Browsing by Author "Stephen Michielsen, Committee Member"
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- Acoustic Properties of Biodegradable Nonwovens(2009-12-07) Yilmaz, Nazire Deniz; Nancy Powell, Committee Co-Chair; Pamela Banks-Lee, Committee Co-Chair; Nancy Cassill, Committee Member; Stephen Michielsen, Committee MemberABSTRACT YILMAZ, NAZIRE DENIZ. Acoustical Properties of Biodegradable Nonwovens.(Under the direction of Nancy Powell and Pamela Banks-Lee.) The purpose of this study is to provide a better understanding of acoustical properties of nonwovens, and to model the noise control behavior in terms of material and treatment parameters. A review of existing models on sound absorption of fibrous materials, coupled with experimental data will help in modeling sound absorption in multi-layer needle-punched nonwovens fabrics of different fibers: hemp, polylactide, polypropylene, and glassfiber. The effects of several treatments, which the materials may undergo during sound absorber manufacturing, namely alkalization, compression and heat treatments are investigated. The collected data is evaluated by experts. Expert evaluation further provides information about the market demands about sound absorbers, and the perception of the designed nonwovens through the eyes of professionals. This research provides a contribution to the body of knowledge on the sound absorption properties of nonwovens, provides a better understanding of the effects of some manufacturing processes on nonwovens’ noise control performance and contributes to the wider adoption of nonwovens as sound absorbers.
- Electroactive Behavior of Nanostructured Polymers(2008-08-03) Shankar, Ravi; Richard J. Spontak, Committee Co-Chair; Saad A. Khan, Committee Member; Russell E. Gorga, Committee Member; Tushar K. Ghosh, Committee Co-Chair; Stephen Michielsen, Committee Member
- Fibrous Scaffolds for Tissue Engineering Applications.(2010-07-27) Chung, Sangwon; Martin King, Committee Chair; Michael Gamcsik, Committee Chair; Nancy Monteiro, Committee Member; Samuel Hudson, Committee Member; Stephen Michielsen, Committee Member; Phillip Russell, Committee Member
- Influence of Surface Modification on the Adhesion between Nitinol Wire and Fluoropolymer Films(2009-01-05) Yoon, Hyounil Joshua; Martin King, Committee Chair; Stephen Michielsen, Committee Member; Ahmed El-Shafei, Committee MemberABSTRACT YOON, HYOUNIL. Influence of Surface Modification on the Adhesion between Nitinol Wire and Fluoropolymer Films. (Under the direction of Dr. Martin W. King.) One of the current challenges for the medical device industry is how to manufacture and assemble biomedical implants consisting of a metallic wire component and a fluorocarbon film without the use of an adhesive. There are many devices such as guide wires, stent/grafts and embolic protection devices which rely on these components being bonded together in order to function inside the body. This study has evaluated the effect of modifying the surfaces of metallic wire and fluorocarbon film prior to thermally bonding these two components together. The surface treatments for Nitinol wire included mechanical roughening with sandpaper, treating with atmospheric helium-plasma, and adding a fluorocarbon coating. The surface treatments for fluorinated ethylene-propylene (FEP) film included helium plasma and helium-oxygen plasma under atmospheric conditions. This produced four types of treated and untreated Nitinol and three types of treated and untreated FEP film which were combined together and thermally bonded to prepare 12 different types of pull-out test specimens. A unique pull-out strength test method was developed to assess the level of adhesion between these various candidates. The pull-out force for untreated Nitinol bonded to untreated FEP film was 30.5±2.4N. Significant improvements of up to 14% in this level of adhesion were obtained with the mechanically roughened Nitinol wire bonded to the helium-plasma treated films and up to 6% of increase with the mechanically roughened Nitinol wire bonded to the helium-oxygen-plasma treated FEP films. However, coating the wire with liquid fluorocarbon solution (TG-10) and then passing it through a helium-plasma to cure and polymerize the fluorocarbon coating was not successful. After thermal bonding to FEP film the level of adhesion fell by over 80%. Scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), and contact angle measurements were also taken to characterize the appearance and chemistry of the surfaces before and after modification.
- Investigation of the utility of islands-in-the-sea bicomponent fiber technology in the spunbond process(2007-10-02) Fedorova, Nataliya Vasylivna; Donald Shiffler, Committee Member; Stephen Michielsen, Committee Member; Trevor Little, Committee Co-Chair; Behnam Pourdeyhimi, Committee Co-Chair; Jan Genzer, Committee Member
- Life Cycle Inventory Analysis of Medical Textiles and Their Role in Prevention of Nosocomial Infections(2009-12-07) Ponder, Celia Steward; Jan Genzer, Committee Member; Marian McCord, Committee Member; Stephen Michielsen, Committee Member; Christine Grant, Committee ChairBiocidal finishes grafted onto medical textiles are a potential technology to reduce nosocomial infection transmission. But is the application and use of biocidal finishes worth the environmental cost? Life cycle inventories (LCI) are a tool to show the resources used and emissions generated over the life cycle of a product. In this research, life cycle inventories are utilized in the design of a reusable medical garment with a biocidal finish to: assess options for the biocidal chemical, compare the reusable garment with a disposable garment, and assess the use of a biocidal finish in a hospital setting. The cradle-to-gate life cycle inventories of two biocidal halamines – 3-allyl-5,5-dimethyl hydantoin (ADMH) and dimethylol-5,5-dimethyl hydantoin (DMDMH) – are compared to allow the manufacturer to select the chemical that consumes less energy and raw materials and generates fewer emissions. The reusable garment is then compared with a disposable gown of similar use to determine, cradle-to-use, which has the better environmental performance. Life cycle inventory analysis is also used to determine the resources and emissions saved by the hypothetical use of a biocidal patient gown and the subsequent reduction in nosocomial infections. This is a novel area for LCI, as no LCI has been studied for treating an infection previously. When a patient contracts an infection while in the hospital, additional materials are used to test the patient, to provide contact isolation, and to treat the patient. Inventories were analyzed for each phase of this treatment using MRSA (Methicillin-resistant Staphylococcus aureus) as the nosocomial infection contracted and treated. In this research study, the drug therapy consists of vancomycin hydrochloride. While previous life cycle inventory studies have determined that solvent usage is the largest user of resources for pharmaceutical production, the current study shows that fermentation is actually the largest consumer of raw materials and energy in the cradle-to-gate (CTG) manufacture of vancomycin hydrochloride. Of the phases in infection treatment studied, contact isolation utilizes the most raw material and energy resources and generates the most emissions due to the use of disposable gowns and gloves. Finally, the LCI for treating an infection was compared with the LCI for using the biocidal finish. If the usage of the biocidal patient gown reduces the nosocomial infection rate more than 2%, the resulting reduction in raw material consumption, energy consumption, and emissions generated is enough to overcome that of using a biocidal garment. In addition, the impact of dyeing processes on the cradle-to-gate inventory of a textile product is investigated using carpet as a case study. Using a life cycle approach, gate-to-gate inventories for five nylon coloring processes are performed and compared to the cradle-to-gate life cycle inventory of the carpet. This analysis shows that dyeing can be a large contributor to the carpet cradle-to-gate energy usage.
- Nanolayer Self-assembly on Ionic Fibers(2009-06-19) Wang, Zhengjia; Orlando Rojas , Committee Member; Peter Hauser, Committee Chair; Stephen Michielsen, Committee Member; Xiangwu Zhang, Committee MemberThe application of electrostatic self-assembly techniques in textiles has been explored. The layer-by-layer and atomic layer deposition have been used as new methods of textile modification. The use of layer-by-layer and atomic layer deposition offer the possibility of achieving fully conformal, uniform functionalization of textile fibers of any shape. The optimum processing conditions that allow the selective and controlled deposition of organic, inorganic, and metallic substances on textile substrates via self-assembled nanolayers and atomic layer deposition techniques have also been investigated. However, non-uniform surface and irregular shapes in yarns and fibers, especially the natural fibers increase the difficulties of these applications. Recent studies stated the feasibility of using electrostatic self-assembly on cationic cotton substrates. The goal of this research was to determine the charge density on ionic cotton fibers, which directly affect the electrostatic self-assembly. The ionic cotton fabric was produced after treatment of the substrate with a salt of chloroacetic acid or 3-chloro-2-hydroxypropyltrimethyl ammonium chloride. This research also provides a better understanding of layer-by-layer adsorption behaviors of positively or negatively charged polymer solutions on ionic cellulose films as measured by quartz microgravimetry. At neutral solution pH the adsorption of polyelectrolytes on ultrathin cellulose films was found to depend mainly on the charge density of the adsorbing macromolecule and that of the substrates. At the same adsorption condition, the thickness and surface excess (surface concentration) of the adsorbed species are controlled by the nature of the substrate and polyelectrolyte solution.
- Vascular Tissue Engineering Scaffolds from Elastomeric Biodegradable Poly(L-lactide-co-epsilon-caprolactone)(PLCL) via Melt spinning and Electrospinning(2006-04-26) Chung, Sangwon; Martin W. King, Committee Chair; Hechmi Hamouda, Committee Member; Stephen Michielsen, Committee MemberThree dimensional scaffolds play an important role in tissue engineering as a matrix that provides the cells with a tissue specific environment and architecture. For cardiovascular applications in particular, the development of elastic scaffolds that can maintain their mechanical integrity while being exposed to cyclic mechanical strains is a necessary criterion. The main objective of this study was to demonstrate the feasibility of fabricating vascular tissue engineering scaffolds via two different approaches, namely; melt spinning and electrospinning from elastomeric biodegradable poly(L-lactide-co-ε-caprolactone) (PLCL) copolymers. Overall, the tubular scaffolds had porosity exceeding 70% and the mechanical properties exceeded the transverse tensile values of the natural arteries of similar caliber. The morphology was also characterized as well as the fiber diameters and the pore sizes of the structures. In addition to spinning the polymer separately into melt spun and electrospun constructs, the novel approach in this study has been to successfully demonstrate that these two techniques can be combined to produce a two layered tubular scaffold containing both melt spun fibers and electrospun nanofibers.
