Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 51 for “"Polymer degradation"”.
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Abiotic and Biotic Polymer Degradation to Inform Sustainable Design
… environmental processes governing plastic degradation is crucial to inform the sustainable design of polymers. This thesis is structured into three chapters, each addressing critical aspects of polymer degradation: In the first chapter, I develop and apply a sequential abiotic …
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A study of chlorinated polymer coatings in a fretting interface
… this study is to determine whether chlorinated polymers such as polyvinylchloride (PVC) and polyvinylidenechloride (PVDC) degrade in a fretting interface. Polymer coated 52100 steel balls are fretted against a polished 1045 steel plate for 30 minutes in air and nitrogen at 25-30 percent and …
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Effect of Laser Induced Crystallinity Modification on Degradation and Drug Release of Biodegradable Polymer
Biodegradable polymers such as poly(L-lactic acid) (PLLA) are promising in drug delivery applications. In biodegradable polymer-based drug delivery systems, drugs are released at a rate determined by polymer degradation. Polymer degradation exhibits an undesirable induction period, during which a …
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In vitro studies of degradation and bioactivity of aliphatic polyesther composites
… involving simultaneously diffusion for polymer degradation and bioactivity through nucleation and growth of apatite in simulated body fluid (SBF) solution. The objective of this study is to contribute to the understanding of the fundamentals in designing non-porous, solid materials for …
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Evaluation of the degree of blending of Reclaimed Asphalt Pavement (RAP) binder for warm mix asphalt
… would not require adverse plant modification. Polymer degradation of WMA was also studied to determine whether lower production temperatures could decrease polymer degradation. Gel permeation chromatography was used to measure molecular weight of polymer and binder particles at original, RTFO …
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An Investigation of Polymer Support Structures In Metal Directed Energy Deposition
… The use of a dissimilar material, such as a polymer, as a support would enable lower cost, easily removable supports. The suitability of polymers as substrates in DED has not been explored due to two key unknowns: (1) the effect of the metal DED process on a polymer substrate and (2) the …
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Modeling the sustained release of PLGA-based drug delivery systems with a physically-based model and pore space characterization
… by incorporating a description of hydrolytic polymer degradation kinetics, which is validated against an extensive data set of drug release, water uptake, and polymer degradation from an in vitro study of a drug-surrogate-embedded PLGA system. Reasonable agreement between model predictions and …
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Drop deformation dynamics in extensional flows : influence of chemical-, mechanical- and photo-degradation.
Polymer drop impact on a solid substrate is commonplace in many industrial applications, such as inkjet printing, agricultural pesticides, and spray coating, where dyes and surfactants are used to enhance various functionalities. Pesticide spray droplets can sometimes deviate from their intended …
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Photo-responsive degradable poly (beta-amino ester) toward non-viral gene delivery
Among synthetic cationic polymers, poly(beta-amino ester) (PBAE) is one of ideal candidates for non-viral gene therapy due to its desired gene delivery efficiency, biocompatibility, and biodegradability. In order to further improve the gene delivery efficiency of PBAE by facilitating the …
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Molecular mechanisms of pathogenesis incited by Erwinia carotovora subsp. carotovora
… thought to play a role in plant cell wall pectic polymer degradation. Restriction endonuclease and Southern hybrididizatian analyses indicate that the EC14 genes on plasmids pDR1 and pDR30 are not part of the same operon. Escherichia coli strain HB101 containing plasmid pDR1 or plasmid pDR30 is …
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Bacterial interactions and enzyme kinetics in environmental polyester degradation
… projected to increase, strategies to enhance polymer degradability in natural systems are necessary to reduce their environmental accumulation. In this dissertation, the environmental biodegradation of copolyesters was explored to understand the biological processes that control the removal of …
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Metal-foam interface stability during the filling of lost foam moulds with aluminium alloys
… and this suggested that the defect was caused by polymer entrapment. A Saffman-Taylor instability was observed at the interface between Hg and a viscous glucose syrup which were contained in an analogue, that was used simulate the casting of Lost Foam moulds at room temperature. The liquid …
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Large contraction conducting polymer molecular actuators
… most complex robotic system to date. Conducting polymers were chosen for research as actuators, based on a review of the relevant properties of all known actuators and active materials. Key features of conducting polymer actuators include low drive voltages (1 - 2 V) and high active strength (10 …
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Phase separation spinning of porous polypropylene hollow fibers
Two phase separation polymer-solvent systems were studied: polypropylene-paraffin wax, and polypropylene-naphthalene. A tube-in-orifice spinneret design was used. All attempts to spin hollow fibers using the polypropyleneparaffin wax system failed. Initial attempts to produce hollow fibers from …
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In vitro Sustained Release Delivery System for Hydrogen Sulfide Analogs
… was to formulate an in situ gel forming smart polymer-based delivery system that would release hydrogen sulfide donor at sustained rate for extended period of time. Therefore, in this study a novel sustained release formulation of sodium hydrogen sulfide (NaHS) (a model H2S donor) was prepared, …
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Development of a Novel Vaccine Adjuvant System Utilizing an In Situ Implant System to Modified Release
… N-Methyl-2-Pyrrolidone, NMP) and hydrophobic polymer (e.g. poly (lactide-co-glycolide), PLGA). We have given this concept the name of AdjuGel to distinguish it from simple drug administration. It was developed by incorporating an oil (e.g. Acetyl Tributyl Citrate, ATBC) into an ISI system. …
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Effects of Therapeutic Radiation on Polymeric Scaffolds
… levels of ionizing radiation are known to cause degradation and/or cross-linking in polymers. Lower levels of ionizing radiation, such as x-rays, are commonly used in the treatment of cancers. Material characterization has not been fully explored for polymeric materials exposed to therapeutic …
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Effect of ultraviolet exposure on the durability of polycarbonate
… the United States Air Force to analyze the photodegradation of polycarbonate caused by ultraviolet radiation. First, aircraft-grade polycarbonate plates were exposed to continuous ultraviolet light in a QUV laboratory weathering chamber for durations of three, seven, ten, and twenty weeks. The …
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Microencapsulation studies with P(HB-HV) polymers
… microparticles from poly--hydroxybutyrate homopolymers and copolymers thereof with 3-hydroxyvalerate [P(HB-HV) polymers]. Variations in the preparative technique have facilitated the manufacture of two structurally distinct forms of microparticle. Thus, monolithic microspheres and …
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Polyimide-Organosilicate Hybrid Materials: Part I: Effects of Annealing on Gas Transport Properties; Part II: Effects of CO2 Plasticization
… from the removal of sol-gel condensation and polymer degradation byproducts. For the second study, the transport properties of four membranes, 6FDA-6FpDA polyimide, 6FDA-6FpDA-DABA polyimide, MTMOS and PTMOS-based hybrid materials, were characterized as a function of feed pressure to evaluate …
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