Dissertations / Theses on the topic 'Polyethylene'
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1
Khan, Mohammad Ashraf. "Surface properties of high density polyethylene and cross-linked polyethylene." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq52587.pdf.
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Bottomley, L. "Heterogeneous polyethylene alloys." Thesis, Brunel University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235021.
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Butler, M. F. "Deformation of polyethylene." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597170.
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In order to characterise deformation as completely and unambiguously as possible it is desirable to eliminate the possibility of sample relaxation by performing measurements in-situ, during deformation. The bulk of the thesis describes a comprehensive series of investigations into the mechanical behaviour of a range of oriented and unoriented commercial grade polyethylenes deformed in tension and compression over a range of temperatures. High intensity synchrotron X-rays and fast electronic area detectors were used to enable the two-dimensional wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) patterns, which reveal information about the molecular and lamellar deformation respectively, to be measured simultaneously during deformation. In addition, the load-extension curve was measured at the same time as the X-ray scattering patterns. Sample relaxation was completely eliminated and for the first time the micro- and macroscopic deformation was precisely and unambiguously correlated. The use of a range of samples, with varying molecular weights, branch densities, branch types, lamellar thicknesses and percentage crystallinities, enabled a study to be made of the influence of microstructural variables (as well as experimental conditions such as deformation temperature) on the mechanical properties. A study was also performed on the mechanical properties of thin solution-cast PE films made from the same commercial grades used for the bulk samples. Crazing mechanisms were observed using optical and transmission electron microscopy. It was found that that results could be rationalised in terms of the degree of entanglement of the chains and the ease by which these entanglements were overcome during deformation. Increasing the entanglement density by increasing the molecular weight or by the incorporation of short chain branches increased the toughness of the films. As for the bulk samples, branch length was unimportant.
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Kay, Christopher James. "Polyethylene block copolymers." Thesis, University of Warwick, 2014. http://wrap.warwick.ac.uk/62620/.
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Chapter 1 introduces the concept of polyethylene (PE) end-functionalisation as a route to block copolymers, reviews the different literature methods for their synthesis this way, and compares the advantages and disadvantages of each. Finally, an existing method which makes use of PE terminated with a styrene derivative is identified as having fewer disadvantages than most literature procedures. Further investigation of the mechanism is proposed. Chapter 2 focusses on the different types of so-called dormant state formed in Ziegler-Natta catalysed olefin polymerisations, and in particular on the dormancy occurring after styrene insertion. Copolymerisations of ethylene with styrene, allylbenzene and 4-phenyl-1-butene in the presence of hydrogen are undertaken, and evidence for the presence of a dormant state or simply competitive rates of hydrogenation vs ethylene insertion is discussed. Increasing styrene concentration beyond that used by Chung is found to yield PE capped at both chain ends with styrene. A new mechanism – Catalytic Hydride Initiated Polymerisation (CHIP) – is consistent with these new observations. Chapter 3 focusses on extending the application of the CHIP mechanism to the synthesis of new examples of end-functional PE. Copolymerisations of ethylene with α-methylstyrene and related monomers 1,3/1,4-diisopropenylbenzene, α-methylstyrene dimer and limonene in the presence of hydrogen are investigated, resulting in the successful synthesis of a range of PE examples initiated with each comonomer. The effects of hydrogen pressure and comonomer concentration are also discussed. The advantages of CHIP are discussed, and the synthesis of end-functionalised PE incorporating DIB is studied in detail. An α-methylstyrene like end group is present at the start of the PE chains. Chapter 4 describes the free-radical copolymerisation of the new functionalised PE with acrylate monomers. Observations are consistent with a new reversible termination mechanism similar to nitroxide mediated polymerisation. The products are characterised by NMR, GPC, DLS, TEM and DSC, and the evidence is found to be consistent with the presence of block copolymers. Chapter 5 details the experimental procedures used to carry out the work in this thesis.
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Green, Christopher Duncan. "Polyethylene-montmorillonite nanocomposites." Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/65001/.
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Nanocomposite materials are currently attracting much interest due to their possibility of global property improvement – mechanical strength, toughness, electrical breakdown strength, electrical erosion resistance and flame retardancy. In order to disperse montmorillonite clay (MMT) into polyethylene (PE), the clay sheets need to be rendered organophilic. Masterbatches with a high level (~40 %wt) of organomodified clay can then be dispersed into a host by a simple mechanical process. Two chemically different masterbatches were purchased: Nanoblend 2101 from PolyOne Corp. and C30PE from Nanocor Inc. These were let down using a RandcastleTM single screw extruder with a patented mixing device to provide elongational flow. Wide angle X-ray diffraction was used together with transmission electron microscopy to evaluate the particle dispersion, which consisted of intercalated clay organised in clusters up to one micron in diameter. The performance of these materials was assessed in terms of AC ramp breakdown statistics, dielectric spectroscopy, dynamic and tensile mechanical properties. Nanoblend masterbatch consistently improved the breakdown statistics, more than overcoming the inherent demerit of extrusion, which mildly aged the unfilled material (as confirmed by Raman spectroscopy.) On the other hand, even low loading levels of Nanocor could result in reduced breakdown strength and increased scatter. Furthermore, both sets of materials demonstrated large dielectric losses at power frequencies and poorer performance under mechanical tension. These materials would therefore require considerable development before they could confidently be used commercially. The nature of the PE-MMT interactions was examined by investigating the crystallisation kinetics and resulting morphologies with differential scanning calorimetry and scanning electron microscopy. By varying the masterbatch type, loading level and crystallisation temperature, it was possible to study a wide range of supercrystalline morphologies using a permanganic etching technique. This is a useful contribution to the field of nanocomposites research. It is known that the morphologies of polymers can affect their mechanical properties and electrical treeing behaviour, and so it is possible that controlled crystallisation could provide a route toward designer materials with optimised behaviour.
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Hanna, Paul R. W. "Studies on the rotational moulding of nanoclay filled polyethylene and polyethylene." Thesis, Queen's University Belfast, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.601653.
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Oluz, Zehra. "Additives For Photodegradable Polyethylene." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614537/index.pdf.
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Polyethylene (PE) is one of the most popular polymers used in daily life. However, saturated hydrocarbons cannot absorb the energy of light reaching to earth, so degradation process is rather slow which in return cause disposal problems. On the other hand, it was observed that in presence of oxygen and impurities in the polymer matrix, degradation can be rendered to shorter time intervals. This study covers investigation of effect of three different additives in UV induced oxidative degradation of polyethylene.
In this work vanadium (III) acetylacetonate, serpentine and Cloisite 30B were used as additives both together and alone to follow photodegradation of polyethylene. Amount of vanadium (III) acetylacetonate was kept constant at 0.2 wt%, while serpentine and Cloisite 30B were used between 1 and 4 wt%.
All compositions were prepared by using Brabender Torque Rheometer, and shaped as thin films by compression molding. Samples were irradiated by UV light up to 500 hours. Mechanical and spectroscopic measurements were carried out in certain time intervals to monitor the degradation.
It can be concluded that all combinations of three additives showed the fastest degradation behavior compared to pure PE. In the absence of vanadium (III) acetylacetonate the degradation was slowed and fluctuations were observed in the residual percentage strain at break values. There was not a significant change in tensile strength of all samples. Carbonyl index values followed by FTIR were always in increasing manner. Thermal properties were also investigated by DSC Thermograms and they did not change significantly.
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Blacker, Richard. "Electrostatic phenomena in polyethylene." Thesis, Loughborough University, 1990. https://dspace.lboro.ac.uk/2134/10330.
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Measurement of the electrostatic nature of materials is an essential step towards understanding the underlying processes and to the eventual modification of charge behaviour. Indirect monitoring was achieved by resistivity measurements, however, this approach is limited to studying the material and not the electrostatic charge and is, in general, not a satisfactory method. Electrostatic field meters allowed the electrical behaviour of polyethylene to be monitored; its charge accumulation and decay processes were accurately monitored, thus giving a good information base for material modification later in the programme. The use of a data-logging system (based on the Apple//e computer) allowed the manipulation and long term storage of information, whilst giving improved presentation of results. High Density Polyethylene is an intrinsically insulating polymer whose electrostatic properties can be greatly modified by the use of internal antistats. Such additives migrate to a surtace and become effective [at reducing surtace resistivity] over a period of time depending on the diffusivity of the antistat species, and on the external atmospheric conditions, particularly humidity. The effusion of antistat onto a surface was monitored by surtace analysis techniques including X-ray photoelectron scattering, goniometry and infra-red spectroscopy, however, whilst such techniques offered a direct indication of the surtace state and the effect of any surtace modification, electrostatic testing was found to be the most sensitive technique for following antistat action. It is possible to tailor individual antistats to specific applications, however such usage provides only specific protection (fast acting but short lived, or slow acting but long lived). Two single antistat species were combined, and a synergistic effect was obtained for fast acting and long lived systems. It was found that antistats operate by welting (coating) an insulating surtace, and then absorbing atmospheric water vapour, thus lowering the surtace resistivity. Complete surtace coverage is not possible over an HDPE surtace due to its low surtace energy (28mNm'1), however, more complete surtace coverage was achieved by surtace oxidation [raising the polar surlace energy). Natural HDPE is not readily susceptible to surface oxidation; therefore oxidation treatment had only a limited effect. An addition of the fully compatible polymer LLDPE raised the oxidation level and allowed more complete antistat coverage, thereby improving antistatic activity and raising the level of protection gained by using a standard level of antistat. A patent is being taken out covering the use of LLDPE in conjunction with mixed antistat systems.
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Chiloyan, Vazrik. "Polyethylene fiber drawing optimization." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68829.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011."June 2011." Cataloged from PDF version of thesis.
Includes bibliographical references (p. 33).
Polymer fiber drawing creates fibers with enhanced thermal conductivity and strength compared to bulk polymer because drawing aligns the molecular chains. I optimize the polymer fiber drawing method in order to achieve polymer fibers that are drawn to lengths exceeding 1cm and develop a method to cut and store them for future experimental purposes. With lengths exceeding 1cm, starting with lengths near 0.5mm, these fibers undergo very large tensile deformations. This ensures the fibers obtained have been ultra drawn, and the polymer chains have aligned, thus enhancing the tensile strength and thermal conductivity of the fiber. By storing these fibers, I can perform experimental measurements in the future to obtain thermal conductivity values for polyethylene fibers and notice the effect of aligning the molecular chains.
by Vazrik Chiloyan.
S.B.
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Clark, Darren Cameron. "Dual monomer grafting of styrene and maleic anhydride onto polyethylene, effect of polyethylene microstructure." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0020/NQ54405.pdf.
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Müller, Stefan. "Biodegradation of polyethylene thermolysis residue." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0005/MQ44028.pdf.
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Müller, Stefan 1971. "Biodegradation of polyethylene thermolysis residue." Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20509.
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The ability of several microorganisms to degrade polyethylene thermolysis residue was investigated. This residue is mainly comprised of n-alkanes and n-1-alkenes ranging in chain length of 15 to 45 carbon units and therefore resembles crude oil. The microorganisms investigated were: Y. lipolytica ATCC 8662, Y. lipolytica ATCC 20460, A. paraffineus ATCC 19558, P. aeruginosa PAO1, P. putida ATCC 12633, R. rhodochrous ATCC 21766 and Rhodococcus sp. ATCC 29671. It was found that all seven microorganisms tested were able to degrade the polyethylene thermolysis residue. Results suggest that R. rhodochrous produced a biosurfactant when growing on the polyethylene thermolysis residue.It was also found that the acclimation of the microorganism to the substrate was an important factor in the degradation of the residue. Using two different acclimation times, two different strains of R. rhodochrous were selected for in the acclimation step. The two different strains showed very different degradation patterns of the polyethylene thermolysis residue. Strain A showed almost no effect of chain length on the degradation rate of the hydrocarbons while the degradation rate of the hydrocarbons for strain B decreased with increasing chain length. This difference in the degradation pattern was attributed to the varying amounts of enzymes present in each strain. Another factor found to affect the degradation pattern was the liquidity of the polyethylene thermolysis residue.
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Haunton, Jan. "Butt fusion welding of polyethylene." Thesis, Brunel University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332077.
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Shingleton, Jason Alan. "Characterisation of peroxide crosslinked polyethylene." Thesis, Loughborough University, 1995. https://dspace.lboro.ac.uk/2134/10832.
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British Gas have been using polyethylene pipe and fittings for gas distribution since 1969. The medium density, and more recently high density polyethylene pipes are produced by a simple and well established extrusion process. Unfortunately the production of fittings, especially large diameter fittings is not so simple. Traditionally pipe fittings are made from either injection moulding or by other fabrication techniques which require subsequent cutting and welding of different parts to produce the finished article. Recently however the methodology has been developed to facilitate the production of fittings by rotational moulding. Incorporated into the new methodology is the ability to produce crosslinked fittings by peroxide inclusion. Crosslinking of the pipe fittings has a major advantage in that it produces a substantial improvement in the mechanical properties of the polymer. Of particular importance is the improvement in stress crack resistance. Stress cracking is presently the primary mode of failure in polyethylene pipelines. Cross linking should help to reduce the susceptibility of the pipeline to failure by this method. The purpose of this project has been to investigate the crosslinking process in two rotational moulding grades of polyethylene. In particular a study has been made of the relationships between various chemical and physical properties, and of how these change upon material modification. A series of compression moulded samples containing increasing levels of peroxide have been produced for both polymers. Characterisation of these samples was undertaken using such techniques as Differential Thermal Analysis, Fourier Transform Infrared Spectroscopy, Gel Permeation Chromatography, Gel Content and Microscopy. The results have shown that as peroxide concentration is increased gel content rises sharply before reaching a maximum value. In contrast to the gel content, the crystallinity of the samples was shown to decrease. Infrared analysis provided the facility to monitor the variation in molecule end group concentration with changing peroxide levels. It was found that increasing the level of peroxide resulted in a decrease in the concentration of terminal vinyl unsaturation in an inverse relationship to gel content results. Subsequent gel permeation chromatography analysis demonstrated that the terminal vinyl groups were being lost in a chain extension mechanism which resulted in an increase in the molecular weight of the samples.
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Coutry, Sandry. "Molecular deformation mechanisms in polyethylene." Thesis, Sheffield Hallam University, 2001. http://shura.shu.ac.uk/6478/.
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This work is concerned with details of the molecular changes caused by deformation and also establishes any conformational differences between linear and branched polyethylene before, during and after deformation. Four blends of isotopically labelled polymers of different types, rapidly quenched from the melt, have been studied by Mixed Crystal Infra-red Spectroscopy and Small Angle Neutron Scattering (SANS), in order to clarify any differences in the molecular basis of drawing behaviour and in the initial labelled chains conformation. For all sample types, the neutron scattering results suggest that adjacent folding is not the major type of chain folding here. This point is confirmed by our infrared results where most of the crystal stems contributing to the doublet components are in groups of only 3 to 4 adjacent labelled stems. Differences in initial conformation between the linear and copolymer samples were highlighted by both SANS and FTIR techniques. The evolution of the radius of gyration as a function of molecular weight following the relationship Rg ∝ Mw ∝ determined from the SANS data, is different for linear and copolymer sample types, suggesting a more compact arrangement as the molecular weight of the copolymer DPE guest molecules increases. This was found consistent with the infrared results, where results from both curve fitting and the simulation of the infrared CD2 bending profiles show that the number of small groups of adjacent labelled stems is significantly larger when the DPE guest is a copolymer molecule. Our comparative studies on various types of polyethylene lead to the conclusion that their deformation behaviour under drawing has the same basis, with additional effects imputed to the presence of tie-molecules and branches. Three major points were identified in this thesis. The changes produced by drawing imply (1) the crystallisation of some of the amorphous polymer and the subsequent orientation of the newly formed crystals, (2) the re-orientation of the crystalline ribbons and (3) the beginning of crystallite break-up. However, additional effects were observed for the high molecular weight linear sample and the copolymer sample and were attributed, respectively, to the presence of tie- molecules and of branches. It was concluded that both the tie-molecules and the branches are restricting the molecular movement during deformation, and that the branches may be acting as "anchors".
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Ovington, Stephen. "Fusion welding of crosslinked polyethylene." Thesis, University of Sunderland, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297127.
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Jones, S. A. "On the morphology of polyethylene." Thesis, University of Southampton, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370343.
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Dumpleton, P. "Fatigue crack propagation in polyethylene." Thesis, Cranfield University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373987.
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Kandan, Karthikeyan. "Dynamic response of polyethylene composites." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608106.
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Mills, David H. "Electroluminescence and ageing of polyethylene." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/338950/.
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Electrical insulation is known to age when under electrical stress. One cause of this is thought to relate to the movement and build up of charge within the insulation. The emission of a low level of light from polymeric materials when under electrical stressing is shown to occur before the onset of currently detectable material degradation. This light is termed electroluminescence (EL)and under an ac electric field is thought to relate to the interaction of charge in close proximity to the electrode-polymer interface. Understanding the cause of this light emission gives a very high resolution way of monitoring charge interaction and its influence on material ageing. This report presents the improvement to a system to measure changes in EL emission during the cycle of the applied field (point on wave measurements) under various electric fields. To investigate the relationship between EL and ageing, 100 �m, low-density polyethylene (LDPE) films were ultraviolet (UV) aged in 3 and 7 day intervals up to 17 days. The samples were aged in both air and nitrogen environments to separate the affect of photo-oxidation from photo irradiation reactions on charge movement. Changes as a result of ageing were characterised in terms of optical, chemical and electrical properties. These were investigated using ultraviolet and visible (UV-Vis) and Fourier transform infrared (FTIR) spectroscopy, ac ramp breakdown measurements and dielectric spectroscopy. The accumulation of space charge (SC) was then investigated using the pulsed electro acoustic (PEA) technique. This collection of results were used to explain changes in EL in terms of intensity and phase difference. A model using the bipolar charge recombination theory was then developed using trends shown in the characterising measurements to explain changes in EL. Results support the use of EL as a tool to investigate changes in charge movement very near the electrode-polymer interface.
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LANGLOIS, ALEONARD VALERIE. "Vieillissement thermique du polyethylene reticule." Paris, ENSAM, 1992. http://www.theses.fr/1992ENAM0003.
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Cette etude s'inscrit dans le cadre du vieillissement a long terme des polymeres et la prevision de leur duree de vie dans les conditions d'emploi. Dans l'intervalle de temperature etudie, compris entre 90 c et 180 c, le vieillissement du polyethylene reticule est domine par l'oxydation. Le comportement a long terme du materiau peut etre decrit comme la succession de deux phases: une periode d'induction pendant laquelle on observe des effets de recuit et une post reticulation. La consommation des antioxygenes (suivie par analyse uv) est distribuee de maniere homogene dans l'epaisseur. Au terme de la periode d'induction, l'oxydation s'autoaccelere et on detecte la formation de groupes carbonyles (par infra-rouge), une chute des proprietes mecaniques, et la disparition rapide des antioxygenes residuels. L'oxydation devient controlee par la diffusion, donc heterogene. Les produits d'oxydation sont concentres dans une zone superficielle dont l'epaisseur est une fonction decroissante de la temperature. Les profils dans l'epaisseur des grandeurs caracterisant l'avancement du vieillissement coincident aux incertitudes de mesure pres. Cependant le profil de l'allongement a la rupture est assez different et revele l'existence d'une couche degradee plus epaisse. La duree de vie a l'etat solide est superieure a celle prevue par la loi d'arrhenius a l'etat fondu. Cette transition au niveau de la temperature de fusion serait assimilable a une transition du premier ordre, avec un changement du coefficient preexponentiel. Le meilleur critere analytique de vieillissement nous parait etre la concentration en stabilisant phenolique. La determination de la duree de vie par cette methode offre une bonne marge de securite
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Champhekar, Mangesh C. "Orientation in Polyethylene-Nanoclay Composites." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1227031718.
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Altintas, Bekir. "Electrical And Mechanical Properties Of Carbon Black Reinforced High Density Polyethylene/low Density Polyethylene Composites." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/2/12604976/index.pdf.
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In this study, the High Density Polyethylene (HDPE) and Low Density Polyethylene (LDPE) blends prepared by Plasticorder Brabender were strengthened by adding Carbon Black (CB).
Blends were prepared at 190 °C. Amounts of LDPE were changed to 30, 40, 50 and 60 percent by the volume and the percent amounts of CB were changed to 5, 10,15, 20 and 30 according to the total volume. Thermal and morphological properties were investigated by using Differential Scanning Calorimeter (DSC), Scanning Electron Microscope (SEM). Mechanical properties were investigated by tensile test and hardness measurements. Melt flow properties were studied by Melt Flow Index (MFI) measurements. Electrical conductivities were measured by four probe and two probe techniques. Temperature dependence of electrical conductivity was also studied. In general, it is observed that stress at break and MFI values decrease by the addition of CB
however, modulus and hardness increase. DSC results indicated that the crystallization of the polymer blend was decreased by the addition of CB. SEM results showed that the components were mixed homogenously. Increasing CB content increased electrical conductivity. Furthermore, by increasing the temperature, positive temperature coefficient behavior was observed which increases when CB content decreased.
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Tam, Mei San. "Study of sisal fiber-reinforced polypropylene, polyethylene and polypropylene/polyethylene blend composites prepared by compression molding." access abstract and table of contents access full-text, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21175123a.pdf.
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Thesis (M.Sc.)--City University of Hong Kong, 2005.At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 4, 2006) Includes bibliographical references.
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Archambault, Jacques Gérard. "Protein adsorption to polyethylene oxide-grafted surfaces /." *McMaster only, 2002.
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Isik, Fatma. "Nanocomposites Based On Blends Of Polyethylene." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/3/12606338/index.pdf.
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In this study the effects of compatibilizer type, organoclay type, and the addition order of components on the morphological, thermal, mechanical and flow properties of ternary nanocomposites based on low density polyethylene, LDPE were investigated. As compatibilizer, ethylene/methyl acrylate/glycidyl methacrylate, ethylene/glycidyl methacrylate, and ethylene/butyl acrylate/maleic anhydrideas organoclay Cloisite&
#61666
15A, Cloisite&
#61666
25A and Cloisite&
#61666
30B were used. All samples were prepared by a co-rotating twin screw extruder, followed by injection molding. Before producing the ternary nanocomposites, in order to determine the optimum amount of the organoclay and compatibilizer, binary mixtures of LDPE/organoclay and LDPE/compatibilizer blends with different compositions were prepared. Based on the results of the mechanical tests, compatibilizer and organoclay contents were determined as 5 wt. % and 2 wt % respectively. After that, ternary nanocomposites were prepared with each compatibilizer/organoclay system and characterization of these nanocomposites was performed. Among the investigated addition orders, mechanical test results showed that the best sequence of component addition was (PCoC), in which LDPE, compatibilizer and organoclay were simultaneously compounded in the first run of the extrusion. Considering the ternary nanocomposites, compositions of LDPE/E-MA-GMA/15A, LDPE/E-GMA/15A and LDPE/E-nBA-MAH/30B showed the highest improvement in mechanical properties. According to the DSC analysis, addition of organoclay and compatibilizer does not influence the melting behavior of the compositions and both compatibilizers and organoclay types have no nucleation activity in LDPE. In the X-Ray analysis, the highest increase of the basal spacing for ternary nanocomposites obtained for LDPE/E-BA-MAH/organoclay nanocomposites. This increase was 83 %, 198 %, and 206 % for samples containing 15A, 25A and 30B respectively.
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Rashid, Haroon. "Butt fusion welding of polyethylene pipes." Thesis, Brunel University, 1997. http://bura.brunel.ac.uk/handle/2438/6623.
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The butt fusion process is extensively used in the joining of polyethylene (PE) pipes by the water and gas industries. This welding process although deceptively simple, is rather poorly understood, with much of the initial developments being of a rather empirical nature. The Water Research centre (WRc) have funded the present research in an attempt to optimise the welding of high pressure pipeline (PE100) systems. The main aims of this research were to investigate the effect of different welding conditions on the physical and mechanical properties of the joints produced and to investigate these effects on the micro- and macro-structures of the joints produced. A series of welds were made using Eltex Tub 124 and Rigidex 002-50 pipes of 180mm diameter. The fusion pressure and heatsoak times were varied. A milling machine witha twin cutter arrangement was used to obtain the test specimens from around the circumference of the pipes. Differential scanning calorimetry was used to study the effect of sample preparation methodology on the thermo-oxidative stability. Polarised light microscopy and image analysis were used to study the macro- and micro-structural developments in the weld joint. Joint strength was evaluated via standard and non-standard tensile test methods. Milling the samples to produce the test specimens was found to decrease significantly the thermo-oxidative resistance of the polymer. Reasons for this behaviour have been proposed. In order to achieve high quality thin films from microtomy, custom-made blades were used. This programme also developed the optimum polishing method for the microtomed blades. The macro-structure of the bead: its shape and dimensions were found to be a function of temperature and pressure. Correlation was found between the bead geometry and the position around the circumference of the pipe. The macrostructures within the weld zone also showed this dependence on the position along the circumference of the pipe. An examination of the microstructures of each weld had shown the presence of five different zones. The feasibility of using microtomed thin sections in a tensile test was demonstrated. The test method provides a means to study failure initiation and propagation in the tensile test specimen. Initial deformation was found to occur in the centre of the melt-affected zone (MAZ) and the final failure occurs at the junction of the weld bead and the bulk polymer. Tests on films without the weld bead showed that maximum deformation occurred at the centre of the sample within the MAZ. The presence of the bead and the asymmetry in the test specimens caused by the welding process were found to have a significant influence on the failure mode and the failure strain. The strain rate was also found to play a significant role in both beaded and debeaded samples. The failure was initiated from the pseudo notches in the beaded samples. In the debeaded sample the failure was within the MAZ.
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Jaafar, Haydar. "Condition assessment of polyethylene pipeline systems." Thesis, Brunel University, 1997. http://bura.brunel.ac.uk/handle/2438/6589.
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This study is an industrial project commissioned by British Gas plc. (UK) to investigate the state of in-service naturally aged polyethylene (PE) buried pipes and to define procedures or techniques available to facilitate the condition assessment programme of PE pipelines systems. The primary goal of this study was to establish a better understanding of the ageing process in commercial piping materials and to understand its effect on long term integrity of PE pipeline systems. Eltex, Rigidex and Aldyl A are trade names of the PE gas grade resins used in this study and they represent the range of pipe materials used in the transport of potable water and gas in the UK. Sections of pipes used in this project were supplied by British Gas plc. in the form of unaged pipes and pipes which were aged in-service. Laboratory based accelerated ageing of the pipe resin samples was also carried out. The ageing regimes considered were water ageing at 23°C, air-oven ageing at 80°C, water ageing at 80 C, vacuum ageing at 80°C and in-service aged samples. Compression moulded plaques were produced as reference material. By utilising specific instrumentation and designs, several reliable procedures were developed to produce specimens directly from pipes. The feasibility of using micro-samples instead of large samples was demonstrated. A methodology was developed to retrieve disk samples using electrofusion "tapping-tee" saddles. Appropriate test specimens were designed for chemical and physical evaluations. This sampling method negates the need for excavating large sections of pipe material for the purpose of condition assessment. Reliable micro and macro-sampling test methods were developed and established as techniques for the condition assessment programme. Characterisation techniques included: (i) differential scanning calorimetry (DSC) to measure (from the same specimen) both the degree of crystallinity and the oxidation induction time (OIT), (ii) HPLC analysis was used to quantify additives concentrations, (iii) Fourier transform infrared spectroscopy was used to monitor the carbonyl index and to identify a pipe resin type from site, (iv) micro- and macro-tensile and fatigue tests to assess the changes in the mechanical properties as function of ageing. The fatigue test procedure was developed to produce brittle fracture at laboratory scale within a shorter period of time as compared to existing procedures such as the hydrostatic test. A reference data-base was created using the above identified tools and the criteria and methodology for carrying out site condition assessment inspection was compiled. The fundamental mechanisms of chemical and physical ageing were studied along with the possibility of their effect on the mechanical properties of PE pipes.
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Tang, Zuojian 1967. "Surface morphology of polyethylene blown films." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=31072.
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The properties of blown polyethylene (PE) films depend on various factors, including crystallinity, morphology, and orientation, in addition to chemical composition. It has been shown that the optical properties are strongly influenced by surface morphology. In this project, we use non-contact atomic force microscopy (AFM) and polarized light microscopy (PLM) to visualize surface and bulk morphology. Various techniques, such as surface and line roughness, surface and line fractal dimension, pair-correlation function and nearest neighbor distance distribution function, are employed to quantify the description of morphology and to compare the morphological characteristics of a number of polyolefin films of commercial interest. A comprehensive quantitative analysis of surface topography has been performed. The co-monomer of the PE resins was found to play a significant role in the formation and the orientation of spherulite-like domains. The film cross-section microstructure has been evaluated qualitatively by using both AFM and PLM. However, quantitative analysis of bulk morphology cannot be obtained due to knife effects.
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McCaffrey, William Chessleigh. "Thermolysis of polyethylene and polyethylenepolystyrene mixtures." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40397.
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Thermolysis was investigated as a process to convert waste olefin-based polymers into value-added products at a moderate temperature. Virgin, linear low density polyethylene was used for the majority of the experiments. The thermolysis of virgin polystyrene, recycled polyethylene and 3:2 mixtures of polyethylene and polystyrene were also investigated. The final process that was developed employed the reactive distillation of polyolefins under an inert atmosphere and at moderate reaction temperatures, ranging from 375 to 450$ sp circ$C. The major products from thermolysis of polyethylene were a distribution of low-molecular-weight straight chain alkanes and $ alpha$-olefins ranging from C$ sb6$ to C$ sb{25}.$ Overall volatile product yields up to 90% were obtained from the starting polymer. The initial molecular structure of the polyethylene was found to have a large effect on the rate of molecular weight reduction. A significantly enhanced rate of thermolysis was also observed when polyethylene was processed as a mixture with polystyrene. The mechanisms of thermolysis of polyethylene, polystyrene and mixtures of the two polymers were elucidated. Furthermore, the mechanism of dimer production from polystyrene was found to be different than what has been reported previously.
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Zhang, Ai Yang. "Physical property enhancement of polyethylene blends." Thesis, Brunel University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285090.
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Soares, R. J. M. "Rotational moulding of cross-linked polyethylene." Thesis, Queen's University Belfast, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395215.
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Larhrib, El Hassane. "Characterisation & compaction of polyethylene glycols." Thesis, Liverpool John Moores University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242150.
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Maslen, C. "The microbial degradation of polyethylene glycols." Thesis, University of Kent, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374694.
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Hallam, M. A. "The fracture behaviour of oriented polyethylene." Thesis, University of Leeds, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377862.
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Matthews, Richard Gary. "The biaxial drawing of polyethylene terephthalate." Thesis, University of Leeds, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410647.
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Pickup, Elaine. "Imaging of pneumatically conveyed polyethylene particles." Thesis, Manchester Metropolitan University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336964.
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Londoño, Ceballos Mauricio. "High-Density Polyethylene/Peanut Shell Biocomposites." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc700037/.
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A recent trend in the development of renewable and biodegradable materials has led to the development of composites from renewal sources such as natural fibers. This agricultural activity generates a large amount of waste in the form of peanut shells. The motivation for this research is based on the utilization of peanut shells as a viable source for the manufacture of biocomposites. High-density polyethylene (HDPE) is a plastic largely used in the industry due to its durability, high strength to density ratio, and thermal stability. This research focuses in the mechanical and thermal properties of HDPE/peanut shell composites of different qualities and compositions. The samples obtained were subjected to dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and mechanical tensile strength tests. TO prepare the samples for analysis, the peanut shells were separated into different mesh sizes and then mixed with HDPE at different concentrations. The results showed that samples with fiber size number 10 exhibited superior strength modulus of 1.65 GPa versus results for HDPE alone at 1.32 GPa. The analysis from the previous experiments helped to determine that the fiber size number 10 at 5%wt. ratio in HDPE provides the most optimal mechanical and thermal results. From tensile tests the highest modulus of elasticity of 1.33 GPa was achieved from the samples of peanut shells size number 10 in HDPE at 20%wt. ratio, while the results for HDPE alone were only of 0.8 GPa. The results proved the hypothesis that the addition of peanut shells to HDPE enhances both the thermal and mechanical properties of the composite.
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Al-Azzawi, Farah. "Degradation studies on recycled polyethylene terephthalate." Thesis, London Metropolitan University, 2015. http://repository.londonmet.ac.uk/917/.
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This project aims to investigate the influence of UV on the properties under natural and artificial weathering. The real-time outdoor weathering exposures provide the most accurate results but, they are very slow and manufacturers cannot afford to wait in order to see if a new or improved product formulation is really an improvement. So, accelerated testing methods are designed to simulate natural weathering with the combined action of the most weathering damaging factors; UV radiation, oxygen, temperature and water. Whatever the application, there is a concern regarding the durability of the products because if its useful lifetime can be estimated in short time, their maintenance and replacement can be planned in advance. In this study, recycled PET samples were exposed to UV outdoors and to accelerated weathering up to 13,000 hr. The mechanical behaviour (tensile and impact), thermal behaviour (DSC), molecular structure analysis (FTIR), flow characteristics (MFI) and surface properties (colour and gloss) of the samples were investigated. The whole body of the samples was substantially unaffected by degradation for long exposure time and this is confirmed by MFI and DSC results. However, the surface of the samples is affected which is seen in FTIR analysis, colour and gloss change. This explains that the photodegradation is a surface effect. FTIR analysis shows an increase in the gauche ratio and decrease in the trans ratio for both types of weathering indicating a less ordered structure after the UV radiation due to chain scission by Norrish Type I and II mechanism. Carboxylic acid is formed as a result of degradation and increases with the extent of UV exposure in both types of weathering, the formation of carboxylic acid by Norrish II is dominated over Norrish I. Colour and gloss measurement shows that the effect of degradation takes place strongly in the first 2000 hr of exposure in natural weathering and extended up to 5000 hr in accelerating weathering due to the formation of microcracks. Mechanical tests show that the UV effect was not significant on bulk properties such as yield stress and elongation at yield for accelerated weathering samples up to 1000 hours, then dropped by 62% and 57% respectively up to 13000hr of exposure and remained unchanged for the whole period of exposure for outdoors samples. The drop in the failure stress and elongation at failure for accelerated weathering samples right from the beginning indicate the formation of microcracks is from the early stages of exposure. For outdoor samples, failure stress remained unchanged for the first 1000 hr of sunlight exposure, then decreases progressively with increasing exposure in the environment. The elongation to failure is unchanged up to 13000 hours. After 13000 hrs of exposure to sunlight, r-PET samples failed to break while those exposed to UV lamps failed in a brittle manner under impact after 250 hrs and this indicates the transition from ductile to brittle behaviour just after 10 days of accelerated UV exposure because of crack formation. For accelerated weathering samples, the impact strength remained unchanged in the first 1000 hr of exposure, then a decrease up to 5000 hr of exposure when the effects of flaws become significant and dropped sharply by 85% after 5000hr of exposure. The correlation between both types of weathering shows that one year in natural weathering is equivalent to one and a half months in accelerated weathering according to colour measurements. The effect of accelerated weathering is much bigger than the natural weathering and this is due to higher radiation dosage, temperature and humidity during the test which accelerate chain scission rate that lead to faster crack growth.
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Chohan, Sukhvinder K. "Environmental degradation of polyethylene-based plastics." Thesis, Aston University, 1996. http://publications.aston.ac.uk/9675/.
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The criteria involved in the degradation of polyethylene-based degradable polymer samples have been investigated, with a view to obtaining a clearer mechanism of photo-biodegradation. The compatibility of degradable polymer samples during materials recycling was also studied. Commercial and laboratory prepared degradable polymer samples were oxidised in different environments and the oxidation products formed were studied using various analytical chromatographic and spectroscopic techniques such as HPLC, FT-IR and NMR. It was found that commercial degradable polymer samples which are based on the ECO systems, degrade predominantly via the Norrish II process, whereas the other degradable systems studied (starch-filled polyethylene systems, transition metal systems, including metal carboxylate based polyethylene systems and the photoantioxidant-activator systems) photodegrade essentially via the Norrish I process. In all cases, the major photoxidation products extracted from the degradable polymer samples were found to be carboxylic acids, although, in the polymer itself a mixture of carbonyl containing products such as esters, lactones, ketones and aldehydes was observed. The study also found that the formation of these hydrophilic carbonyl products causes surface swelling of the polymer, thus making bioerosion possible. It was thus concluded that environmental degradation of LDPE is a two step process, the initiation stage being oxidation of the polymer which gives rise to bioassimilable products, which are consequently bioeroded in the second stage, (the biodegradation step). Recycling of the degradable polymer samples as 10% homogeneous and heterogeneous blends was carried out using a single screw extruder (180°C and 210°C) and an internal mixer (190°C). The study showed that commercial degradable polymer samples may be recycled with a minimal loss in their properties.
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Zhu, Zhengmao. "Photochemical modification of polyethylene terephthalate surface." W&M ScholarWorks, 2005. https://scholarworks.wm.edu/etd/1539623471.
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The prospect of obtaining desired surface-mediated characteristics while retaining bulk-mediated physical properties and avoiding potential environmental issues with wet chemical technology lends considerable appeal to photochemical approaches to surface modification.;We undertook a combined experimental and computational approach to investigate the effect of deep UV irradiation on the polyethylene terephthalate (PET) surface. its response to 172 nm UV from a xenon examiner lamp in the absence of oxygen was characterized with X-ray Photoelectron Spectroscopy (XPS), Time of Flight/Secondary Ion Mass Spectrometry (ToF/SIMS), transmission infrared spectroscopy (IR), and Atomic Force Microscopy (AFM). The surface chemistry details suggested that the primary photochemical reactions involved a Norrish type I based decarbonylation and a Norrish type II process yielding terminal carboxylic acid groups, consistent with the possible photochemistry from n-pi* type lowest singlet excited states of PET according to the computational modeling results. By directly populating n-pi* type excited states, 172 nm UV promoted effective surface photochemistry of PET with further helps from the high UV absorptivity and the high surface mobility of the molecules.;Utilizing this active surface radical chemistry, a new grafting strategy was developed to impart desirable functional properties to the surface. A broad range of grafting chemicals can be employed in their vapor forms, demonstrated with an alkene or an alkane. Surface analysis with XPS, ToF/SIMS, AFM, and water contact angle measurements confirmed the effectiveness of the approach, supporting the notion of the surface radical initiated processes.;A potentially useful anti-stain/soil coating was developed by grafting with a fluorocarbon species. Surface analysis suggested that the grafted fluorocarbon formed a nano-scale self-assembled monolayer. The coating had a similar water contact angle as that of a pure fluoropolymer but a better oil repellency due to the special molecular orientation in the graft layer.;A potential antimicrobial application was demonstrated with amine chemicals. Structure characterization and computational modeling results suggested that the photochemistry of the UV active grafting chemicals also played an important role in the grafting process. A double bond structure in the amine species protected the amine functional groups and the resulting coating demonstrated antimicrobial activity against E. coli.
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Mohammadi, Hadi. "On the Melting and Crystallization of Linear Polyethylene, Poly(ethylene oxide) and Metallocene Linear Low-Density Polyethylene." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/84921.
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The crystallization and melting behaviors of an ethylene/1-hexene copolymer and series of narrow molecular weight linear polyethylene and poly(ethylene oxide) fractions were studied using a combination of ultra-fast and conventional differential scanning calorimetry, optical microscopy, small angle X-ray scattering, and wide angle X-ray diffraction.
In the case of linear polyethylene and poly(ethylene oxide), the zero-entropy production melting temperatures of initial lamellae of isothermally crystallized fractions were analyzed in the context of the non-linear Hoffman-Weeks method. Using the Huggins equation, limiting equilibrium melting temperatures of 141.4 ± 0.8oC and 81.4 ± 1.0oC were estimated for linear polyethylene and poly(ethylene oxide), respectively. The former and the latter are about 4oC lower and 12.5oC higher than these predicted by Flory/Vrij and Buckley/Kovacs, respectively. Accuracy of the non-linear Hoffman-Weeks method was also examined using initial lamellar thickness literature data for a linear polyethylene fraction at different crystallization temperatures. The equilibrium melting temperature obtained by the Gibbs-Thomson approach and the C2 value extracted from the initial lamellar thickness vs. reciprocal of undercooling plot were similar within the limits of experimental error to those obtained here through the non-linear Hoffman-Weeks method.
In the next step, the Lauritzen-Hoffman (LH) secondary nucleation theory was modified to account for the effect of stem length fluctuations, tilt angle of the crystallized stems, and temperature dependence of the lateral surface free energy. Analysis of spherulite growth rate and wide angle X-ray diffraction data for 26 linear polyethylene and 5 poly(ethylene oxide) fractions revealed that the undercooling at the regime I/II transition, the equilibrium fold surface free energy, the strength of the stem length fluctuations and the substrate length at the regime I/II transition are independent of chain length. The value of the equilibrium fold surface free energy derived from crystal growth rate data using the modified Lauritzen-Hoffman theory matches that calculated from lamellar thickness and melting data through the Gibbs-Thomson equation for both linear polyethylene and poly(ethylene oxide). Larger spherulitic growth rates for linear polyethylene than for poly(ethylene oxide) at low undercooling is explained by the higher secondary nucleation constant of poly(ethylene oxide). While the apparent friction coefficient of a crystallizing linear polyethylene chain is 2 to 8 times higher than that of a chain undergoing reptation in the melt state, the apparent friction coefficient of a crystallizing poly(ethylene oxide) chain is about two orders of magnitude lower. This observation suggests that segmental mobility on the crystal phase plays a significant role in the crystal growth process.
In case of the statistical ethylene/1-hexene copolymer, the fold surface free energies of the copolymer lamellae at the time of crystallization and melting increase with increasing undercooling, approaching the same magnitude at high undercooling. As a result of this temperature dependence, the experimental melting vs. crystallization temperature plot is parallel to the Tm = Tc line and the corresponding Gibbs-Thomson plot is non-linear. This behavior is attributed to the fact that longer ethylene sequences form a chain-folded structure with lower concentration of branch points on the lamellar surface at lower undercooling, while shorter ethylene sequences form lamellar structures at higher undercooling exhibiting a higher concentration of branch points on the lamellar surface. Branch points limit the ability of lamellar structures to relax their kinetic stem-length fluctuations during heating prior to melting.Ph. D.
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Basu, Nadita [Verfasser], and Günter [Akademischer Betreuer] Reiter. "Investigation of melting and re-crystallisation behavior of polyethylene nanocrystals = Untersuchung des Schmelz- und Rekristallisationsverhaltens von Polyethylen-Nanokristallen." Freiburg : Universität, 2012. http://d-nb.info/1123471568/34.
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Howard, Matthew A. Neau Steven H. "The application of polyethylene oxide (PolyOx®) and methoxypolyethylene glycol (Carbowax Sentry®) in the production of extruded-spheronized beads with a high drug load." Diss., UMK access, 2004.
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Thesis (Ph. D.)--School of Pharmacy and Dept. of Chemistry. University of Missouri--Kansas City, 2004."A dissertation in pharmaceutical sciences and chemistry." Advisor: Steven H. Neau. Typescript. Vita. Description based on contents viewed Feb. 24, 2006; title from "catalog record" of the print edition. Includes bibliographical references (leaves 129-141). Online version of the print edition.
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Sheth, Samir A. "Effect of low level radiation on the barrier qualities of spunbounded olefin /." Online version of thesis, 1991. http://hdl.handle.net/1850/11144.
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Men, Yongfeng. "Understanding of the mechanical response of semicrystalline polymers based on the block like substructure of crystalline lamellae a comprehensive study of mechanical relaxation, tensile deformation and yielding properties of two model polymers: polyethylene and syndiotactic polypropylene /." [S.l. : s.n.], 2001. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB9590128.
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Schicks, Judith Maria. "Winkelabhängige Streulichtexperimente unter hohen Drücken an Polyethylen-, n-Alkan-Systemen." [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=95859967X.
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Beerbaum, Heike. "Ermittlung strukturbezogener bruchmechanischer Werkstoffkenngrössen an Polyethylen-Werkstoffen." [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=960900179.
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Warnecke, Ragnar. "Technikumsversuche zur thermolytischen Behandlung von Polyethylen /." Clausthal-Zellerfeld : Papierflieger, 2001. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=009649776&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Jansen, Kirsten. "Säureeinfluss auf die photochemische Alterung UV-stabilisierter Polyethylenfolien." [S.l. : s.n.], 2003. http://www.diss.fu-berlin.de/2003/161/index.html.
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