To see the other types of publications on this topic, follow the link: Ultra-high-molecular-polyethylene.
Dissertations / Theses on the topic 'Ultra-high-molecular-polyethylene'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Ultra-high-molecular-polyethylene.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Karanfilov, Christopher. "ION IMPLANTATION OF ULTRA-HIGH MOLECULAR WEIGHT POLYETHYLENE." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243981285.
Full text
2
Roukema, Mees. "High-speed spinning of ultra-high molecular weight polyethylene fibres." [S.l. : [Groningen : s.n.] ; University Library Groningen] [Host], 1991. http://irs.ub.rug.nl/ppn/291241077.
Full text
3
Zhang, Zhijie. "A study of ultra-high-molecular-weight polyethylene, UHMWPE, foams." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ60758.pdf.
Full text
4
Boontongkong, Yot. "Orientation of channel die-compressed ultra-high molecular weight polyethylene." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/46093.
Full text
5
Wernle, James David. "Micron-scale wear mechanisms in ultra high molecular weight polyethylene." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2008. http://wwwlib.umi.com/cr/syr/main.
Full text
6
Titone, John Carlos. "Supercritical carbon dioxide sterilization of ultra-high molecular weight polyethylene." Connect to resource, 2009. http://hdl.handle.net/1811/37004.
Full text
7
Ruan, Shilun. "Multi-walled carbon nanotube reinforced ultra-high molecular weight polyethylene composites /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?MECH%202006%20RUAN.
Full text
8
Ma, Yue. "Polymer grafted carbon nanotube reinforced ultra high molecular weight polyethylene fibre." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/45828.
Full textAbstract:
In this research, a series of experiments have been conducted to develop a high performance ultra-high molecular weight polyethylene (UHMWPE) fibre with improved mechanical properties. A novel process was developed whereby polyethylene grafted multi-walled carbon nanotubes (PE-g-MWCNTs) were used to reinforce UHMWPE fibre. PE-g-MWCNT/UHMWPE fibres with remarkable modulus and tensile strength of 125.5 GPa and 4.0 GPa, respectively, were successfully fabricated and showed definite potential for reducing the weight of body armour.
A systematic study was carried out to investigate the effects of gel spinning conditions on tensile properties and morphologies of UHMWPE fibre. Spinning parameters, including polymer concentration, spinning temperature and winding-up speed, were selected and studied systematically and the spinning condition of UHMWPE fibre was optimized by design of experiment.
Intensive experiments were conducted to investigate the feasibility of reinforcing UHMWPE fibre with pristine multi-walled carbon nanotubes (MWCNTs). Various mechanical methods include ultra-sonication, ball milling, microfluidizing, etc. were applied for dispersing pristine MWCNTs. Studies on tensile properties and morphologies of formed MWCNT/ UHMWPE fibre demonstrated that pristine MWCNTs tend to exist in micro-meter size agglomerations and no improvement in tensile properties of the MWCNT/UHMWPE fibres was found.
Finally, chemical functionalization of MWCNTs using a coupling agent and polymer grafting technology was studied. The effective modulus and strength of MWCNTs were calculated based on the ‘rule of mixture’. Compared to coupling agent functionalization, polymer grafting has been found to be more effective in improving reinforcement of MWCNTs in UHMWPE fibre due to a stronger load transfer on the interface. The reinforcement mechanism of polymer grafted MWCNTs was analyzed based on experimental observations.
9
Webber, Robert Stephen. "The strain dependent behaviour of microporous ultra-high molecular weight polyethylene." Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263897.
Full text
10
Chang, Natasha Anna 1974. "The effect of molecular orientation on the wear of ultra-high molecular weight polyethylene." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/46240.
Full text
11
Elmkharram, Hesham Moh A. "Mechanically Processed Alumina Reinforced Ultra-high Molecular Weight Polyethylene (UHMWPE) Matrix Composites." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/31522.
Full textAbstract:
Alumina particles filled Ultra-high Molecular Weight Polyethylene (UHMWPE), with Al2O3 contents 0, 1, and 2.5 wt% were milled for up to 10 hours by the mechanical alloying (MA) process performed at room temperature to produce composite powders. Compression molding was utilized to produce sheets out of the milled powders. A partial phase transformation from orthorhombic and amorphous phases to monoclinic phase was observed to occur for both the un-reinforced and reinforced UHMWPE in the solid state, which disappeared after using compression molding to produce composite sheets. The volume fraction of the monoclinic phase increased with milling time, mostly at the expense of the amorphous phase. The melting temperature decreased as a function of milling time as a result of modifications in the UHMWPE molecular structure caused by the milling. At the same time, for a given alumina composition the activation energy of melting increased with milling time. Generally, the crystallinity of the molded sheets increased with milling time, and this caused the yield strength and elastic modulus to increase with milling time for a given alumina composition. However, the tensile strength and ductility remained about the same.<br>Master of Science
12
Tam, Yee Kam. "Mechanism study of carbon nanotube reinforced ultra-high molecular weight polyethylene fibers /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?CBME%202008%20TAM.
Full text
13
Medhekar, Vinay Shantaram. "Modeling and simulation of oxidative degradation of Ultra-High Molecular Weight Polyethylene (UHMWPE)." Link to electronic thesis, 2001. http://www.wpi.edu/Pubs/ETD/Available/etd-0828101-135959.
Full text
14
Goktepe, Canan. "Water Soluble Monomer Grafting On Thin Films Of Ultra High Molecular Weight Polyethylene." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/4/1081546/index.pdf.
Full textAbstract:
This study covers grafting of Acrylic Acid (AA) and Methacrylic Acid (MAA) on Ultrahigh Molecular Weight Polyethylene (UHMWPE) thin films by surface grafting and xylene-swollen grafting methods with Co-60 &<br>#947<br>-ray in air. Also characterizations of pure, irradiated and grafted films were made by applying gravimetric, spectroscopic, thermal and mechanic tests. The thin films of UHMWPE were prepared by using compression molding. AA and MAA grafting on thin UHMWPE films were carried out by surface grafting and xylene-swollen grafting methods. During grafting processes, homopolymerization of monomers was avoided by using Fe2+ and Cu2+ ions. Grafting degree of AA and MAA were calculated for the samples irradiated at different doses. To verify grafting of AA and MAA on UHMWPE films, FTIR spectra of grafted films were used. Metal-uptake capacity is important property of grafted polyethylene for environmental applications. Thus, we examined metal-uptake capacities of AA and MAA grafted films for Fe(III) and Ni (II) and it was found that AA and MAA grafted UHMWPE films showed good affinity towards Fe(III) and Ni(II) metals. Thermal behavior of films were examined by DSC analysis. First run and second run DSC thermograms showed the thermal stability of films under heat. Mechanical properties of UHMWPE decrease with irradiation and grafting. However stress at break values of xylene-swollen grafted samples tend to increase with irradiation dose. In conclusion, water soluble monomers were successfully grafted on UHMWPE and these AA and MAA grafted UHMWPE films can be used in biomedical, environmental applications and other related areas.
15
Yu, Jie. "Oxidation of ultra high molecular weight polyethylene, UHMWPE, containing traces of cobalt ion." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0018/MQ53349.pdf.
Full text
16
Bruton, Allison Renee. "Manufacturing and performance of titanium dioxide-ultra high molecular weight polyethylene nanocomposite materials." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 175 p, 2007. http://proquest.umi.com/pqdweb?did=1251905071&sid=1&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Full text
17
Wu, Jun Jie. "The integrity of moulded ultra-high molecular weight polyethylene for joint replacement prostheses." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325574.
Full text
18
Bell, Carol Jane. "Variability, oxidation resistance and wear of 'medical grade' ultra-high molecular weight polyethylene." Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394335.
Full text
19
Miler, Josef L. "Methods for increasing the thermal conductivity of ultra-high molecular weight polyethylene (UHMWPE)." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36291.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.<br>"June 2006."<br>Includes bibliographical references (p. 31-33).<br>A two-part study was conducted to determine methods for producing ultra-high molecular weight polyethylene with high thermal conductivity by way of polymer chain orientation. The first portion of this report surveys current research involving polyethylene chain orientation and manufacturing. This section includes analysis of shish-kebab morphology, past polymer thermal studies, self-reinforcement studies, manufacturing techniques, and experimental techniques for low thermal conductivity materials. The second portion reviews the results of an experiment conducted to test the feasibility of stretched thermoforming of UHMW-polyethylene. Sheets of UHMWPE were stretched and tested for anisotropy in thermal conductivity. For samples with draw ratios of X 10, anisotropy in thermal conductivity was observed to increase. These results show potential for future development of this proposed methodology.<br>by Josef L. Miler.<br>S.B.
20
Lau, Kwan Yee. "An environmentally friendly process for the preparation of high performance ultra-high molecular weight polyethylene thin films /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?CENG%202002%20LAU.
Full textAbstract:
Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002.<br>Includes bibliographical references (leaves 106-111). Also available in electronic version. Access restricted to campus users.
21
Camacho, Nayeli. "Wear analysis on retrieved ultra-high-molecular weight polyethylene tibial components from total knee replacements." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2008. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
Full text
22
Turell, Mary Elizabeth. "Effect of Counterfaceroughness on the Cross-Path Wear of Ultra-High Molecular Weight Polyethylene." Yale University, 2006. http://ymtdl.med.yale.edu/theses/available/etd-06282006-145406/.
Full textAbstract:
Ultra-high molecular weight polyethylene (UHMWPE) is used worldwide as a bearing material in total joint replacement prostheses. Despite its excellent biocompatibility and high wear resistance, wear of UHMWPE components continues to be a major problem limiting the clinical lifespan of UHMWPE-containing orthopaedic implant devices. Multi-directional motion or cross-path motion is known to affect wear rates of UHMWPE in total knee and hip replacement prostheses. The purpose of this study was to quantify the effect of counterface roughness on the cross-path wear of UHMWPE and to determine if the previously established unified theory of wear model could accurately predict wear rates in an abrasive wear environment. UHMWPE pins were articulated against both smooth (centerline roughness, Ra, of 0.015 µm) and rough (Ra = 0.450µm) cobalt-chromium counterfaces in a series of six rectangular wear paths (width = A, length = B) with systematically increasing aspect ratios (B/A) and linear tracking (A = 0), all with identical path lengths (20mm) per cycle. Gravimetric weight loss was converted into volumetric wear rates and wear factors, k. The results showed that for both smooth and rough-counterface tests, wear reached a maximum when a 3mmx7mm wear path was employed. The unified theory of wear was generally accurate in predicting wear rates; however, for rough-counterface tests there was a larger increase in the wear factor for higher aspect ratio rectangular wear paths. The ratio [k rough/ k smooth] decreased monotonically as a function of increasing width of rectangles, normalized by total path length, or A/(A +B). This study showed that wear of UHMWPE articulating in a rectangular motion path likely occurs via a two-step mechanism beginning with molecular orientation followed by material fracture from the UHMWPE surface. The models inability to accurately predict UHMWPE wear for rectangular paths with lower aspect ratios suggests that there may be other operative wear mechanisms including significant re-orientation in the perpendicular sliding direction. In conclusion, it is possible to predict the wear behavior of UHMWPE using mathematical models. A robust model would have an important role in characterizing and predicting performance of currently used and potential future orthopaedic implant materials.
23
Ophir, Amos. "Toughness enhancement of poly(ethylene terephthalate) with chemically modified ultra high molecular weight polyethylene." Thesis, Loughborough University, 1997. https://dspace.lboro.ac.uk/2134/13881.
Full textAbstract:
The present work was concentrated on exploring and developing a toughening material system to be used in engineering products made of high crystalline PET [poly(ethylene terephthalate)]. The work addressed some fundamental objectives in the technology. of crystallised PET (CPET) related to toughness and thermoforming. PET is widely used in fibres and oriented films but is also an attractive material for moulded products, owing to its high melting point and solvent resistance. Crystalline PET, however, is brittle and susceptible to hydrolytic degradation through water absorption. The polymeric toughening system was based on suitably modified UHMWPE (ultra high molecular weight polyethylene) a crystalline polymer with very high fracture toughness under plane strain conditions, low water absorption, but with a relatively low melting point. Being a thermoplastic it has a modulus about 1,000 times higher than the equivalent hydrocarbon elastomer usually used to toughen PET and polyamides. Hence, deterioration of strength and stiffness is minimized. Blending PET with UHMWPE produces coarse microstructures and poor mechanical properties due to lack of compatibility of the two polymers. Compatibility is expected to be improved by reducing the interfacial tension and increasing the adhesion between the two phases; the first will reduce the size of the dispersed phase, while the latter would improve the mechanical properties. Compatibilisation of a pair of immiscible polymers, like in blend of PET with UHMWPE, can be achieved by incorporation of reactive units along the main chains of the UHMWPE, which are capable of strong interactions with the matrix component (PET). The methods used in this investigation involved smface grafting and irradiation treatment to produce chemically active groups on the UHMWPE polymer chain to achieve the required level of interfacial adhesion assisting the agglomerate particle breakdown into small size and to develop strong bonding to the PET when the two polymers are blended in a high shear mixing. The results obtained with several modified UHMWPE powders incorporated into PET by melt mixing showed a clear formation of small primary particles of UHMWPE strongly bonded to the matrix, thereby achieving a vast improvement in toughness while preserving other important fundamental properties related to both the end product and the material processing.
24
DesJardins, John D. "Tribological systems for the evaluation of supercritical carbon dioxide sterilized ultra-high molecular weight polyethylene." Connect to this title online, 2006. http://etd.lib.clemson.edu/documents/1171901535/.
Full text
25
Nguyen-Tra, Hong Phuong. "Melting behavior of strained crystals of ultra high molecular weight polyethylene with and without solvent." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74682.
Full textAbstract:
The origin of the gel formation in dilute solutions of ultra high molecular weight polyethylene (UHMWPE) is the subject of this thesis. At low heating rates v, 0.5 12 K/h, it cannot be detected in the usual DSC runs made at v = 600 K/h or higher.<br>The crystallinity found including fraction (III) (0.84-0.94) upgrades the calorimetric crystallinity to the values found by techniques not involving melting. Arrested melting which occurs between fractions (II) and (III) reveals the existence of a network whose cohesive junctions are unmelted and stabilized by strain. The amount of fraction (III) which is about 20% in the nascent sample increases to about a third of all crystals in a sample submitted to cycles of slow melting and slow crystallization.<br>Fraction (III) is stable in the presence of a solvent. However, its concentration in the sample can be made to vary between 5 and 25% by the appropriate choice of the solvent and thermal history. The network is stabilized during the dissolution of fraction (II) in decalin while it is reduced if the solvent is trichlorobenzene. Other thermal histories minimize the effect of solvent on the partition of the crystals between fractions (II) and (III). Crystallization in a temperature gradient is effective in diminishing fraction (III) and increasing fraction (II). A hypothesis to explain the high crystallinity of gels obtained by quenching is proposed.<br>The metastable states obtained during dissolution do not revert to the equilibrium state when the solvent is evaporated. Mechanical properties such as drawability and also the melting trace of the dried gels are affected by the solvent-induced changes in the melting pattern. The amount of fraction (III) appears to be a good test of drawability.<br>The dissolution traces at low v provide a much-needed quantitative characterization of UHMWPE gels, the crystals formed on quenching having a dissolution trace distinguishable from those grown isothermally or under shear.<br>Since fraction (III) results from a general process of melting, its occurrence in other polymers is expected and indeed has been found in preliminary experiments on poly-4-methylpentenel (P4MP1) and polypropylene (PP). (Abstract shortened by UMI.)
26
Rimell, James Tristan. "Selective laser sintering of ultra high molecular weight polyethylene and Rapidsteel 2.0 for biomedical applications." Thesis, University of Birmingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246693.
Full text
27
Shibata, Nobuyuki. "Fatigue Damage of Ultra-high Molecular Weight Polyethylene (UHMWPE) and its Control in Joint Prostheses." 京都大学 (Kyoto University), 2002. http://hdl.handle.net/2433/149441.
Full text
28
Dwyer, Kimberly A. "Effect of heterogeneous structure on ultra high molecular weight polyethylene, failure mechanisms in total joint arthroplasty." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq20558.pdf.
Full text
29
Lee, Angela Wai-Wai. "In vitro degradation of ultra high molecular weight polyethylene, UHMWPE, by oxidative and/or hydrolytic processes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0014/MQ34115.pdf.
Full text
30
Kenyon, Philip [Verfasser]. "Disentangled Ultra-High Molecular Weight Polyethylene by Ni(II)-Catalysed Polymerisation in Compartmentalised Systems / Philip Kenyon." Konstanz : KOPS Universität Konstanz, 2019. http://d-nb.info/1236503058/34.
Full text
31
Urkaç, Sokullu Şadiye Emel Tıhmınlıoğlu Funda. "Characterization of Ultra High Molecular Weight Polyethylene (Uhmwpe) Modified By Metal-Gas Hybrid Ion Implantation Technique/." [s.l.]: [s.n], 2006. http://library.iyte.edu.tr/tezlerengelli/master/malzemebilimi/T000576.pdf.
Full text
32
Schnitte, Manuel [Verfasser]. "Catalysts and Process Design for Living Aqueous Polymerization to Ultra High Molecular Weight Polyethylene Nanocrystals / Manuel Schnitte." Konstanz : KOPS Universität Konstanz, 2021. http://d-nb.info/1229837639/34.
Full text
33
Azam, Asad Muhammad. "Spectroscopic Optical Band Gap Properties and Morphological Study of Ultra-High Molecular Weight Polyethylene Nano Composites with Mg0.15Ni0.15Zn0.70Fe2O3." Thesis, Umeå universitet, Institutionen för fysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-115809.
Full textAbstract:
Ultra high molecular weight polyethylene has been commonly used as a biomaterial for hip and knee implants. This thesis concerns optical and three phase morphology of nano composites of ultra high molecular weight polyethylene (UHMWPE) with Mg0.15Ni0.15Zn0.70Fe2O3 using analytical techniques such as UV-visible spectroscopy and Raman spectroscopy. Muller matrix spectro-polarimeter has been used to study the absorption behavior over the visible spectral range i.e. 400-800 nm. The results show significant changes in the absorption behavior of UHMWPE/Zn nano ferrite samples. To analyze these changes in pure and UHMWPE/Zn-nano ferrite composites, the Urbach edge method was used for the calculation of optical activation energy. Moreover, direct and indirect energy band gaps, and the number of carbon atoms in C=C unsaturation have been evaluated by using the modified Urbach formula and Tauc’s equation, respectively. The results show that the optical activation energy decreases more with the addition of 2wt% Mg0.15Ni0.15Zn0.70Fe2O3 than 1wt% of Mg0.15Ni0.15Zn0.70Fe2O3. The values of direct and indirect energy band gaps are also found to decrease more with 2wt% of Mg0.15Ni0.15Zn0.70Fe2O3. Furthermore, indirect energy gaps are found to have lower values as compared to direct energy gaps. The numbers of carbon atoms in clusters determined from modified Tauc’s equation were approximately the same for 1wt% and 2 wt% of Mg0.15Ni0.15Zn0.70Fe2O3 but differ for pure UHMWPE. The degree of crystallinity obtained from Raman spectroscopy was 42%, 43%, and 42% for UHMWPE, UHMWPE+1% of Mg0.15Ni0.15Zn0.70Fe2O3, and UHMWPE+2% of Mg0.15Ni0.15Zn0.70Fe2O3, respectively, i.e. about the same, but the relative amount of interphase and amorphous regions varied. Optical activation and sub band gap energies can be estimated for utilization of this composite in applications such as optical sensors, solar cells etc.
34
Pascaud, Raphaël Stéphane. "On the influence of gamma-irradiation sterilisation and ageing on the fracture properties of ultra high molecular weight polyethylene." Thesis, University of South Wales, 1996. https://pure.southwales.ac.uk/en/studentthesis/on-the-influence-of-gammairradiation-sterilisation-and-ageing-on-the-fracture-properties-of-ultra-high-molecular-weight-polyethylene(6e08a3dc-6ee0-422e-9471-16fc1d1246f4).html.
Full textAbstract:
Pitting and delamination wear of ultra high molecular weight polyethylene (UHMW-PE) tibial plateaux for total joint replacements have habitually been attributed to a fatigue crack growth mechanism associated with a combination of high sub-surface cyclic shear stresses and degradation of the chemistry and structure of UHMW-PE caused by the gamma-irradiation sterilisation standard procedure. However, the exact mechanisms by which cracks initiate and grow in UHMWPE are not known and the relationships between these mechanisms and pitting and delamination are only assumptions based on qualitative observations. A fracture mechanics approach based on the J-integral concept of plane strain crack initiation toughness was therefore applied in order to firstly obtain the fracture toughness and crack growth stability of UHMW-PE and secondly to determine the mechanisms by which pitting and delamination occur in vivo. It was necessary to modify the existing standard ASTM E813-89 for the treatment of experimental J data in order to accommodate for the large crack tip plasticity and pronounced ductile tearing. This modified method was then applied to a detailed investigation of the influence of sterilisation and ageing on the chemical, physical and mechanical properties of UHMW-PE. Simulated shelf and in vivo environments enabling a rapid ageing of UHMW-PE corresponding to 10 years of natural ageing were developed. Sterilisation was either conducted by gamma-irradiation in air or nitrogen, or by gas plasma. In virgin UHMW-PE, cracks propagated by a succession of plastic deformation and craze nucleation over thin layers of material, yielding a very high value of J (90 kJ/m 2 ) at 37 : C. Gammairradiation in air followed by 10 years ageing resulted in a highly brittle material with a crack initiation fracture toughness reduced by 78% and a mechanical behaviour approaching that of a linear elastic material i.e. creation of a "cup-and-cone" in tension and formation of 45" shear lips in threepoint bending. On the other hand, gas plasma sterilised UHMW-PE could not be differentiated from unsterile UHMW-PE in either its physical nor mechanical properties. Qualitative correlations existed between the presence and location of highly oxidised regions and the crack initiation fracture toughness of the material. Quantitatively, the J-initiation toughness exhibited a hyperbolic decrease with increasing density and oxidation index while the tensile secant modulus linearly increased with density. From these empirical relationships, a model was created which described the variation of the fracture toughness with depth within a UHMW-PE sample. This model indicated that the zones of high density, oxidation and crystallinity correspond to the areas of maximum shear stress and minimum fracture toughness and that the propensity of UHMW-PE to suffer pitting, delamination and high wear rates through a fracture mechanism is significantly increased by extensive oxidative degradation.
35
Abou, Taha Mohammad. "Reversible modification of the surface properties of silica incorporated in ultra high molecular weight polyethylene : application to batteries separators." Electronic Thesis or Diss., Lyon, 2020. http://www.theses.fr/2020LYSE1299.
Full textAbstract:
Malgré la croissance du marché des batteries lithium-ion, les batteries plomb-acide offrent toujours des avantages que les nouvelles ne sont pas en mesure d'assimiler, notamment en termes de coût, de procédés de fabrication et des besoins réels du marché. Dans ce contexte, l'objectif de ce travail est de valoriser les propriétés des séparateurs PE de batteries plomb-acide qui dominent 90% du marché des séparateurs de batteries plomb-acide. Ces membranes poreuses sont principalement constituées de silice précipitée, un squelette de polyéthylène haute masse molaire (UHMWPE) et elles sont élaborées par un procédé de séparation de phase induite thermiquement (TIPS) avec de l'huile naphténique qui est ensuite extraite. La porosité résultante est ensuite infiltrée avec l'électrolyte de la batterie. Cependant, en raison de la mouillabilité limitée des pores de la membrane par l'électrolyte polaire, seule une fraction de la porosité disponible est efficace. Cette thèse se concentre sur l'amélioration d'une telle porosité mouillable par l'électrolyte afin de réduire la résistivité électrique du séparateur. La mouillabilité des pores n'est pas seulement liée à la présence de silice mais également à la nature de sa surface. Paradoxalement, la silice hydrophobe favorise la qualité du mélange et la dispersion des agrégats; tandis que la silice hydrophile favorise la mouillabilité de la porosité par l'électrolyte. Pour remplir ces critères et obtenir un matériau le plus homogène possible avec une porosité maximale accessible, une modification réversible de la surface de la silice a été réalisée par imprégnation physique de tensioactifs ou par modification chimique avant le procédé d’élaboration de la membrane. Dans un premier temps, des mesures rhéologiques des suspensions de silice dans l’huile, les isothermes de sorption, l’angle de contact et d'autres techniques ont été utilisées pour évaluer le changement des propriétés de surface de la nouvelle silice. Ensuite, les silices préparées ont été dispersées dans les membranes et la porosité, l’état de dispersion, la structure, les propriétés électriques et mécaniques ont été étudiées<br>Notwithstanding the growth of the market of the new lithium-ion batteries, lead-acid batteries still offer advantages that the new ones are not able to equate especially in terms of cost, manufacturing base and the actual market need. In this context, the aim of this work is to enhance the properties of lead-acid batteries PE- separators that predominate 90% of the market of lead-acid batteries separators. These porous membranes consist mainly of precipitated silica, a backbone of ultra-high molecular weight Polyethylene (UHMWPE) and they are processed using a thermally induced phase separation process (TIPS) with naphthenic oil that is subsequently extracted. The resulting porosity is thereafter infiltrated with the electrolyte of the battery. Yet, due to the limited wettability of the pores of the membrane by the polar electrolyte, only a fraction of the available porosity is efficient. This thesis focuses on the enhancement of such wettable porosity by the electrolyte in order to reduce the electrical resistivity of the separator. The wettability of the pores is not only related to the presence of silica but also to the nature of silica surface. Paradoxically, hydrophobic silica favors the blend and the dispersion of aggregates; while hydrophilic silica promotes the wettability of the porosity by the electrolyte. To fulfill these criteria and obtain a material as homogeneous as possible with maximum accessible porosity, a reversible modification of the surface of silica was realized by physical impregnation of surfactants or by chemical modification before the blending and the dispersion in the membrane. Therefore, rheological characterization of the suspensions, contact angle and sorption isotherms and other techniques were used to evaluate the change in the surface properties of the new silica. Then, these tuned silica were dispersed in membranes and the prorosity, the structure, the electrical and mechanical properties were investigated
36
Rosário, Salmo Cordeiro do. ""Estudo do efeito da radiação ionizante por feixe de elétrons sobre o polietileno de ultra alto peso molecular virgem e reciclado industrial"." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/85/85131/tde-29052007-142007/.
Full textAbstract:
O polietileno de ultra alto peso molecular (UHMWPE) é um plástico de engenharia que tem várias aplicações atualmente, mormente em áreas específicas da indústria e da medicina. O UHMWPE pode ser utilizado ainda em outras aplicações: defensas portuárias; guias de corrente; revestimentos de caçambas, silos e calhas; engrenagens; buchas; guias de correias e próteses cirúrgicas. Esta gama de aplicações se deve ao fato das excelentes características técnicas que este material possui, como: alta resistência a abrasão, elevada resistência ao impacto, anti-aderência, atóxico, excelente resistência química, baixo peso específico, fácil usinagem e alta resistência a fadiga. Os tipos de polietileno de ultra alto peso molecular (UHMWPE) utilizados neste trabalho foram o UTEC 3041 e UTEC 6541 da Braskem. A reciclabilidade do UHMWPE ganhou interesse, porque a utilização desta matéria-prima na última década cresceu mais de 600%, tornando-se um dos plásticos de engenharia mais utilizados para obtenção de peças usinadas depois da poliamida. Com o crescimento na utilização deste polímero na confecção de peças para maquinários, o seu desperdício tem sido muito grande, porque o resto deste material é desprezado, geralmente não sendo reaproveitado. Este trabalho tem como objetivo reciclar o UHMWPE UTEC 3041 e estudar as propriedades deste material virgem e reciclado e comparar os resultados entre si e com o UHMWPE UTEC 6541, e com estes materiais submetidos a diferentes doses de radiação.<br>Ultra High Molecular Weight Polyethylene (UHMWPE) is an engineering plastic which has several applications, chiefly, in specific areas of the industry and medicine. UHMWPE can be even for other applications such as: port fenders, current guide, bucket coating, silos and gutters, plugs, pulleys and surgical prosthesis. This range of applications is due to the excellent technical characteristics that this material owns, such as; high resistance to wear, high resistance to impact, anti-adherence, non toxic, excellent chemical resistance, low specific weight, easy mill processing, and high resistance to fatigue. The UHMWPE type used in this work were UTEC 3041 and UTEC 6541 of the Braskem. The recycling process of UHMWPE raised much interest, because the utilization of this rawmaterial grew over 600% in the last decade, becoming one of the most used engineering plastics for attainment of mill processed parts after polyamide. As the utilization of this polymer in the manufacturing of parts for machinery has grown, its waste is very big, because the rest of this material is thrown out, usually not being reused. The goal of this work is to recycle the UHMWPE UTEC 3041 and study the properties of this recycled and virgin material and compare the results between both with these materials submitted to different radiation dose.
37
Ravi, Kesavan. "Mechanistic understanding of high strain rate impact behavior of ultra-high molecular weight polyethylene and the mechanism of coating formation during cold spraying." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI008/document.
Full textAbstract:
Des travaux récents ont montré que des revêtements polymères étaient réalisables par procédé connu sous le nom de Cold-Spray. Ces travaux sont particulièrement importants pour le polyéthylène de très haute masse molaire (UHMWPE) qui ne peuvent pas être mis en forme par les méthodes conventionnelles. Mais les mécanismes d'obtention des dépôts n'avaient pas été analysés. Cette thèse présente une analyse expérimentale mécanique détaillée du comportement à l'impact de particules d'UHMWPE et des mécanismes de formation du revêtement polymère sur un substrat en aluminium (Al) sous l'effet de la pulvérisation à froid de ces particules. La formation du revêtement se décompose en deux étapes : (1) se rapporte à la formation de la première couche de particules (interaction polymère-substrat), (2) à la croissance (par ajout de couches successives) du revêtement polymère (interaction polymère-polymère). La première étape de la formation du revêtement a été étudiée grâce à une technique expérimentale développée dans le cadre de cette thèse et appelée "Méthode de dépôt de particules isolées" (IPD). Il s'agit de déposer des particules isolées de UHMWPE sur un substrat en Al, en utilisant la même machine Cold-Spray, tout en contrôlant de manière précise la température du gaz et la teneur en FNA. Grâce à l'utilisation d'une caméra rapide, il a été possible de déterminer la vitesse des particules d'UHMWPE et par le calcul d'évaluer leur température avant et pendant leur impact. L'efficacité augmente avec d'une part la température et d'autre part la fraction de FNA. Cette efficacité dépend de la compétition entre l'énergie cinétique stockée sous forme d'énergie élastique Eel et l'énergie d'adhésion Ead du polymère à la surface du substrat. Pour que le film polymère se forme, il faut que Ead > Eel. Par ailleurs, Ead dépend de l'interface entre polyéthylène et aluminium, et de la présence de FNA. Les liaisons H disponibles sur la surface des FNA contribuent à l'adhésion, ce qui augmente le domaine de température favorable à la réalisation du dépôt. Concernant la croissance du revêtement, il s'agit cette fois-ci de l'adhésion polyéthylène-polyéthylène, avec toujours l'effet des nanoparticules FNA. Les études microstructurales et mécanique ont montré qu'en frittage conventionnel du UHMWPE sous forte pression, l'ajout de FNA renforce la cohésion des matériaux obtenus, mais que l'effet inverse est observé pour un frittage incomplet (sous faible pression). Enfin, afin d'explorer l'effet de vitesse de sollicitation de l'UHMWPE comparable à celles observées pour le Cold-Spray, des expériences utilisant des barres dites de Split-Hopkinson (SHPB) ont été menées. Les courbes obtenues permettent de disposer d'une cartographie complète du comportement thermo-viscoélasto-plastique de ce polymère, pur ou additionné de FNA<br>Recent developments showed polymer coatings to be feasible by cold spray (CS) technique on different surfaces. This is especially important for Ultra-High Molecular Weight Polyethylene (UHMWPE) which cannot be classically processed. But the mechanisms behind coating formation was not largely understood. The thesis presents a mechanistic understanding of high strain rate impact behavior of Ultra-High Molecular Weight Polyethylene and the mechanism of coating formation during CS. The coating formation is first broken down into two major categories: 1. Interaction of UHMWPE with Al substrate (impacting particle-substrate interaction) during a high-speed impact and interaction of UHMWPE with already deposited UHMWPE particles (impacting particle-deposited particles) leading to a buildup in the coating. First stage of coating formation was understood from a technique developed for this work called Isolated Particle Deposition (IPD). In the experimental IPD process, effects of gas temperature and FNA content were calibrated empirically by depositing UHMWPE particles in an isolated manner on an Al substrate. The Deposition efficiency increased with gas temperature and FNA content. The use of an ultrafast video-camera helped to determine the particle velocity, and theoretical calculations helped to evaluate the temperature of UHMWPE particles before and during the impact process. Mechanical response of UHMWPE at different temperatures were understood by calculating elastic strain energy of UHMWPE which decreased with increasing material temperature and increased with the strain rate. Rebound of UHMWPE particles on Al surface depended upon whether UHMWPE particles after impact furnished a contact area with an interfacial bond stronger than elastic strain energy of the particle. External contributions like H-bonds on the FNA surface provide sufficiently strong extra bonds at the contact surface to increase the window of deposition at higher temperatures, which was otherwise very low. Second stage of coating formation was understood from the mechanism of welding of UHMWPE grains at different interfacial loading conditions and at varying FNA contents. The morphological and mechanical characterization showed that when UHMWPE was processed under high loading conditions (using classical sintering technique), FNA particles reinforced the UHMWPE interface. On the contrary, when UHMWPE was processed under low loading conditions, FNA particles weakened the interface. Last to be discussed in the thesis is the strain rate effect of UHMWPE using Split-Hopkinson Pressure Bar (SHPB) experiments, in order to approach comparable conditions to what happens during particle impacts. This part of the study discussed in detail the effects a high strain-rate compression has on UHMWPE by analyzing its stress-strain curves, with and without FNA. Thus, the mechanical response data with the inclusion 0%, 4% and 10% FNA to UHMWPE is also presented and discussed
38
Wampler, Amos. "Resolution of crystalline phases in polymorphic gel-spun ultra-high molecular weight polyethylene fibers using restrained differential scanning calorimetry and x-ray diffraction." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 70 p, 2008. http://proquest.umi.com/pqdweb?did=1597633731&sid=6&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Full text
39
Baier, Moritz C. [Verfasser]. "Living Polymerization to Ultra-High Molecular Weight and Dye-Labeled Polyethylene for Single-Molecule Fluorescence Microscopy and Reactor Blends / Moritz C. Baier." Konstanz : Bibliothek der Universität Konstanz, 2016. http://d-nb.info/1173616454/34.
Full text
40
RIBEIRO, Márcia Cristina de Moraes Reis. "Avaliação do efeito da radiação ultravioleta sobre polietileno de ultra-alto peso molecular usado implantes para artroplastia." Universidade Federal de Campina Grande, 2014. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/384.
Full textAbstract:
Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-04-13T17:46:55Z
No. of bitstreams: 1
MÁRCIA CRISTINA DE MORAES REIS RIBEIRO - DISSERTAÇÃO PPG-CEMat 2014..pdf: 1739612 bytes, checksum: 483de315f077aaf3a1be5bb9bddc6639 (MD5)<br>Made available in DSpace on 2018-04-13T17:46:55Z (GMT). No. of bitstreams: 1
MÁRCIA CRISTINA DE MORAES REIS RIBEIRO - DISSERTAÇÃO PPG-CEMat 2014..pdf: 1739612 bytes, checksum: 483de315f077aaf3a1be5bb9bddc6639 (MD5)
Previous issue date: 2014-07-16<br>O polietileno de ultra alto peso molecular (PEUAPM) é um polímero com
excelentes propriedades físicas e mecânicas tendo como mais notáveis a sua
inércia química, a lubricidade, resistência impacto e resistência a abrasão.
Exibe um papel relevante no sucesso na Artroplastia Total de Joelho (ATJ) e
Artroplastia Total de Quadril (ATQ). A Artroplastia se caracteriza pela
substituição da articulação natural por uma articulação artificial. As articulações
artificiais são formadas por um conjunto de componentes, sendo fabricados de
matéria prima metálica ou cerâmica e um componente, normalmente feito em
PEUAPM, que é interposto entre componentes metálicos. Alguns fatores
contribuem para um maior desgaste do componente de polietileno. Os
componentes fabricados em polietileno PEUAPM não possuem
fotoestabilizadores. E em inspeções realizadas em fabricantes e distribuidores
destes produtos foi observado que durante seu processamento fabril e
comercialização eles não são adequadamente protegidos da iluminação direta.
As características consideradas importantes para o desempenho in vitro destes
dispositivos estão definidas em normas técnicas, mas muitas destas normas
somente recomendam determinados requisitos considerados importantes do
ponto de vista técnico. Atualmente a área de materiais de uso em saúde
trabalha em regulamentos que visam instituir os requisitos mínimos para
registro de implantes ortopédicos. Desta forma, este trabalho propôs avaliar as
possíveis alterações de componentes fabricados em polietileno de ultra alto
peso molecular utilizados em procedimentos cirúrgicos de artroplastia e joelho
e quadril, exposto a radiação ultravioleta. O trabalho foi dividido em 4 grupos:
grupo 1 (material não exposto a UV); grupo 2 (material exposto a UV por 1h);
grupo 3 (material exposto a UV por 24h) e grupo 4 (material exposto a UV por
48h). Todas as amostras foram caracterizadas por Difração de Raio X (DRX),
Espectroscopia de Absorção de Infravermelho por Transformada de Fourier
(FTIR), Microscopia Ótica (MO), Microscopia Eletrônica de Varredura (MEV)
com mapeamento por EDS e Microscopia de Força Atômica (AFM) com o
intuito de avaliar as possíveis degradações do PEUAPM submetidos a radiação
UV. Os resultados demonstraram que a exposição do polímero a radiação UV
em todos os tempos testados neste trabalho promoveu alterações nas
amostras, pois foi observado, principalmente, nos ensaios de DRX e EDS que
ocorreu respectivamente, um discreto aumento da cristalinidade do material e
diminuição no percentual de oxigênio. Desta forma, pode-se concluir que o
aumento da cristalinidade pode, pela ação da radiação UV, afetar nas
propriedades do material contribuindo para o aumento do desgaste e
diminuição do tempo de vida útil do implante.<br>The polyethylene, ultra high molecular weight (UHMWPE) is a polymer with
excellent physical and mechanical properties with the most notable its chemical
inertness, lubricity, impact resistance and abrasion resistance. Displays a
relevant role in the successful Total Knee Arthroplasty (TKA) and Total Hip
Arthroplasty (THA). The arthroplasty is characterized by replacement of the
natural joint with an artificial joint. Artificial joints are formed by a set of
components, being manufactured from metal or ceramic raw material and a
component normally done in UHMWPE, which is interposed between the metal
components. Some factors contribute to increased wear of the polyethylene
component. Components manufactured in polyethylene UHMWPE not have
photostabilizers. And inspections on manufacturers and distributors of these
products was observed that during its industrial processing and marketing they
are not adequately protected from direct light. Characteristics considered
important for the in vitro performance of these devices are set in technical
standards, but many of these standards only recommend certain requirements
considered important from a technical standpoint. Currently the area of
materials for use in healthcare working on regulations that seek to establish the
minimum requirements for registration of orthopedic implants. Thus, this study
aimed to evaluate the possible changes of components manufactured in
polyethylene, ultra high molecular weight used in surgical procedures and knee
arthroplasty and hip, exposed to ultraviolet radiation. The work was divided into
4 groups: group 1 (material not exposed to UV); group 2 (material exposed to
UV for 1 h); group 3 (material exposed to UV for 24 h) and group 4 (material
exposed to UV for 48 h). All samples were characterized by X-Ray Diffraction
(XRD), Absorption Spectroscopy Fourier Transform Infrared (FTIR), optical
microscopy (OM), scanning electron microscopy (SEM) with EDS mapping and
Atomic Force Microscopy (AFM) in order to evaluate the possible degradation of
UHMWPE subjected to UV radiation. The results showed that exposure of the
polymer to UV radiation at all times tested in this study modified the samples, it
was observed mainly in the experimental XRD and EDS which occurred
respectively a slight increase in crystallinity and decrease in the percentage
oxygen. Thus, it can be concluded that the increase in crystallinity can by the
action of UV radiation, affect the material properties contributing to increased
wear and reduced useful life of the implant.
41
Bruck, Angela Lynette. "Friction and wear behavior of ultra-high molecular weight polyethylene as a function of crystallinity and in the presence of the phospholipid DPPC (dipalmitoyl phosphatidylcholine)." [Ames, Iowa : Iowa State University], 2007.
Find full text
42
Ebringerová, Veronika. "Deformačně napěťová analýza kyčelního spojení s totální endoprotézou s uvažováním otěru." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-230390.
Full textAbstract:
The presented work deals with the creation of computational model of total hip endoprosthesis and the subsequent stress-strain analysis. The models of geometry of the pelvis and femur were created on base of CT data. In this model were fitted components od endoprosthesis, i.e. femoral stem and acetabular cup (metal and polyethylene pad) and also cement. On this system was subsequently modelled the rals loads conditions. Just the real loading of the prosthesis leads to the wear. It has a great influence on the quality of bone tissue, what is deteriorated. The deteriorated tissue was simulated under the acetabular component. The behaviour of the whole system is assessed on base of stress-strain analysis. This problems is very topical these days.
43
Vase, Ajoy. "The effects of material treatments on the surface properties of polymeric biomaterials." Pomona College, 2007. http://ccdl.libraries.claremont.edu/u?/stc,19.
Full textAbstract:
This work examines the chemical and physical effects of a material treatment process on the biopolymers PEEK, POM-h, POM-c, PTFE and UHMWPE. The polymers are analyzed physically and chemically using atomic force microscopy, profilometry, scanning electron microscopy, optical microscopy, contact angle measurement, FT infra-red spectroscopy and energy dispersive X-ray spectrometry. PEEK is found to be the most suitable polymer and FT Infra-red spectroscopy an informative analytic tool.
44
Low, Benjamin. "Design of a 3 axis wear testing device to evaluate the effect of slide to roll ratio on ultra high molecular weight polyethylene wear in total knee replacements." Thesis, University of Canterbury. Mechanical Engineering, 2005. http://hdl.handle.net/10092/1105.
Full textAbstract:
Multidirectional motion occurs in total knee replacements (TKR), is a major factor in ultra high molecular weight polyethylene (UHMWPE) wear and is a requirement for wear tester and simulators. There are three ways the femoral component can move relative to the tibial component; sliding, rolling and gliding and these are defined by the slide to roll ratio. Previous wear tester research has investigated the effects of multidirectional motion and slide to roll ratio, individually but not combined. The project aim was to design a machine that combined multidirectional motion with variable slide to roll ratio. A three station wear testing machine was designed and built featuring flexion extension, variable anterior posterior translation, variable internal external rotation and a 2KN load per station. The TKR was simplified to a cylinder on flat. Lubrication was 25% bovine serum and each station had its own recirculation system. A million cycle validation test was successfully carried out on non-irradiated UHMWPE samples using a slide to roll ratio of 1 : 0.5 and the mean wear rate was 14.7mg/10^6 cycles. Polished areas and scratches from 3rd body abrasion were observed. Magnification revealed a fine ripple pattern with a 1-2 micron periodicity. Ripples were randomly oriented, perpendicular to the primary direction of motion and a small number were running parallel to the primary direction of motion, indicative of rolling motion. The results from the validation study show that the knee joint wear tester is capable of producing wear rates and wear mechanisms similar to those observed in other wear testers and knee joint simulators and has met the aim of the project.
45
Mendes, Luciana Biagini. "Caracterização do polietileno de ultra alta massa molar processado por moagem de alta energia." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2010. http://tede2.uepg.br/jspui/handle/prefix/1398.
Full textAbstract:
Made available in DSpace on 2017-07-21T20:42:32Z (GMT). No. of bitstreams: 1
Luciana Biagini Mendes.pdf: 7206159 bytes, checksum: d493f2f21ec603c56bf971cd0445a8f6 (MD5)
Previous issue date: 2010-08-05<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>This research was an exploratory study of the changes that high energy mechanical milling can induce in ultra high molecular weight polyethylene (UHMWPE), using the
mills Spex, Attritor and Planetary, and several times and reasons for grinding. The milling products were characterized using scanning electron microscopy (SEM), optical microscopy (OM), differential scanning calorimeter (DSC), x-ray diffraction
(XRD), x-ray fluorescence (XRF), and intrinsic viscosity for calculate the viscosity average molecular weight. For the analysis of micrographs observed the morphological change of particles with the grinding, the particles are initially rounded
and the milling time increases the aspect ratio, acquire the form of flakes. Changing the shape in Spex mill occurs in less time, because it is a mill more energetic that Attritor and Planetary. By analysis of DSC was possible to observe the influence of high energy mechanical milling on melting and crystallization temperatures, and the percentage of crystalline phase of UHMWPE. Was used deconvolution of peaks in xray
diffraction patterns for better identification of the peaks of monoclinic and orthorhombic crystalline structures. Observed the formation of monoclinic phase in the UHMWPE processed in high energy mills, to a greater percentage in the mill
Attritor, possibly because it has a temperature control and avoiding a reversal of the monoclinic crystalline structure in orthorhombic crystalline structure.<br>Este trabalho foi realizado para um estudo exploratório das modificações que a moagem de alta energia pode provocar no polietileno de ultra alta massa molar (PEUAMM), utilizando os moinhos Spex, Attritor e Planetário, e variando tempo e poder de moagem. Os produtos de moagem foram caracterizados utilizando microscopia eletrônica de varredura (MEV), microscopia ótica (MO), calorimetria exploratória diferencial (DSC), difração de raios x (DRX), fluorescência de raios x
(FRX), e medidas de viscosidade intrínseca para o cálculo da massa molar viscosimétrica média. Pelas análises das micrografias observou-se a mudança morfológica das partículas com a moagem, inicialmente as partículas são
arredondadas e com o tempo de moagem aumentam a razão de aspecto, adquirem a forma de flakes. Para o moinho Spex a mudança da forma das partículas ocorre em menor tempo, por este ser um moinho mais energético que o Attritor e Planetário. Pela análise do DSC foi possível observar a influência da moagem de alta energia nas temperaturas de fusão e cristalização, e na porcentagem de fase
cristalina do PEUAMM. Foi utilizada a deconvolução de picos nos difratogramas de raios x para melhor identificação dos picos das estruturas cristalinas ortorrômbica e monoclínica. Com a moagem de alta energia ocorreu a formação da estrutura cristalina metaestável monoclínica, em maior porcentagem no moinho Attritor, possivelmente por este possuir um controle de temperatura e evitando uma reversão
da estrutura cristalina monoclínica em ortorrômbica.
46
Deplancke, Tiana. "Approche des mécanismes de frittage du UHMWPE : étude du comportement mécanique à l’état solide et à l’état fondu." Thesis, Lyon, INSA, 2013. http://www.theses.fr/2013ISAL0143/document.
Full textAbstract:
Le polyéthylène à ultra haute masse molaire (UHMWPE) présente une viscosité si forte à l’état fondu que seuls des procédés de mise en forme de type frittage peuvent être employé. Ce procédé rarement utilisé pour les polymères reste peu étudié. En particulier les deux principaux mécanismes généralement mentionnés que sont le réenchevêtrement et la cocristallisation aux interfaces sont difficilement observables séparément. Le UHMWPE, grâce à sa très haute viscosité à l’état fondu et grâce à son plateau caoutchoutique extrêmement étendue en température, peut faire l’objet d’essais mécaniques à la fois à l’état semi-cristallin et à l’état fondu. Des poudres natives de UHMWPE de masses molaires comprises entre 0,6 et 10,5 Mg.mol-1 sont utilisées comme matériau de départ pour leur mise en oeuvre par frittage. La consolidation des interfaces par soudage des particules a été effectuée sous pression à différentes températures supérieures au point de fusion et pour différentes durées. Des expériences de traction effectuées soit à température ambiante soit au-dessus du point de fusion ont permis de distinguer le rôle de l'interdiffusion des chaînes au travers des interfaces de celle de la cocristallisation dans les mécanismes de soudage de particules. Il s'est avéré qu’un soudage efficace se produit dans une échelle de temps très courte. La très faible influence de la durée de frittage par rapport à celle de la température de frittage a prouvé que l'interdiffusion des chaînes n'est pas régie par un mécanisme de reptation. L'explosion à la fusion des cristaux « hors-équilibre » de la poudre native est suggérée être le mécanisme principal permettant un réenchevêtrement dans un laps de temps beaucoup plus court que celui de la reptation. La cocristallisation est un phénomène si efficace dans la consolidation de l'interface à l'état solide qu'elle masque significativement la cinétique de réenchevêtrement gouverné par la température, visible dans les tests mécaniques à l’état fondu<br>One of the main issues of ultra-high-molecular-weight polyethylene (UHMWPE) is to overcome its very high viscosity. Powder sintering is then often required instead of injection or extrusion. However, sintering mechanisms remain partially understood. Indeed, the two main mechanisms generally mentioned for interparticle welding, i.e. re-entanglement and cocrystallization, can hardly be observed separately. Fortunately, due to its very high molecular weight, UHMWPE exhibits an exceptionally broad rubbery plateau so that mechanical tensile tests can be easily performed both below and above the melting point. Four UHMWPE of molecular weight in the range of 0.6.106 g.mol-1 to 10.5.106 g.mol-1 have been processed by means of sintering of nascent powders. The interface consolidation or particle welding was carried out under pressure at various temperatures above the melting point and for various durations. Tensile drawing experiments performed either at room temperature or above the melting point enabled to discriminate the role of chain interdiffusion through the particle interface from that of cocrystallization in the mechanism of particle welding. It turned out that an efficient welding occurred within a very short time scale. The very weak influence of sintering time compared to that of sintering temperature gave evidence that chain interdiffusion was not governed by a reptation mechanism. The entropy-driven melting explosion of the “non-equilibrium” crystals in the nascent powder is suggested to be the main mechanism of the fast chain reentanglement and subsequent particle welding within a time scale much shorter than the reptation time. Cocrystallization is so much efficient in the interface consolidation in the solid state that it significantly hides the temperature-governed kinetics
47
Gabriel, Melina Correa. "Estudo do processamento de polietileno de ultra-alta massa molar(Peuamm)e polietileno glico (PEG) por moagem de alta energia." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2010. http://tede2.uepg.br/jspui/handle/prefix/1395.
Full textAbstract:
Made available in DSpace on 2017-07-21T20:42:32Z (GMT). No. of bitstreams: 1
Melina Correa Gabriel.pdf: 5915390 bytes, checksum: bae67fca28fd7999823fa6ec6ac98844 (MD5)
Previous issue date: 2010-03-29<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>The intention of this exploratory research is to study the modifications provided by high-energy mechanical milling in ultra-high molecular weight polyethylene (UHMWPE) and mixtures of this polymer with polyethylene glycol (PEG). These modifications can be of interest for future processing of UHMWPE. The mechanical milling was performed in an attritor mill, a type of mill that can be used in laboratory as well as in industry. The millings of UHMWPE were performed in different rotation speeds. For mixtures of UHMWPE and PEG, the amounts of PEG were also different. The samples were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The mechanical milling modified the UHMWPE particles morphology: with milling, the almost rounded shape became flat-like shape. This caused the reduction of apparent density of polymer after milling. The mechanical milling also provided structural changes. With the increasing of the rotation speed,there was the increasing of the monoclinic phase and the decreasing of the orthorhombic, up to 500 rpm. For 600 rpm, the amount of monoclinic phase decreased. In this rotation, the deformation rate probably increased the process
temperature, allowing the monoclinic phase to return to its initial structural orthorhombic form. In mixtures of UHMWPE and PEG, after mechanical milling, the
particles of PEG were probably reduced and better dispersed in the UHMWPE matrix. Changes in thermal characteristics of polymers also could be noted. The
kinetics of UHMWPE crystal growth changed, as well as the behavior of PEG crystallization. Feasibly, dispersed particles of PEG acted as physical barriers against the crystalline phase growth of UHMWPE and the crystallization temperature of PEG decreased, when the UHMWPE and PEG mixtures were milled.<br>Este trabalho exploratório teve por objetivo estudar as modificações promovidas por moagem de alta energia no de polietileno de ultra-alta massa molar (PEUAMM) e
sua mistura com polietileno glicol (PEG), que podem ser de interesse para auxiliar um posterior processamento do PEUAMM. As moagens foram realizadas em um
moinho do tipo attritor, um tipo de moinho que pode ser usado tanto em laboratório quanto em escala industrial. Foram variadas as velocidades de rotação na moagem
do PEUAMM, além das concentrações de PEG, quando feita a mistura. As amostras foram caracterizadas por microscopia eletrônica de varredura (MEV), microscopia de
força atômica (MFA), calorimetria exploratória diferencial (DSC) e difração de raios X. A moagem de alta energia do material modificou a forma das partículas de PEUAMM, passando de arredondadas a flakes, com a evolução do processo de moagem, fazendo com que a densidade aparente do polímero diminuísse muito
comparado ao polímero não moído. A moagem também proporcionou mudança estrutural, permitindo a formação de fase monoclínica em detrimento da ortorrômbica. A medida que se aumentou a rotação do moinho até 500 rpm, houve um crescimento da fase monoclínica. Apenas para 600 rpm, a quantidade dessa fase sofreu decréscimo, devido possivelmente ao aumento da frequência de choques e da temperatura de processamento, fazendo com que a estrutura monoclínica retornasse à estrutura ortorrômbica original. Na mistura de PEUAMM com PEG, a moagem provavelmente permitiu redução das partículas e a melhor
dispersão de PEG na matriz de PEUAMM. Também se observaram mudanças nas características térmicas dos polímeros na mistura após moagem. Ocorreu mudança
na cinética de crescimento dos cristais de PEUAMM e mudança no comportamento de cristalização do PEG, comportamento este que não ocorreu para o PEUAMM
moído ou para a mistura de PEUAMM com PEG antes da moagem. Possivelmente, as partículas dispersas de PEG atuaram como barreiras ao crescimento da fase
cristalina do PEUAMM e houve diminuição da temperatura de cristalização do PEG, na mistura com PEUAMM após moagem.
48
Morais, Bolner Felipe. "Fe- and Ti-catalyzed Ziegler-Natta-type Polymerization for Polyolefins : from Catalyst to Process." Electronic Thesis or Diss., Lyon 1, 2023. https://n2t.net/ark:/47881/m67p8zh4.
Full textAbstract:
Le développement d'un nouveau catalyseur de type Ziegler-Natta à base de Fe, FeCl2/MgCl2(THF)x/BCl3, s'inscrit dans un contexte mondial d'augmentation des ressources en métaux alternatifs pour la catalyse et les nouveaux matériaux polymères. L'objectif de cette thèse était d'obtenir un catalyseur à base de Fe plus reproductible, de le comparer aux catalyseurs à base de Ti, de mieux comprendre l'effet de l'acide de Lewis, et de créer des catalyseurs dinucléaires Ti/Fe aux propriétés hybrides<br>The development of a new Fe-based Ziegler-Natta-type catalyst, FeCl2/MgCl2(THF)x/BCl3, comes in a worldwide context of finding alternative metal resources for catalysis and new polymer materials. The objective of this thesis was to obtain a more reproducible Fe-based catalyst, to compare it with Ti-based catalysts, to better understand the Lewis acid effect, and create dinuclear Ti/Fe catalysts with hybrid properties of both metal sites
49
Doucet, Nolwenn. "Compaction à Grande Vitesse de poudres de polymères semi-cristallins : mécanismes de frittage et modélisation du procédé." Thesis, Lyon, INSA, 2012. http://www.theses.fr/2012ISAL0053.
Full textAbstract:
La Compaction à Grande Vitesse (CGV) est un procédé efficace pour mettre en oeuvre par frittage, et dans un temps court, des poudres polymères semi-cristallins quelle que soit leur viscosité en partant d’une température inférieure au point de fusion. L’échauffement et la fusion du matériau est obtenu par une succession d’impacts à une énergie donnée ce qui offre la possibilité de définir finement la quantité d’énergie que l’on souhaite apporter au matériau et la qualité du frittage. Une fusion partielle de la poudre permet de profiter de la cristallinité élevée de la poudre native, un compromis est alors possible entre de hautes propriétés élastiques et une ductilité élevée. La contre-partie de cette efficacité est une mise au point délicate du procédé. Dans le cas du polyéthylène ultra haute masse molaire (UHMWPE), il a été montré que le procédé permet une quasi-abstraction des effets de la masse molaire. Le frittage du UHMWPE demande seulement une réorganisation à courte distance des chaînes qui peut se faire dans un temps très limité. La cohésion de la poudre est assurée essentiellement par la cocristallisation et la création de nouveaux enchevêtrements. La modélisation du procédé a permis de comprendre comment l’énergie cinétique lors des impacts est transformée en chaleur dans la poudre et elle a permis l’établissement d’un critère de processabilité par CGV. Ce critère de processabilité repose sur la déformabilité de la poudre contenu dans la matrice au moment de l’impact. Celle-ci doit être suffisante pour que l’énergie dissipée dans le matériau permette sa fusion en moins de cent coups. Ceci a permis de comprendre pourquoi le polyoxyméthylène peut difficilement se mettre en forme par CGV<br>High Velocity Compaction (HVC) is an efficient process to mold, in a short time, semicrystalline polymers powders any about their viscosity by starting from a temperature below melting point. Heating and melting occur by successive impacts at a preset energy that offers the possibility to set accurately the energy amount that we would bring to the material and the sintering quality. Partial melting of powder enable to take advantage of the high cristallinity of nascent powders, a compromise is possible between high elastic properties and high ductility. The flip-side of this efficiency is a delicate process settings. For the ultra high molecular weight polyethylene (UHMWPE), it has been shown that the process makes it possible a quasi abstraction of molecular weight effects. UHMWPE sintering needs only a short length reorganisation of chains that could be done in a really short time. Powder cohesion is essentially bring by cocrystallisation and by new entanglements creation. Process modelling allowed to understand how kinetic energy during hits is converted into heat in powder and it’s enable to define a HVC processability criterion. This processability criterion rests on the strainability of powder place in a die during a hit. It has to be sufficient to the dissipated energy in material allows his melting in less than one hundred impacts. This criterion allows to understand why the polyoxymethylene is hard to mold by HVC
50
Vase, Ajoy. "The effect of materials preparation on polymer surfaces." Pomona College, 2007. http://ccdl.libraries.claremont.edu/u?/stc,25.
Full textAbstract:
This work examines the chemical and physical effects of a material treatment process on the biopolymers PEEK, POM-h, POM-c, PTFE and UHMWPE. The polymers are analyzed physically and chemically using atomic force microscopy, profilometry, scanning electron microscopy, optical microscopy, contact angle measurement, FT infra-red spectroscopy and energy dispersive X-ray spectrometry. PEEK is found to be the most suitable polymer and FT Infra-red spectroscopy an informative analytic tool.