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Decrosslinking of Crosslinked Polyethylene via Ultrasonically Aided ExtrusionHuang, Keyuan 21 May 2015 (has links)
No description available.
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Microstructures and multifunctional microsystems based on highly crosslinked polymersSingamaneni, Srikanth 02 July 2009 (has links)
The work elucidates the novel physical and thermal properties of thin and ultra-thin films of crosslinked polymer and organized microstructures with a special emphasis on surface and interfacial effects and the structure-property relationships. Two major crosslinked polymer coatings have been thoroughly investigated: polymer microstructures fabricated by multi-laser interference lithography (IL), and plasma polymer coatings. We unveiled intriguing thermal properties of plasma polymer films originating from their physical state and exploiting the same for the design of ultrasensitve chemical sensors.
A novel paradigm of surface coatings, single and bi-component periodic, porous crosslinked polymeric structures, has been introduced and thoroughly studied. Surface, interfacial, and mechanical properties of these novel class crosslinked polymer coatings clearly demonstrate the enormous potential of the IL microstructures as organized multicomponent polymer systems. When subjected to external or internal stresses the periodic porous structures can exhibit a sudden and dramatic pattern transformation resulting in remarkable change in the photonic, phononic and mechanical properties of these structures. Furthermore, the confinement of these instabilities to localized regions results in complex hierarchical structures. The two polymer coatings (plasma polymers and IL microstructures) with complementary attributes (such as periodic structure, vertical stratification, residual internal stresses, and high surface and interface tunability) enabled us to understand and design novel multifunctional polymer coatings.
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Surface Topography and Aesthetics of Recycled Cross-Linked Polyethylene Wire and Cable CoatingsXie, Wa 12 1900 (has links)
Our research focuses on re-using a waste a material, cross-linked polyethylene abbreviated XLPE, which is a widely used coating for wires. XLPE is strong and has excellent thermal properties due to its chemical structure - what leads to the significance of recycling this valuable polymer. Properties of XLPE include good resistance to heat, resistance to chemical corrosion, and high impact strength. A wire is usually composed of a metal core conductor and polymeric coating layers. One creates a new coating, including little pieces of recycled XLPE in the lower layer adjacent to the wire, and virgin XLPE only in the upper layer. Industries are often wasting materials which might be useful. Mostly, some returned or excess products could be recycled to create a new type of product or enable the original use. This method helps cleaning the waste, lowers the costs, and enhances the income of the manufacturing company. With the changing of the thickness of the outer layer, the roughness changes significantly. Moreover, different processing methods result in surfaces that look differently.
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Materiais compósitos biocidas baseados em resinas reticuladas contendo nanopartículas de prata / Biocide composite materials based on crosslinked resins containing silver nanoparticlesJacqueline Dias Corrêa de Souza 27 April 2007 (has links)
Nesta dissertação, duas resinas reticuladas comerciais (denominadas, AmberliteGT73 e AmberliteIRC748) foram empregadas para suportar partículas de prata. Os grupos tiol da GT73 e ácido iminodiacético da IRC748 presentes nessas resinas foram empregados para a fixação de íons Ag+ a partir de solução aquosa. Posteriormente, os íons Ag+ foram reduzidos pelo emprego de três redutores diferentes em pH alcalino, denominados hidrazina, hidroxilamina e formaldeído (pH  12). A morfologia e a impregnação de prata dos materiais binários assim obtidos foram avaliadas por meio de microscópio eletrônico de varredura equipado com detector de elétrons retro-espalhados (SEM-BSE). O detector de espectrometria de energia dispersiva de raios-X (EDAX) acoplado ao SEM permitiu a observação de partículas de prata. Os espectros de raios-X revelaram a presença do metal nas superfícies interna e externa das microesferas dos compósitos. A quantidade de prata incorporada foi determinada pelo método titulométrico, empregando solução padrão de tiocianato de potássio. As características antibactericidas dos compósitos foram avaliadas em colunas contendo pérolas de resina por onde foram percoladas suspensões da bactéria Escherichia coli auxotrópica AB1157 (tipo selvagem) nas concentrações de 103 a 107 células/mL. A avaliação biocida mostrou que estes materiais foram completamente bactericidas, sendo efetivos na eliminação da bactéria em poucos minutos. Esta ação biocida foi atribuída à combinação da atuação da prata e dos grupos funcionais das resinas / In this work, two different commercial cross-linked resins (namely, Amberlite GT73 and AmberliteIRC748) were employed for anchoring silver. The SH and the N(CH2COOH)2 groups, respectively present on these resins, were used for the Ag+ chelation from aqueous solution. The Ag+ ions were reduced by employing three different reductants, namely hydrazine, hydroxylamine and formaldehyde (under alkaline pH). The produced composites were characterized by thermogravimetry (TG-DTG) and scanning electron microscopy equipped with backscattered scanning electron detector (SEM-BSE). Energy dispersive X-ray spectroscopy (EDS) coupled to SEM allowed the observation of submicron particles of silver and chemical microanalysis of emitted X-rays revealed the presence of metal on the internal and external surfaces of the composite microspheres. The amount of incorporated silver was determined by titration. The antibacterial activity of the silver/resin composites were determined towards 103 to 107 cells/mL dilutions of the auxotrophic AB1157 Escherichia coli strain, showing that the networks containing anchored submicron silver particles were completely bactericidal within a few minutes due to the combined action of silver and functional groups of the resins
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Design of New Polyester Architectures through Copolymerization, Crosslinking, and Diels-Alder GraftingVargas, Marian 12 April 2004 (has links)
The compound 2,6-anthracenedicarboxylic acid is used as a comonomer for the synthesis of poly(ethylene terephthalate). The resulting copolymers are characterized and further functionalized by Diels-Alder grafting or crosslinking through the anthracenate unit. Diels-Alder reaction is used to graft small molecules and oligomers endcapped with maleimide as dienophiles on to poly(ethylene terephthalate-co-2,6-anthracenedicarboxylate),PET-co-A. Maleimide-capped poly(ethylene glycol) is grafted onto PET-co-A to improved its hydrophilicity.
2,6-Anthracenedicarboxylic acid is also incorporated into the known liquid crystalline polymer, LCP, poly(4-oxybenzoate-co-1,4-phenylene isophthalate), HIQ40. The resulting copolymer, poly(4-oxybenzoate-co-1,4-phenylene isophthalate-co-2,6-phenylene anthracenate), HIQ40-co-A, shows LCP behavior. These HIQ40-co-A copolymers are grafted with maleimide end-capped monomers and polymers andcrosslinked with bismaleimides through a Diels-Alder mechanism.
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Crosslinkable Polyimide Mixed Matrix Membranes for Natural Gas PurificationHillock, Alexis Maureen Wrenn 17 October 2005 (has links)
Crosslinkable mixed matrix membranes represent an attractive technology that promises both outstanding separation properties and swelling resistance for the purification of natural gas. This approach relies upon dispersal of a CO2/CH4 size-discriminating zeolite in a crosslinkable polymer, which is resistant to CO2 swelling when crosslinked. The resulting membrane has the potential to separate CO2 from CH4 more effectively than traditional pure polymer membranes, while also providing needed membrane stability in the presence of aggressive CO2-contaminated natural gas streams. Control studies are conducted using the pure crosslinkable polymer to observe the separation properties and swelling resistance. Initial crosslinkable mixed matrix membrane experiments are then performed and result in an increase in membrane productivity, instead of the expected increase in selectivity. Traditionally, this is caused by material incompatibility at the polymer/zeolite interface, so the crosslinkable mixed matrix membranes are characterized to examine this issue. During the material characterization, a new non-ideal transport phenomenon is discovered in the zeolite phase. A model is developed to better understand the transport and predict subsequent experimental results. Once the independent materials are proven to be viable, crosslinkable mixed matrix membranes that show enhancements in both efficiency and productivity and exhibit stability in the presence of aggressive CO2 feeds are created.
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Polymerization Of 2,4,6 Trichlorophenol By Microwave InitiationOkyay, Ozden 01 December 2006 (has links) (PDF)
Polymerization reaction is carried out by the reaction of 2,4,6 trichlorophenol with
sodium hydroxide, in the presence of small amount of water by microwave initiation.
Synthesis of polymers were successfully performed under microwave enegy. The use
of microwave energy was due to advantages of shorter processing time. The main
focus of attention was the 90 to 600 watt microwave energy. Polymerizations were
performed with different time intervals by keeping the microwave energy and water
content constant / or with different energy levels by keeping the time interval and
water content constant / or by varying the amount of water by keeping the time and
energy level constant.Beside poly(dichlorophenylene oxide), conducting polymer, ion-radical polymer,
crosslinked polymer were also be successfully synthesized and characterized.
Characterizations of the products were performed by FTIR, 1H-NMR, 13C-NMR,
DSC, TGA and elemental analysis. Molecular weight distribution was measured by
PL-GPC 220 Polymer Laboratories Instrument. Conductivity measurements were
performed by four probe technique.
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The Effect Of Potassium Hydroxide On The Polymerization Of Trichlorophenol, Pyrrole And Thiophene By Microwave InitiationUnsal Gungor, Elif Mufide 01 June 2008 (has links) (PDF)
The synthesis of black conducting polymer (CP) and/or crosslinked polymers
(CLP) and/or radical ion polymer (RIP) and/or white polymers (WP) and/or
orange polymer (OP) were achieved by using KOH with TCP, pyrrole and
thiophene via microwave energy in a very short time interval.
Polymerizations were carried out by constant microwave energy with different
time intervals varying from 1 to 25 min / or at constant time intervals with
variation of microwave energy from 90 to 900 watt / or varying the water content
from 0, 0.5 to 5 ml at constant time intervals and microwave energy, or at
constant time interval, water content, microwave energy with variation of
amount of KOH 0.03 mol to 6x10-4 mol. The effects of heating time, microwave
energy, water content and amount of KOH on the percent conversion and the
polymer synthesis were also investigated.White, orange polymers and radical ion polymers were characterized by FTIR
(Fourier Transform Infrared), 1H-NMR (Proton Nuclear Magnetic Resonance),
13C-NMR (Carbon-13 Nuclear Magnetic Resonance), TGA/ FTIR (Thermal
Gravimetric Analysis / Fourier Transform Infrared), DSC (Differential Scanning
Calorimeter), SEM (Scanning Electron Microscope), ESR (Electron Spin
Resonance), GPC (Gel Permeation Chromatography), UV-Vis (UV-Visible
Spectroscopy) and Light Scattering. Conducting and crosslinked polymers were
characterized by FTIR, TGA/ FTIR, DSC, SEM, ESR, XRD (Powder Diffraction
X-Ray) and conductivity.
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Artificial Aging Of Crosslinked Double Base PropellantsBaglar, Emrah 01 December 2010 (has links) (PDF)
In this study, shelf life of three different crosslinked double base (XLDB) propellants stabilized with 2-nitrodiphenylamine (2-NDPA) and n-methyl-4-nitroaniline (MNA) were determined by using the stabilizer depletion method. Depletions of the stabilizers were monitored at different aging temperatures using High Performance Liquid Chromatography (HPLC). Kinetic models of pseudo zero, pseudo first, pseudo second and shifting order were used to find the best model equation that fits the experimental data. The rates of depletion of stabilizers were calculated at 45, 55 and 65° / C based on the best fit kinetic models. Using the rate constants at different temperatures, rate constants at room temperature were calculated by Arrhenius equation. The activation energies and frequency factors for the depletion of 2-NDPA and MNA were obtained for all XLDB propellants. Moreover, the results were evaluated based on the NATO standard / STANAG 4117 and the propellants were found stable according to the standard. Vacuum thermal stability (VTS) tests were also conducted to evaluate the stability of XLDB propellants. The propellant that includes the stabilizer mixture of MNA and 2-NDPA was found to have less stability than the propellants that include 2-NDPA only. However, there were rejection (puking) and migration of stabilizer derivatives for the aged samples of propellants that were stabilized with only 2-NDPA. Moreover, formation of voids and cracks were observed in block propellant samples due to excess gas generation.
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Microwave Initiated Polymerization Of Trihalophenyleneoxide And AnilineLevent, Fulya 01 February 2011 (has links) (PDF)
The aim of the study is to synthesize poly(dibromophenyleneoxide) and polyaniline separately applying different microwave energies (90-900 watt), water amounts (1-5 ml) and time intervals (2-10 min) and investigate the effects of these parameters on the percent conversion of the polymers. The synthesis of poly(dibromophenyleneoxide) (P), radical ion polymer (RIP) and crosslinked polymer (CLP) were achieved by using tribromophenol (TBP) and Ca(OH)2 via microwave energy in a very short time interval.
P and RIP were characterized by ATR-FTIR, 1H-NMR, 13C-NMR, TGA-FTIR, ESR, GPC, UV-VIS, DLS and SEM. Crosslinked polymers were characterized by ATR-FTIR and TGA-FTIR and polyaniline was characterized by ATR-FTIR.
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