en résiduel ou à chaud peuvent être liés aux modes opératoires. Enfin, dans la dernière partie une investigation sur le phénomène d’éclatement explosif en lien avec la composition du matériau est menée. Une nouvelle méthode d’investigation expérimentale de la sensibilité des formulations à l’instabilité thermique est proposée avec une étude sur des sphères portées en température. Cette méthode devra être comparée aux méthodes traditionnelles d’investigation. L’analyse des résultats des essais permet de discuter sur les causes de l’instabilité thermique et de caractériser les propriétés du béton en température, données indispensables à la modélisationThe study of the behaviour of concrete at high temperatures is of great importance to determine the stability and strength of concrete structures in fire conditions. Spectacular fires, these last years, showed that the concrete could be very strongly solicited. Thus it appears that to ensure a very good behaviour of the concrete at temperature it is saved people and reduced the expenses of immobilisation and repair of the damaged structures. The aims of the present work, by the experimental study, are to provide a better comprehension of the involved phenomena during the exposure to the high temperatures of the high performance concretes (HPC). It focuses, in particular, on the fluids transfers (permeability) and the study of the thermal instability (spalling) of high performance concrete. The thesis work was conducted on high-performance concrete (80 MPa) with 5% silica fume (low permeability material to improve durability), and different amount of polypropylene fibres. The use of polypropylene fibres (PP) is regarded as an effective technical solution to improve the behaviour of the HPC at fire conditions, in particular thanks to the physical phenomena appearing at the temperatures lower than 200°C. Our work is concerned, initially, on the characterization of the evolution of physical properties (porosity, mass loss), thermal properties (conductivity and diffusivity) and mechanical properties (compressive strength and tensile) and the sorption isotherms. The second part concerns the study of the evolution of the permeability, as a main property characterising the hydrous transfers inside the concrete exposed to temperature. An experimental study is conducted concerning the evolution of the permeability of concrete as a function of temperature (up to 200 ° C). The studied parameters are: the type of concrete (with and without fibres), two types and geometry of fibres, the nature of the fluid (air and vapour) and the measurement methods (residual and under temperature). The experimental results shows that the existing fibres generate a most important permeability beyond 150°C and that the obtained results, by residual or under temperature measurements, may be related to the operating procedures. Finally, in the last part an investigation on the spalling phenomenon related to the material compositions is conducted. A new experimental method of investigation of the sensitivity of the formulations to thermal instability is proposed: the study of spherical specimens exposed in high temperatures. This method will be compared to the traditional methods of investigation. The analysis of the test results makes to discuss the thermal instability causes and to characterize the concrete properties at high temperatures, important data to modelling
11
Abu-Zurayk, R. A. R. "The effect of processing on structure and properties of polypropylene/clay nanocompsites." Thesis, Queen's University Belfast, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.515684.
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Campbell, P. M. S. "The effect of nickel oxime chelates on the thermal and photochemical stability of polypropylene." Thesis, University of Ulster, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378966.
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Khoathane, MC, OC Vorster, and ER Sadiku. "Hemp Fiber-Reinforced 1-Pentene/Polypropylene Copolymer: The Effect of Fiber Loading on the Mechanical and Thermal Characteristics of the Composites." SAGE, 2008. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1000586.
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One of the recent developments in composite technology in South Africa is the increasing use of natural fiber materials in the manufacture of plastic products. Most of the previous
work on natural fiber-reinforced composites has focused on sisal fiber as it was commercially available. In this study, the mechanical and thermal properties of composites made with locally produced hemp fibers, were compared with composites made with hemp fibers produced in France.
New commercial polypropylene random copolymer was used as matrix because it can be processed at lower temperatures when compared with other commercial propylene copolymers. The composites were produced by extrusion compounding and were further processed into tensile test bars by injection molding. Up to 30% fiber loading could be achieved. It was observed in all composites that increasing the amount of fiber resulted in an increase in tensile strength, elastic
modulus, and flexural strength and a decrease in impact strength. The thermal properties of the composites were analyzed by the thermogravimetric method. It was found that the fiber/PP
composites showed excellent properties when compared to fiber and the matrix separately. The addition of hemp fibers shifted the start of the degradation process towards higher temperatures.
The results obtained show that the mechanical and thermal properties of South African long hemp fiber composites compare favorably well with the French bleached and unbleached hemp fibers.
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Kalyanam, Sriram. "Effect of silane coupling agents on the mechanical properties of glass polypropylene composites." Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/8563.
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Richardson, Alan Elliott. "An investigation into the effect of polypropylene fibres on the durability of concrete." Thesis, University of Newcastle Upon Tyne, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500949.
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The problem with understanding the properties of polypropylene fibres in concrete is that there are many types of fibre, with many suggested properties and conflicting claims made by both manufacturers of polypropylene fibres and researchers in the field of material science as to the effects of fibres on compressive strength, flexural strength, post crack performance, absorption reduction and freeze/thaw durability of concrete. From an initial pilot study, utilising standard BSI and ASTM tests and devised non-standard tests, including measurement of grout resistivity an extensive test programme was conductec to determine the effect of polypropylene fibres on the freeze/thaw behaviour of concrete.
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Sadiku, E. R. "The effect of physical ageing on the structural and mechanical characteristics of polypropylene." Thesis, University of Strathclyde, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372099.
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Marsh, M. G. "The effect of a temperature gradient on high temperature fretting wear." Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267625.
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Francois, heude Alexandre. "Kinetic modeling of the polypropylene photothermal oxidation." Phd thesis, Ecole nationale supérieure d'arts et métiers - ENSAM, 2014. http://pastel.archives-ouvertes.fr/pastel-01069008.
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Developing numerical tools for polymer lifetime prediction constitutes a promising opportunity for shortening the duration of material certification procedures in the automotive industry without decreasing their reliability. This PhD thesis aims at modeling the photothermal oxidation of isotactic polypropylene (iPP), which is responsible for the alteration of both its mechanical and aspect properties. The adopted approach consists in coupling the kinetics of photo- and thermo-oxidation reactions with physical phenomena, such as oxygen transport and UV-light attenuation in the material thickness, in order to describe all the physico-chemical changes. Upper-scale properties, from which will be defined the end-of-life criteria, will be calculated afterwards by applying the suitable structure-property relationships. The main challenge was to extend the pre-existing kinetic model of thermal ageing to photothermal ageing by taking into account initiation reactions of photolysis. Heavy campaigns of ageing and characterization tests made on a reference iPP, as well as an exhaustive capitalization of literature data of other iPPs, have allowed elaborating a kinetic model of photothermal oxidation and to generalize it to the whole iPP family in large domains of oxygen partial pressure (from 0.2 to 50 bars), temperature (from 40 to 230°C) and UV-light exposure (variable intensities and light sources) describing both natural and accelerated ageing conditions. The experimental validation of the model has allowed substantiating the kinetic approach and showing its limitations, as well as highlighting some numerical issues. The model has been designed in order to be an upgradable numerical tool which will allow, at term, optimizing the representativeness of the ageing testing devices and the performance of commercial iPP formulations. All these theoretical and numerical developments are prone to be applied to the photothermal degradation of other types of polymer substrates, but also in other application fields of the macromolecular photochemistry such as UV-photopolymerization.Keywords: Polypropylene, photothermal oxidation, oxygen diffusion control, screen effect, kinetic modeling, lifetime prediction.
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Kanbur, Yasin. "Conductive Polymer Nanocomposites Of Polypropylene And Organic Field Effect Transistors With Polyethylene Gate Dielectric." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613312/index.pdf.
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One of the aim of this study is to prepare conductive polymer nanocomposites of polypropylene to obtain better mechanical and electrical properties. Composite materials based on conductive fillers dispersed within insulating thermoplastic matrices have wide range of application. For this purpose, conductive polymer nanocomposites of polypropylene with nano dimentional conductive fillers like carbon black, carbon nanotube and fullerene were prepared. Their mechanical, electrical and thermal properties were investigated.
Polypropylene (PP)/carbon black (CB) composites at different compositions were prepared via melt blending of PP with CB. The effect of CB content on mechanical and electrical properties was studied. Test samples were prepared by injection molding and compression molding techniques. Also, the effect of processing type on mechanical and electrical properties was investigated. Composites become semiconductive with the addition of 2 wt% CB.
Polypropylene (PP) / Carbon Nanotube (CNT) and Polypropylene / Fullerene composites were prepared by melt mixing. CNT&rsquos and fullerenes were surface functionalized with HNO3 : H2SO4 before composite preparation. The CNT and fullerene content in the composites were varied as 0.5, 1.0, 2.0 and 3.0 % by weight. For the composites which contain surface modified CNT and fullerene four different compatibilizers were used. These were selected as TritonX-100, Poly(ethylene-block-polyethylene glycol), Maleic anhydride grafted Polypropylene and Cetramium Bromide. The effect of surface functionalization and different compatibilizer on mechanical, thermal and electrical properties were investigated. Best value of these properties were observed for the composites which were prepared with maleic anhydride grafted polypropylene and cetramium bromide. Another aim of this study is to built and characterize transistors which have polyethylene as dielectric layers. While doing this, polyethylene layer was deposited on gate electrode using vacuum evaporation system. Fullerene , Pentacene ve Indigo were used as semiconductor layer. Transistors work with low voltage and high on/off ratio were built with Aluminum oxide - PE and PE dielectrics.
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Lufitha, Mundel. "Effect of substrate temperature on coating adhesion." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ58842.pdf.
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Mitchell, Angela. "The effect of temperature on starch synthesis." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243060.
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Phillips, Lisa Elaine. "The effect of low temperature on Salmonella." Thesis, University of Exeter, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286534.
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Prasad, Renee Priya. "The effect of rearing temperature on performance of Trichogramma sibericum at ambient temperature." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ51451.pdf.
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Cheruthazhekatt, Sadiqali. "Novel multidimensional fractionation techniques for the compositional analysis of impact polypropylene copolymers." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80118.
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Thesis (PhD)--Stellenbosch University, 2013.ENGLISH ABSTRACT: Impact Polypropylene Copolymers (IPCs) are extremely complex materials, consisting of a mixture of polypropylene homopolymer and copolymers having different comonomer (ethylene) contents and chemical composition distributions. IPC can only be effectively analysed by multidimensional analytical approaches. For this, initially, the individual components have to be separated according to any of their molecular characteristics, either by chemical composition distribution (CCD) or molar mass distribution (MMD), followed by further analysis of these separated fractions with conventional analytical techniques. The combination of preparative temperature rising elution fractionation (TREF) with several other analytical techniques have been reported for the thorough characterization of this material. However, even the combinations of these methods were of limited value due to the complex nature of this polymer. Therefore, novel analytical approaches are needed for a more detailed compositional analysis of IPCs. This work describes a number of multidimensional analytical techniques that are based on the combination of fractionation and hyphenated techniques. Firstly, preparative TREF was combined with high temperature size exclusion chromatography-FTIR (HT SEC-FTIR), HT SEC-HPer DSC (High Performance Differential Scanning Calorimetry) and high temperature two-dimensional liquid chromatography (HT 2D-LC) for the comprehensive analysis of a typical impact polypropylene copolymer and one of its midelution temperature TREF fractions. HT SEC-FTIR analysis provided information regarding the chemical composition and crystallinity as a function of molar mass. Thermal analysis of selected SEC fractions using a novel DSC method - High Speed or High Performance Differential Scanning Calorimetry (HPer DSC) - that allows measuring of minute amounts of material down to micrograms, yielded the melting and crystallization behaviour of these fractions which is related to the chemical heterogeneity of this complex copolymer. High temperature 2D-LC analysis provided the complete separation of this TREF fraction according to the chemical composition of each component along with its molar mass distribution. In a second step, the compositional characterization by advanced thermal analysis (HPer DSC, Flash DSC 1, and solution DSC) of the TREF-SEC fractions was extended to all semi-crystalline and higher temperature TREF fractions. By applying HPer DSC at scan rates of 5−200°C/min and Flash DSC 1 at scan rates of 10−1000°C/s, the metastability of one of the fractions was studied in detail. DSC measurements of TREF-SEC cross-fractions at high scan rates in p-xylene successfully connected reversely to the slow scan rate in TREF elution, if corrected for recrystallization. Finally, the exact chemical structure of all HT HPLC separated components was determined by coupling of HT HPLC with FTIR spectroscopy via an LCTransform interface. This novel approach revealed the capability of this hyphenated technique to determine the exact chemical composition of the individual components in the complex TREF fractions of IPCs. The HT HPLC–FTIR results confirmed the separation mechanism in HPLC using a solvent gradient of 1-decanol/TCB and a graphitic stationary phase at 160°C. FTIR analysis provided information on the ethylene and propylene contents of the fractions as well as on the ethylene and propylene crystallinities.
AFRIKAANSE OPSOMMING: Impak Polipropileen Kopolimere (IPKe) is uiters komplekse materiale, bestaande uit 'n mengsel van polipropileen homopolimeer en kopolimere met verskillende komonomeer (etileen) inhoud en chemiese samestelling verspreiding. IPKe kan slegs doeltreffend ontleed word deur multidimensionele analitiese benaderings te volg. Hiervoor moet die individuele komponente aanvanklik eers geskei word volgens enige van hul molekulêre eienskappe, hetsy deur die chemiese samestelling verspreiding (CSV) of molêre massa verspreiding (MMV), gevolg deur 'n verdere ontleding van hierdie geskeide fraksies met konvensionele analitiese tegnieke. Die kombinasie van voorbereidings temperatuur-verhogings eluasie fraksionering (TVEF) met verskeie ander analitiese tegnieke is gerapporteer vir die deeglike karakterisering van hierdie materiaal. Maar selfs die kombinasies van hierdie metodes was van beperkte waarde as gevolg van die komplekse aard van hierdie polimeer. Daarom word nuwe analitiese benaderings benodig vir 'n meer gedetailleerde komposisionele ontleding van IPKe. Hierdie studie beskryf 'n aantal multidimensionele analitiese tegnieke wat gebaseer is op die kombinasie van fraksionering en gekoppelde tegnieke. Eerstens is voorbereidings TVEF gekombineer met hoë temperatuur grootte-uitsluitingschromatografie-FTIR (HT GUC-FTIR), HT GUC-HPer DSK en hoë temperatuur twee-dimensionele vloeistof chromatografie (HT 2D-VC) vir die omvattende ontleding van 'n tipiese impak polipropileen kopolimeer en een van sy mid-eluasie temperatuur TVEF fraksies. HT GUC-FTIR analiese het inligting verskaf met betrekking tot die chemiese samestelling en kristalliniteit as 'n funksie van molêre massa. Termiese analiese van geselekteerde GUC fraksies deur gebruik te maak van 'n nuwe-DSK metode - Hoë Spoed of Hoë Prestasie Differensïele skandeer kalorimetrie (HPer DSK) - wat die meting van klein hoeveelhede materiaal tot by mikrogram hoeveelhede toelaat, het die smelt en kristallisasie gedrag van hierdie fraksies bepaal wat verwant is aan die chemiese heterogeniteit van hierdie komplekse kopolimeer. Hoë temperatuur 2D-LC analiese het die volledige skeiding van hierdie TVEF fraksie volgens die chemiese samestelling van elke komponent saam met die molêre massa verspreiding moontlik gemaak. In 'n tweede stap, is die komposisionele karakterisering deur gevorderde termiese analiese (HPer DSK, Flash DSK 1 en oplossing DSK) van die TVEF-GUC fraksies uitgebrei na alle semi-kristallyne en hoër temperatuur TVEF fraksies. Deur die gebruik van HPer DSK, teen ’n skandeerspoed van 5-200°C / min, en Flash DSK 1, teen ’n skandeerspoed van 10-1000°C / s, is die meta-stabiliteit van een van die fraksies in detail bestudeer. DSK metings van TVEF-GUC kruis-fraksies by 'n hoë skandeeerspoed in p-xyleen het suksesvol omgekeerd verbind aan die stadige skandeerspoed in TVEF eluasie, wanneer gekorrigeer vir dekristallisatie. Ten slotte is die presiese chemiese struktuur van al die HT HPVC geskeide komponente bepaal deur die koppeling van HT HPVC met FTIR spektroskopie deur middel van 'n LC-transform-koppelvlak. Hierdie nuwe benadering het die vermoë van die gekoppelde tegniek om die presiese chemiese samestelling van die individuele komponente in die komplekse TVEF fraksies of IPKe te bepaal aan die lig gebring. Die HT HPVC-FTIR resultate het die skeidingsmeganisme in HPVC bevestig deur die gebruik van ’n oplosmiddelgradiënt van 1-dekanol/TCB en 'n graphitiese stasionêre fase by 160°C. FTIR analiese verskaf inligting in verband met die etileen en propileen inhoud van die fraksies sowel as die etileen en propileen krystalliniteit.
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Lisy, Frederick Joseph. "Effect of orientation on properties of reinforced polypropylene and evaluation of materials with scanning acoustic microscopy." Case Western Reserve University School of Graduate Studies / OhioLINK, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=case1060794951.
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Hoza, Adam. "Effect of Ethylene and Propylene on Performance of Ziegler - Natta Catalyst in Stopped - Flow Polymerization." Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2017. http://www.nusl.cz/ntk/nusl-320775.
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Výzkum v této práci byl zaměřen na přípravu a charakterizaci blokových kopolymerů typu polypropylen-blok-poly(propylenu-co-ethylenu) (dále jen PP-blok-EPR). Tyto materiály jsou považovány za účinné kompatibilizátory mezi semi-krystalickou polypropylenovou (PP) matricí a amorfními doménami statistického kopolymeru propylenu a etylenu (EPR) v rázuvzdorném sekvenčním kopolymeru (ICP) a proto byl výzkum zaměřen na zkoumání vlivu přídavku blokového kopolymeru PP-blok-EPR na vlastnosti komerčního ICP. Blokové kopolymery byly připraveny za použití techniky „stopped-flow“. Pro tento účel byla zkonstruována vysokotlaká polymerační „stopped-flow“ aparatura, která umožňuje syntézu kopolymerů PP-blok-EPR za podmínek blízkých podmínkám v průmyslových reaktorech pro výrobu komerčních ICP materiálů. Aparatura umožňuje vyrábět PP-blok-EPR polymer v množství dostačující na jeho charakterizaci a následnou přípravu směsí s komerčním ICP. Velmi krátké polymerační časy (obvykle kolem 0.2 s) kterých bylo dosaženo v kapilárním reaktoru aparatury „stopped-flow“ zajišťuje, že aktivní centra Ziglorova-Nattova katalyzátoru produkují polymer řetězce skládající se z bloku semikrystalického polypropylenu a bloku amorfního EPR kopolymeru. Takovéto molekuly jsou v literatuře popsány jako „skutečné blokové kopolymery PP-blok-EPR“. Kopolymery syntetizované v aparatuře „stopped-flow“ byly frakcionovány preparativní TREF (Temperature Rising Elution Fractionation) metodou a získané frakce byly následně analyzovány pomocí DSC, 13C-NMR a GPC/SEC. Tyto analýzy odhalily přítomnost amorfního EPR ve vysoce krystalické frakci (100-140 °C). Toto zjištění potvrdilo, že významná část polymerních řetězců, připravených v aparatuře „stopped-flow“ jsou blokové kopolymery skládající se z bloku semikrystalického PP homopolymeru a bloku amorfního EPR kopolymeru v jednom polymerním řetězci. Kopolymery získané metodou „stopped-flow" byly v tavenině smíchány s komerčním rázuvdorným kopolymerem ICP. U takto připravených směsí byly vyhodnoceny mechanické vlastnosti, DTMA a reologické vlastnosti a výsledky byly srovnány s vlastmi původního komerčního ICP kopolymeru. Dále byly studovány rozdíly v morfologii a umístění EPR domén v matrici PP prostřednictvím SEM. Zřetelný vliv kopolymeru PP-blok-EPR na vlastnosti ICP byl pozorován zejména v morfologických změnách EPR domén dispergovaných v PP matrici. Tyto změny mají pozitivní vliv na rovnováhu mezi modulem v ohybu a rázovou pevností ICP materiálu. Vliv kopolymeru PP-blok-EPR na reologické vlastnosti ICP byl nevýznamný. Podobně také v případě DTMA nebyl pozorován významný vliv kopolymeru PP-blok-EPR na vlastnosti ICP.
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Kakireddy, Veera Raghava R. "Effect of temperature on copper chemical mechanical planarization." [Tampa, Fla.] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0001973.
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Griškevičius, Mečislavas. "High Temperature Effect On Resistance Of Timber Structures." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2010. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2010~D_20101119_134602-29128.
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The present dissertation and its main subjects inquires into the pine and oak timber strength property changes-temperature relations. It also explores the behaviour of slender timber elements in axial compression at higher temperatures; and the comparative analysis of obtained results.
The work seeks to accomplish the following major tasks: to obtain test data about the influence of high temperature on the properties of different natural – pine and oak – timber; to investigate the behaviour of slender timber elements under axial compression exposed to fire. Taking into account the investigated real fire effect to correct accordingly the existing in LST EN 1995-1-2 procedure for the fire resistance calculation of timber slender elements in compression.
The dissertation consists of an introduction, five chapters, general conclusions, a list of references, a list of author’s publications on the dissertation subject, and 2 Annexes.
Chapter 1 provides a literature review. It focuses on the publications inquiring into the loss of strength properties by timber at higher temperatures, the fire resistance of timber structures in compression. The chapter ends with the formulation of conclusions and the adjustment of research tasks.
Chapter 2 offers the methodology of the research on strength properties of timber at higher temperatures, and the schemes of the developed testing equipment.
Chapter 3 presents the procedure of the research on the behaviour of slender timber elements... [to full text]Disertacijoje nagrinėjami pušinės ir ąžuolinės medienos stipruminių savybių pokyčių temperatūriniai sąryšiai bei medinių centriškai gniuždomų liaunų elementų elgsena veikiant aukštesnėms temperatūroms. Pagrindiniai tyrimo objektai yra Lietuvos spygliuočių ir lapuočių medienos savybių pokyčiai didėjant temperatūrai ir centriškai gniuždomų liaunų medinių elementų elgsenos veikiant kaitrai eksperimentiniai tyrimai bei rezultatų lyginamoji analizė. Darbe spręsti tokie pagrindiniai uždaviniai: gauti eksperimentinius duomenis apie aukštos temperatūros poveikį skirtingos natūralios – pušinės ir ąžuolinės – medienos savybėms, atlikti centriškai gniuždomų liaunų medinių elementų elgsenos ugnyje tyrimus. Atsižvelgiant į tyrinėtą tikrovišką gaisro poveikį patikslinti esamą EN 1995-1-2 medinių liaunų gniuždomų elementų atsparumo ugniai skaičiavimo metodiką. Disertaciją sudaro įvadas, penki skyriai, bendrosios išvados, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai ir du priedai. Pirmasis skyrius skirtas literatūros apžvalgai. Jame pateikta darbų, kuriuose nagrinėjamas aukštesnės temperatūros veikiamos medienos, stipruminių savybių mažėjimas ir kuriuose pateikiami gaisro sąlygomis gniuždomų medinių elementų laikomosios galios tyrimų rezultatai. Pabaigoje formuluotos išvados ir disertacijos tikslai ir uždaviniai. Antrajame skyriuje pateikta medienos stipruminių savybių aukštesnėse temperatūrose tyrimo metodika ir sukurtų nestandartinių bandymo įrenginių schemos... [toliau žr. visą tekstą]
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Huang, Yan, and 黃燕. "Temperature dependent hall effect: studies ofGaN on sapphire." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B42577068.
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Harvey, Roy Edward. "The effect of high temperature on yeast fermentations." Thesis, Heriot-Watt University, 1988. http://hdl.handle.net/10399/1000.
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McGinnity, Frank A. "The effect of temperature on engine gas dynamics." Thesis, Queen's University Belfast, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241518.
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Parks, Olivia Waverly. "Effect of water temperature on cohesive soil erosion." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/49663.
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In light of increased stream temperatures due to urbanization and climate change, theeffect of water temperature on cohesive soil erosion should be explored. The objectives of this study are to: determine the effect of water temperature on the erosion rates of clay; determine how erosion rates vary with clay mineralogy; and, explore the relationship between zeta potential and erosion rate. Samples of kaolinite- and montmorillonite-sand mixtures, and vermiculite-dominated soil were placed in the wall of a recirculating flume channel using a vertical sample orientation. Erosion rate was measured under a range of shear stresses (0.1-20 Pa) for a period of five minutes per shear stress at water temperatures of 12, 20, and 27�"C. The zeta potential was determined for each clay type at the three testing temperatures and compared to mean erosion rates. The kaolinite erosion rate doubled when the temperature increased from 12 to 20�"C, and erosion of vermiculite samples tripled when the temperature increased from 20 to 27�"C. The montmorillonite samples generally eroded through mechanical failure rather than fluvial erosion, and the limited fluvial erosion of the montmorillonite-sand mixture was not correlated with water temperature. The data suggest correlation between zeta potential and erosion rate; however, due to the small sample size (n=3), statistically significant correlation was not indicated. Research should continue to explore the influence of water temperature on cohesive soil erosion to better understand the influence of clay mineralogy. Due to the high degree of variability in cohesive soil erosion, multiple replications should be used in future work. The vertical sample orientation enabled discrimination between fluvial erosion and mass wasting and is recommended for future studies.
Master of Science
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Doluweera, D. G. Sumith Pradeepa. "Effect of Weak Inhomogeneities in High Temperature Superconductivity." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1227215152.
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Pack, Jessica Spencer. "Effect of Localized Temperature Change on Vigilance Performance." Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1429286666.
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Porter, Heidi S. "The effect of febrile temperature on Plasmodium falciparum /." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd2225.pdf.
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Takahashi, Junji 1951. "Effect of high temperature on lettuce seed development." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276828.
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More vegetable seeds are needed for developing countries to produce more vegetables. However, high temperature in these areas limits vegetable seed production. Leaf lettuce (Lactuca sativa L.) was grown in growth chambers at 21°C and exposed to different temperatures (28, 35, 38 and 42°C) for different exposure times (1, 4 and 7 hours) when flowers were at seven stages of development near anthesis.
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Porter, Heidi Sue. "The Effect of Febrile Temperature on Plasmodium falciparum." BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/1573.
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Previously it has been shown that cultures of Plasmodium falciparum died following exposure to a febrile temperature of 40°C, as demonstrated by a decrease in parasitemia of the following generation. In the current study, the effect of 40°C treatment on culture media, erythrocytes, and parasite glucose consumption, were ruled out as possible influences on parasite death, demonstrating that 40°C impacted the parasites directly. Metabolic profiling of DNA synthesis, protein synthesis, and glucose utilization during exposure to 40°C clearly indicated that febrile temperatures had direct effect on major metabolic pathways and parasite development, beginning 20-24 hr after erythrocyte invasion. The ring stages were relatively refractory to heat and recovered completely if returned to 37°C. The mechanism of parasite death was investigated for evidence of an apoptosis-like pathway in cells treated with 40°C, chloroquine, and staurosporine. Lack of typical physiological hallmarks, namely, caspase activation, characteristic mitochondrial membrane potential changes, and DNA degradation as indicated by DNA laddering, eliminated ‘classical’, apoptosis as a mechanism of parasite death. Parasites dying under the influence of 40°C, staurosporine, and chloroquine initially appeared pyknotic in light and electron microscopy, as in apoptosis, but eventual swelling and lysis of the food vacuole membrane led to secondary necrosis. Initially, chloroquine did induce DNA laddering, but it was later attributed to occult white blood cell contamination. While not apoptosis, the results do not rule out other forms of temperature-induced programmed cell death.
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Xiong, Bijin. "Contribution to the study of elastic and plastic deformation mechanisms of polyethylene and polypropylene as a function of microstructure and temperature." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0120/document.
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Les propriétés mécaniques des polymères semi-cristallins en relation avec leur microstructure ont fait l'objet d'un grand nombre d'études. Cependant, il reste encore des questions non résolues, concernant les mécanismes de la déformation plastique à température élevée, les propriétés intrinsèques de la phase amorphe interlamellaire ou encore la distribution des contraintes locales dans les sphérolites… L'objectif de cette thèse est d‘adresses ces questions dans les cas du PE et du PP en fonction de la température. Pour atteindre cet objectif, une série d'échantillons de PE et PP des différents microstructures ont été préparées et caractérisés par DSC, SAXS, WAXS et spectroscopie Raman. Dans le domaine élastique, la déformation locale (εlocal) dans les régions équatoriales et polaires des sphérolites ont été mesurés par SAXS in situ. Le ratio εlocal / εmacro a été utilisé dans un modèle mécanique permettant le changement d‘échelle de mésoscopique macroscopique. En outre, le module apparent de la phase amorphe interlamellaire Ma a été estimé par la contrainte et la déformation locale. Les Ma valeurs du PE sont dans la gamme 250 - 500 MPa, ce qui est très élevé par rapport au module du PE amorphe caoutchoutique. Dans le domaine plastique, la cavitation, la transformation martensitique et le cisaillement du cristal ont été observées par SAXS et WAXS in situ. Une concurrence entre ces mécanismes plastiques a été mise en évidence. L‘augmentation de la température entraine une disparition progressive de la cavitation et un retard de la transformation martensitique vers de plus haute déformation. La structure fibrillaire, induite par étirage à différentes températures a été étudiée par SAXS in-situ. Il a été observé que la longue période et le diamètre des micro-fibrilles dépendent de la température d‘étirage de la structure initiale, via les mécanismes de « fusion-recristallisation » et « fragmentation-réarrangement ». Une étude similaire a été effectuée pour le PPThe mechanical properties of semicrystalline polymers in relation to microstructure have been the subject of a large number of studies. However, there are still some unresolved issues, for instance, plastic deformation mechanisms in elevating temperature, intrinsic properties of interlamellar amorphous phase, local stress distribution in spherulites etc. The aim of this thesis is to address these issues in the case of PE and PP in different temperatures. A series of PE and PP samples with wide range of microstructures thanks to various thermal treatments were characterized by DSC, SAXS, WAXS and Raman spectroscopy. In elastic domain, the local strain εlocal in equator and polar regions of spherulites were measured by in situ SAXS. The ratio is a constant which only depends on drawing temperature. This ratio was used in a mechanical modelling as a transition factor from mesoscopic to macroscopic scale. Furthermore, the apparent modulus of the interlamellar amorphous phase Ma was estimated by the measured local stress and strain. The Ma of PE was found to be in the range 250 - 500 MPa which is surprisingly high comparing with the modulus of bulk rubbery PE. In the plastic domain, cavitation, martensitic transformation and crystal shear were observed by in situ SAXS and WAXS and their respective strain onsets were shown to be strongly dependent on crystallite thickness and temperature. It was found that competition exists between these plastic mechanisms. With increasing temperature, cavitation gradually disappears and martensitic transformation is delayed. A map for the onset of these plastic mechanisms was produced. In addition, the fibrillar structure induced by drawing at different temperature was studied by in situ SAXS. The long period and diameter of micro-fibrils proved to be dependent on the drawing temperature and also the initial structure via the melting-recrystallization and fragmentation-rearrangement mechanism. Similar investigations were performed with PP
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Chaishome, Jedsada. "The effect of processing parameters on the mechanical properties of vacuum formed flax fibre reinforced polypropylene composites." Thesis, University of Nottingham, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.594739.
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The main aim of this thesis is to gain an improved understanding of the use and limitations of flax fibres as a reinforcement for thermoplastic composites manufactured by the vacuum forming process. The effect of process variables on void content and on mechanical properties of flax fibre/polypropylene composites has been investigated. An isothermal vacuum forming process has been studied and the following process parameters varied : consolidation time; fibre volume fraction; moisture content; reinforcement stacking sequence. The thermal degradation of untreated and alkaline treated flax fibres and its effect on the composite properties has been investigated using fourier transform infrared spectrometry (FTIR) and thermogravimetry (TG) techniques. Characterisation of the micro structure of failure surfaces following tensile testing of the composites has also been observed using scanning electron microscopy (SEM). The results of the investigation show that an increase in consolidation time at temperature and/or a reduction in fibre volume fraction reduces void content, as expected . By contrast and in spite of the reduction in voidage levels, mechanical tests show that an increase in consolidation time reduces ultimate tensile strength (UTS), strain to failure and impact strength of the composite. This reduction in properties is attributed to increased thermal degradation of the flax fibres and consequently the composite. Degradation manifests itself as hemicellulose and pectin decomposition in the fibres, particularly at low heating rates. Alkaline treatment was investigated as a potential method of improving the thermal stability of the fibres by reducing the low thermal stability hemicellulose and pectin components. Furthermore, such treatment improves the surface roughness of the fib res and results in an improved consolidation due to the reduction in void content. However, these positive effects did not significantly improve composite strength because of an apparent reduction in reinforcement volume fraction resulting from reduced fibre volume.
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Wang, Kui. "Characterization and modeling of the thermomechanical behavior of polypropylene-based composites : effect of recycling and filler content." Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-00962217.
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The use of thermoplastic olefins like polypropylene is currently growing in the automotive industry. However, the increase of wastes from end of life vehicles represents a threat to our environment. Mechanical recycling is the most acceptable and ecological method. The purpose of this thesis is to identify the thermomechanical degradation mechanisms of PP-based composites, as a function of fillers content. Recycling was simulated by multiple extrusions. The considered fillers consist of ethylene octene copolymer and talc. The different properties of recycled PP-based composites were studied by a multiphysical approach. A detailed study of high strain rate and temperature sensitivities of recycled PP-based composites is achieved. The micromechanical modeling is used to predict the yield and the elastic behaviors of non-recycled and recycled materials.
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Bellam, Balaji Anand. "Effect of e-beam sterilization on polypropylene/ethylene propylene diene monomer and ethylene vinyl acetate thermoplastic elastomer." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/52484/.
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Thermoplastic elastomer is one of the priority polymeric compound identified for promotion and further development, given the growing demand for a number of commercial industries such as automobile, construction, footwear, healthcare, medical and food packaging sectors. In this study polypropylene (PP)/ethylene propylene diene monomer (EPDM) based thermoplastic elastomers are preferred for improving their properties as it can serve as a good replacement for PP or EPDM material, bridging the gap between thermoset and thermoplastic materials. This study focuses to develop PP/EPDM which can resist changes or improve properties when exposed to E-beam radiation, as E-beam also offers sustainable sterilization at low cost. The PP/EPDM blends with mixing ratios of 80/20, 50/50 and 20/80 were melt blended with the process parameters optimized using Design of experiments (DOE). The effect of E-beam on mechanical properties, thermal stability, crystallization and dynamic mechanical properties over the dose of 0 to 100 kGy were studied. The blends with high EPDM content (20PP/80EPDM) showed improvement in tensile strength up to 36% (at 40kGy and 60kGy) and resistant to impact strength up to 100 kGy, at the expense of elongation at break. On the other hand, the blends with high PP content (80 PP/20 EPDM and 50 PP/50 EPDM) showed detrimental effects on mechanical properties at all radiation dose studied and found to be not compatible for E-beam sterilization. Further, ethylene vinyl acetate (EVA) was incorporated to PP/EPDM blends at 10EVA/40EPDM/50PP, 20EVA/30 EPDM/50PP, 30EVA/20 EPDM/50PP and 40EVA/10 EPDM/50PP ratios. The gel content analysis showed that the efficiency of crosslinking decreased with increase in EVA loading. However, the presence of EVA in ternary blend especially facilitated the induction of sufficient crosslinks leading to improvement in tensile strength (up to 29% at 60 kGy), impact strength (up to 15% at 80 kGy) and retention of stiffness and thermal properties under radiation at the expense of elongation at break. In order to develop antibacterial ternary blends, silver nanoparticles (AgNP) were added by varying the loading from 0.3wt% to 1wt%. The Ag-ternary blends showed enhancement in impact properties (up to 9%) at the expense of decrement in tensile properties due to the agglomeration of AgNP. When, exposed to E-beam radiation, the mechanical and thermal properties exhibited similar trend of increment and decrement across radiation dose similar to the blends without AgNP. While, 1% Ag blend composites showed bacteriostatic effect on Staphylococcus aureuson, no significant reduction of Pseudomonas aeruginosa bacteria was observed. All the blends, before and after sterilization showed no significant toxicity on HaCaT cells investigated using in vitro analysis. Thus, the blends showed an instinct that their application could be extended to manufacturing of healthcare products and food packaging sector, as they are biocompatible and can withstand E-beam sterilization as demanded by the respective application. Among all the blends ternary blends studied (that exhibited biocompatibility even after radiation), 20EVA/30EPDM/50PP without AgNP showed the highest tensile strength of 18.41 MPa and impact strength of 43.64 J/m. Only a slight increase in tensile and impact properties was witnessed upon addition of 20% EVA to PP/EPDM blend in comparison to the binary blend (50PP/50EPDM blend). However, unlike the binary blend (whose properties decreased upon radiation), the ternary blend (20EVA/30EPDM/50PP) showed improvement in tensile strength up to 29% at 60kGy and up to 15% increase in impact strength at 80kGy.
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Khatua, Sourav. "Effect of Accelerated Corrosion on the Bond Strength of Corrosion Resistant Reinforcing Bars Embedded in Concrete." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1513944280521728.
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Kirca, Onder. "Temperature Effect On Calcium Aluminate Cement Based Composite Binders." Phd thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607454/index.pdf.
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In calcium aluminate cement (CAC) systems the hydration process is different than portland cement (PC) systems. The hydration products of CAC are subjected to conversion depending on temperature, moisture, water-cement ratio, cement content, etc. Consequently, strength of CAC system can be seriously reduced. However, presence of other inorganic binders or additives may alter the hydration process and improve various properties of CAC based composites.
The objective of this study is to investigate the temperature effect on the behaviour of CAC based composite binders. Throughout this research, several combinations of CAC-PC, CAC-gypsum, CAC-lime, CAC-ground granulated blast furnace slag (CAC-GGBFS) were studied. These CAC based composite binders were subjected to seven different curing regimes and their strength developments were investigated up to 210 days. In addition, the mechanism of strength development was examined by XRD analyses performed at 28 and 210 days. Finally, some empirical relationships between strength-time-curing temperatures were formulated.
Experimental results revealed that the increase in ambient temperature resulted in an increase in the rate of conversion, thereby causing drastic strength reduction, particularly in pure CAC mix. It has been observed that inclusion of small amount of PC, lime, and gypsum in CAC did not induce conversion-free CAC binary systems, rather they resulted in faster conversion by enabling rapid formation of stable C3AH6 instead of metastable, high strength inducing CAH10 and C2AH8. On the other hand, in CAC-GGBFS mixes, the formation of stable straetlingite (C2ASH8) instead of calcium aluminate hydrates hindered the conversion reactions. Therefore, CAC-GGBFS mixes, where GGBFS ratio was over 40%, did not exhibit strength loss due to conversion reactions that occurred in pure CAC systems.
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Calmunger, Mattias. "Effect of temperature on mechanical response of austenitic materials." Thesis, Linköpings universitet, Konstruktionsmaterial, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-73748.
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Global increase in energy consumption and global warming require more energy production but less CO2emission. Increase in efficiency of energy production is an effective way for this purpose. This can be reached by increasing boiler temperature and pressure in a biomass power plant. By increasing material temperature 50°C, the efficiency in biomass power plants can be increased significantly and the CO2emission can be greatly reduced. However, the materials used for future biomass power plants with higher temperature require improved properties. Austenitic stainless steels are used in most biomass power plants. In austenitic stainless steels a phenomenon called dynamic strain aging (DSA), can occur in the operating temperature range for biomass power plants. DSA is an effect of interaction between moving dislocations and solute atoms and occurs during deformation at certain temperatures. An investigation of DSA influences on ductility in austenitic stainless steels and nickel base alloys have been done. Tensile tests at room temperature up to 700°C and scanning electron microscope investigations have been used. Tensile tests revealed that ductility increases with increased temperature for some materials when for others the ductility decreases. This is, probably due to formation of twins. Increased stacking fault energy (SFE) gives increased amount of twins and high nickel content gives a higher SFE. Deformation mechanisms observed in the microstructure are glide bands (or deformations band), twins, dislocation cells and shear bands. Damage due to DSA can probably be related to intersection between glide bands or twins, see figure 6 a). Broken particles and voids are damage mechanisms observed in the microstructure.
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Naperalsky, Michael E. "Effect of post-exercise environmental temperature on glycogen resynthesis." The University of Montana, 2009. http://etd.lib.umt.edu/theses/available/etd-06052009-115319/.
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Hotter environments can often alter the normal exercises responses of metabolism and work performance compared to exercise in a more neutral condition. The goal of this study was to determine the effects of a hot (H) and room temperature (RT) environment on glycogen resynthesis during recovery from exercise. Recreationally active males (n = 9) completed two trials, each with 60-min of cycling exercise at 60% of maximum watts in a temperature-controlled chamber (32.6°C), followed by 4 hours of recovery at the same temperature (H) or 22.2°C (RT). Subjects were fed a carbohydrate beverage (1.8 g/kg bodyweight) at 0 and 2 hours post-exercise. Muscle biopsies were taken from the vastus lateralis at 0, 2, and 4 hours post-exercise for analysis of muscle glycogen. Blood samples were collected at 0, 30, 60, 120, 150, 180, and 240 minutes of recovery for glucose and insulin analysis. Ambient and core temperatures were monitored for the duration of the trial. Expired gas was collected prior to 2- and 4-hour biopsies for calculation of whole-body carbohydrate (CHO) oxidation. Glycogen, core temperature, CHO oxidation, and blood marker values were analyzed using two-way ANOVA with repeated measures. Average core temperature was significantly higher in H compared to RT (38.1°C ± 0.01° vs. 37.9°C ± 0.08°, p<0.05) during recovery. Glycogen was not different at 0 and 2 hours post-exercise. However, at 4 hours post-exercise muscle glycogen was significantly higher in RT vs. H (105 ± 28 vs. 88 ± 24 mmolkg-1 wet weight, respectively). Blood glucose levels were similar between H and RT for the first two hours, but showed lower values (p<0.05) in RT compared to H at time points 150, 180, and 240 minutes post-exercise. CHO oxidation during recovery was higher in H compared to RT (0.36 ± 0.04 g/min vs. 0.22 ± 0.03 g/min, respectively, p<0.05), with greater CHO oxidation at 4-hours post-exercise in both trials. Glycogen resynthesis during recovery is impaired in a hot environment, likely due to increased oxidation of CHO instead of synthesis.
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Chang, Chia-Wei, and 張家維. "Temperature/Moisture Effect on Bending Fatigue Strength of Glass/Polypropylene/Aluminum Foam Sandwich Structures." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/18583303239687497381.
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碩士國立臺灣海洋大學
機械與機電工程學系
101
The goal of this thesis is to experimentally study the hygrothermal effect on the static and fatigue four-point bending strengths of the sandwich structures with glass/polypropylene faces and aluminum foam cores. Results show that under the conditions of fixed moderate humidity, the static and fatigue bending strengths of the studied sandwich beams decrease significantly as the environmental temperature increases. However, the effect of humidity is not evident on the strengths under controlled hygrothermal conditions. The relationship between the static bending strength and the temperature can be described using a liner function. Moreover, the Arrehenius models are successful to describe the relationship between the fatigue strength coefficients employed in the power laws of the S-N curves and the testing temperatures. The variation of the fatigue strength exponents with the testing temperature is not apparent based on the analysis of experimental data. The testing temperatures were found to have slight influence on the trend of stiffness degradation of the studied sandwich specimens. However, different trends of the stiffness degradation curves were observed when the specimens were fatigue tested under various hydgrothermal conditions. A prediction parameter based on the loading level was employed to correlate the experimental fatigue data obtained at various hygrothermal conditions, and good performance of the utilized parameter was observed.
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Deng, D., Benjamin R. Whiteside, F. Wang, Keith Norris, and Z. Zhang. "Epitaxial growth and morphological characteristics of isotactic polypropylene/polyethylene blends: Scale effect and mold temperature." 2014. http://hdl.handle.net/10454/10052.
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NoThis study investigates the influence of length scale effects (micro- and macro-injection molded parts) and mold temperature on the epitaxial growth and morphological characteristics in injection-molded bars of isotactic polypropylene (iPP)/high-density polyethylene (HDPE) blends. After preparing the blends with an iPP content of 70 wt% via melt extrusion, the injection-molded bars were formed using both micro and conventional injection molding. Samples were subsequently prepared from the moulded components to allow investigation of the internal morphology using wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and polarized light microscopy (PLM). The results indicated that the matching of micro scale and appropriate mold temperature was most favorable for epitaxial crystallization. The micro-parts had a large fraction of shear layer compared with macro-parts. The SEM observations showed that the shear layer of the former consisted of a highly oriented shish-kebab structure. Moreover, the effects of different methods of injection molding on the morphological characteristics of the micro-parts and macro-parts in different layers were elucidated in detail using PLM and SEM.
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Chen, Bo-Shiun, and 陳柏勳. "Pyrolysis of Polypropylene in a Fluidized Bed Reactor – Effects of the Reaction Temperature and Flow Rate of Steam on the Product Yields." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/10281504848015488099.
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碩士長庚大學
化工與材料工程研究所
97
Polypropylene (PP) was selected as fed material to study the product distribution of the pyrosis reaction carried out in a assembly gas-solid fluidized bed equipment. Super-heated steam was used as fluidized gas due to the less production of carbon black and the enhancement of H2 and CO yield. Experimental study of the effects of reaction temperature (500 , 550 and 600℃) and steam flow rate (19.54 - 37.85 g/min) on the solid residue , liquid yield , and gas yield was performed . The components and composition of the gas product were determined by gas chromatography. Experimental results showed that at steam flow rate of 19.54 g/min and reaction temperature of 600℃ , there are the minimum solid residue , minimum liquid yield , and the maximum gas yield , i.e. 0.71 wt% of solid residue , 5.20 wt% of liquid yield , and 76.81 wt% of gas yield. However , at the steam flow rate of 37.85 g/min and temperature of 500℃ , there are the highest solid residue , highest liquid yield , and the lowest gas yield , i.e. 2.88 wt% of solid residue , 20.13 wt% of liquid yield , and 62.21 wt% of gas yield , respectively. Experimental results also showed the effects of reaction temperature and steam flow rate on the gas chromatography of the pyrolysis of PP. The yield of the CH4 and the CO decrease with the increase of the flow rate of steam , but the yield of CO2 , C2H6 , and C2H4 are less influenced by the flow rate of steam. It also showed that increases the pyrolysis temperature , led to increases the various gas yield , i.e. H2 , CO , CO2 , C2H4 , C2H6 , and other gases.
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Chahyadi, Ichwan Susanto. "Effect of maleated polypropylene on polypropylene-wood flour composites." 1989. http://catalog.hathitrust.org/api/volumes/oclc/20078460.html.
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Thesis (M.S.)--University of Wisconsin--Madison, 1989.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 72-75).
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Majithiya, Kamleshkumar M. "The Effect of Molecular Weight on Polypropylene Foaming." Thesis, 2012. http://hdl.handle.net/1807/32605.
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The effect of molecular weight on polypropylene (PP) extrusion foaming was investigated and the process to make soft touch, largely expanded, high cell density non-crosslinked PP foam using environmental friendly CO2 is presented. In previous research, when the cell density was high, cell opening was dominant and large expansion could not be achieved even in HMS PP materials. The effects of processing and material parameters on the foam morphologies of PP materials with three different melt flow rate (MFR) were studied using single-screw tandem foam extrusion system. By selecting proper material and die, and by tailoring the processing conditions, large expansion (25 fold) and high cell density (>109 cells/cm3) was successfully achieved in the high MFR PP without any additives. The mechanism of locally induced crystallization was found to be significantly affecting the foaming behavior of PP and was successfully verified using SEM, DSC, HPDSC, shear viscosity and solubility measurements.