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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
181

Cheap Quality & Urban Unrest : The prettiest words are the ones we don't say

Kallioinen Lundgren, Sara January 2021 (has links)
With a background in ceramics and graphic designI have developed my thoughts about craft as a combination of verbal and nonverbal communication, but in textiles. With the written word as one of my main materials this project looks into class and material hierarchies filtered through autofictivestories from my life. This paper explores themes that impact my decisions in the making process, choosing materials, motifs, texts and words, politics and poetry. It deals with all the information I push into patchworking, shirring, tufting and sculpting textiles, with the goal to paint a picture of an often unwanted section of society. To discuss this I have chosen references dealing with sloppy craft, text based art, graffiti and craft traditions, in a mix with news articles and economy. Through all parts of the project I am on balancing line between chaos and perfection, truth and fiction.
182

Synthesis and Characterization of Novel Telechelic High Performance Polyester Ionomers

Kang, Huaiying 04 December 2001 (has links)
Novel poly(ethylene isophthalate) (PEI) and poly(ethylene terephthalate) (PET) polymers containing terminal units derived from sodio 3-sulfobenzoic acid (SSBA) were synthesized using catalyzed melt polymerization techniques. Various concentrations of the ionic end group, SSBA, were successfully incorporated in a telechelic fashion. For comparison, polyesters containing telechelic alkyl groups with controllable molecular weights were also synthesized. Furthermore, ionic copolymers of dimethyl isophthalate and trans-cyclohexane dicarboxylate, dimethyl isophthalate and dimethyl terephthalate were synthesized to study the influences of polarity and rigidity of the polymer chain backbone on material properties. Novel branched polyester ionomers using trimellitic anhydride were also prepared. In addition to modifying the polymer compositions, PET ionomers were blended with zinc stearate to investigate the effect of plasticizer on the melt processibilty of the ionomers. FTIR spectroscopy, which was used to quantify the sulfonate end groups for all of the ionomers, indicated an absorbance peak for the S-O stretching mode between 600-700 cm⁻¹. ¹H NMR spectroscopy was used to confirm the structure of the ionic and non-ionic polyesters, as well as to verify the presence of the terminal groups. By systematically varying the chemical structure of these ionomer model systems (i.e., altering the contents of ionic functional groups), detailed characterizations were carried out, wherein the ionic interactions/aggregations in the ionomers were found to play an important role in the resulting material properties. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) measurements were performed to study the effects of ionic groups and oligomer composition on the thermal properties of the polyesters. The glass transition temperatures of the ionomers revealed that the ionic interaction helped to maintain the structural integrity of the polymer chains, thus limiting their mobility. The dilute solution viscosity behavior of the ionomers exhibited upward curvature, which is a key characteristic of an ionomer. In PEI ionomers, the ionic aggregates formed at lower temperatures (<150 °C), while at higher temperatures (>150 °C), the ionic aggregations dissociated and behaved similarly to oligomers with lower molecular weights. Dodecanol was used as an effective end-capper to control the molecular weight of the non-ionic polyesters. In addition to telechelic ionic PEI and PET homopolymers, copolymers of poly(ethylene isophthalate-co-trans-1,4-cyclohexane dicarboxylate) (PEI-co-trans-CHDC) and poly(ethylene isophthalate-co-terephthalate) (PEIT) telechelic ionomers were also synthesized and characterized. Introducing trans-1,4-cyclohexane dicarboxylate into PEI ionomers decreased the polarity and packing regularity of the polymer chains. Also, the kinked-structure of dimethyl isophthalate reduced the regularity of the polymer chains in PET ionomers, thus reducing their propensity for rapid crystallization. Crystallization kinetics were studied for both ionic and alkyl telechelic polyesters, and resulting data revealed that the nature of the endgroup had a dramatic effect on crystallization from the melt state. The catalyst residue in the polymers also affected the crystallization rate for both ionic and non-ionic polyesters. With regard to the ionomers, antimony catalyst interacted with ionic aggregates, further increasing the crystallization rate. Branched PEI and PET ionomers showed an increase in melt strength. After blending with zinc stearate, the melt viscosity of the PET ionomers dropped dramatically. / Master of Science
183

CONTROLLED RELEASE OF ETORICOXIB FROM POLY(ESTER UREA) FILMS FOR POST-OPERATIVE PAIN MANAGEMENT

Brigham, Natasha Caterina 29 August 2019 (has links)
No description available.
184

Polyester Polymer Concrete for Bridge Deck Overlays

Stevens, Robert James 13 April 2020 (has links)
The objectives of this research were to 1) compile a synthesis of information about polyester polymer concrete (PPC) from the literature; 2) conduct a scanning tour to observe PPC construction, inspect in-service PPC overlays, and discuss topics related to PPC; 3) revise the existing Utah Department of Transportation (UDOT) PPC specification; 4) document a PPC field demonstration project; and 5) perform laboratory characterization of the material properties of field-mixed PPC. The scope of the research included a scanning tour, field testing, and laboratory experimentation. The objectives of the scanning tour included observation of a PPC overlay placement, inspection of existing overlays, and discussion of selected topics related to PPC. The scanning tour comprised a 3-day visit to California. Items related to material properties, mixture and overlay design, laboratory testing, and construction and field testing were investigated. Several recommendations relevant to Utah bridge deck preservation practice were developed based on the findings and then incorporated into a revised UDOT PPC specification. The objective of the field testing was to evaluate specific aspects of construction, quality assurance, and performance of PPC overlays on concrete bridge decks. The scope of the project included testing of a PPC test section overlay and three PPC bridge deck overlays during and after construction. Hardness tests were performed on the test section placements, and hardness, skid resistance, impact-echo, impedance, and resin content determination tests were performed on each of the bridge deck overlays. The field testing yielded valuable information about PPC overlays. Recommendations regarding hardness testing, skid resistance testing, patching, and surface preparation were developed based on the findings. The objectives of the laboratory experimentation were to characterize several material properties of field-mixed PPC sampled from actual bridge deck overlay placements in Utah and compare them to properties of laboratory-mixed PPC reported in the literature. Laboratory testing was conducted on a typical PPC mixture. Properties that were measured include density, modulus of elasticity, coefficient of thermal expansion, hardness, unconfined compressive strength, splitting tensile strength, rapid chloride permeability, and resin content. Measured properties were consistent with typical ranges cited in the literature.
185

Investigating the Effect of Thermal Stresses on the Hollow Glass Microsphere/Polyester Composites Interfacial strength by Acoustic Emission Method

Mousavi Khalkhali, Zeinab January 2016 (has links)
The effect of coatings on the interfacial strength of a hollow glass microsphere/polyester composite and their capacity to endure thermal stresses were studied by mechanical testing and an active Acoustic Emission (AE) method. AE was postulated to provide more local information at or near the glass/polyester interface due to the sensitivity of elastic waves to the rigidity of polymer chains at the glass sphere/polyester interface compared to mechanical testing. Three frequency ranges identified by multivariate statistics yet consolidated for the initial analysis into a band of 140-240 kHz, were found to be changing with the different coated glass filler for different glass content and heating state. Considering the acoustic behavior of the composites containing different levels of glass sphere content (1-10 vol%), a lower concentration (aminoethylamino)-propyl-trimethoxy silane coated glass (AS6), demonstrated the lowest attenuation after heating (associated with higher interfacial strength). As anticipated, the highest attenuation after heating was observed for uncoated glass (16K) due to expectedly weaker associations. Mechanical testing results after heating were consistent with the AE response for AS6 and 16K for this frequency range. Trends in amplitude for the three narrower, frequency ranges of 130-160 kHz, 180-220 kHz and 230-260 kHz were compared against that of 140-240 kHz and very small differences were observed. It was found that the frequency range of 130-60 kHz was more descriptive of the changes of interfacial strength in composites (at 10 vol%), being consistent with the mechanical test results. Considering the AE response at 130-160 kHz and mechanical data, higher concentration (aminoethylamino)-propyl-trimethoxy silane (AS12), better endured thermal stresses compared to other coatings. A smaller trial looked at the effect of moisture aging and subsequent thermal cycling on the glass/polymer interface strength as another method to perturb the interface. Attenuation for the band of 180-260 kHz was studied for aged versus non-aged composites. The commercial coating, L21 demonstrated a better moisture resistance before and after thermal cycling compared to uncoated glass spheres. An improved evaluation of interfacial strength in glass/polyester was expected using AE technique versus mechanical testing due to its higher sensitivity to changes in internal structure, however; no significant improvement compared to mechanical testing was observed, at least based on the analysis technique currently being used. / Thesis / Master of Applied Science (MASc) / Sheet molded compound (SMC) is a polymer material reinforced by fibers providing a combination of light weight and high mechanical properties and is used in automotive industry. Light weight fillers (hollow glass microspheres) are used to obtain further weight reduction; however, addition of these fillers leads to reduced mechanical properties and further problems during painting process known as ‘paint popping’. The former is due to uncertain interfacial state between polymer and fillers and the latter results from different thermal expansion behavior of the polymer and filler materials while the material is exposed to high temperatures for painting process. This research aims to devise a highly sensitive technique and evaluate its suitability compared to mechanical testing for investigation of the origin of aforementioned problems. Acoustic Emission (AE) is a method with high sensitivity to changes in internal structure of the material which is postulated to provide a better insight on material microstructure compared to more commonly used method i.e. mechanical testing. Use of interfacial controlling agents was examined to reduce the problems as a result of introduction of fillers. The effect of using surface modified fillers and the effect of thermal stresses on material was investigated using AE technique. Application of AE method in this study provided a good insight about the changes in material internal structure; however, it did not demonstrate a significant improvement in detecting the origins of studied problems compared to mechanical testing at least based on the analysis technique used in this study.
186

PROCESS OPTIMIZATION OF PHOTOCURABLE POLYESTER GEL COAT AND LAMINATE

Crump, Larry Scott 11 June 2014 (has links)
No description available.
187

Development of a Pavement Marking Striping Strategy for ODOT District 11.

Quasem, Tanvir January 2016 (has links)
No description available.
188

Synthesis and Characterization of Branched Macromolecules for High Performance Elastomers, Fibers, and Films

Unal, Serkan 30 November 2005 (has links)
An A2 + B3 polymerization for the synthesis of hyperbranched polymers was altered using oligomeric precursors in place of either one or both of the monomer pairs to synthesize highly branched macromolecules. Unique topologies that are intermediates between long-chain branched and hyperbranched structures were obtained and the term "highly branched" was used to define these novel architectures. Various types of highly branched polymers, such as polyurethanes, poly(urethane urea)s, poly(ether ester)s, and poly(arylene ether)s were synthesized using the oligomeric A2 + B3 strategy. The molar mass of the oligomeric precursor permitted the control of the molar mass between branch points, which led to interesting macromolecular properties, such as superior mechanical performance to conventional hyperbranched polymers, disrupted crystallinity, improved processibility, and a multitude of functional end groups. Highly branched poly(urethane urea)s and polyurethanes exhibited microphase-separated morphologies as denoted by dynamic mechanical analysis. The similarity in soft segment glass transition behavior and mechanical properties of the branched systems with that of the linear analogues suggested these materials have considerable promise for a variety of applications. When a polycaprolactone triol was utilized as the B3 oligomer for the synthesis of highly branched polyurethane elastomers, the high degree of branching resulted in a completely amorphous soft segment, whereas the linear analogue with equivalent soft segment molar mass retained the crystallinity of polycaprolactone segment. Oligomeric A2 + B3 methodology was further utilized to tailor the degree of branching of poly(ether ester)s that were developed based on slow addition of dilute solution of poly(ethylene glycol) (PEG) (A2) to a dilute solution of 1,3,5-benzenetricarbonyl trichloride (B3) at room temperature in the presence of triethylamine. A revised definition of the degree of branching was proposed to accurately describe the branched poly(ether ester)s and the degree of branching decreased as the molar mass of the PEG diols was increased. Moreover, branched poly(arylene ether)s were prepared via a similar oligomeric A2 + B3 polymerization of phenol endcapped telechelic poly(arylene ether sulfone) oligomers (A2) and tris(4-fluorophenyl) phosphine oxide (B3) in solution. Highly branched poly(ether ester)s were also synthesized in the melt phase using the oligomeric A2 + B3 polymerization strategy. Melt polymerization effectively limited the cyclization reactions, which are common in A2 + B3 polymerizations in solution, and overcame the need for large amounts of polymerization solvent typical of A2 + B3 systems. Finally, a new family of telechelic polyester ionomers was synthesized based on phosphonium bromide salt end groups and branching allowed the incorporation of higher levels of ionic end groups compared to linear analogues. / Ph. D.
189

Structure-Property Relationships of Polyester Regioisomers and Pendant Functionalized Polyetherimides

Mondschein, Ryan Joseph 11 July 2019 (has links)
Step-growth polymerization enabled the synthesis of novel polyester regioisomers and pendant functionalized polyetherimides (PEI)s. Novel monomers incorporated at targeted mol % produced series of polyesters and PEIs, suitable for systematic analysis of key polymer properties. Subsequent compositional, thermal, mechanical, and rheological characterization forged structure-property relationships to further understand the influence of composition on performance. Altering regiochemistry is a subtle way to maintain the same polymer composition but tune desired properties. Similarly, introducing functional pendant groups expands the property profile of common industrial polymers and installs a handle for secondary chemistry after synthesizing the main polymer. Both altering regiochemistry and adding pendant groups alters polymer properties without the need for large changes in synthetic requirements or reaction conditions, ideal for industrial adoption. Incorporation of a kinked bibenzoate (BB)-based diester monomers into the commonly utilized linear regioisomer afforded processable amorphous and semi-aromatic (co)polyesters. BB-(co)polyesters with ethylene glycol (EG) possessed improved barrier performance compared to poly(ethylene terephthalate) (PET) while improving on mechanical properties, including tensile and flexural modulus/strength, rivaling bisphenol-A polycarbonate (BPA-PC). Replacement of EG with 1,4-cyclohexanedimethanol (CHDM) improved thermal properties closer to BPA-PC, while enabling melt rheological analysis due to its amorphous morphology. Time-temperature superposition (TTS) analysis produced master curves provided insight into the entanglement molecular weight (Me) and entanglement density. More kinked structures possessed a lower Me and more entanglements. Introducing kinked monomers posed the question of cyclic speices generation during polymerization, common in step-growth reactions. Thus, systematic incorporation of meta-substituted hydroxyethylresorcinol and para-substituted hydroxyethylhydroquinone regioisomers into PET analogues enabled the characterization of cyclic formation due to monomer regioisomers. Increased meta substitution produced increased amounts of cylic species, analyzed by size exclusion chromatography (SEC). Adding functionality to high performance polyetherimides (PEI)s is difficult due to the high temperatures required for processing. The lack of thermal stability for commonly utilized H-bonding/reactive groups limits viable moieties. Utilizing the high temperture processing, PEIs incorporating pendant carboxylic acids reacted in the melt to form branched PEIs. These branched PEIs exhibited steeper shear thinning as well as improved flame resistance, limited in thin film commercial PEIs. / Doctor of Philosophy / My research focused on making new plastics (polymers) for use in consumer and performance markets. Typical applications utilizing these plastics include food packaging, consumer goods, automotive, aerospace, microelectronics, construction, and medical devices. Large changes such as intricate new chemicals used to make the plastics increase the difficulty in incorporating these new materials into existing synthesis and processing techniques and infrastructure. Thus, my research revolved around subtle changes to the chemical structure of the plastic, suitable for easy industrial adoption while also improving targeted properties necessary for the aforementioned applications. Polyesters are a class of polymers commonly used for food packaging and consumer goods. Thus, improving gas barrier performance and mechanical integrity/strength is crucial when designing new polyesters. Changing the bond angles through the linear versus kinked nature of the polymer chain imparts processability and improved gas barrier, compared to commercial poly(ethylene terepthalate) (PET), commonly used in food packaging applications. The density of the polyesters is also increased, which improves mechanical strength. The specific structures used also increased the thermal resistivity compared to PET. This higher thermal resistivity enables use in applications where high temperature cleaning such as steam sterilization and dish-washing could deform products or processing such as filling food packaging containers with hot foods. Similar types of polymers which possess much higher thermal resistivity are classified as high performance polymers. One class of these include polyetherimides (PEIs). The specific chemical structures and their high thermal resistance makes them great candidates for applications in automotive, aerospace, and microelectronic applications; although, these same properties make these polymers very difficult and expensive to process into the desired parts. Thus, adding functionality to the polymer by putting specific chemical groups off of the main chain enabled easier processing and improved other polymer properties. Adding the functionality to these polymers allowed them to react and change structure at high temperatures (during processing) to achieve a different shape, thus improving desired properties, such as how easy they flow like liquids at high temperatures and processing conditions. Another benefit realized from this change during processing was the improvement of flame resistance. Due to the chemical structure of the PEIs, they inherently possess resistance to catching on fire, remaining on fire, and dripping flaming material. Although PEIs typically possess good flame resistance, thin films or small parts made from these polymers do not possess the same flame resistance and can produce flaming drips, undesirable for applications requiring flame resistance. Chemically modifying these polymers with the aforementioned functionality and processing them increased the flame resistance to eliminate flaming drips and lessen the amount of time the polymer was on fire.
190

High Performance Engineering Polymers: Design, Properties, and Performance

Dennis, Joseph M. 18 April 2017 (has links)
The facile synthesis of engineering thermoplastics enabled the development of structure-morphology-property relationships for a wide range of applications. Utilizing step-growth polymerization techniques, a myriad of reaction conditions probed various polymer families including polysulfones, polyesters, polyimides and polyureas. Copolymers ranging from random to segmented sequences provided insight into the influence of segment length on physical properties. Melting temperatures, glass transition temperatures, and mechanical properties responded systematically to segment length and morphology. Leveraging several complementary analytical techniques identified critical segment lengths required for phase separation and crystallization within these copolymers. Introduction of hydrogen bonding further complicated the interrelationships between thermal and mechanical properties, and possible co-crystallization between dissimilar segments occurred. Finally, branching out from linear copolymers to other topologies determined the influence of branch length on rheological and mechanical properties. The commercially-viable synthesis of these various thermoplastics further highlights the immediate impact on state-of-the-art materials, and the fundamental development described herein provides a road map for future development in this field. / Ph. D.

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