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1
Mizutani, T., H. Semi, and K. Kaneko. "Space charge behavior in low-density polyethylene." IEEE, 2000. http://hdl.handle.net/2237/6796.
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Yiangou, Savvakis Chrysostomou. "Fatigue crack propagation in low density polyethylene." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47317.
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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 °<br>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<br>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.
4
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 &ndash<br>Methyl acrylate &ndash<br>Glycidyl methacrylate terpolymer (E-MAGMA)
and Ethylene &ndash<br>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<<br>LLDPE<<br>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<br>s modulus of nanocomposites increased significantly in the presence
of compatibilizers.
5
Karl, Michelle Marie. "Modelling the viscoelastic properties of low density polyethylene." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0013/MQ52585.pdf.
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Rabie, Allan John. "Blends with low-density polyethylene (LDPE) and plastomers." Thesis, Stellenbosch : Stellenbosch University, 2004. http://hdl.handle.net/10019.1/49870.
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Thesis (MSc)--Stellenbosch University, 2004.<br>ENGLISH ABSTRACT: This study describes the design, building and optimization of a fully functional
preparative TREF (Prep-TREF) apparatus. This apparatus allows for the fractionation of semicrystalline
polyolefins according to the crystallizability of the molecules. Various factors, such as
the sample cooling rate and the effect of on-support and off-support crystallization, are
investigated.
The preparative TREF is used to fractionate a commercial low-density polyethylene
(LOPE), two commercially available plastomers (polyethylene-l-octene copolymers), as well as
blends of the LOPE and the respective plastomers. It is shown that in each case the samples
fractionated by crystallizability. The fractions recovered from the Prep-TREF were characterized
by CRYSTAF, OSC and NMR analysis. It is shown how the results of this preparative
fractionation allow for a better understanding of the molecular heterogeneity in the LOPE and
plastomers.
New ways of presenting the data from the preparative fractionation, in terms of 3-
dimensional plots, are also investigated. These plots offer a novel way of presenting the
molecular heterogeneity in the samples in terms of the molecular crystallizability. These plots
highlight features that are difficult to detect in the conventional two-dimensional plots.
In conclusion, the influences of various blending ratios of LOPE and plastomer on the
morphological and physical properties of the blends, such as haze, clarity, and tear-and impact
strength are determined.<br>AFRIKAANSE OPSOMMING: Die doel van hierdie studie was die ontwikkeling en optimisering van 'n ten volle
funksionerende TREF. Hierdie tegniek word gebruik om polimeermengsels te fraksioneer deur
gebruik te maak van die kristaliseerbaarheid van polimere. Verskeie faktore soos die afkoel
spoed en die effect van met en sonder 'n ondersteuning(seesand) vir kristaliseering was
ondersoek.
Hierna is navorsing gedoen om 'n beter begrip ten opsigte van die meganiese, fisiese en
optiese eienskappe van lae-digtheid poliëtileen (LDPE) te ontwikkel. Hierdie LDPE is met die
affiniteitsreeks plastomere van die maatskappy, Dow Chemicals, gemeng om tendense in die
gefraksioneerde polimere te indentifiseer.
Een van Sasol se kommersiële LDPE produkte en twee van Dow Chemicals se
plastomere is individueel gefraksioneer. Die mengsel van die twee ongefraksioneerde LDPE en
plastomere is nog nooit voorheen op 'n molekulêre basis ondersoek nie. Dit is in hierdie studie
gedoen deur van TREF gebruik te maak.
Nuwe maniere is ontwikkel om data op 'n nuwe manier voor te stel deur middel van 3
Dimensionele grafieke te skep om resultate voor te stel wat andersins baie moelilik was om
voor te stel in een dimensie agv die hoeveelheid data wat geinterpreteer word.
Ten slotte is die invloed van die verskillende mengverhoudings van LDPE en plastomere
op die morfologiese en fisiese eienskappe soos deursigtigheid, helderheid, skeur- en
impaksterkte, ook ondersoek.
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Mizutani, T., H. Semi, K. Kaneko, T. Mori, and M. Ishioka. "Space Charge and Field Distributions in Low-Density Polyethylene." IEEE, 2000. http://hdl.handle.net/2237/7178.
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Feng, Lijun 1966. "Melting and crystallization behavior of linear low-density polyethylene." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86069.
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The melting and crystallization behavior of linear low-density polyethylene (LLDPE) is of great scientific and industrial importance. It depends strongly on polymer molecular structural characteristics and processing conditions, and determines polymer application properties. In this work, we study three different types of LLDPE polymers: metallocene-based LLDPEs (m-LLDPEs), Ziegler-Natta-based LLDPEs (ZN-LLDPEs), and m-LLDPE blends.<br>A generalized equation is introduced to clarify conceptual definitions of polymer melting temperatures. It incorporates the effects of comonomer volume, crystal length, folding surface free energy and enthalpy of fusion. It is successful in describing the characteristic melting temperatures of various alpha-alkene-ethylene copolymers. The proposed equation is used, along with melting traces obtained by differential scanning calorimetry (DSC), to estimate the crystal size number distributions. Furthermore, the melting temperature characteristics are identified, using crystal size number distributions.<br>The crystallization behavior of LLDPEs is studied by polarized light microscopy (PLM) and DSC. A modified Hoffman-Lauritzen (MHL) expression is proposed for the linear crystallization kinetics by replacing the equilibrium melting temperature, Tm0, with the melting temperature of the crystal stem with the maximum possible length, TmC,n*. The concept of the effective nucleation induction time is introduced, in order to employ the Avrami equation to analyze the overall crystallization kinetics during the initial crystallization stage.<br>The MHL analysis suggests the presence of three crystallization regimes: regimes III and II, and a special regime IM. The Avrami exponents are respectively 2, 1.5, and 1 in these regimes. The typical optical morphology of LLDPEs is spherulitic. As the crystallization temperature increases, the morphology changes from spherulites without ring bands, to ring-banded spherulites and sometimes to irregular structure with rough ring bands. These structural characteristics seem to correspond to MHL regimes.<br>Non-linear spherulitic growth behavior is observed in regimes II and IM. This behavior is explained by the reduction of the concentration of crystallizable ethylene sequences in the melt phase. The MHL expression may be still used to analyze non-linear growth crystallization kinetics by employing a variable TmC,n*.
9
Burnett, Connah Andrew. "Radical block copolymers of linear low density polyethylene macromonomers." Thesis, University of Warwick, 2018. http://wrap.warwick.ac.uk/106401/.
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Chapter 1 introduces the concept of wax crystal modification in middle distillate fuels and reviews the more common chemical additives used commercially, and by examination of the advantages and drawbacks of these additives discusses the possible benefits of polyolefin block copolymers. From this end functionalisation of polyethylene (PE) as a route to block copolymers is reviewed from different literature methods for their synthesis. Chapter 2 introduces the catalytic hydride insertion polymerisation mechanism as a route to end functional polyolefins and goes on to focus on the production of end functional ethylene/hexene copolymers. Using a range of comonomer concentrations and a number of catalysts, end-functional copolymers with a range of comonomer incorporation are produced. The thermal properties of these polymers are investigated and matrix assisted laser desorption/ionisation (MALDI) mass spectra were acquired. Finally, the chapter discusses the synthesis of short chain analogues of end functional PE. Chapter 3 describes the production of polyolefin-polar block copolymers via the free radical polymerisation of the functional polyolefins with a range of polar monomers. A reversible termination mechanism similar to nitroxide mediated polymerisation is proposed. The products are analysed by gel permeation chromatography (GPC) and by an in detail 2D NMR study to confirm block copolymer structure. Chapter 4 examines the physical properties of the synthesised block copolymers. The tendency of the copolymers to aggregate in solution into particles of varying size is investigated by VT NMR and dynamic light scattering (DLS), these findings were supported by transmission electron microscopy (TEM). The thermal properties of these copolymers were studied by differential scanning calorimetry (DSC). Following this the efficacy of these polymers as wax crystal modifiers (WCM) for fuels was investigated by cold flow plugging point (CFPP), optical microscopy and DSC of the treated fuels. Finally, the behaviour of the polymers in solid polyethylene wax was investigated by drop shape analysis (DSA) and x-ray photoelectron spectroscopy (XPS). Chapter 5 details the various experimental procedures used to carry out the work in this thesis. Appendix A gives an overview of polymerisations between ethylene and α- methylstyrene comonomers catalysed by hafnocene catalysts and goes on to detail the investigation of the materials acquired. Analysis was conducted using 2-D NMR, MALDI and diffusion-ordered spectroscopy (DOSY). Appendix B contains the DLS correlograms for samples analysed in chapter 4. Appendix C contains the schematic diagram for the gas burettes system used for metallocene polymerisations.
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Sworen, John Christopher. "Modeling linear-low density polyethylene copolymers containing precise structures /." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0006610.
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Brunson, Jerilyn. "Hopping Conductivity and Charge Transport in Low Density Polyethylene." DigitalCommons@USU, 2010. https://digitalcommons.usu.edu/etd/562.
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The properties and behaviors of charge transport mechanisms in highly insulating polymers are investigated by measuring conduction currents through thin film samples of low density polyethylene (LDPE). Measurements were obtained using a constant voltage method with copper electrodes inside a chamber adapted for measurements under vacuum and over a wide range of temperatures and applied fields. Field-dependent behaviors, including Poole-Frenkel conduction, space charge limited current (SCLC), and Schottky charge injection, were investigated at constant temperature. These field-dependent mechanisms were found to predict incorrect values of the dielectric constant and the field dependence of conductivity in LDPE was not found to be in agreement with SCLC predicted behavior. A model of thermally assisted hopping was a good fit at low applied fields and produced activation energies within the accepted range for LDPE. Low applied field measurements over the range of 213 K to 338 K were used to investigate two prominent hopping conduction mechanisms: thermally assisted hopping and variable range hopping. The observed temperature dependence of LDPE was found to be consistent with both thermally assisted hopping and variable range hopping. Activation energies determined for the range of temperatures were consistent with values reported in the literature for LDPE under similar conditions. A third aspect of charge transport behavior is a bulk response with time dependence. Conductivity behavior is examined in relation to transient current behavior, long time decay currents, and electrostatic discharge. Comparing charging and discharging cycles allowed qualitative separation of polarization and multiple trapping behaviors.
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Kaneko, K., H. Semi, T. Mizutani, T. Mori, and M. Ishioka. "Charge Transport and Space Charge Formation in Low-Density Polyethylene." IEEE, 2000. http://hdl.handle.net/2237/7177.
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Taniguchi, Yoshihide, Kazue Kaneko, Teruyoshi Mizutani, and Mitsugu Ishioka. "Space Charge in Low Density Polyethylene Prepared by Metallocene Catalyst." IEEE, 2001. http://hdl.handle.net/2237/7164.
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Hori, T., K. Kaneko, T. Mizutani, and M. Ishioka. "Space charge distribution in low-density polyethylene with blocking layer." IEEE, 2003. http://hdl.handle.net/2237/7165.
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Xu, Zhiqiang. "Space charge measurement and analysis in low density polyethylene films." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/69927/.
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The growing requirement of reliability for an insulation system gives researchers greater responsibility to investigate new techniques for monitoring and diagnosing dielectrics subjected to an electric field. It is well known that the presence of space charge is one of the important factors causing premature failure of polymeric high voltage cables. Space charge surveillance is becoming the most general applied skill to evaluate polymeric materials, particularly high voltage cables. The well-known pulsed electroacoustic method (PEA), a reliable non-destructive method, gives a reasonable resolution to the concentration of the space charge in the insulation material. My work contributes to the measuring of space charge in low density polyethylene using PEA. From the experiments to study space charge formation and distribution at the interface on multi-layer sample under DC and AC applied voltage, electrode materials and frequency are determined as two important factors in measuring the charge injection and distribution; the interface between films acts as a trap for charge carriers, especially for electrons; and positive charge has a high mobility compared to negative charge. Surface potential decay was studied to explain the crossover phenomenon and to find physical mechanism on charge decay of the corona charged film sample. Charge mapping technique (PEA) was successfully introduced to the potential study and it provides an alternative way to investigate charge decay process and allows monitoring charge migration through the bulk of corona charged film. One essential phenomenon, bipolar charge injection, has been first derived from the results of space charge distribution. The advanced PEA measurement system with high rate test and excellent phase resolving capability was designed in the last part of the study. Compared with the old system the new system can provide the enhanced experiment result for fast change situation, which can achieve high-quality diagnosis for the virtual industry situation such as polarity reversal and transient voltage failure.
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Häfele, Martin. "Modelling and analysis of a production plant for low density polyethylene." [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=983643849.
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Dogan, Erkan. "Ter Blend Of Poly (ethylene Terephthalate), Polypropylene And Low Density Polyethylene." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/4/1045574/index.pdf.
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This study covers the recycling of waste poly(ethylene terephthalate) (PET) bottles through melt blending with low density polyethylene (LDPE) and polypropylene (PP). In general, polymer blends are known to be immiscible and incompatible with poor mechanical properties. This problem is due to the low intermolecular forces between the components of the immiscible blends. In order to enhance the interaction and compatibility between these matrices, some reactive or non-reactive copolymers were used. In this work<br>PET was treated with silane coupling agent (SCA) (low molecular weight reactive additive) for compatilization of LDPE-PP-PET blends. LDPE-PP-PET blends were prepared in different compositions (by weight) with and without silane coupling agent at high temperatures by a single screw extrusion and injection molding. Mechanical properties of treated and non-treated blends were studied in terms of tensile strength, strain at break and impact strength. Melt flow properties of blends were investigated by melt flow index. The impact fractured surfaces and thermal behaviour of the blends were examined with Scanning Electron Microscope (SEM) and Differential Scanning Calorimeter (DSC), respectively. Through out the studies, good adhesion between PET and LDPE-PP matrix was successfully achieved by the surface treatment of PET particles. The adhesion was also observed in SEM studies. Also the variation in mechanical properties was found to be highly dependent on the number of extrusion.
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Mizutani, Teruyoshi, Kenta Shinmura, Yoshihide Taniguchi, Kazue Kaneko, and Mitsugu Ishioka. "Effect of Anti-Oxidants on Space Charge in Low-Density Polyethylene." IEEE, 2001. http://hdl.handle.net/2237/7171.
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Pena, Vivar Jose Miguel. "Interactions of carbon black with stabilisers in low density polyethylene stabilisation." Thesis, Manchester Metropolitan University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324004.
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Ellis, Vibhootr. "A study of the rotational moulding of linear low density polyethylene." Thesis, De Montfort University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.685933.
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Mohammadi, Hadi. "On the Melting and Crystallization of Linear Polyethylene, Poly(ethylene oxide) and Metallocene Linear Low-Density Polyethylene." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/84921.
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The crystallization and melting behaviors of an ethylene/1-hexene copolymer and series of narrow molecular weight linear polyethylene and poly(ethylene oxide) fractions were studied using a combination of ultra-fast and conventional differential scanning calorimetry, optical microscopy, small angle X-ray scattering, and wide angle X-ray diffraction.
In the case of linear polyethylene and poly(ethylene oxide), the zero-entropy production melting temperatures of initial lamellae of isothermally crystallized fractions were analyzed in the context of the non-linear Hoffman-Weeks method. Using the Huggins equation, limiting equilibrium melting temperatures of 141.4 ± 0.8oC and 81.4 ± 1.0oC were estimated for linear polyethylene and poly(ethylene oxide), respectively. The former and the latter are about 4oC lower and 12.5oC higher than these predicted by Flory/Vrij and Buckley/Kovacs, respectively. Accuracy of the non-linear Hoffman-Weeks method was also examined using initial lamellar thickness literature data for a linear polyethylene fraction at different crystallization temperatures. The equilibrium melting temperature obtained by the Gibbs-Thomson approach and the C2 value extracted from the initial lamellar thickness vs. reciprocal of undercooling plot were similar within the limits of experimental error to those obtained here through the non-linear Hoffman-Weeks method.
In the next step, the Lauritzen-Hoffman (LH) secondary nucleation theory was modified to account for the effect of stem length fluctuations, tilt angle of the crystallized stems, and temperature dependence of the lateral surface free energy. Analysis of spherulite growth rate and wide angle X-ray diffraction data for 26 linear polyethylene and 5 poly(ethylene oxide) fractions revealed that the undercooling at the regime I/II transition, the equilibrium fold surface free energy, the strength of the stem length fluctuations and the substrate length at the regime I/II transition are independent of chain length. The value of the equilibrium fold surface free energy derived from crystal growth rate data using the modified Lauritzen-Hoffman theory matches that calculated from lamellar thickness and melting data through the Gibbs-Thomson equation for both linear polyethylene and poly(ethylene oxide). Larger spherulitic growth rates for linear polyethylene than for poly(ethylene oxide) at low undercooling is explained by the higher secondary nucleation constant of poly(ethylene oxide). While the apparent friction coefficient of a crystallizing linear polyethylene chain is 2 to 8 times higher than that of a chain undergoing reptation in the melt state, the apparent friction coefficient of a crystallizing poly(ethylene oxide) chain is about two orders of magnitude lower. This observation suggests that segmental mobility on the crystal phase plays a significant role in the crystal growth process.
In case of the statistical ethylene/1-hexene copolymer, the fold surface free energies of the copolymer lamellae at the time of crystallization and melting increase with increasing undercooling, approaching the same magnitude at high undercooling. As a result of this temperature dependence, the experimental melting vs. crystallization temperature plot is parallel to the Tm = Tc line and the corresponding Gibbs-Thomson plot is non-linear. This behavior is attributed to the fact that longer ethylene sequences form a chain-folded structure with lower concentration of branch points on the lamellar surface at lower undercooling, while shorter ethylene sequences form lamellar structures at higher undercooling exhibiting a higher concentration of branch points on the lamellar surface. Branch points limit the ability of lamellar structures to relax their kinetic stem-length fluctuations during heating prior to melting.<br>Ph. D.
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Coppard, Robert William. "Contamination and fine melt filtration of low density polyethylene power cable insulation." Thesis, Brunel University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253456.
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Oldervoll, Frøydis. "Electrical and Thermal Ageing of Extruded Low Density Polyethylene Insulation Under HVDC Conditions." Doctoral thesis, Norwegian University of Science and Technology, Department of Electrical Power Engineering, 2000. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-208.
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<p>After extensive research during the last decades extruded polymeric insulation is now becoming an alternative to the traditional oil-paper systems for high voltage DC (HVDC) cables. Durability is of great importance for power cables, and the main purpose of this work has been to increase the knowledge of factors controlling the endurance of an extruded polymeric insulation under HVDC conditions. The effect of electrical and thermal ageing on electrical properties like space change accumulation, DC breakdown strength and electrical tree initiation has been investigated and related to changes in morphology, oxidation level and antioxidant concentration.</p><p>Low density polyethylene (LDPE) with and without an antioxidant additive was selected as insulating material. Test objects with plane electrodes or needle-plane electrodes were prepared by pressure moulding and equipped with aluminium electrodes. Iron particles with a diameter of 45 – 55 μm were introduced to simulate conducting contaminations in the insulation. The test objects were subjected to thermal ageing of 70°C and 90°C and the applied electrical field during ageing ranged from zero to 150 kV/mm. ageing was conducted both with constant DC polarity and with polarity reversals. The ageing period ranged from 4 weeks to 5 months.</p><p>Thermal oxidation was observed in LDPE without antioxidant and this clearly affected the electrical properties. The DC breakdown voltage was reduced by 40% and this was explained by enhanced high-field conduction and increased joule heating due to the oxidation products. It was found that oxidation was prohibited when the thickness of the aluminium electrodes increased. </p><p>Introduction of iron particles reduced the short term DC strength by 20 – 30%, but during long term ageing with constant DC voltage no difference was observed between test objects with and without particles. This was probably caused by screening of the particles by accumulated space charge. </p><p>The experiments showed that abrupt grounding or polarity reversal initiated electrical trees from the needle-electrodes. The longest trees were observed when the test objects had first been subjected to thermal and electrical ageing. The tree formation was caused by the high electrical field arising when the accumulated homocharge around the needle was converted to heterocharge at polarity or grounding,</p><p>The following main conclusions were made from the work:</p><p>*Oxidation is detrimental and must be avoided in HVDC insulation.</p><p>* The antioxidant additive can have a negative influence on the electrical properties under HVDC stress.</p><p>*Polarity reversal or abrupt grounding can initiate electrical trees from protrusions present at the electrode-insulation interface of a HVDC insulation system. </p>
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Singh, Priti. "Morphology and rheology of binary blends of polypropylene and linear low density polyethylene." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0019/MQ49686.pdf.
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GOMES, BRUNA MARIA DA CUNHA. "PRODUCTION AND CHARACTERIZATION OF LOW DENSITY POLYETHYLENE FILMS REINFORCED WITH TIO2 BASED NANOMATERIALS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2011. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=21691@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO<br>Materiais plásticos são largamente utilizados em nosso dia-a-dia em
embalagens, sacos e outros produtos. Este tipo de material é utilizado devido a
suas propriedades como baixo custo, fácil processabilidade, baixa densidade,
resistência a microorganismos e água, estabilidade química e durabilidade. Devido
às duas últimas propriedades, os polímeros apresentam baixa degradabilidade,
causando problemas ambientais. Como óxido de titânio (TiO2) tem se apresentado
eficiente como fotocatalisador, reforçar plástico com partículas deste material tem
sido uma nova maneira de decompor polímeros a céu aberto. Nanotubos de
trititanato (TTNT) podem ser tratados para produzir nanomateriais à base de TiO2
com alta atividade fotocatalítica para a degradação de gases poluentes. Desta
forma, o presente trabalho tem como objetivo produzir e caracterizar filmes de
polietileno reforçados com quatro tipos de nanomateriais à base de TiO2: TTNT
sem pós-tratamento (A1), TTNT pós-tratado termicamente a 550 graus Celsius (A5), TTNT
pós-tratado com ácido (A11) e, como referência, partículas de óxido de titânio
comercial fornecido pela Degussa (P-25). Os filmes foram expostos à luz UV em
uma caixa fechada por 350 horas em temperatura ambiente. A degradação foi
avaliada por meio da perda de peso do filme ao longo do tempo. Os filmes virgens
e fotodegradados foram caracterizados por Difração de Raios-X (DRX),
Calorimetria diferencial de Varredura (DSC), Termogravimetria (TGA) e
Microscopia Eletrônica de Varredura (MEV). Os filmes com TTNT pós-tratado
fotodegradaram mais do que os com TTNT não tratado, mas menos que os que continham TiO2. Este resultado foi parcialmente atribuído à dificuldade de
dispersão dos nanomateriais.<br>Plastic materials are widely used in our daily lives in bags, food packaging
and other products and applications. This type of material is used because of
properties such as low-cost, easy processability, low density, resistance to water
and microorganisms, and chemical stability and durability. Due to the last two
properties, polymers show low biodegradability causing enviro nmental pollution.
As titanium dioxide (TiO2) has been shown to be an efficient photocatalyst, the
mixture of plastic with this material has been proven to be a new and useful way
to decompose solid polymers in open air. Trititanate nanotubes (TTNT) can also
be used as a route for developing TiO2-based nanomaterials with high
photocatalytic activity for degradation of gas pollutants. Thus, the present
research aims to produce degradable polyethylene polymer (PE) films composed
with four types of TiO2-based nanomaterials: TTNT as synthesized (A1), TTNT
with thermal post-treatment at 550 Celsius degrees (A5), TTNT with acid post-treatment (A11),
and, as a reference, commercial TiO2 nanoparticles from Degussa Company
(P25).The main characterization tool was the weight reduction measurement
during the degradation process. The films were exposed to artificial UV light
under ambient air for 350 hours. Virgin and degraded filmes where characterized
by X-ray Diffraction, UV-Vis absorption, Differential Scanning Calorimetry
(DSC), Thermogravimetric Analysis (TGA), and Scanning Electron Microscopy
(SEM). Films with post-treated TTNT showed stronger degradation than films
with non-treated loads, but weaker than films containing TiO2. This result was
partially assigned to the poor dispersion of the nanomaterials.
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Keulder, L. "The effect of molecular composition on the properties of linear low density polyethylene." Thesis, Stellenbosch : University of Stellenbosch, 2008. http://hdl.handle.net/10019.1/2929.
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Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2008.<br>In this study linear low density polyethylene (LLDPE), a copolymer consisting of ethylene and 1-butene, was fractionated by the use of temperature rising elution fractionation (TREF). These fractions were then analyzed by crystallisation analysis fractionation, 13C NMR, high temperature size exclusion chromatography and DSC. The molecular distribution of the polymer was investigated. It was found that the polymer had a very broad distribution in its chemical composition. From these results it was also clear that the catalysts used for the polymerisation consist out of different active sites, producing chains with different molecular architecture.
Subsequently the polymer was fractionated again by TREF and certain fractions were removed and the remaining material recombined. The removed fractions and recombined material were analyzed by 13C NMR, high temperature size exclusion chromatography, DSC and DMA. The results were compared with the bulk material and from this we could conclude the influence of the fractions removed on the material properties. This gave us more information on the influence of the chemical structure of the polymer on its mechanical properties. It was clear that by removing certain fractions with a certain chemical composition, the properties of the polymer are significantly influenced.
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Hussin, Nuriziani. "The effects of crosslinking byproducts on the electrical properties of low density polyethylene." Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/201957/.
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Crosslinked polyethylene (XLPE) is widely used for high voltage insulation in power transmission systems. However, it has been found that, after crosslinking with Dicumyl Peroxide (DCP), the crosslinking byproducts such as acetophenone, α-methylstyrene and cumyl alcohol have a significant influence on electrical properties of XLPE power cables. This thesis distinguished the individual contribution of the crosslinking byproducts on space charge formation, dielectric properties, dc conductivity as well as the ac breakdown strength. Percentage weight increases as well as the Fourier Transform Infrared (FTIR) spectrum were used to monitor the chemical level in the soaked samples. Despite high concentration of byproducts in the LDPE film compared to practical, the measurement results have successfully reveal the contribution of each byproduct on the electrical properties. It should be noted that some consideration should be taken when taking the quantitative value from the result obtained. Space charge accumulation was measured using the pulsed electroacoustic (PEA) technique. Homocharges are observed in acetophenone and α-methylstyrene soaked LDPE. Meanwhile heterocharge formed in cumyl alcohol soaked LDPE. From the charge decay profile in dc condition, these chemicals are observed to assist the transportation of the charges in the sample bulk due to shallow traps from the byproducts. These shallow traps assist the trapping process into deep traps when ac field is applied to the byproduct soaked LDPE. As a result, more charges trapped in deep traps were found in soaked LDPE compared to clean LDPE. In addition, from the space charge measurement in ac condition, it is proved that the amount of charge trapped in deep traps also depends on the population of shallow traps in the polymer which is contradicted to the literature where the byproducts are normally associated to the deep traps. Permittivity values of acetophenone, α-methylstyrene soaked LDPE and cumyl alcohol are slightly higher than permittivity value of the clean untreated LDPE. Cumyl alcohol soaked LDPE has higher dielectric loss at lower frequency due to Maxwell-Wagner-Sillars polarisation as well as space charge polarisation effect. In contrast, acetophenone does not change the dielectric loss value and α-methylstyrene gives very little effect. These byproducts have very high dc conductivity values. It is also proposed that the chemicals provide shallow traps that aid the charge movement and this is consistent with the mobility values that calculated from the conduction current result. The ac breakdown results however show no significant difference from the breakdown strength of clean LDPE. Based on ac space charge results and ac breakdown test results, it is concluded that the byproducts have little effects in ac condition
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Moynihan, Randall H. "The flow stability of linear low-density polyethlene at polymer and metal interfaces." Diss., This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-07132007-143144/.
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Isik, Fatma. "Nanocomposites Based On Blends Of Polyethylene." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/3/12606338/index.pdf.
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In this study the effects of compatibilizer type, organoclay type, and the addition order of components on the morphological, thermal, mechanical and flow properties of ternary nanocomposites based on low density polyethylene, LDPE were investigated. As compatibilizer, ethylene/methyl acrylate/glycidyl methacrylate, ethylene/glycidyl methacrylate, and ethylene/butyl acrylate/maleic anhydride<br>as organoclay Cloisite&<br>#61666<br>15A, Cloisite&<br>#61666<br>25A and Cloisite&<br>#61666<br>30B were used. All samples were prepared by a co-rotating twin screw extruder, followed by injection molding.
Before producing the ternary nanocomposites, in order to determine the optimum amount of the organoclay and compatibilizer, binary mixtures of LDPE/organoclay and LDPE/compatibilizer blends with different compositions were prepared. Based on the results of the mechanical tests, compatibilizer and organoclay contents were determined as 5 wt. % and 2 wt % respectively. After that, ternary nanocomposites were prepared with each compatibilizer/organoclay system and characterization of these nanocomposites was performed.
Among the investigated addition orders, mechanical test results showed that the best sequence of component addition was (PCoC), in which LDPE, compatibilizer and organoclay were simultaneously compounded in the first run of the extrusion. Considering the ternary nanocomposites, compositions of LDPE/E-MA-GMA/15A, LDPE/E-GMA/15A and LDPE/E-nBA-MAH/30B showed the highest improvement in mechanical properties.
According to the DSC analysis, addition of organoclay and compatibilizer does not influence the melting behavior of the compositions and both compatibilizers and organoclay types have no nucleation activity in LDPE.
In the X-Ray analysis, the highest increase of the basal spacing for ternary nanocomposites obtained for LDPE/E-BA-MAH/organoclay nanocomposites. This increase was 83 %, 198 %, and 206 % for samples containing 15A, 25A and 30B respectively.
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Yilmaz, Gokhun. "Effects Of Titanate Coupling Agents On Low Density Polyethylene And Polypropylene Blends And Composites." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12610135/index.pdf.
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The objective of this study is to investigate the effects of titanate coupling agents on low density polyethylene (LDPE) and polypropylene (PP) blends and composites in terms of their mechanical and morphological properties. PP and LDPE composites were produced separately in a Brabender internal mixer, and CaCO3 was used as inorganic filler with compositions of 20, 40 and 60 %. PP/LDPE blends were produced in a twin-screw extruder with ratios of 75/25, 50/50 and 25/75. Their composites were prepared with addition of untreated and titanate-treated CaCO3 at 20% filler content.
Titanate coupling agent which is appropriate for LDPE, PP and CaCO3 was used to improve the mechanical properties of the blends and composites. For this purpose, &ldquo<br>Lica 12&rdquo<br>which is a kind of neoalkoxy organotitanate was used. Two forms of Lica 12 were used: powder form (Capow L12) and pellet form (Caps L12).
Samples with and without titanate were prepared and then they were injection molded to make specimens for tensile and impact tests. Tensile fracture surfaces of samples were examined by scanning electron microscopy (SEM). Their mechanical and morphological properties were compared with each other to determine the effects of Lica 12.
This study showed that Capow L12 improved strain at break and impact strength of PP/CaCO3 composites and PP/LDPE blends containing 75% and 50% PP. The strain at break value of of PP75 composite with 20% titanate-treated filler increased significantly up to 509% which is the highest value among all blends and composites in this study. Capow L12 exhibited its functions in PP matrix much more effectively than in LDPE matrix.
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Matsunaga, Masashi. "Development of physico-chemical pretreatments to enhance the biodegradability of synthetic low-density polyethylene film." Thesis, University of Surrey, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343487.
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Azahari, Baharin Bin. "An investigation into the relationship between processing, orientation and properties of low density polyethylene films." Thesis, London Metropolitan University, 1990. http://repository.londonmet.ac.uk/2992/.
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The effect of changing processing conditions on the mechanical properties of LDPE, LLDPE and blends of LDPE and LLDPE blown films was studied. The results were analysed by relating the change in mechanical properties with the change in the residual strain of manufactured film. The residual strain was measured by using a shrinkage method.
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Bermingham, Siobhan Clara. "The effect of processing parameters on the properties of blown films produced from blends of a low density and a butene based linear low density polyethylene." Thesis, Queen's University Belfast, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282120.
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Khatami, Hassan. "Influence of titanium dioxide pigments on the thermal and photochemical oxidation of low density polyethylene film." Thesis, Manchester Metropolitan University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283081.
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Tijen, Seyidoglu. "Purification And Modification Of Bentonite And Its Use In Polypropylene And Linear Low Density Polyethylene Matrix Nanocomposites." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612204/index.pdf.
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The potential use of Resadiye/Tokat bentonite as a reinforcement in
polypropylene (PP) and linear low density polyethylene (LLDPE) polymer
matrix nanocomposites filler was investigated. At first, organoclays (OC)
were prepared by cation exchange reaction (CER) between the raw
bentonite (RB) and three quaternary ammonium salts with long alkyl tails
(QA): hexadecyl trimethyl ammonium bromide [HMA] [Br], tetrabutyl
ammonium tetrafluoroborate [TBA] [BF4], tetrakisdecyl ammonium bromide
[TKA] [Br] and one quaternary phosphonium (QP) salt: tetrabutyl
phosphonium tetrafluroborate [TBP] [BF4]. Characterization of resulting
materials by XRD, TGA, FTIR and chemical analysis confirmed the
formation of organoclays. Ternary composites of PP/organoclay/ maleic
anhydride grafted polypropylene (MAPP) were prepared with two different
grades of PPs in a co-rotating twin screw extruder. Composites prepared
with these organoclays and PPs showed microcomposite formation.
In the second part of the study, raw bentonite was purified by
sedimentation, and characterization of purified bentonite (PB) by XRD,
cation exchange capacity (CEC) measurement and chemical analysis (ICP) confirmed the success of purification method. PB was then modified with
two QA`s: dimethyl dioctadecylammonium chloride [DMDA] [Cl], tetrakis
decylammonium bromide [STKA] [Br] and one QP: tributyl hexadecyl
phosphonium bromide [TBHP] [Br].
Organoclays from PB were used with the PP with lower viscosity, and
ternary nanocomposites (PP/Organoclay2/MAPP5) were prepared in the
extruder followed by batch mixing in an intensive batch mixer. Use of
DMDA and TBHP OCs resulted in nanocomposite formation, while STKA
resulted in microcomposite formation as observed by XRD and TEM.
Young`s modulus and yield stress of the samples were enhanced through
nanocomposite formation.
In the last part of the study, ternary composites of LLDPE/Organoclay/
compatibilizer, a random terpolymer of ethylene, butyl acrylate and maleic
anhydride (E-BA-MAH, Lotader®<br>3210), were prepared by melt
compounding in the batch mixer at two different clay concentrations (2 and
5 wt %) and fixed compatibilizer/organoclay ratio (&alpha<br>=2.5). A commercial
organoclay, I34, was also used in LLDPE based nanocomposites to make
a comparison. XRD and TEM analyses of the compounds prepared by
DMDA and TBHP showed mixed nanocomposite morphologies consisting
of partially intercalated and exfoliated layers. Young`s modulus and tensile
strength of nanocomposites prepared with DMDA and TBHP showed
generally higher values compared to those of neat LLDPE, while results
were the highest in the composites prepared with commercial organoclay
I34. Parallel disk rheometry was used as a supplementary technique to
XRD, TEM and mechanical characterizations, and it was shown to be a
sensitive tool in assessing the degree of dispersion of clay layers in the
polymer matrix.
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Zhou, Lucy Ying Jr. "Quantitative Analysis of Additives in Low Density Polyethylene Using On-line Supercritical Fluid Extraction /Supercritical Fluid Chromatography." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36786.
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<p>Polymer additives exemplify many classes of compounds which possess a wide variety of chemical (i.e., phenols, amides, esters) and physical (i.e., volatility, solubility) properties. They are incorporated into polyolefins and other such polymeric materials for a number reasons: (a) to prevent degradation by ultraviolet light, heat, and oxygen; (b) to aid in the processing of the polymer; and (c) to modify the physical properties of the polymer. Since the purity and amount of additive can affect polymer properties, it is very important to characterize and quantify additives in polymer products. Traditional liquid solvent/polymer extraction methods, which involve dissolution/precipitation, are time-consuming, uneconomical, and the recoveries are significantly lower than 90%.</p>
<p>In recent years, analysis with supercritical fluids (SFs) has emerged as an alternative analytical technique because SFs afford higher diffusivity and lower viscosity. In this research, an on-line Supercritical Fluid Extraction (SFE)/Supercritical Fluid Chromatography (SFC) system was assembled to provide efficient extraction and separation of polymer additives with quantitative results. The effects of various SFE/SFC parameters, such as trapping temperature, injection temperature, extraction pressure and temperature, dynamic extraction time, and fluid flow rate on extraction and separation efficiencies of different additive standards (i.e., BHT, BHEB, Isonox 129, Irganox 1076 and Irganox 1010) were investigated. Optimized conditions were employed to quantitatively extract additives from LDPE. Identification of additives was performed by comparing the retention time with each additive standard. Results obtained from on-line SFE/SFC were compared to results from off-line SFE/High Performance Liquid Chromatography (HPLC) and off-line Enhanced Solvent Extraction (ESE)/HPLC. </p><br>Master of Science
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Nolutshungu, Lita. "A laboratory investigation on the shear strength characteristics of soil reinforced with recycled linear low-density polyethylene." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29304.
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Since the development of plastics in the 1930’s, plastics have increasingly become widely used for packaging in the commercial market place. With this application being for immediate disposal, the amount of plastic waste generated presents a challenge in the disposal thereof. The risks associated with non-biodegradable products on humans and animal life, pressure on existing landfills and the increasing costs thereof have necessitated the development of alternative options for waste management over the years. Research has resulted in various forms of treatments and recycling processes adopted and implemented as environmentally and economically viable solutions. The use of this recycled material in various applications, such as soil reinforcement addresses the need for engineering solutions with a multifaceted approach which strike a balance between environment, economy and equity. This has been the driving force behind research on the use of alternative materials in engineering design. This study aimed to present an investigation into the use of recycled Linear Low-Density (LLDPE) as reinforcement in Cape Flats sand. To understand the implication of the main aim of the investigation, a review of literature on soil reinforcement theory, various forms of reinforcement material and previous studies was conducted. The selected material for testing was in the form of pellets and flakes produced during the recycling process. Triaxial tests were done on samples where the concentration of the inclusions and compaction effort was varied. The test data presented showed that both pellets and flakes affected the shear strength by plotting Mohr’s circles and the relationship between shear stress and normal stress, which revealed changes in the shear strength parameters. The friction angle was increased by 3.35% at an optimum pellet concentration of 5%. Inclusion of the flakes, however, resulted in a maximum improvement in cohesion of 295% at 0.25% concentration. A discussion on the stress- strain relationship gave an indication on the effect on the stiffness. This showed that the peak shear stress was reached at higher strains when the flakes and pellets were included, compared to the unreinforced sand. Improvements by up to 25% were recorded from the initial 6% strain at peak shear stress of unreinforced sand. In concluding the study, Slide7.0 was used to conduct a 2D finite element analysis using Bishop’s method to analyse the practical application of LLDPE flakes and pellets for slope stability. The optimum shear strength parameters were used in the model, which resulted in an improved global factor of safety meeting the minimum requirement of 1.25.
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Nagle, Dylan John. "Infrared spectroscopic investigation of the effects of titania photocatalyst on the degradation of linear low density polyethylene film for commercial applications." Thesis, Queensland University of Technology, 2009. https://eprints.qut.edu.au/32077/1/Dylan_Nagle_Thesis.pdf.
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There is a need in industry for a commodity polyethylene film with controllable degradation properties that will degrade in an environmentally neutral way, for applications such as shopping bags and packaging film. Additives such as starch have been shown to accelerate the degradation of plastic films, however control of degradation is required so that the film will retain its mechanical properties during storage and use, and then degrade when no longer required. By the addition of a photocatalyst it is hoped that polymer film will breakdown with exposure to sunlight. Furthermore, it is desired that the polymer film will degrade in the dark, after a short initial exposure to sunlight. Research has been undertaken into the photo- and thermo-oxidative degradation processes of 25 ìm thick LLDPE (linear low density polyethylene) film containing titania from different manufacturers. Films were aged in a suntest or in an oven at 50 °C, and the oxidation product formation was followed using IR spectroscopy. Degussa P25, Kronos 1002, and various organic-modified and doped titanias of the types Satchleben Hombitan and Hunstsman Tioxide incorporated into LLDPE films were assessed for photoactivity. Degussa P25 was found to be the most photoactive with UVA and UVC exposure. Surface modification of titania was found to reduce photoactivity. Crystal phase is thought to be among the most important factors when assessing the photoactivity of titania as a photocatalyst for degradation. Pre-irradiation with UVA or UVC for 24 hours of the film containing 3% Degussa P25 titania prior to aging in an oven resulted in embrittlement in ca. 200 days. The multivariate data analysis technique PCA (principal component analysis) was used as an exploratory tool to investigate the IR spectral data. Oxidation products formed in similar relative concentrations across all samples, confirming that titania was catalysing the oxidation of the LLDPE film without changing the oxidation pathway. PCA was also employed to compare rates of degradation in different films. PCA enabled the discovery of water vapour trapped inside cavities formed by oxidation by titania particles. Imaging ATR/FTIR spectroscopy with high lateral resolution was used in a novel experiment to examine the heterogeneous nature of oxidation of a model polymer compound caused by the presence of titania particles. A model polymer containing Degussa P25 titania was solvent cast onto the internal reflection element of the imaging ATR/FTIR and the oxidation under UVC was examined over time. Sensitisation of 5 ìm domains by titania resulted in areas of relatively high oxidation product concentration. The suitability of transmission IR with a synchrotron light source to the study of polymer film oxidation was assessed as the Australian Synchrotron in Melbourne, Australia. Challenges such as interference fringes and poor signal-to-noise ratio need to be addressed before this can become a routine technique.
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Kodavati, Venkata Seshank, and Devi Prasad Buraga. "Study of Numerical Model Parameters and Crack Tip of a Packaging Materials." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-13840.
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Packaging industries widely use Low-Density Polyethylene (LDPE) in manufacturing different types of containers to store the food products. They are difficult to model numerically in order to have similar experimental response. This research deals with the study of numerical material model parameters of continuum LDPE. It is carried out with the help of experiments along with the numerical simulation of LDPE. Study of stress-strain distribution at crack tip and elements close to the tip is carried out in the LDPE material with the pre-existing center crack with varying lengths. By implementing an optimization algorithm and automating the simulation with the help of python code, we obtain a set of parameters. This obtained data for the material can be used directly for numerical simulation in the future without carrying out additional experimental studies. After implementing the optimization algorithm is also validated, against the results that were close to the experimental response.
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Li, Tao. "New compatibilizing agents for blends of linear low-density polyethylene and polystyrene as model systems of the post-consumer plastic waste stream." Case Western Reserve University School of Graduate Studies / OhioLINK, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=case1061478646.
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Pirondelli, Andrea. "Production and Electrical Characterization of Low Density Polyethylene-based Micro- and Nano-dielectrics containing Graphene Oxide, Functionalized Graphene and Carbon Black additives." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016.
Find full textAbstract:
Oggigiorno la ricerca di nuovi materiali per gradatori di campo da impiegarsi in accessori di cavi ha iniziato a studiare alcuni materiali nano dielettrici con proprietà elettriche non lineari con la tensione ed aventi proprietà migliorate rispetto al materiale base. Per questo motivo in questo elaborato si sono studiati materiali nanostrutturati a base di polietilene a bassa densità (LDPE) contenenti nano polveri di grafene funzionalizzato (G*), ossido di grafene (GO) e carbon black (CB). Il primo obiettivo è stato quello di selezionare e ottimizzare i metodi di fabbricazione dei provini. La procedura di produzione è suddivisa in due parti. Nella prima parte è stata utilizzatala tecnica del ball-milling, mentre nella seconda un pressa termica (thermal pressing). Mediante la spettroscopia dielettrica a banda larga (BDS) si sono misurate le componenti reali e immaginarie della permettività e il modulo della conducibilità del materiale, in tensione alternata. Il miglioramento delle proprietà rispetto al provino di base composto dal solo polietilene si sono ottenute quando il quantitativo delle nanopolveri era maggiore. Le misure sono state effettuate sia a 3 V che a 1 kV. Attraverso misurazioni di termogravimetria (TGA) si è osservato l’aumento della resistenza termica di tutti i provini, soprattutto nel caso quando la % di nanopolveri è maggiore. Per i provini LDPE + 0.3 wt% GO e LDPE + 0.3 wt% G* si è misurata la resistenza alle scariche parziali attraverso la valutazione dell’erosione superficiale dei provini. Per il provino contenente G* è stato registrato una diminuzione del 22% del volume eroso, rispetto al materiale base, mentre per quello contenente GO non vi sono state variazioni significative. Infine si è ricercata la resistenza al breakdown di questi ultimi tre provini sopra citati. Per la caratterizzazione si è fatto uso della distribuzione di Weibull. Lo scale parameter α risulta aumentare solo per il provino LDPE + 0.3 wt% G*.
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Naidoo, Preloshni. "A comparative analysis of the chemical composition of linear low density polyethylene polymers synthesised with 1- hexene comonomer under different catalytic conditions." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80272.
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Thesis (MSc)--Stellenbosch University, 2013.<br>ENGLISH ABSTRACT: A comparative study of the chemical composition of linear low density polyethylene polymers, synthesised with 1 - hexene as comonomer was conducted. Catalyst trials were conducted on the linear low density 1 - hexene polymer grade material to evaluate alternative catalysts. A comparative analysis was performed in order to investigate if the samples synthesised under catalyst trial conditions showed any significant differences in terms of crystallinity and mechanical properties with the reference sample that was synthesised using the reference catalyst. The results showed that the macro product properties, namely melt flow Index, density, and level of hexene extractables are different for the trial samples in comparison with the reference sample. The differences observed implied that the trial samples were synthesised with differences on a molecular level. The differences in the chemical composition between the reference sample and the comparative samples were fully explored using a wide range of analytical techniques, namely crystallisation analysis by fractionation (CRYSTAF), temperature rising elution fractionation (TREF), differential scanning calorimetry (DSC), Carbon 13 nuclear magnetic resonance (13C NMR), Size exclusion chromatography (SEC), Positron analysis lifetime spectroscopy (PALS) and micro hardness analysis. The results of the characterisation studies indicated the following:
- Crystallinity and hardness analysis of the reference sample, catalyst trial sample 1 and catalyst trial sample 2 indicate that the catalyst trial sample 2 having a low cocatalyst concentration is the most crystalline of all the samples. - The reference sample, catalyst trial sample 1 and catalyst trial sample 2 were further fractionated using TREF at fractionation temperature intervals of 10°C. TREF analysis indicates that the bulk of the material is observed to elute between 70°C - 10°C. - 13C NMR analyses of the TREF fractions identified four populations of fractions that could be selectively removed, allowing the bulk of the material to be recombined. As these highly crystalline fractions were removed, there was an observed decrease in the total crystallinity of the bulk recombined material. This trend was further verified by the free volume analysis. - Free volume analysis indicated of the bulk recombined material indicated a general increase in the T3 lifetime and T4 lifetime intervals. Free volume analysis further confirmed a decrease in crystallinity of the bulk recombined material as highly crystalline material was removed. - Micro hardness analysis of the polymers further verified the crystallinity trends observed. As the molecular composition of the polymer changed due to removal of highly crystalline fractions, the total mechanical strength of the material indicated by the hardness value decreased.
The study showed that by changing the chemical composition of the polymer by removing highly crystalline fractions, there was an observed change in the mechanical properties of the polymer. It can be concluded that the samples synthesised under catalyst trial conditions show significant differences in terms of crystallinity and mechanical properties in comparison with the sample that was synthesised using the standard reference catalyst.<br>AFRIKAANSE OPSOMMING: ‘n Vergelykende analise studie is onderneem van die chemiese samestellings van lineêre lae digtheid poliëtileen polimere, gesintetiseer met 1-hekseen as ko-monomeer. Alternatiewe kataliste is ge-evavuleer ten opsigte van lineêre lae digtheid 1-hekseen Sasol polimeer graad materiaal. Die vergelykende analise is uitgevoer om die monsters onder katalis proef kondisies te evalueer en te merk of enige beduidende verskille in terme van kristalliniteit en meganiese eienskappe met die verwysings monster voorkom. Die resultate toon dat die makro-produk eienskappe, naamlik smelt vloei indeks, digtheid en vlak van hekseen onttrekking, verskillend is vir die proef monsters in vergelyking met die verwysings monster. Die waargenome verskille impliseer dat die proef monsters op molekulêre vlak verskil. Die verskille in chemiese samestelling tussen die verwysings monster en die vergelykende monsters is ten volle ondersoek deur gebruik te maak van 'n wye verskeidenheid van analitiese tegnieke, naamlik kristallisasie analise fraksionering (CRYSTAF), temperatuur stygende eluering fraksionering (TREF), differensiële skandeer kalorimetrie (DSC), koolstof 13 kernmagnetiese resonansie (13C KMR), gelpermeasie chromatografie (SEC), positron analise leeftyd spektroskopie (PALS) en mikro-hardheid analise. Die resultate van die karakterisering studies het die volgende aangedui:- Kristalliniteit en hardheid analises van die verwysings monster en katalis proef monsters 1 en 2 het getoon dat katalis proef monster 2, wat ‘n lae ko-katalis konsentrasie bevat, die mees kristallyn is. - Die verwysings monster en katalis proef monster 1 en 2 is gefraksioneer met behulp van ‘n TREF met temperatuur tussenposes van 10°C. TREF analise toon dat oormaat materiaal ge-elueer word tussen 70°C en 100°C. - 13C KMR analise van die TREF fraksies het 4 verskillende fraksies geidentifiseer wat selektief verwyder kan word. Dit laat ook toe dat die grootste deel van die materiaal weer geherkombineer kan word. Soos die hoogs kristallyne fraksies verwyder is, is ‘n afname in die totale kristalliniteit van die geherkombineerde materiaal waargeneem. Hierdie tendens is bevestig deur vrye volume analises. - Vrye volume analises van die geherkombineerde materiaal toon ‘n algemene toename in die T3en T4 leeftyd aan. Vrye volume analises toon verder dat ‘n afname in die kristalliniteit van die geherkombineerde materiaal plaasvind soos meer kristallyne fraksies verwyder word. - Verdere mikro-hardheid analises van die polimere bevestig die waargenome kristalliniteit tendense. Soos die molekulêre samestelling van die polimere verander as gevolg van die verwydering van die hoogs kristallyne fraksies, so neem die totale meganiese sterkte van die materiaal af; soos aangedui deur die afname in hardheid waarde. Die studie toon dat die verandering van die chemiese samestelling van die polimeer, deur die verwydering van hoogs kristallyne fraksies, 'n waargenome verandering in die meganiese eienskappe van die polimeer laat plaasvind. Daar kan afgelei word dat die monsters, vervaardig onder die katalis proef voorwaardes, beduidende verskille toon in terme van kristalliniteit en meganiese eienskappe in vergelyking met die monster vervaardig deur die huidige verwysings katalis.
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Yoo, SeungRan. "The effect of high pressure processing on the mass transfer of Irganox 1076 in low-density polyethylene films and in 95% ethanol as a food simulant." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1181749497.
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Peiti, Christian. "Modification des propriétés rhéologiques des polymères branchés par traitement thermomécanique : application aux défauts d'extrusion des PEBD." Phd thesis, Ecole Nationale Supérieure des Mines de Paris, 2012. http://pastel.archives-ouvertes.fr/pastel-00820611.
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L'objectif de cette thèse est d'observer la modification du comportement rhéologique dedifférents polyéthylènes branchés, suite à un traitement de cisaillement. Après avoir décrit lesmatériaux et les moyens utilisés, nous avons caractérisé le plus complètement possible lecomportement rhéologique des différents matériaux, aussi bien en cisaillement qu'en élongation.Nous avons également déterminé des données calorimétriques et des informations sur lescaractéristiques moléculaires, permettant entre autres de définir la masse entre enchevêtrements.Nous avons ensuite mesuré l'évolution de la viscosité dans différentes conditions de pré‐cisaillement,en faisant varier le temps et le taux de cisaillement dans un rhéomètre cône‐plan et dans unegéométrie de Couette montée en amont d'un rhéomètre capillaire. Nous avons montré que lesmécanismes de désenchevêtrement sont complexes et qu'ils ne sont pas directement explicables parun seul paramètre, comme la masse entre enchevêtrements. Enfin, l'observation des extrudats à lasortie de la filière nous a permis de mettre en évidence la modification des défauts d'extrusion sousl'effet d'un pré‐cisaillement.
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Ersu, Dilek. "Preparation And Characterization Of Nanocomposites With A Thermoplastic Matrix And Spherical Reinforcement." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/3/12607447/index.pdf.
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The aim of this study is to investigate the effects of compatibilizers, fumed silica and mixing order of components on morphological, thermal, mechanical and flow properties of LDPE/Fumed silica nanocomposites. As compatibilizer(Co)<br>ethylene/n-butyl acrylate/maleic anhydride (E-nBA-MAH), ethylene/glycidyl methacrylate (E-GMA) and ethylene/methyl acrylate/glycidyl methacrylate (E-MA-GMA) Lotader®<br>resins<br>as silica Cab-o-sil®<br>M5 fumed silica were used. All samples were prepared by means of a lab scale co-rotating twin screw extruder and injection molded into standard samples.
In the first step, individual effects of filler and compatibilizers were studied in binary systems with LDPE. Then, keeping the amount of compatibilizer constant at 5%, ternary nanocomposites were prepared by adding 2 or 5% of fumed silica using different component mixing orders.
Among investigated mixing orders, mechanical test results showed that the best sequences of component addition are FO1 [(LDPE+Co)+M5] and FO2 [(LDPE+M5)+Co] mixing orders. Considering the compatibilizers, E-nBA-MAH terpolymer showed the highest performance in improving the mechanical properties, E-GMA copolymer also gave satisfactory results.
According to the DSC analysis, since addition of fumed silica and compatibilizer does not influence the crystallization behavior of the compositions, it is concluded that, neither fumed silica nor any of the compatibilizers have nucleation activity on LDPE.
MFI test results showed that, addition of fumed silica increases the melt viscosity, decreasing MFI values of samples. This change seems to be directly proportional to fumed silica amount.
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Papet, Gérard. "Etude cinetique du vieillissement radiochimique du polyethylene." Paris, ENSAM, 1987. http://www.theses.fr/1987ENAM0009.
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Etude de la radiolyse gamma du polyethylene basse densite dans l'air et a temperature ambiante. Les profils de distribution dans l'epaisseur de la concentration en carbonyles presentent une decroissance a une profondeur d'environ 180 microns. Determination des parametres cinetiques dans le cas ou la diffusion ne controle pas le vieillessement. Etude de modeles theoriques et de l'evolution des proprietes mecaniques pendant la degradation radiochimique
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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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Euzébio, Junior Silvio Hendez. "Influência das ceras orgânicas nas propriedades de filmes tubulares de PEBD." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/186153.
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As poliolefinas, em especial os polietilenos (PE) são materiais poliméricos muito utilizados para a produção de filmes tubulares, sendo um dos materiais mais amplamente empregado na indústria de embalagens flexíveis. Dentre os diversos PE industriais, o polietileno de baixa densidade (PEBD) apresenta propriedades reológicas únicas em comparação aos PE lineares e os de alta densidade. A alta viscosidade e as numerosas ramificações longas encontradas neste polímero influenciam na redução da produtividade quando processados. Aditivos das mais variadas composições são adicionados ao polietileno durante o processo de extrusão tubular a fim de melhorar suas propriedades. Um dos aditivos mais empregados para facilitar o fluxo do fundido para processamento de filmes são as ceras sintéticas, sendo a mais usada a de polietileno oxidado (CP). Na procura de alternativas de cera de fonte orgânica e/ou de fonte natural, o objetivo deste trabalho é avaliar a influência do tipo e teor de cera na processabilidade e propriedades finais de filmes tubulares de PEBD. Foram usados 3 tipos de ceras: CP (cera de polietileno), a carnaúba (CC) e o monoestearato de glicerol (CM), sendo processadas 4 formulações de PEBD/cera nas proporções mássicas de 99,5/0,5; 99/1; 98/2 e 96/4 m/m com os três tipos de cera e comparados com o PEBD sem cera. Os filmes foram caracterizados através de ensaios físicos, ópticos, químicos, térmicos, reológicos e mecânicos. Propriedades ópticas como o brilho e opacidade foram alteradas pela adição das ceras pois um aumento na concentração das ceras aumenta o grau de cristalinidade dos filmes. A cera de carnaúba apresentou amarelamento nos filmes produzidos com maiores concentrações. Resultados deste estudo mostraram que o uso da cera sintética, CP e da natural de carnaúba, aumentam a produtividade do filme tubular de PEBD, sendo o teor ótimo de 1% de cera, sem ter influência significativa na espessura e largura do filme tubular. O uso de agentes de fluxo alternativos de natureza orgânica é viável pois obtiveram resultados similares e superiores ao padrão nos filmes testados.<br>Polyolefins, especially polyethylenes (PE) are widely used polymeric materials for the production of tubular films, being one of the most widely used materials in the flexible packaging industry. Among the various industrial PE, low density polyethylene (LDPE) has unique rheological properties compared to linear and high density PE. The high viscosity and the numerous long branches found in this polymer influence the reduction of productivity when processed. Additives of the most varied compositions are added to the polyethylene during the tubular extrusion process in order to improve their properties. One of the most used additives to facilitate the flux of melt for film processing is synthetic waxes, the most used being oxidized polyethylene (CP). In the search for organic and / or natural source wax alternatives, the objective of this work is to evaluate the influence of the type and content of wax on the processability and final properties of tubular films of LDPE. Three types of waxes were used: CP (polyethylene wax), carnauba (CC) and glycerol monostearate (CM), and 4 formulations of LDPE / wax were processed in mass proportions of 99.5 / 0.5; 99/1; 98/2 and 96/4 m / m with the three types of wax and compared with LDPE without wax. The films were characterized by physical, optical, chemical, thermal, rheological and mechanical tests. Optical properties such as brightness and opacity are altered by the addition of waxes as an increase in the concentration of the waxes increases the degree of crystallinity of the films. Carnauba wax shows a yellowing in the films produced with higher concentrations. Results of this study showed that the use of synthetic wax, CP and natural carnauba, increase the productivity of the tubular film of LDPE, being the optimal content of 1% of wax, without having a significant influence on the thickness and width of the tubular film. The use of alternative flow agents of organic nature is feasible because they obtained similar and superior results to the standard in the films tested.
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Gupta, Pankaj. "Processing-Structure-Property Studies of: I) Submicron Polymeric Fibers Produced By Electrospinning and II) Films Of Linear Low Density Polyethylenes As Influenced By The Short Chain Branch Length In Copolymers Of Ethylene/1-Butene, Ethylene/1-Hexene & Ethylene/1-Octene Synthesized By A Single Site Metallocene Catalyst." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/30090.
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The overall theme of the research discussed in this dissertation has been to explore processing-structure-property relationships for submicron polymeric fibers produced by electrospinning (Part I) and to ascertain whether or not the length of the short chain branch has any effect on the physical properties of films of linear low-density polyethylenes (LLDPEs) (Part II). Electrospinning is a unique process to produce submicron fibers (as thin as 100 nm) that have a diameter at least two orders of magnitude smaller than the conventional fiber spinning processes based on melt and solution spinning. As a result, the electrospun fibers have a very high specific surface. The research efforts discussed in Part I of this dissertation relate to some fundamental as well as more applied investigations involving electrospinning. These include investigating the effects of solution rheology on fiber formation and developing novel methodologies to fabricate polymeric mats comprising of high specific surface submicron fibers of more than one polymer, high chemical resistant substrates produced by in situ photo crosslinking during electrospinning, superparamagnetic flexible substrates by electrospinning a solution of an elastomeric polymer containing ferrite nanoparticles of Mn-Zn-Ni and substrates for filtration applications. More specifically, it was found that the solution rheological parameters like concentration and viscosity, in addition to molecular weight play an important role in governing the fiber formation during electrospinning of polymer solutions. Furthermore, it was found that fiber formation depends strongly on the solution concentration regime, i.e., at low and dilute concentrations, droplets and beaded fibers were formed whereas uniform fibers were observed to form at a solution concentration greater than at least six times than that of the critical chain overlap concentration, c*, for linear homopolymers of poly(methyl methacrylate) that had molecular weight distributions ranging from 1.03-1.35 (Mw/Mn). In contrast, uniform fibers were observed at ten times the value of c* for the relatively broader molecular weight polymers (Mw/Mn~1.6-2.1). Novel methodologies were developed to in situ photocrosslink the electrospun jet to produce a crosslinked network in the form of a submicron fiber that could potentially be utilized for applications where a high resistance to chemical environments is required. In addition, flexible superparamagnetic substrates were developed by electrospinning a solution of an elastomeric polymer containing magnetic nanoparticles based on "mixed" ferrites of Mn-Zn-Ni where the specific saturation magnetization and the magnetic permeability of these substrates were found to increase linearly with the wt% loading of the nanoparticles. The methodology to simultaneously electrospin two polymer solutions in a side-by-side fashion was developed to produce bicomponent fibers with the rationale that the resulting electrospun mat will have properties from a combination from each of the polymer components. Bicomponent electrospinning of poly(vinyl chloride)- polyurethane and poly(vinylidiene fluoride)-polyurethane was successfully performed. In addition, filtration properties of single and bicomponent electrospun mats of polyacrylonitrile and polystyrene were investigated. Results indicated lower aerosol penetration or higher filtration efficiencies of the filters based on submicron electrospun fibers in comparison to the conventional filter materials.
In addition, Part II of this dissertation explores whether or not the length of the short chain branch affects the physical properties of blown and compression molded films of LLDPEs that were synthesized by a single site metallocene catalyst. Here, three resins based on copolymers of ethylene/1-butene, ethylene/1-hexene, and ethylene/1-octene were utilized that were very similar in terms of their molecular weight and distribution, melt rheology, density, crystallinity and short chain branching content and its distribution. Interestingly, at higher deformation rates (ca. 1m/s), the breaking, tear and impact strengths of films based on ethylene/1-hexene and ethylene/1-octene were found to be superior than those based on ethylene/1-butene. While the origin of these differences in mechanical properties with increasing short chain branch length was not fully understood, the present investigation did confirm this effect to be pronounced only at high deformation rates for both the blown and compression molded LLDPE films.<br>Ph. D.
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MADDALA, PRANAY RAJ REDDY. "Investigation of Polymer packaging films behavior subjected to tension and tearing." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-15002.
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The course of polymer film functioning has been a crucial concern in the advent of packaging technology. The thesis project aims towards obtaining an understanding of mechanical properties for a class of these materials, namely LDPE and PET. A constitutive understanding of this behavior in the case of LDPE is acquired through incorporating a plastic stress strain relationship in an iterative approach with focus put on the sensitivity of a few parameters by following a simple linear curve-fit technique in a way that the global as well as the local response are predictable. FE-models also developed in this way are validated with experimental data. An inverse analysis testing validity or usefulness of DIC technique in identifying a material model is done and some discussions are drawn towards this area. A relative numerical study with respect to experimentally obtained global response for tearing of these polymers is done through use of a similar material model developed from tensile tests and the challenges faced in this area have been addressed.