Thesis (M.S.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 51).

Thesis (Ph.D)--Aerospace Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Hanagud,Sathya; Committee Member: Apetre, Nicoleta; Committee Member: Kardomateas, George; Committee Member: McDowell, David L.; Committee Member: Ruzzene, Massimo. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (B.S.)--Virginia Polytechnic Institute, 1966. / Vita. Abstract. Includes bibliographical references (leaves 36-37). Also available via the Internet.

Thesis (Ph. D.)--Ohio University, June, 1987. / Title from PDF t.p.

Thesis (M.S.)--State University of New York at Binghamton, Dept. of Mechanical Engineering, 2007. / Includes bibliographical references.

Polytetrafluoroethylene (Teflon®) is encountered in many environments – frying pans, clothing, osmotic distillation membranes, to name a few – yet the solubility and clustering behaviour of water with this material was not found in the open literature. This information may be useful in applications where an absence of water is desired, such as in clothing and textiles. Previous work on polyethylene + water has shown that small water clusters form in the amorphous portion of the polymer. This work investigated this phenomenon for the case of polytetrafluoroethylene + water. Initially, a test system of light alcohols + water + n-dodecane was investigated using Gibbs Ensemble Monte Carlo simulations and compared to previous laboratory experiments. This test system was investigated in order to gain expertise in the methodologies and theory behind Monte Carlo simulation, as well as to gain experience with using the necessary software. For this test system, it was found that the TraPPE parameters representing the interactions between the alcohols and the n-dodecane were not adequate and lead to increasing deviations with increasing carbon number in the alcohol. To replicate the conditions of the amorphous polymer matrix, liquid-liquid equilibrium between water and the polymer was investigated. Gibbs Ensemble Monte Carlo simulations have been performed for systems of perfluoroalkanes and water to determine the influence of temperature and carbon number on the solubility and clustering behaviour of water within the perfluoroalkanes. The temperature range in this study was from 450 K to 600 K, and the perfluoroalkane carbon number range was from 8 to 300 carbon atoms. With increasing carbon number, it was found that there was an asymptotic value of 98.0 mole percent water in the polymer phase. With increasing temperatures it was found that there were exponential increases in solubility of water into the polymer matrix. Previous work on clustering and supramolecular structure of perfluoroalkanes described the rigidity of the perfluoroalkane chains in comparison to alkane chains, thus explaining the large increases in free volume with increasing temperature in the polymer matrix observed in this work. A discontinuity with regard to both solubility and clustering behavior was observed for a polymer carbon number of 10 to 12 carbon atoms. Prior work on the energy contributions towards the helical structure of perfluoroalkanes showed a shift in the energy contribution regime for carbon numbers larger than ~10 carbon atoms, which may explain this discontinuity. It was found that linear water clusters accounted for up to ~90 percent of the water clusters, concurring with previous work on water clustering in polyethylene. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2011.

Polymer samples of polytetrafluoroethylene (PTFE) and a PTFE-glass weave (RF- 35P) are exposed to low pressure, non-equilibrium glow discharge plasmas for enhanced wettability as measured by static contact angles. Plasma treatments are performed in two parallel plate RF plasma systems, a downstream microwave plasma and a barrel etcher using feed gases composed of H₂, N₂, Ar, He, and 0₂. Surface analysis of the topography and chemical composition of treated samples is performed by atomic force microscopy (AFM), attenuated total reflection infrared (ATR-IR) spectroscopy, x-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectroscopy (ToF SIMS). Optical emission spectroscopy is used to correlate wettability to reactive species in the plasma, and plasma parameters to species emission. In the parallel plate plasma systems, the contact angle can change from approximately 95° to 5° with treatment while treatments in the downstream and barrel etcher systems do not result in a contact angle change. The difference in plasma performance is attributed to ion bombardment. Plasmas composed of 20 to 80% H₂O in (H₂ + N₂) give the best wettability improvement. Plasma exposure significantly reduces the surface fluorine content followed by incorporation of nitrogen, oxygen and hydrogen, apparently as amino, hydroxyl and carbonyl functional groups with evidence of an amide. The incorporation of oxygen likely originates through peroxy radicals subsequent to plasma exposure. It is proposed that using a higher applied power creates a more reactive surface. A larger percentage of H₂ in the plasma tends to passivate the surface, leading to a smaller wettability improvement which is correlated to the atomic hydrogen concentration in the plasma. The addition of He or Ar into the H₂/N₂ plasma tends to dilute or weaken the plasma effect on wettability. To a much greater extent, the addition of oxygen also decreases the wettability. This latter effect is attributed to etching reactions which result in a more hydrophobic surface. An etch rate of approximately 0.2 μ/min is observed, and this is the first report of PTFE etching with 0₂/H₂/N₂. The distance between the parallel plate electrodes (gap) is a significant factor for the wettability of treated polymers, while power, pressure and flow rate are not. The optimal storage conditions to retain the wettability of H₂/N₂ plasma-treated RF-35P are low pressure and low temperature. The following model of PTFE surface modification is proposed. Ion bombardment creates reactive sites that initiate surface reactions. Reactive species from the H₂/N₂ plasma modify the surface through incorporation of amino, hydroxyl and carbonyl surface groups. These new groups increase the polymer wettability. Atomic hydrogen in the mixture is required to improve the wettability, but too high of a concentration will passivate the surface and lessen the wettability improvement. If oxygen is present, the modified surface is etched away leaving a refreshed, more hydrophobic surface. / Graduation date:2006

Thesis (M.S.) -- Worcester Polytechnic Institute. / Keywords: Teflon ablation; pulsed plasma thrusters; numerical analysis; PPT; depolymerization. Includes bibliographical references (p.102-105).

Thesis (M.S.)--Ohio University, August, 1993. / Title from PDF t.p.

Thesis(M.S.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references (p.89-92).