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Siskind, Esther. "Market development for recycled high density polyethylene (HDPE)." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/70176.
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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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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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Hepburn, Derek Sinclair. "An investigation of the effect of structure on the fracture resistance of pipes and welds of Eltex TUB 120 Series HDPE." Thesis, Manchester Metropolitan University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386440.
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Ayche, Nadim S. "The Effect of High Density Polyethylene (HDPE) Pipe Profile Geometry on its Structural Performance." Ohio University / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1127140719.
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Svensson, Sofie. "Reprocessing and Characterisation of High Density Polyethylene Reinforced with Carbon Nanotubes." Thesis, Högskolan i Borås, Akademin för textil, teknik och ekonomi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-12853.
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Nanokomposit innehållande högdensitetspolyeten och kolnanorör återvanns och analyseradesför att undersöka hur materialets egenskaper påverkas av återvinning. Kompositenproducerades med 3 viktprocent kolnanorör och återvanns tio gånger genom att extrudera ochmala ner materialet. Analyser gjordes efter varje cykel av extrudering. Dessutom utfördessimulerade tester med kontinuerlig extrudering i 20, 100 och 200 minuter motsvarande 10, 50och 100 cykler. Därav kunde nedbrytningen av kompositen efter längre tids bearbetninganalyseras. I projektet studerades ett referensmaterial bestående av den rena polymeren för attkunna jämföra resultat. Karaktärisering av materialen för att bestämma mekaniska egenskapergjordes med dragprovning, böjningstest och slagprovning. För att undersöka termiskaegenskaper användes Differential Scanning Calorimetry (DSC) och Gel PermeationChromatography (GPC) användes för att hitta molekylviktsändringar. Fourier TransformInfrared Spectroscopy (FTIR) utfördes för att identifiera materialet. Resultaten visade ingenstörre skillnad i egenskaper efter tio återvinningscykler, vilket indikerade att materialet harförmåga att behålla sina egenskaper vid återvinning. I de simulerade cyklerna minskade denoxidativa induktionstiden efter 50 och 100 cykler, vilket berodde på att antioxidanterkonsumerats under bearbetningen. Efter 50 simulerade cykler hade molekylvikten börjat sjunkaoch efter 100 cykler kunde en signifikant minskning obseveras, vilket tydde på attpolymerkedjorna förkortats under bearbetningen. För kompositen däremot var molekylviktenstabil, på grund av att kolnanorören skyddade polymeren vid nedbrytning.Nanocomposite containing High Density Polyethylene (HDPE) and Carbon Nanotubes (CNTs)was reprocessed and characterised to investigate the effect on properties during recycling. Thecomposite was prepared with 3 wt-% CNTs and was recycled ten times by alternatereprocessing and grinding and thereafter the material was characterised. Furthermore, simulatedcycles with continuous processing at 20, 100 and 200 minutes were conducted, representing 10,50 and 100 cycles respectively, in order to investigate the degradation after longer time ofprocessing. In both trials, a reference material containing neat HDPE was studied. Thecharacterisation of the materials produced was conducted using tensile, flexural and charpyimpact testing for investigation of mechanical properties. Differential Scanning Calorimetry(DSC) was used for determining the thermal behaviour and Gel Permeation Chromatography(GPC) to find molecular weight changes. Fourier Transform Infrared Spectroscopy (FTIR) wasused for identification of the material. The results showed no major difference in propertiesafter ten recycling steps, which indicated that the material had the ability to retain its propertiesduring recycling. In the simulated cycles, the oxidative induction time was decreased after 50and 100 cycles, meaning that antioxidants had been consumed during processing. After 50cycles the molecular weight for the reference material was slightly decreased and after 100cycles significantly decreased, indicating chain scission of the polymer chains. For thecomposite the molecular weight was stable, due to that the carbon nanotubes protect thepolymer matrix during degradation.
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Chehab, Abdul Ghafar. "Time dependent response of pulled-in-place HDPE pipes." Thesis, Kingston, Ont. : [s.n.], 2008. http://hdl.handle.net/1974/1239.
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Hudson, Benjamin S. "The Effect of Liquid Hot Filling Temperature on Blow-Molded HDPE Bottle Properties." Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2716.pdf.
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Waldron, Calvin Michael. "Efficacy of Delmopinol in Preventing the Attachment of Campylobacter jejuni to Chicken, Stainless Steel and High-Density Polyethylene." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/50861.
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Campylobacter spp. are the second leading bacterial cause of food borne illness in the U.S. New antimicrobials that prevent bacterial attachment may be effective for reducing Campylobacter. Delmopinol hydrochloride (delmopinol) is a cationic surfactant that is effective for treating and preventing gingivitis and periodontitis. This study evaluated the effectiveness of delmopinol for reducing attachment of Campylobacter jejuni to chicken, stainless steel and high-density polyethylene.
Chicken pieces, steel and HDPE coupons were spot-inoculated with 0.1 mL of a Campylobacter jejuni culture. After 10 min, samples were sprayed with 0.5% or 1.0% delmopinol, 0.01% sodium hypochlorite, or distilled water. Contact times were 1, 10, or 20 min prior to rinsing with buffered peptone water. Rinses were serially diluted onto Campy Cefex Agar for enumeration. For additional samples, solutions were applied first, followed by inoculation with C. jejuni after 10 min. Cultures remained undisturbed for 1, 10, or 20 min. Then samples were rinsed and plated as above.
When C. jejuni was inoculated before treatments, 1% delmopinol application led to mean log reductions of 1.26, 3.70, and 3.72 log CFU/mL, greater than distilled water, for chicken, steel and HDPE respectively. When C. jejuni was inoculated after spray treatments, 1% delmopinol reduced C. jejuni by 2.72, 3.20, and 3.99 mean log CFU/mL more than distilled water for chicken, steel and HDPE respectively. Application of 1% delmopinol, either before or after bacteria inoculation, resulted in a significantly (p<0.05) greater log reduction than 0.01% sodium hypochlorite or distilled water. Delmopinol may be a promising antimicrobial treatment.Master of Science in Life Sciences
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Enriquez, Sevilla Luis Javier. "Activity of phosphite antioxidants in synergistic blends in the thermal and photooxidation of high-density polyethylene (HDPE)." Thesis, Manchester Metropolitan University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364483.
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Pinto, Angela Marie III. "Quantitative Analysis of Antioxidants from High Density Polyethylene (HDPE) by off-line Supercritical Fluid Extraction Coupled High Performance Liquid Chromatography." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/36932.
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Plastics are widely used and they vary in their applicability, ranging from automobile parts, components for houses and buildings, and packaging for everything from food to electronic parts. The diverse applications of plastics, such as polystyrene, polyolefins and polyester, are credited to the incorporation of additives. Additives improve the performance of these and other polymer resins. Without the incorporation of such additives, for example Ethanox ® 330, some plastics would degrade during processing or over time. To ensure that the specified amount of an additive or combination of additives are incorporated into a polymer after the extrusion process, a rapid and accurate analytical method is required. Quantitation of additive(s) in the polymer is necessary, since the additive(s) may degrade and the amount of additive(s) can influence the physical nature of the polymer. Conventional extraction techniques for polymer additive(s), such as, Soxhlet or dissolution / precipitation are labor intensive, time consuming, expensive, and the optimal recovery is significantly less than 90 percent. In addition, a large amount of solvent , such as toluene or decalin, must be eliminated in order to concentrate the sample prior to chromatographic separation.
Supercritical Fluid Extraction (SFE) has been employed as an alternative polymer preparation technique. SFE is a favorable means for various analytical sample preparation applications, credited to its short extraction times. This research employs SFE for the extraction of the antioxidant Ethanox® 330 from high density polyethylene (HDPE) followed by HPLC/UV analysis. The effects of temperature, modifier type, and modifier concentration were investigated. Once the optimal extraction conditions were determined, the extraction efficiency of Ethanox ® 330 as a single additive and in the presence of co-additives from HDPE were investigated. Recoveries of greater than 90% were obtained for Ethanox ® 330 when a secondary antioxidant was present in the HDPE.
Master of Science
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Yazdani, Iman. "High density polyethylene (HDPE) containers as an alternative to polyethylene terephthalate (PET) bottles for solar disinfection of drinking water in northern region, Ghana." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39273.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2007.Includes bibliographical references (leaves 76-82).
The purpose of this study is to investigate the technical feasibility of high density polyethylene (HDPE) containers as an alternative to polyethylene terephthalate (PET) bottles for the solar disinfection of drinking water in the Northern Region of Ghana, in a process know as SOLAIR. This study is in line with the intention of Pure Home Water, a registered non-profit organization in Ghana, to offer a variety of low-cost household water treatment and safe storage (HWTS) products as it continues to grow, including the possibility of offering a solar disinfection product in the future. If successful, SOLAIR is practically advantageous over SODIS, which uses smaller PET bottles, chiefly due to the ability to use a larger water container (2-25L), and one that is more likely to be available in a rural setting, given the widespread use of HDPE jerry cans as water collection and storage vessels in many developing countries. The main idea behind the SOLAIR system is to keep high dissolved oxygen (DO) levels in the water which, in turn, enhances disinfection. A study done by Meyer et al. (2000), in South Africa, showed that regular shaking of the water-filled HDPE container keeps DO at sufficiently high levels to augment disinfection.
(cont.) The SOLAIR results, using 10L translucent HDPE containers, obtained in Tamale, Ghana over the month of January, 2007, show that complete solar disinfection of water over the course of 7 consecutive hours of solar exposure, did not take place. It is believed that the primary reason for the low degree of disinfection is the scattering and absorption of UV radiation by the aerosol particles present in the seasonal Harmattan (Sahara dust) haze, which thereby reduces the amount of UV light that reaches the earth's surface. Using radiation measurements, obtained in Tamale, a model relating the solar radiation intensity versus NASA's OMI Aerosol Index (AI), which is a measure of the amount of particulates in the atmosphere, was derived. Another key conclusion suggested by this study is that shaking does not increase the DO concentration in the SOLAIR water to sufficient levels, if at all, to augment photo-oxidative disinfection, due to the fact that the oxygen level of the sample water was already near saturation. Laboratory tests performed substantiate this claim. In brief, this solar disinfection process, using translucent 10L HDPE containers, in January in Northern Region, Ghana, does not produce a safe drinking water.
by Iman Yazdani.
M.Eng.
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Shaheer, Muhammad. "Effects of welding parameters on the integrity and structure of HDPE pipe butt fusion welds." Thesis, Brunel University, 2017. http://bura.brunel.ac.uk/handle/2438/16919.
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Butt fusion welding process is an extensively used method of joining for high density polyethylene (HDPE) pipe. With the increasing number of HDPE resin and pipe manufacturers and the diversity of industries utilising HDPE pipes, a wide range of different standards have evolved to specify the butt fusion welding parameters with inspection and testing methods, to maintain quality and structural integrity of welds. There is a lack of understanding and cohesion in these standards for the selection of welding parameters; effectiveness, accuracy, and selection of the test methods and; correlation of the mechanical properties to the micro and macro joint structure. The common standards (WIS 4-32-08, DVS 2207-1, ASTM F2620, and ISO 21307) for butt fusion welding were used to derive the six welding procedures. A total of 48 welds were produced using 180 mm outer diameter SDR 11 HDPE pipe manufactured from BorSafe™ HE3490-LS black bimodal PE100 resin. Three short term coupon mechanical tests were conducted. The waisted tensile test was able to differentiate the quality of welds using the energy to break parameter. The tensile impact test due to specimen geometry caused the failure to occur in the parent material. The guided side bend specimen geometry proved to be too ductile to be able to cause failures. A statistical t-test was used to analyse the results of the short term mechanical tests. The circumferential positon of the test specimen had no impact on their performance. Finite element analysis (FEA) study was conducted for the long term whole pipe tensile creep rupture (WPTCR) test to find the minimum length of pipe required for testing based on pipe geometry parameters of outer diameter and SDR. Macrographs of the weld beads supplemented with heat treatment were used to derive several weld bead parameters. The FEA modelling of the weld bead parameters identified the length to be a key parameter and provided insight into the relationship between the geometry of the weld beads and the stresses in the weld region. The realistic bead geometry digitised using the macrographs contributed a 30% increase in pipe wall stress due to the stress concentration effect of the notches formed between the weld beads and the pipe wall. The circumferential position of the weld bead had no impact on the pipe wall stresses in a similar manner to the results of the different mechanical tests. IV Nanoindentation (NI) and differential scanning calorimetry (DSC) techniques were used to study the weld microstructure and variation of mechanical properties across the weld at the resolutions of 100 and 50 microns, respectively. NI revealed signature 'twin-peaks and a valley' distribution of hardness and elastic modulus across the weld. The degrees of crystallinity obtained from DSC followed the NI pattern as crystallinity positively correlates with the material properties. Both techniques confirm annealing of the heat affected zone (HAZ) material towards the MZ from the parent material. The transmission light microscopy (TLM) was used to provide dimensions of the melt zone (MZ) which displays an hour glass figure widening to the size of the weld bead root length towards the pipe surfaces. Thermal FEA modelling was validated using both NI and TLM data to predict the HAZ size. The HAZ-parent boundary temperature was calculated to be 105 ⁰C. The 1st contribution of the study is to prove the existence of a positive correlation between the heat input calculated from FEA and the energy to break values obtained from the waisted tensile test. The 2nd contribution providing the minimum length of pipe for WPTCR based on the pipe dimensions. The 3rd contribution is the recommendation for the waisted tensile test with the test using the geometry designed to minimise deformation of the loading pin holes. The 4th contribution related the weld bead parameters to pipe wall stresses and the effect of notches as stress concentrators. The 5th contribution is a new method of visualising a welding procedure that can be used to not only compare the welding procedures but also predict the size of the MZ and the HAZ. The 6th contribution of the study is the proposal of new weld bead geometry that consist of the MZ bounded by the HAZ, for butt fusion welded joints of HDPE pipes.
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Casas, Carné María del Pilar. "Study of compatibilization methods for high density polyethylene and ground tyre rubber : exploring new route to recycle scrap tyres." Doctoral thesis, Universitat Politècnica de Catalunya, 2010. http://hdl.handle.net/10803/6482.
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Cotxes, camions, tractors, avions... tots necessiten els neumàtics com a component imprescindible per al seu funcionament. Malauradament, degut al desgast per ús, els neumàtics tenen una vida útil limitada que obliga a renovar-los cada cert temps passant a ser Neumàtics Fora d'Ús (NFU). Paradògicament, els neumàtics són formulats per a suportar condicions extremes d'ús i, entre d'altres matèries primeres contenen cautxú vulcanitzat, una elevada quantitat d'estabilitzants i d'altres additius que fan dels neumàtics un material no biodegradable. Fins al 2006, era possible desar els NFU en abocadors però aquesta pràctica va ser prohibida per la Comunitat Europea (directiva 1993/31/EC). Aquesta directiva conjuntament amb la creixent consciència mediambiental ha potenciat la investigació per a trobar noves aplicacions per les 3.4milions de tones de NFU que es generen a l'any a Europa. Els NFU són emprats com a font d'energia o en aplicacions civils, però cada vegada més, són emprats en autopistes o per usos decoratius després de patir un procés de separació i trituració (NFU triturat). Les propietats físico-químiques dels NFU en fan un material molt interessant per la comunitat científica internacional que es centra en buscar noves vies de reciclatge mitjançant aplicacions d'alt valor afegit.Una opció per reciclar grans volums de NFU és utilitzar-los granulats com a càrrega en matrius termoplàstiques, encara que aquesta és una tasca difícil degut a la baixa compatibilitat entre aquests dos materials. Les seves característiques superficials són les responsables d'aquesta baixa compatibilitat. Cal afegir també que el tamany de les partícules de NFU obtingudes a partir de processos industrials és entre 400 and 600μm, sent aquest un tamany massa gran per poder ser fàcilment embolcallades per qualsevol matriu. D'altra banda, el cautxú dels neumàtics és troba altament vulcanitzat i, per tant, aquest reaccionarà químicament amb dificultats amb d'altres materials. Totes aquestes propietats fan dels NFU un material difícil de treballar-hi.
La present tesis estudia diferents mètodes de compatibilització d'un Polietilè D'alta Densitat (PEAD) de grau d'injecció i NFU triturat obtingut a partir de processos estàndards de molturació. La resina de PEAD va ser escollit com a matriu degut al seu ampli rang d'aplicacions d'injecció. L'objectiu principal és explorar diferents mètodes de compatibilització d'aquests dos materials per obtenir òptimes propietats mecàniques, tèrmiques i morfològiques en aplicacions d'injecció. Els composites són optimitzats per a que continguin la màxima quantitat de NFU, una adequada transformació i el mínim cost.
Després d'un estudi preliminar de composites basats en NFU i PEAD s'han estudiat tres mètodes diferents per millorar l'adhesió entre aquests dos materials. El primer mètode consisteix en oxidar la superfície de les partícules de NFU granulat amb tractament basats en àcids, amb l'objectiu de proporcionar rugositat per a un anclatge mecànic. En el segon mètode s'han emprat additius humectants i ceres, ja que aquestes substàncies redueixen la tensió interfacial entre les partícules de NFU i la matriu de PEAD. En l'últim mètode, es va estudiar la influència de l'Etilè Propilè Diè Monòmer (EPDM). Amb aquest mètode, les partícules de NFU són embolcallades per l'EPDM, aquest efecte pot ser millorat amb l'ús de peròxids. Les propietats dels "composites" són bastant diferents en funció del mètode emprat.
Després d'una comparació dels "composites" obtinguts pels tres mètodes, s'ha trobat que el que conté 30% d'EPDM i dos peròxids, corresponent a la formulació::
30% NFU + 40% PEAD + 30% EPDM + 0.5% Trigonox 311 + 0.1% Peròxid de Dicumil
compleix els objectius fixats en la tesis: bona adhesió entre les partícules de NFU i el PEAD on l'elevat valor d'elongació n'és una conseqüència directa, la seva obtenció mitjançant un procés de compatibilització de cost reduït, un nou material amb una elevada quantitat de NFU (30%), la seva facilitat de transformació,, i el més important, una nova via de reciclatge dels NFU per a una aplicació d'alt valor afegit.
Cars, trucks, tractors, airplanes. all need tyres as essential component to work. Unfortunately, due to its continuous use, tyres suffer from wear and have a limited lifetime; therefore, they must be changed every certain time becoming end of life tyres (EOL tyres). Paradoxically tyres are formulated to withstand difficult conditions and among other raw materials, they contain vulcanizated rubbers, high amount of stabilizers and other additives that turn tyres into non biodegradable material. Until 2006, disposal of EOL tyres in landfills was a common practice but it was banned by the European Community (directive 1993/31/EC). This European legislation together with an increasing environmental consciousness has instigated researchers to find applications for 3.4million tonnes of used tyres generated per year in Europe. Some extended uses for EOL tyres are energy recover and civil applications but the use of tyres after separation and grinding processes (material know as Ground Tyre Rubber - GTR), has increased during the last decade. Physical and chemical properties of EOL tyres make them an interesting material for the international research community focused today on finding new ways to recycle tyres for value added applications.
A good option to recycle big volumes of discarded tyres is using GTR particles as filler in thermoplastic matrixes, although this is a difficult task due to the low compatibility between the two materials. The surface characteristics of the GTR particles are responsible of this low compatibility. Despite these facts, the particle size obtained from standard industrial grinding processes is between 400 and 600μm. These particles are too large to be entrapped easily in polymeric matrixes. These characteristics in conjunction with the fact that GTR is made of highly crosslinked rubber with difficulties to react chemically to other materials, make GTR a material very difficult to work with.
The present thesis deals with the study of different compatibilization methods for an injection moulding grade of High Density Polyethylene (HDPE) and GTR obtained from standard industrial grinding process. The HDPE resin was chosen due to its wide range of injection moulding applications. The aim is to explore different methods to mix these two materials and obtain optimum mechanical, thermal and morphological properties for injection moulding applications. The composites are optimized to obtain the highest GTR amount, adequate processability and minimum cost.
After a preliminary study of the composites based on GTR and HDPE, three different methods to improve the adhesion between these two materials are studied. The first method consists in an oxidizing treatment on GTR particles surface in order to promote mechanical anchoring. In the second method the influence of wetting additives and waxes is studied. These substances reduce interfacial tension between GTR particles and HDPE matrix. The third and last method, study the influence of Ethylene Propylene Diene Monomer (EPDM) addition with and without peroxides. In this method, GTR particles are encapsulated by EPDM and this effect can be boosted by the use of peroxides. The composites properties are quite different depending on the used method.
After a comparison of the composites obtained by the three different compatibilization methods, it is found that the one with 30% of EPDM plus two peroxides, corresponding to
30% GTR + 40% HDPE + 30% EPDM + 0.5% Trigonox 311 + 0.1% Dicumyl Peroxide
fulfil the objectives of the thesis. This composite has good adhesion between GTR and HDPE that results in high elongation, it is obtained by a cheap compatibilization process and contains a high amount of recycled tyres (30%), it is easy to process, and the most important thing, it represents a new route to recycle scrap tyres for a value added application.
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Trindade, Nuno Miguel Passarinho. "Stochastic modeling of the thermal and catalytic degradation of polyethylene using simultaneous DSC/TG analysis." Master's thesis, Faculdade de Ciências e Tecnologia, 2012. http://hdl.handle.net/10362/8468.
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Dissertação para obtenção do Grau de Mestre em
Engenharia Química e BioquímicaIn the present work a stochastic model to be used for analyzing and predicting experimental data from simultaneous thermogravimetric (TG) and differential scanning calorimetry (DSC) experiments on the thermal and catalytic degradation of high-density polyethylene (HDPE) was developed. Unlike the deterministic models, already developed, with this one it’s possible to compute the mass and energy curves measured by simultaneous TG/DSC assays, as well as to predict the product distribution resulting from primary cracking of the polymer, without using any experimental information. For the stochastic model to predict the mass change as well as the energy involved in the whole process of HDPE pyrolysis, a reliable model for the cracking reaction and a set of vaporization laws suitable to compute the vaporization rates are needed. In order to understand the vaporization process, this was investigated separately from cracking. For that, a set of results from TG/DSC experiments using species that vaporize well before they crack was used to obtain a global correlation between the kinetic parameters for vaporization and the number of C-C bonds in the hydrocarbon chain. The best fitting curves were chosen based on the model ability to superimpose the experimental rates and produce consistent results for heavier hydrocarbons. The model correlations were implemented in the program’s code and allowed the prediction of the vaporization rates. For the determination of the global kinetic parameters of the degradation reaction to use in the stochastic model, a study on how these parameters influence the TG/DSC curves progress was performed varying those parameters in several simulations, comparing them with experimental data from thermal and catalytic (ZSM-5 zeolite) degradation of HDPE and choosing the best fitting. For additional improvements in the DSC stochastic model simulated curves, the thermodynamic parameters were also fitted. Additional molecular simulation studies based on quantum models were performed for a deeper understanding on the reaction mechanism and progress. The prediction of the products distribution was not the main object of the investigation in this work although preliminary results have been obtained which reveal some discrepancies in relation to the experimental data. Therefore, in future investigations, an improvement of this aspect is necessary to have a stochastic model which predicts the whole information needed to characterize HDPE degradation reaction.
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Yi, Nan. "Influence of the molecular orientation of high density polyethylene by mechanical drawing on the surface mechanical behaviors." Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAE015.
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Les polymères semi-cristallins ont de multiples applications tribologiques et il est très intéressant d’avoir une compréhension globale de la relation structure-propriété afin d’améliorer leurs performances. Cette thèse porte sur les réponses mécaniques anisotropes des surfaces de polymères semi-cristallins orientés. Ces travaux sur du polyéthylène haute densité (PEHD) ont mis en évidence l’effet de cette anisotropie induite sur le comportement viscoélastique étudié par une méthode de fluage de contact et de récupération, ainsi que sur le comportement plastique en rayure. Les dépendances de l'orientation sur les réponses élastiques, plastiques et viscoélastiques ont été analysées. Une nouvelle configuration expérimentale permet l’observation in situ lors du fluage de contact et de la recouvrance de l’empreinte. Pour la réponse en rayure, le coefficient de frottement apparent a été utilisé pour caractériser le comportement pendant le temps de contact et la géométrie du sillon résiduel pour le comportement post-mortem. En conclusion, il est confirmé que les propriétés intrinsèques volumiques régissent les comportements mécaniques de surface. Le module de Young et le module de relaxation contrôlent principalement le comportement de fluage de contact, tandis que la déformation au seuil de plasticité contrôle les déformations en rayureSemi-crystalline polymers have versatile tribological applications and it is of great interest to have a comprehensive understanding of the structure-property relationship, in order to produce better and durable products. This thesis focuses on the anisotropic mechanical responses of oriented semi-crystalline polymer surfaces. A benchmark study with high-density polyethylene (HDPE) highlighted the effect of this induced anisotropy on the viscoelastic behavior studied by a method of contact creep and recovery, and the plastic behavior examined by single-asperity scratching. In this thesis, the relations between microstructure, intrinsic and surface mechanical properties have been investigated. Orientation dependencies of elastic, plastic, and viscoelastic response were analyzed. A new experimental set-up permits the first-time in-situ observation during the contact creep and recovery test on non-transparent surfaces. For friction response, the apparent coefficient of friction was used to characterize the behavior during the contact time, and the geometry of the residual track for the behavior during the lifetime of the track. In conclusion, it is confirmed that the intrinsic properties govern the surface mechanical behaviors. Young’s moduli and intrinsic creep compliances dominate the contact creep behaviors. Meanwhile, the scratch responses are largely dictated by the yield behaviors
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Araújo, Maria José Gomes de. "Misturas de PEAD/quitosana: morfologia e caracterização térmica e mecânica." Universidade Federal da Paraíba, 2014. http://tede.biblioteca.ufpb.br:8080/handle/tede/449.
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Previous issue date: 2014-03-21Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
This research have the aim of prepare mixture of high density polyethylene (HDPE) and chitosan (CS) with and without compatibilizers agents. To this, have developed in laboratory, powders by two different methods, precipitation and evaporation. It was used like compatibilizers agents on mixture HDPE/CS. They are chemically modified chitosan with the ammonium alkil organic salt codified as (CS+MA)evap, (CS+MA)prec and the chemically modified clay AN with the respectives samples codified as AN(CS+MA)evap e AN(CS+MA)prec. Next, the HDPE/CS mixture with different proportion 90/10, 80/20, 70/30 and 60/40 in weight fractions with and without compatibilizers, respectively was prepared by internal mixer torque rheometry Haake, operating at 170°C, 60 rpm for 10 min. Every samples was analysed morphologically, thermically and mechanically. Was observed in the differents compositions of MIXTURE that when we decrease the chitosan proportion of the mixture HDPE/CS we have a discrete increase on the crystallinity percentage and an increase on the thermal stability. The FTIR results pointing to absence on interation between both components of mistute HDPE/CS, indicating immiscibility of mixture the obtained analyses by MEV of the fracture surface of mixture 80/20 HDPE/CS for different compositions showing a weak interfacial adhesion. However, the addiction of compatibilizer agent, specially the chemically modified clay AN(CS+MA)prec resulted in greater tendency in the interaction between the components HDPE/CS as consequence of better dispersion of chitosan on HDPE.
A pesquisa teve como objetivo preparar misturas de polietileno de alta densidade (PEAD) e quitosana (CS) sem e com agentes compatibilizantes. Para tanto, foram desenvolvidos em nosso laboratório, pós por dois diferentes métodos, precipitação e evaporação, visando usá-los como agentes compatibilizantes nas misturas PEAD/CS, sendo eles: quitosana modificada quimicamente com o sal orgânico alquil amônio (MA) codificadas como (CS+MA)evap e (CS+MA)prec e a argila AN modificada quimicamente com as respectivas amostras, codificadas como AN(CS+MA)prec e AN(CS+MA)evap. Em seguida, as misturas de PEAD/CS com diferentes proporções 90/10, 80/20, 70/30 e 60/40 em frações mássicas, respectivamente, sem e com agentes compatibilizantes foram preparadas num misturador interno do reômetro de torque Haake, operando a 170°C, 60rpm por 10min. Todas as amostras foram analisadas morfologicamente e caracterizadas termicamente e mecanicamente. Observa-se nas diferentes composições das misturas que à medida que se diminui o teor de quitosana nas misturas PEAD/CS tem-se discreto aumento no grau de cristalinidade assim como aumento na estabilidade térmica das mesmas. Os resultados de FTIR apontam ausência de interação entre ambos os componentes da mistura PEAD/CS, indicando imiscibilidade das mesmas. As análises obtidas por microscopia eletrônica de varredura das superfícies de fratura das misturas 80/20 PEAD/CS para diferentes composições mostraram fraca adesão interfacial. Entretanto, a adição de agentes compatibilizantes, especialmente, a argila modificada quimicamente AN(CS+MA)prec resultou numa maior tendência a interação entre os componentes PEAD/CS como consequência de uma melhor dispersão da quitosana no PEAD.
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Scapini, Patrícia. "Morfologia e propriedades térmicas de compósitos de HDPE/EVA com POSS." reponame:Repositório Institucional da UCS, 2008. https://repositorio.ucs.br/handle/11338/370.
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Neste trabalho foram estudados compósitos que apresentam como matriz polimérica uma blenda composta por polietileno de alta densidade (HDPE) e copolímero etileno acetato de vinila (EVA) e como nanocarga, silsesquioxano poliédrico oligomérico (POSS). Os compósitos foram processados em câmara de mistura fechada e caracterizados quanto às propriedades térmicas e morfológicas. Para a preparação dos compósitos foram variadas as concentrações dos componentes da blenda (0, 25, 50, 75 e 100%) e da nanocarga (0, 0,5, 1, 1,5, 2, 5 e 10%). Os resultados de processamento mostraram que o aumento da concentração de POSS na matriz polimérica provocou a agregação do mesmo na matriz polimérica. As análises de calorimetria diferencial de varredura e termogravimetria indicaram que o POSS não afetou as temperaturas de fusão, cristalização e degradação da matriz polimérica. Os resultados de raios X indicaram que a presença do EVA no compósito promoveu o aparecimento de domínios cristalinos em concentrações menores de POSS. A microscopia eletrônica de varredura indicou que as amostras com 1% de POSS apresentam distribuição homogênea na matriz polimérica. Por outro lado, ocorreu a formação de agregados nas amostras com 5% de POSS. Os valores de Tg obtidos por análise térmica dinâmico-mecânica indicaram que o POSS causou um efeito plastificante na fase HDPE e uma redução da mobilidade na fase EVA. Ocorreu um aumento nos valores de módulo de armazenamento com a incorporação de POSS na matriz polimérica.Submitted by Marcelo Teixeira (mvteixeira@ucs.br) on 2014-05-22T19:03:21Z No. of bitstreams: 1 Dissertacao Patricia Scapini.pdf: 2020883 bytes, checksum: 2c7249d3915135dd5f3cba151cf459db (MD5)
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In this study composites with a polymeric matrix comprising a blend of high density polyethylene (HDPE) and the copolymer ethylene vinyl acetate (EVA), and with polyhedral oligomeric silsesquioxane (POSS) as the nanoclay, were processed and characterized. The composites were processed in a closed mixing chamber and characterized in terms of their thermal and morphological properties. For the preparation of the composites the concentrations of the blend components (0, 25, 50, 75 and 100%) and of the nanoclay (0, 0.5, 1, 1.5, 2, 5 and 10%) were varied. The results of the processing showed that an increase in the POSS concentration in the polymeric matrix caused the aggregation of the system. The differential scanning calorimetry and thermogravimetry analyses indicated that the POSS did not affect the melt, crystallization and degradation temperatures of the polymeric matrix. The X-ray results indicated that the presence of EVA in the composite led to the appearance of crystalline domains at lower POSS concentrations. Scanning electron microscopy indicated that the samples with 1% of POSS have a homogeneous distribution in the polymeric matrix. However, the formation of aggregates occurred in samples with 5% of POSS. The Tg values obtained from the thermo dynamic mechanical analysis indicated that the POSS had a plasticizing effect on the HDPE phase and caused a reduction in the mobility of the EVA phase. There was an increase in the storage modulus values with the incorporation of POSS into the polymeric matrix.
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Palmer, Hilary R. "Bottle water storage location and its impact on microbiogical quality." Honors in the Major Thesis, University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/1304.
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This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.Bachelors
Engineering and Computer Science
Environmental Engineering
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Gill, Yasir Q. "Preparation and characterization of polyethylene based nanocomposites for potential applications in packaging." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/18052.
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The objective of my work was to develop HDPE clay nanocomposites for packaging with superior barrier (gas and water) properties by economical processing technique. This work also represents a comparative study of thermoplastic nanocomposites for packaging based on linear low density polyethylene (LLDPE), high density polyethylene (HDPE) and Nylon12. In this study properties and processing of a series of linear low density polyethylene (LLDPE), high density polyethylene (HDPE) and Nylon 12 nanocomposites based on Na-MMT clay and two different aspect ratio grades of kaolinite clay are discussed.
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Melo, Jessyka Meierjurgen. "Caracterização de compósito produzido com diferentes frações de pó de madeira e polietileno de alta densidade." Universidade Presbiteriana Mackenzie, 2015. http://tede.mackenzie.br/jspui/handle/tede/1359.
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Previous issue date: 2015-06-15The present work aimed to highlight the study of polymeric composite development to be responsible with the environment and with the growth of the recycling of materials, from the use of high-density polyethylene (HDPE) with eucalyptus wood dust from the manufacturing furniture. The study started from a literature search where were analyzed the factors involving the subject in question, highlighting the concept of polymer, synthetic fibers, wood dust presence, and composites to identify and understand the problem in issue. Mechanical, morphological and rheological tests were done with composites with concentrations of 5, 10 and 20% of wood dust in relation to the polymer matrix in order to characterize and compare the obtained materials. It was noted that during the study samples with wood dust had higher mechanical performance compared to pure HDPE sample. Based on this context, this study was developed to analyze the possibilities ahead so the production of HDPE composite from different wood dust fractions.
O presente trabalho teve como objetivo destacar o estudo de desenvolvimento de compósito polimérico responsável com o meio ambiente e com o crescimento da reciclagem de materiais, a partir da utilização de polietileno de alta densidade (PEAD) com pó de madeira de eucalipto, proveniente da fabricação de móveis. O estudo iniciou a partir de uma pesquisa bibliográfica onde foram analisados os principais fatores que envolvem o tema em questão, destacando o conceito de polímero, das fibras sintéticas, a presença do pó de madeira, seus compósitos a fim de identificar e conhecer o problema em questão. O estudo desenvolveu-se a partir de ensaios mecânicos, morfológico e reológico, dos compósitos com as concentrações de 5, 10 e 20% de madeira em relação à matriz polimérica, a fim de caracterizar e comparar os materiais obtidos. Notou-se que durante os estudos as amostras com pó de madeira apresentaram maior desempenho mecânico comparado a amostra de PEAD puro. Baseado neste contexto, este estudo foi desenvolvido visando assim analisar as possibilidades frente a produção do compósito de PEAD a partir de diferentes concentrações de pó de madeira.
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Ansari, Mahmoud. "Rheology and processing of high-density polyethylenes (HDPEs) : effects of molecular characteristics." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/43283.
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In this study, the linear viscoelastic properties of two series of Ziegler-Natta and metallocene HDPEs (ZN-HDPEs and m-HDPEs respectively) of broad molecular weight distribution (MWD) have been studied. Relationships between the zero-shear viscosity and molecular weight (Mw) and molecular weight distribution show that the breadth of the molecular weight distribution (MWD) for m-HDPEs plays a significant role. Other interesting correlations between the crossover modulus and steady state compliance with MWD of both these classes of polymers have also been derived. Finally, the steady-shear viscosities from capillary rheometry are compared with LVE data to check the applicability of the empirical Cox-Merz rule. It is shown that the original Cox-Merz rule is approximately applicable for HDPEs for narrow to moderate MWD and fails for those HDPEs having a wide MWD due to the occurrence of wall slip.
The processing behavior of both series of HDPEs was investigated. Their melt fracture behaviour was studied primarily as a function of Mw and MWD, and operating conditions i.e. temperature and geometrical details and type of die (capillary, slit and annular). It is found that sharkskin and other melt fracture phenomena are very different for these two classes of polymers, although their rheological behaviors are nearly the same for many of these. It is also found that critical conditions for the onset of various melt fracture phenomena depend significantly on the type of die used for their study.
The slip behaviour of these resins was also studied as a function of Mw and MWD. It is found that the slip velocity increases with decrease of Mw, which expected to decay to zero as the Mw approaches a value with characteristic molecular dimension similar to surface asperities. For HDPEs that exhibit stick-slip transition (narrow to moderate MWD), the slip velocity has been found to increase with increase of polydispersity. The opposite dependence is shown for HDPEs of wider molecular weight distribution that do not exhibit stick-slip transition. A criterion is also developed as to the occurrence or not of the stick-slip transition which is found to depend strongly on Mw and its distribution.
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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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Parmar, Harisinh, and h_arzoo@yahoo com. "Rheology Of Peroxide Modified Recycled High Density Polyethylene." RMIT University. Civil, Environmental and Chemical Engineering, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080724.164249.
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Consumption of plastics has increased exponentially, in line with the world's population. Not surprisingly this is reflected in enormous growth of the plastic industry especially during the last five decades. Commensurate with this, waste produced from plastics consumption has created a major environmental problem. Many types of waste disposal methods have been used all over the world so far, but all of them have disadvantages. Furthermore, some methods are responsible for the generation of green house gases and further contribution to global warming. Recently, reduction of green house gas emission has become a target of most industries. Plastic recycling and reuse breaks the cycle of endless production of virgin polymer and thus contributes to a net reduction of green house gas emission. Recycling of plastics should produce materials with improved properties to replace virgin plastics for a variety of applications. Improvement in the properties of recycled plastics can be achieved by blending with other plastics, by filler addition and by modification using free radical initiators. Introduction of the free radical initiator (organic peroxide) during reprocessing of the recycled plastics has been found to offer significant property improvements to the recycled materials. Extremely small amounts of a free radical initiator (typically ranging between 0.01 wt% to 0.2 wt%) is capable of enhancing the properties of the recycled plastics to a great extent. This project investigates the use of free radical initiators in the recycling of post consumer recycled high density polyethylene using reactive extrusion. Both molecular and rheological characterisation of recycled and reprocessed materials was carried out and this was followed by tensile testing of the modified materials to satisfy end use applications such as packaging and drainage piping. Post consumer recycled high density polyethylene (R-HDPE) resin and virgin high density polyethylene (V-HDPE) were reactively extruded with low concentrations of dicumyl peroxide (DCP) and 1, 3 1, 4 Bis (tert- butylperoxyisopropyl) Benzene (OP2) respectively in a twin screw extruder in order to produce modified materials with varying composition (0.0 wt%, 0.02 wt%, 0.05 wt%, 0.07 wt%, 0.10 wt% and 0.15 wt%) of both organic peroxides. Morphological characterisation using modulated differential scanning calorimetry (MDSC) demonstrated that there is a decrease in the crystallinity level for all the modified samples. Shear rheological tests were carried out to study the structure of the modified materials within the linear viscoelastic region. Viscoelastic parameters, such as storage modulus (G'), loss modulus (G
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Lim, Bah Chin. "Impact of blow-moulded high density polyethylene containers." Thesis, Queen Mary, University of London, 1986. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1360.
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SCHINAZI, GUSTAVO. "HIGH-DENSITY POLYETHYLENE COMPOSITES REINFORCED WITH IN2W3O12 NANOPARTICLES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2016. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=29717@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
FUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO
BOLSA NOTA 10
O Polietileno de Alta Densidade (PEAD) é um dos materiais mais conhecidos e é utilizado em diversos campos de aplicação. Apesar de suas inúmeras qualidades, como baixa densidade, alta ductilidade e alta resistência específica, esse material possui algumas desvantagens que limitam a sua aplicabilidade, tais como baixa rigidez, baixa estabilidade térmica e alta expansividade térmica. Por outro lado, existe uma classe seleta de materiais que possuem coeficiente de expansão térmica (CET) negativo ou próximo de zero. Pertencem a esse grupo, por exemplo, as cerâmicas da família A2M3O12, como o In2W3O12 (tungstato de índio). Tendo isso em vista, a proposta deste trabalho foi estudar diferentes métodos de mistura física entre esses dois materiais para fabricar e caracterizar compósitos de PEAD reforçados por nanopartículas de In2W3O12 com CET reduzido e propriedades mecânicas aumentadas em relação ao polímero. Primeiramente, sintetizaram-se nanopartículas de In2W3O12 pelo método de coprecipitação. Suas temperaturas de cristalização (aproximadamente 530 graus Celsius) e de transformação de fase monoclínica/ortorrômbica (259 graus Celsius) foram determinadas por análise térmica simultânea, e seus parâmetros de rede à temperatura ambiente foram determinados por DRX. Além disso, calcularam-se os CET s intrínsecos do In2W3O12 para ambas as suas fases por DRX in situ com temperatura variável. Foi encontrado, pela primeira vez, um CET intrínseco negativo para sua fase ortorrômbica, de alpha1 igual a menos 1,5 multiplicado por 10 elevado a menos 6 e K elevado a menos 1. Em seguida, fabricaram-se compósitos a partir de pellets de PEAD e das nanopartículas de In2W3O12 por microextrusão e microinjeção precedidas por uma etapa de pré-mistura. Dois parâmetros do processo de fabricação foram variados: a fração de carga no compósito (0,5; 2; 4 e 10 por cento) e o método de pré-mistura (sem pré-mistura; por vibração dentro de um moinho sem as bolas de moagem; e em uma autoclave giratória a 190 graus Celsius e pressão ambiente). Finalmente, os compósitos foram caracterizados por ensaios de tração, dilatometria e análise termogravimétrica. Todos os compósitos apresentaram incremento no módulo de elasticidade e no limite de escoamento, obtendo-se aumentos de até 45 por cento e 17 por cento, respectivamente, em relação ao PEAD puro. Os materiais preparados no moinho com 10 por cento p de reforço apresentaram os melhores resultados. De forma geral, os compósitos submetidos a algum tipo de pré-mistura tiveram melhores propriedades mecânicas do que os que não foram pré-misturados. Por outro lado, os compósitos não apresentaram uma grande redução no CET em relação ao PEAD. O melhor resultado encontrado foi uma redução de 6 por cento para os materiais sem pré-mistura com 4 por cento p de reforço. A temperatura de degradação dos compósitos sem pré-mistura também não apresentou melhora significativa. O maior incremento foi de 1,5 por cento em relação ao PEAD puro, encontrado para os materiais com 0,5 por cento p de carga. Finalmente, amostras de PEAD puro submetidas aos diferentes métodos de pré-mistura foram analisados por DSC. Constatou-se que a temperatura de fusão não é alterada, mas a entalpia de fusão e o grau de cristalinidade aumentam com a pré-mistura por vibração (8 por cento) e ainda mais com a pré-mistura na autoclave (15 por cento) em relação ao PEAD puro como recebido.
High-density polyethylene (HDPE) is one of the most widely used materials. Despite its numerous qualities, such as low density, high ductility, and high specific strength, HDPE presents certain disadvantages that limit its applicability, like low stiffness, low thermal stability, and high thermal expansion. In contrast, there is a select group of materials that display negative or near-zero coefficient of thermal expansion (CTE). Ceramics belonging to the A2M3O12 family, which includes In2W3O12 (indium tungstate), are examples of such materials. Therefore, this dissertation proposes to examine different methods of physical mixture in order to produce and characterize HDPE composites reinforced with In2W3O12 nanoparticles with reduced CTE and better mechanical properties than the neat polymer. Firstly, In2W3O12 nanoparticles were synthesized by coprecipitation. Simultaneous thermal analysis proved their crystallization temperature and monoclinic/orthorhombic phase transition temperature to be approximately 530 Celsius degrees and 259 Celsius degrees, respectively. The lattice parameters at room temperature were determined by XRD, and the intrinsic CTE s for both phases were calculated by variable-temperature in situ XRD. For the first time, a negative intrinsic CTE was found for the orthorhombic phase (Alpha 1 equal than minus 1.5 multiplied 10 power minus 6 and K power minus 1). Secondly, composites were produced from HDPE pellets and the In2W3O12 nanoparticles by microextrusion and microinjection preceded by a pre-mixing step. Two fabrication parameters were analyzed: the filler content (0.5, 2, 4, and 10wt percent were used) and the pre-mixing method (no pre-mixture, by vibration within a mill without balls, and in a rotating autoclave at 190 Celsius degrees and ambient pressure). Finally, the composites were characterized by tensile tests, dilatometry, and thermogravimetric analysis. All of the composites presented higher Young s modulus and yield stress than neat HDPE, with increases of up to 45 percent and 17 percent, respectively. The best results were displayed by the materials that were pre-mixed in the mill with 10wt percent filler fraction. In general, both pre-mixing methods improved the composites mechanical properties. On the other hand, the polymer s CTE was not significantly reduced, being decreased by 6 percent in the best case. The degradation temperature showed almost no improvement, with a 1.5 percent increase for the composites with 0.5 percent filler content. Lastly, neat HDPE samples exposed to the different pre-mixing methods were analyzed by differential scanning calorimetry and compared with the as-received pellets. Results showed that the melting temperature was not affected by the mixing techniques, but both the enthalpy of fusion and the degree of crystallinity were increased by 8 percent and 15 percent for the samples pre-mixed by vibration in the mill and by rotation in the autoclave, respectively.
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Lutton, R. "The effect of Maleic Anhydride-grafted-high density polyethylene combatibilisers on the structure and properties of high density polyethylene/montmorillonite nanocomposities." Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.679044.
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Nanocomposites have received a great deal of attention in recent years; particularly polymer layered silicate nanocomposites such as montmorillonite, where the surface to volume ratio is exceptionally high. As a result of their ultrafine phase dimensions, these layered silicate nanocomposites possess unique properties typically not shared by more conventional microcomposites and, therefore, offer new technology and business opportunities. However, despite the attention, the influence of compatibilisers on the nanocomposites is not well understood; more critically, the literature exposes a large degree of disagreement as to the required compatibiliser type for optimal function. This study examines the effect of Maleic Anhydride grafted HDPE compatibilisers, with differing MFls and grafting contents, on the mechanical, thermal an.d rheological properties of HDPE. The materials were compounded in a twin screw extruder before being compression moulded into plaques for characterisation and analysis; this consisted of structural analysis utilising XRD and tensile testing; thermal and rheological characterisation using power compensated DSC, DMTA and a rotational rheometer. The results confirm organo-modification of MMT as sufficient in producing a miscible polymer system; however addition of compatibiliser is best. In an unfilled system, the incorporation of MAH groups cause axis distortion and rearrangement of chain conformation and lattice structure, crosslin king and increase RAF. With the addition of MMT, the MAH groups preferentially interact with the clay changing the crystal type to transcrystalline layers, lowering the Tg whilst simultaneously increasing the modulus. The most effective compatibilisers have a characteristic enabling a more dominant exfoliation mechanism. Intercalated nanocomposites presented the more improved systems, with 4:1 and 5:1, plus 5% clay, being the optimal due to crystallisation between layers. Changes in MFI and grafting are a complicated matrix but higher mobility and grafting is preferred: as opportunity for interaction increases, the likelihood of formation of nanocomposites, and improvement in material properties, increases.
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Rajasekaran, Nepolean. "A Nonlinear Constitutive Model for High Density Polyethylene at High Temperature." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1298041213.
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Lewucha, Cezary. "Stabilisation and characterisation of peroxide-crosslinked high density polyethylene." Thesis, Aston University, 2012. http://publications.aston.ac.uk/26117/.
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Benoit, Nathalie. "Mechanical recycling of high density polyethylene/flax fiber composites." Doctoral thesis, Université Laval, 2017. http://hdl.handle.net/20.500.11794/27713.
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Ce travail de doctorat est consacré à la production, au recyclage mécanique long-terme et à la caractérisation de matériaux polymères et composites à base de polyéthylène haute densité (HDPE) et de fibre de lin. L’objectif est de déterminer l’aptitude au recyclage long-terme de ces composites et de leur matrice, tout en évaluant la perte de performance subie. Le recyclage est réalisé ici par une extrusion en boucle fermée, durant 50 cycles, sans ajout intermédiaire de matières vierges et sans prise en compte de la détérioration et de la contamination subies lors du cycle de vie des produits. Dans la première partie, une revue de littérature présente l’état de l’art concernant le recyclage mécanique des composites thermoplastiques. Les différents types de recyclage de composites sont présentés, ainsi que les différents travaux réalisés sur le recyclage de composites thermoplastiques à base de fibres naturelles ou inorganiques. Enfin, les différentes limitations rencontrées lors du recyclage de ces composites sont mises en lumière et des solutions sont présentées. Au cours de cette revue, des lacunes importantes sur le recyclage mécanique long-terme de ces composites sont observées. Dans la seconde partie de ce travail, le polyéthylène haute densité est étudié et recyclé seul afin de connaître ses propriétés et son comportement au recyclage, tout en servant de base de comparaison pour les composites produits par la suite. L’étude des propriétés physique, thermique, moléculaire et mécanique permet d’analyser les différents mécanismes de dégradation induits par le recyclage mécanique. Les résultats montrent une diminution de la contrainte au seuil d’écoulement et une forte augmentation de l’élongation à la rupture avec le recyclage, indiquant que des phénomènes de rupture de chaînes ont lieu dans le polymère. La plupart des autres propriétés demeurent constantes et confirment le maintien des performances du polymère avec le recyclage. Dans la dernière partie de cette thèse, deux séries de composites sont produites à partir du polyéthylène haute densité et de la fibre de lin (15% en masse), avec et sans polyéthylène greffé d’anhydride maléique (MAPE) comme agent couplant. Toutes deux seront caractérisées similairement au polymère afin d’évaluer l’effet de la présence de fibre dans le polymère. Une analyse de la distribution de fibres est aussi réalisée afin d’observer l’effet du recyclage mécanique sur la taille des fibres. L’analyse mécanique révèle que la fibre fournit un renfort efficace au polymère, en particulier avec l’agent couplant, mais les propriétés à la rupture diminuent. Cet effet diminue avec le recyclage, alors que les propriétés à l’élongation augmentent, du fait de la réduction de longueur des fibres. L’effet de l’agent couplant disparaît aussi au cours du recyclage. Toutefois, la majorité des performances mécaniques après recyclage restent supérieures à celles du polymère.This thesis focuses on the production, the mechanical recycling and the characterization of polymers and composites based on high density polyethylene (HDPE) and flax fibers. It aims to determine the materials potential towards long-term recycling and to evaluate the resulting loss of performance. The recycling is realized by closed-loop extrusion, and repeated up to 50 times, without any addition of new material, and without any consideration of the possible degradation and contamination undergone during the life-cycle of the products. In the first part, a literature review presents the state of the art concerning the mechanical recycling of thermoplastic composites. The various types of composites recycling are introduced, as well as the various works conducted on the recycling of thermoplastic composites reinforced with both natural and inorganic fillers. Finally, the various limitations to the composites recycling are presented and some solutions are suggested. During this review an important lack of knowledge on the long-term mechanical recycling of these composites is observed. In the second part of this work, the high density polyethylene is studied and recycled in order to know its properties and its behavior towards recycling, as well as to be used as a comparison basis for the further parts. The study of the mechanical, thermal, molecular and physical properties leads to the better understanding of the various degradation mechanisms induced by mechanical recycling. The results show a decrease of the yield stress and an important increase of the strain at break with recycling, indicating that chain scissions take place in the polymer during recycling. Most of the other properties remained stable, and confirmed the conservation of the polymer performances with recycling. In the last part of this work, high density polyethylene is used to produce two series of composites with 15% wt. of flax fiber, with and without maleic anhydride grafted polyethylene (MAPE) as a coupling agent. Similar characterizations as for the matrix are conducted on both composites as to evaluate the effect of the fibers in the polymer matrix. A complete analysis of the fiber distribution is also performed to observe the effect of mechanical recycling on the fiber dimensions. The mechanical analysis reveals that the fibers provides an efficient reinforcement to the matrix, and especially with coupling agent, but the properties at break decrease. Nevertheless, this effect decreases with recycling, while the elongation properties increase due to the fiber size reduction. The effect of the coupling agent disappears with recycling. However, most mechanical properties remain higher for the composites after recycling than for the neat matrix.
31
Ou, Byoung S. "Laser welding of high density polyethylene and polypropylene plates." Connect to resource, 1992. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1155307464.
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Lima, Stevie Hallen. "Degrada??o catal?tica de polietileno de alta densidade sobre a ze?lita HZSM." Universidade Federal do Rio Grande do Norte, 2009. http://repositorio.ufrn.br:8080/jspui/handle/123456789/17613.
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Previous issue date: 2009-08-31Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
In last years it has talked a lot about the environment and the plastic waste produced and discarded. In last decades, the increasing development of research to obtain fuel from plastic material, by catalytic degradation, it has become a very attractive looking, as these tailings are discarded to millions worldwide. These materials take a long time to degrade themselves by ways said natural and burning it has not demonstrated a viable alternative due to the toxic products produced during combustion. Such products could bring serious consequences to public health and environment. Therefore, the technique of chemical recycling is presented as a suitable alternative, especially since could be obtain fractions of liquid fuels that can be intended to the petrochemical industry. This work aims to propose alternatives to the use of plastic waste in the production of light petrochemical. Zeolites has been widely used in the study of this process due to its peculiar structural properties and its high acidity. In this work was studied the reaction of catalytic degradation of high-density polyethylene (HDPE) in the presence HZSM-12 zeolites with different acid sites concentrations by thermogravimetry and pyrolysis coupled with GC-MS. The samples of the catalysts were mixed with HDPE in the proportion of 50% in mass and submitted to thermogravimetric analyses in several heating rates. The addition of solids with different acid sites concentrations to HDPE, produced a decrease in the temperature of degradation of the polymer proportional the acidity of the catalyst. These qualitative results were complemented by the data of activation energy obtained through the non-isothermal kinetics model proposed by Vyazovkin. The values of Ea when correlated to the data of surface acidity of the catalysts indicated that there is a exponential decrease of the energy of activation in the reaction of catalytic degradation of HDPE, in function of the concentration of acid sites of the materials. These results indicate that the acidity of the catalyst added to the system is one of the most important properties in the reaction of catalytic degradation of polyethylene
Nos ?ltimos anos tem-se falado muito sobre o meio ambiente e sobre o lixo pl?stico produzido e descartado. Nas ?ltimas d?cadas, o crescente desenvolvimento de pesquisas com o intuito de obter combust?veis a partir de material pl?stico, via degrada??o catal?tica, tem-se tornado uma busca muito atrativa, j? que esses rejeitos s?o descartados aos milh?es em todo mundo. Esses materiais levam muito tempo para se degradar por meios ditos naturais e sua incinera??o n?o tem se demonstrado uma alternativa vi?vel devido aos produtos t?xicos produzidos durante sua combust?o. Tais produtos conseq?entes poderiam trazer s?rios problemas de sa?de p?blica e ambiental. Logo, a t?cnica da reciclagem qu?mica apresenta-se como uma alternativa adequada, inclusive porque podemos obter fra??es leves do petr?leo que podem ser destinadas ao setor petroqu?mico. Este trabalho tem como objetivo propor alternativas para o aproveitamento de lixo pl?stico na produ??o de combust?veis l?quidos. Ze?litas tem sido amplamente utilizada no estudo desse processo devido ?s suas propriedades estruturais peculiares e sua alta acidez. Neste trabalho, investigou-se a rea??o de degrada??o de Polietileno de Alta Densidade (PEAD) na presen?a de HZSM-12, com diferentes concentra??es de s?tios ?cidos, atrav?s da termogravimetria e pir?lise acoplada ? cromatografia ? g?s e ao espectr?metro de massa (Py-GC-MS). As amostras de catalisadores foram misturadas com PEAD na propor??o de 50% em massa e submetidas a an?lises em diferentes taxas de aquecimento. A adi??o de catalisadores com diferentes concentra??es de s?tios ?cidos produziu uma diminui??o na temperatura de degrada??o do pol?mero proporcional ? acidez do catalisador. Estes resultados qualitativos foram complementados por dados da energia de ativa??o (Ea) obtidos atrav?s do modelo cin?tico n?o-isot?rmico proposto por Vyazovkin. Os valores das Ea quando correlacionados com os dados da acidez superficial dos catalisadores, indicaram que h? uma redu??o exponencial da Ea da rea??o catal?tica de degrada??o em fun??o da concentra??o dos s?tios ?cidos dos materiais, indicando que esta propriedade ? significativa neste tipo de rea??o
33
Isik, Coskunses Fatma. "Ternary Nanocomposites Of Low Density,high Density And Linear Low Density Polyethylenes With The Compatibilizers E-ma_gma And E-ba-mah." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613294/index.pdf.
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The effects of polyethylene, (PE), type, compatibilizer type and organoclay type
on the morphology, rheological, thermal, and mechanical properties of ternary
low density polyethylene (LDPE), high density polyethylene (HDPE), and linear
low density polyethylene (LLDPE), matrix nanocomposites were investigated in
this study. Ethylene &ndashMethyl acrylate &ndash
Glycidyl methacrylate terpolymer (E-MAGMA) and Ethylene &ndash
Butyl acrylate- Maleic anhydrate terpolymer (E-BA-MAH) were used as the compatibilizers. The organoclays selected for the study were Cloisite 30B and Nanofil 8. Nanocomposites were prepared by means of melt blending via co-rotating twin screw extrusion process. Extruded samples were injection molded to be used for material characterization tests. Optimum amounts of ingredients of ternary nanocomposites were determined based on to the mechanical test results of binary blends of PE/Compatibilizer and binary nanocomposites of PE/Organoclay. Based on the tensile test results, the optimum contents of compatibilizer and organoclay were determined as 5 wt % and 2 wt %, respectively. XRD and TEM analysis results indicated that intercalated and partially exfoliated structures were obtained in the ternary nanocomposites. In these nanocomposites E-MA-GMA compatibilizer produced higher d-spacing in comparison to E-BA-MAH, owing to its higher reactivity. HDPE exhibited the highest basal spacing among all the nanocomposite types with E-MA-GMA/30B system. Considering the polymer type, better dispersion was achieved in the order of LDPE<
LLDPE<
HDPE, owing to the linearity of HDPE, and short branches of LLDPE. MFI values were decreased by the addition of compatibilizer and organoclay to the matrix polymers. Compatibilizers imparted the effect of sticking the polymer blends on the walls of test apparatus, and addition of organoclay showed the filler effect and increased the viscosity. DSC analysis showed that addition of compatibilizer or organoclay did not significantly affect the melting behavior of the nanocomposites. Degree of crystallinity of polyethylene matrices decreased with organoclay addition. Nanoscale organoclays prevented the alignment of polyethylene chains and reduced the degree of crystallinity. Ternary nanocomposites had improved tensile properties. Effect of compatibilizer on property enhancement was observed in mechanical results. Tensile strength and Young&rsquo
s modulus of nanocomposites increased significantly in the presence of compatibilizers.
34
Zhang, Jingyu Hsuan Grace. "Experimental study of stress cracking in high density polyethylene pipes /." Philadelphia, Pa. : Drexel University, 2006. http://dspace.library.drexel.edu/handle/1860/747.
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Cagirici, Seda. "Graft Copolymerization Of P-acryloyloxybenzoic Acid Onto High Density Polyethylene." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/12607968/index.pdf.
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The monomer, p-acryloyloxybenzoic acid (ABA) was synthesized by condensation reaction of acryloyl chloride and p-hydroxybenzoic acid in alkaline medium. Polymerization of the monomer and grafting of the produced
polymer (PABA) onto high density polyethylene (HDPE) were expected to be carried simultaneously in melt mixing at high temperature. The graft copolymerization was studied at varying concentrations of the monomer in the reaction mixture at constant temperature (200 0C).
Grafted HDPE samples were investigated by several techniques such as DSC, FTIR, MFI and mechanical testing.
The tensile tests of PABA-g-HDPE showed an improvement particularly in stress at yield and Young&rsquos modulus whereas the strain at break values showed a decrease for all compositions compared to neat HDPE.
36
Nahid, Farzana. "The temperature dependence of positronium formation in high density polyethylene." Thesis, Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/HKUTO/record/B39558642.
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Paxton, Naomi C. "Additive manufacturing patient-specific porous high-density polyethylene surgical implants." Thesis, Queensland University of Technology, 2020. https://eprints.qut.edu.au/205616/1/Naomi_Paxton_Thesis.pdf.
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This thesis investigated how 3D printing technology can be used to manufacture patient-specific surgical implants for maxillofacial and cranial reconstruction. Novel 3D printed implants were compared to current clinical gold-standard implants to assess material properties, implant structure and internal architecture, and the impact of manufacturing conditions such as porosity and surface treatments on cell attachment and soft tissue healing in a small animal model. These novel implants demonstrated rapid soft tissue and vascular ingrowth, showing promise for patient-specific implant manufacturing.
38
Joseph, Roy. "Development of an injection moulding grade hydroxyapatite polyethylene composite." Thesis, Queen Mary, University of London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395936.
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Konaganti, Vinod Kumar. "Extrudate swell of high density polyethylene in capillary and slit dies." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/60136.
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The analysis of extrudate swell in polymer melts is of great importance in many polymer processing operations and has been the subject of interest both experimentally and numerically. The main objectives of this research work are to obtain systematic and reliable extrudate swell data of a high molecular weight HDPE, to identify a suitable constitutive model that can precisely represent extrudate swell phenomena and to predict extrudate swell accurately under various processing and operating conditions. A novel extrudate swell measuring system with an online data acquisition system is designed for the present work. This system allows one to measure extrudate swell profile under different conditions such as steady state or transient, gravity free, isothermal and non-isothermal conditions. Further, the set-up is suitable for both capillary and slit extrudates. A comprehensive analysis on the applicability and validity of various rheological (integral and differential/molecular) models in describing extrudate swell of a highly viscoelastic HDPE polymer over a broad range of shear rates (5 to 100s-¹) is carried out using FEM based ANSYS POLYFLOW®. The simulation results indicated that the integral constitutive equations of K-BKZ type can account for the significant memory effects of viscoelastic polymer melts such as HDPE. Overprediction of extrudate swell by the integral K-BKZ model invoked the importance of obtaining non-linear viscoelastic properties for a broader range of deformations/deformation rates. The newly available CPP fixture from AntonPaar is used to procure such non-linear viscoelastic data and thus to determine the accurate damping function. The simulation results of extrudate swell in capillary and slit dies are in good agreement with the experimental measurements using the newly determined damping function. In addition, non-isothermal extrudate swell of the HDPE polymer is studied using the pseudo-time integral K-BKZ Wagner (i.e., the non-isothermal form) model with the differential Nakamura equation for the crystallization kinetics. The model is implemented in ANSYS POLYFLOW®. Extrudate swell measurements are obtained by extruding the polymer melt at 200ºC through long capillary and slit dies to ambient air at 25ºC and 110ºC. The numerical results are found to be in very good agreement with the experimental observations.Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate
40
Barreto, Marie de Chantal. "Crystallisation kinetics of high density polyethylene pre-sheared in the melt." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61763.
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Money, Mark William. "Instrumental falling weight impact testing of polymethacrylate and high density polyethylene." Thesis, Queen Mary, University of London, 1988. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1583.
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A study has been made of the Instrumented Falling Weight Impact Test, investigating and analysing the effect of test parameters and specimen geometry on the characteristic results of the test. Two materials, poly(methylmethacrylate) and high density polyethylene are chosen, which exhibit typical extremes of brittle or ductile behaviour. High speed photography is used to monitor the development of deformation and progress of failure during the impact test. The major features of typical force-time curves obtained from the tests on PMMJL and HDPE are thus characterised in terms of failure development and quantified. Analyses are adopted which enable materials property data, such as modulus, E , fracture or yield stress, [Sigma][Subscript] f , [Sigma] [Subscript] y and a fracture parameter, G [Subscript] c to be obtained from the tests conducted on flat plates. A framework is proposed which would enable extraction of similar materials data from a wide range of plastics during routine testing with the falling weight test method.
42
Xu, Songbo. "Mechanical and Tribological Properties of Carbon Nanofiber Reinforced High Density Polyethylene." Diss., North Dakota State University, 2014. https://hdl.handle.net/10365/27288.
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High density polyethylene (HDPE) is widely used as a bearing material in industrial application because of its low friction and high wear resistance. Reinforcing polymers with the appropriate nanofillers is an effective way to obtain a variety of enhanced material properties. Carbon nanofibers (CNFs) with silane coatings (two thicknesses: 2.8 nm and 46 nm) were added into high density polyethylene (HDPE) to improve the tribological properties of the nanocomposite material. The goal of the present study is to investigate how the mechanical, thermal, and wear behavior of HDPE can be altered by the addition of either pristine or silane treated CNFs at different loading levels (0.5 wt.%, 1 wt.%, and 3 wt.%) and to model the wear of the HDPE/CNF nanocomposites under both dry and lubricated conditions. In this study, the wear and friction tests are performed on a pin-on-disc tribometer under dry, bovine serum, and phosphate buffered saline lubricated conditions. The thermal, mechanical, properties, and biocompatibility of HDPE/CNF nanocomposites are characterized and compared with those of the neat HDPE. The correlations of the wear and factors such as work of fracture, thermal conductivity, and friction force are explored. An energy-based wear model is proposed for the dry sliding condition in which a thermal analysis is derived to trace the friction energy loss in the wear process. A wear model for the lubricated condition is developed with incorporation of elastohydrodynamic lubrication theory and Reye's wear model to predict the long term wear.
43
Taylor, Scott. "The catalytic transformation of polymer waste using modified clay catalysts." Thesis, Sheffield Hallam University, 2002. http://shura.shu.ac.uk/20428/.
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A variety of modified minerals have been screened to determine their effectiveness as agents for the catalytic transformation of the thermally generated off gases arising from the pyrolysis of the polyolefinic plastic High Density Polyethylene (HDPE). This polymer has been shown to degrade through a series of known mechanisms to yield a hydrocarbon product mixture consisting of an homologous series of saturated and unsaturated hydrocarbons which include alk-1-enes, n-alkanes, alk-x-enes and a-w-dienes. Modification treatments have been wide ranging having included activation of the parent mineral by means of pillaring, ion exchange and acid activation. The activated products have been characterised by XRD, XRF, TGA and vibrational spectroscopy. Moreover, evolved gas analysis has been employed to perform catalytic screening runs on these modified minerals. In particular, attention has been paid to the activity of these materials in respect of the formation of potentially fuel applicable hydrocarbons, namely those exhibiting high octane ratings, including aromatics and branched aliphatics from the feedstock species present in the HDPE pyrolysate gas mixture. Pillared clays (PILC's) have proven ineffective in this role as a consequence of their poor reproducibility and lack of selectivity towards the formation of single ring aromatics. Likewise, ion exchange has been found to influence strongly the catalytic behaviour of previously acid activated clays, with autotransformed samples offering dehydrocyclisation (DHC) activity at levels significantly greater than seen with some ion exchanged samples, particularly protons. Acid activated metakaolinites have demonstrated poor selectivity in terms of aromatic formation, although total DHC activity is good. Metakaolin also gave rise to appreciable activity in respect of the formation of the single ring aromatics selected for monitoring in this work. Isomerisation activity was prevalent over these materials, but coking levels were high. Acid activated smectites represent the most suitable candidates to fulfil the role of single step fuel generation from the transformation of the gas stream resulting from HDPE pyrolysis. It has been found that careful control over the chemical and physical properties of acid activated clays can be achieved through consideration of the severity of the activation parameters chosen to induce modification. In addition, the nature of the activated product is strongly dependant on the nature of the base clay. In particular, acid activated beidellites have been shown to exhibit high levels of surface acidity as determined through the thermal desorption of cyclohexylamine. These materials consequently give rise to respectable activity and selectivity in terms of the formation of highly octane rated methyl substituted single ring aromatics, principally trimethylbenzene. In contrast, acid activated montmorillonites have been seen to offer lower levels of total surface acidity and have been shown to be active in promoting skeletal isomerisation reactions to yield branched aliphatics, again, highly octane rated. This activity variation has been attributed to the formation of highly Bronsted acidic silanol containing Surface Localised Acid Pools (SLAP's) on the exposed surfaces of the former as a consequence of the isomorphous substitution patterns observed in the tetrahedral sheets of beidellites.
44
Zhang, Chuntao. "Non-linear mechanical response of high density polyethylene in gravity flow pipes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq21324.pdf.
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Zhang, Yu. "Further application of hydroxyapatite reinforced high density polyethylene composite - skull reconstruction implants." Thesis, Queen Mary, University of London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414001.
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Petiraksakul, Pinsupha. "Effect of stearate/stearic acid coating on filled high density polyethylene properties." Thesis, Loughborough University, 2000. https://dspace.lboro.ac.uk/2134/11166.
Full textAbstract:
High density polyethylene (HDPE) is a widely used plastic but it is also a combustible material. One way of reducing flammability is to add fillers, such as magnesium hydroxide (Mg(OH)2). However, this has a deleterious effect on the mechanical properties of composites. It has been found that one possible method of restoring mechanical properties is to modifY the filler particles with coating agents, such as stearic acid. In the present work, this idea was taken a stage further with the use of various metal stearates (e.g. magnesium stearate, calcium stearate, and zinc stearate) for modifying filler. The fillers examined were magnesium hydroxide and calcium carbonate. A filler loading of 40% w/w was used in all samples. Samples were moulded into a variety of shapes for mechanical testing. Such tests included, tensile, flexural, and impact testing. To obtain deeper understanding of the effect of the coating agents on the fillers, a variety of fundamental tests were carried out. These included Diffuse Reflectance FTIR (DRIFT), Thermal Analysis using a DSC cell, Xray Diffraction (XRD), contact angle measurement. Unfilled HDPE, uncoated filled-HDPE, and coated filled-HDPE were compared using uncoated filled-HDPE as a base line. Uncoated filled-HDPE is more brittle than unfilled HPDE. Surface modification of filler improves the toughness properties. Comparing coated filled-compounds, stearic acid and zinc stearate caused a small improvement, magnesium stearate improved the properties significantly with calcium carbonate while calcium stearate gave the best results for coating magnesium hydroxide. One monolayer coating gave the best compound properties compared to other degrees of coating. Although, tensile/flexural strength was not greatly affected elongation at yield, extension at maximum load, and impact properties increased significantly. DSC was used to observe the disappearance and conversion of coating agents as coating proceeded. X-ray diffraction showed the effect of injection moulding on the orientation of the filler and polymer. During coating of the filler particles, XRD and DSC were used to follow incorporation of stearate particles to produce the monolayer coverage. Surface free energy results showed that surface modification of filler resulted in the reduction of hydrophilicity of filler leading to tougher composites compared with uncoated filled-compounds.
47
Xiang, Dong. "Processing and properties of melt processed high density polyethylene-carbon nanofiller composites." Thesis, Queen's University Belfast, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.676504.
Full textAbstract:
The main aim of this work was to investigate the process-structure-property relationship of high density polyethylene (HOPE)/carbon nanofiller composites. A secondary aim was to develop thin thermoplastic films with enhanced electrical and mechanical properties for the potential use in aerospace applications. Three types of carbon nanofillers with different dimensions, multi-walled carbon nanotubes (MWCNTs), graphite nanoplatelets (GNPs) and carbon black (CB) respectively, were used to reinforce the polymer matrix. The melt-mixed HOPE/carbon nanofiller composites were processed by compression moulding, biaxial stretching and blown film extrusion, and the structure and properties of the resulting composites were characterised. The crystallinity and melting temperature of the material are barely influenced by the addition of carbon nanofillers, while the crystallization temperature is slightly increased due to a heterogeneous nucleation effect. The incorporation of carbon nanofillers has a positive effect on the modulus of the composites studied and a negative effect on the stress at break and strain at break. The relative effectiveness of generating rheological and conductive networks in the polymer is as follows: GNPs < CB < MWCNTs. The inclusion of carbon nanofillers led to significant strain hardening during the biaxial stretching of the material. The carbon nanofillers were further dispersed in the matrix by biaxial stretching. The mechanical properties of all the HOPE/carbon nanofiller composites were clearly improved after biaxial stretching. However, the volume resistivity of biaxially stretched HOPE/carbon nanofiller composites, at loadings lower than 4 wt%, was increased due to the deagglomeration of nanofillers and increased inter-particle distance. Blown films of the HOPE/MWCNT composites were manufactured at blow-up-ratios (BURs) of 2 to 3. The stress at break and strain at break of the composite films increases steadily with increasing BURs. Blown film extrusion also has a destructive effect on the conductive network of MWCNTs. However, there is no significant increase in the resistivity of the composite containing 8 wt% MWCNTs after film blowing at increasing BURs due to a sufficient density of nanotubes forming a robust conductive network .
48
Mitroka, Susan M. "Modulation of Hydroxyl Radical Reactivity and Radical Degradation of High Density Polyethylene." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/77137.
Full textAbstract:
Oxidative processes are linked to a number of major disease states as well as the breakdown of many materials. Of particular importance are reactive oxygen species (ROS), as they are known to be endogenously produced in biological systems as well as exogenously produced through a variety of different means. In hopes of better understanding what controls the behavior of ROS, researchers have studied radical chemistry on a fundamental level. Fundamental knowledge of what contributes to oxidative processes can be extrapolated to more complex biological or macromolecular systems.
Fundamental concepts and applied data (i.e. interaction of ROS with polymers, biomolecules, etc.) are critical to understanding the reactivity of ROS. A detailed review of the literature, focusing primarily on the hydroxyl radical (HO•) and hydrogen atom (H•) abstraction reactions, is presented in Chapter 1. Also reviewed herein is the literature concerning high density polyethylene (HDPE) degradation. Exposure to treated water systems is known to greatly reduce the lifetime of HDPE pipe. While there is no consensus on what leads to HDPE breakdown, evidence suggests oxidative processes are at play.
The research which follows in Chapter 2 focuses on the reactivity of the hydroxyl radical and how it is controlled by its environment. The HO• has been thought to react instantaneously, approaching the diffusion controlled rate and showing little to no selectivity. Both experimental and calculational evidence suggest that some of the previous assumptions regarding hydroxyl radical reactivity are wrong and that it is decidedly less reactive in an aprotic polar solvent than in aqueous solution. These findings are explained on the basis of a polarized transition state that can be stabilized via the hydrogen bonding afforded by water. Experimental and calculational evidence also suggest that the degree of polarization in the transition state will determine the magnitude of this solvent effect.
Chapter 3 discusses the results of HDPE degradation studies. While HDPE is an extremely stable polymer, exposure to chlorinated aqueous conditions severely reduces the lifetime of HDPE pipes. While much research exists detailing the mechanical breakdown and failure of these pipes under said conditions, a gap still exists in defining the species responsible or mechanism for this degradation. Experimental evidence put forth in this dissertation suggests that this is due to an auto-oxidative process initiated by free radicals in the chlorinated aqueous solution and propagated through singlet oxygen from the environment. A mechanism for HDPE degradation is proposed and discussed. Additionally two small molecules, 2,3-dichloro-2-methylbutane and 3-chloro-1,1-di-methylpropanol, have been suggested as HDPE byproducts. While the mechanism of formation for these products is still elusive, evidence concerning their identification and production in HDPE and PE oligomers is discussed.
Finally, Chapter 4 deals with concluding remarks of the aforementioned work. Future work needed to enhance and further the results published herein is also addressed.Ph. D.
49
Traina, Matteo. "Preparation and properties of micro- and nanocomposites based on high density polyethylene." Doctoral thesis, Università degli studi di Trento, 2008. https://hdl.handle.net/11572/368262.
Full textAbstract:
The primary objectives of this thesis were to investigate and compare the fracture and creep behaviour of micro- and nanocomposites based on polyethylene (PE) produced by melt mixing. To achieve these objectives, different fillers were considered: micrometric copper particles, nanometric carbon blacks (CBs) and multiwalled carbon nanotubes (MWCNTs).
In the first part of this dissertation, the fracture behaviour of PE-CB composites was investigated via the Essential Work of Fracture (EWF) approach by producing composites with different CBs in order to investigate the effect of the filler particle size. Moreover, several processing (i.e., extrusion) parameters were varied to obtain different degrees of filler dispersion. Experimental results reveal that fracture toughness increases significantly when CB particle size is smaller and as the extent of dispersion of the filler in the polymer matrix is better. Fracture toughness depends on the thermo-mechanical degradation of the polymer matrix that occurs during extrusion.
In the second part of this project, creep behaviour of PE-based composites was investigated at several temperatures with assistance from the principle of time-temperature superposition. In particular, the effect of filler dimensions was analyzed by comparing viscoelastic results for composites that contain micrometric copper particles (with an average diameter of 15 and 45 μm) and nanometric carbon blacks (with an average diameter of 15 and 30 nm). In general, these fillers substantially increase the creep resistance of PE, and this phenomenon was more prominent at smaller particle size. This effect was detectable in the linear viscoelastic region (i.e. at low stresses or temperatures), and it became more evident in the non-linear viscoelastic region (i.e. at high stresses or temperatures). In particular, creep compliance and creep rate decrease at smaller particle size. It is postulated that filler particles function as physical crosslink junctions which hinder polymer chain motion and reduce creep deformation. When particle size is reduced at constant filler volume fraction, the physical crosslink density increases such that chain mobility decreases significantly under stress.
Finally, the creep behaviour of PE-MWCNT composites were investigated via direct dispersion of MWCNT in the polymer matrix and by using a commercial masterbatch of MWCNT. In all cases, the increase in creep resistance is statistically significant in the linear viscoelastic region (i.e. at low stresses or temperatures) when sufficient dispersion of the nanotubes is achieved. Interestingly enough, creep resistance increases in the non-linear viscoelastic region (i.e. at high stresses or temperatures) regardless of the degree of nanotube dispersion in the matrix. This phenomenon is attributed to nanotube orientation induced by high levels of stress.
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Traina, Matteo. "Preparation and properties of micro- and nanocomposites based on high density polyethylene." Doctoral thesis, University of Trento, 2008. http://eprints-phd.biblio.unitn.it/105/1/TRAINA-Matteo_PhD-thesis-2008_200DPI.pdf.
Full textAbstract:
The primary objectives of this thesis were to investigate and compare the fracture and creep behaviour of micro- and nanocomposites based on polyethylene (PE) produced by melt mixing. To achieve these objectives, different fillers were considered: micrometric copper particles, nanometric carbon blacks (CBs) and multiwalled carbon nanotubes (MWCNTs).
In the first part of this dissertation, the fracture behaviour of PE-CB composites was investigated via the Essential Work of Fracture (EWF) approach by producing composites with different CBs in order to investigate the effect of the filler particle size. Moreover, several processing (i.e., extrusion) parameters were varied to obtain different degrees of filler dispersion. Experimental results reveal that fracture toughness increases significantly when CB particle size is smaller and as the extent of dispersion of the filler in the polymer matrix is better. Fracture toughness depends on the thermo-mechanical degradation of the polymer matrix that occurs during extrusion.
In the second part of this project, creep behaviour of PE-based composites was investigated at several temperatures with assistance from the principle of time-temperature superposition. In particular, the effect of filler dimensions was analyzed by comparing viscoelastic results for composites that contain micrometric copper particles (with an average diameter of 15 and 45 μm) and nanometric carbon blacks (with an average diameter of 15 and 30 nm). In general, these fillers substantially increase the creep resistance of PE, and this phenomenon was more prominent at smaller particle size. This effect was detectable in the linear viscoelastic region (i.e. at low stresses or temperatures), and it became more evident in the non-linear viscoelastic region (i.e. at high stresses or temperatures). In particular, creep compliance and creep rate decrease at smaller particle size. It is postulated that filler particles function as physical crosslink junctions which hinder polymer chain motion and reduce creep deformation. When particle size is reduced at constant filler volume fraction, the physical crosslink density increases such that chain mobility decreases significantly under stress.
Finally, the creep behaviour of PE-MWCNT composites were investigated via direct dispersion of MWCNT in the polymer matrix and by using a commercial masterbatch of MWCNT. In all cases, the increase in creep resistance is statistically significant in the linear viscoelastic region (i.e. at low stresses or temperatures) when sufficient dispersion of the nanotubes is achieved. Interestingly enough, creep resistance increases in the non-linear viscoelastic region (i.e. at high stresses or temperatures) regardless of the degree of nanotube dispersion in the matrix. This phenomenon is attributed to nanotube orientation induced by high levels of stress.