Industrial utilization of polymeric gas separation membranes is predicted to increase significantly over the next 20 years. This growth will be driven by application of membrane based separations to increasingly aggressive feed streams. In this work, the performance of defect-free Matrimid asymmetric hollow fiber membranes in the presence of high pressure carbon dioxide and trace levels of toluene and n-heptane in the feed stream are studied. Specifically, this work shows a significant decrease in the carbon dioxide plasticization pressure and the carbon dioxide permeance prior to plasticization as a result of accelerated physical aging at ambient temperature. Interestingly, sub-Tg thermal annealing at 220 oC reverses the effects of physical aging by increasing the plasticization pressure and the carbon dioxide permeance prior to plasticization for a typical polyimide commonly used in membranes. The performance of Matrimid asymmetric hollow fiber membranes in feed streams contaminated with up to 1200 ppm toluene and 2000 ppm n-heptane is investigated. In the presence of both feed stream contaminants, the productivity and efficiency of the membrane are observed to significantly decrease in this work. These decreases in performance are shown to be the result of antiplasticization, and a free volume based model is developed to correlate the effect of feed stream contamination on membrane performance

In this study, the effect of compatibilizers on the gas separation performance of polycarbonate (PC) membranes was investigated. Membranes were prepared by solvent evaporation method. They were characterized by single gas permeability measurements of O2, N2, H2 and CO2 as well as scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Fourier transform infrared spectrometry (FTIR). Membranes containing 0.5 to 10 w% p-nitroaniline (pNA) were prepared to study the effect of compatibilizer concentration on the membrane performance. Permeabilities of all gases decreased but selectivities increased with pNA concentration. The membranes with 5 w% pNA showed a selectivity of 114.5 for H2 over N2, 53.9 for CO2 over N2 and 13.4 for O2 over N2 at room temperature, whereas, the H2/N2, CO2/N2 and O2/N2 selectivities for pure PC membranes were 43.5, 20.6 and 5.6, respectively. The N2 permeabilities through pure PC membrane and 5 w% pNA/PC membrane were 0.265 and 0.064 barrer, respectively. The glass transition temperature of the membranes decreased with increasing pNA concentration. FTIR spectra showed that the peaks assigned to nitro and amine groups of pNA shifted and/or broadened. The DSC and FTIR results suggested an interaction between PC and pNA. The effect of type of compatibilizer was also studied. The compatibilizers were 4-amino 3-nitro phenol (ANP), Catechol and 2-hydroxy 5-methyl aniline (HMA). Similar to membranes prepared with pNA, membranes prepared with these compatibilizers had a lower permeability and glass transition temperature but higher selectivity than pure PC membranes. Their FTIR spectra were also indicated a possible interaction between PC and compatibilizer. In conclusion, PC/compatibilizer blend membranes for successful gas separation were prepared. Low molecular weight compounds with multifunctional groups were found to effect membrane properties at low concentration range, 0.5-5 w%.

The increasing use of polymeric materials in food packaging applications is due to many factors; however, most are related to cost. While poly(ethylene terephthalate) (PET) is currently the industry standard for soft-drink bottles, more stringent requirements on the barrier properties to oxygen are needed for PET to expand further into more demanding markets (i.e., juice, etc). The current work examines the fundamental oxygen and carbon dioxide permeation and sorption properties of amorphous, caffeine antiplasticized PET and amorphous poly(ethylene furanoate) (PEF), which is a new biologically sourced polyester that exhibits significantly enhanced performance compared to petroleum-sourced PET. The fundamental transport data reported herein at 35°C illustrate that amorphous PEF exhibits significant reductions in permeability for oxygen (11X), carbon dioxide (19X), and water (2X) compared to amorphous PET. Such impressive barrier enhancements are unexpected since PEF exhibits a higher free volume compared to PET. Further investigation into the fundamental chain motional processes which contribute to penetrant diffusion, as probed via dynamic mechanical and solid-state NMR methods, reveals that the polymer ring-flipping motions in PEF are largely suppressed compared to those for PET. Such behavior allows for rationalization of the reduced transport properties compared to PET. Additional characterization techniques (i.e., thermal, mechanical, density, etc.) are used to develop a more complete understanding of PEF and caffeine antiplasticized PET, with the ultimate goal of relating these properties to penetrant transport.

ABSTRACT EFFECT OF PREPARATION AND OPERATION PARAMETERS ON PERFORMANCE OF POLYETHERSULFONE BASED MIXED MATRIX GAS SEPARATION MEMBRANES Karatay, Elif M.Sc., Department of Chemical Engineering Supervisor : Prof. Dr. Levent Yilmaz Co-supervisor : Assoc. Prof. Dr. Halil Kalip&ccedil / ilar August 2009, 126 pages Membrane processes have been considered as promising alternatives to other competing technologies in gas separation industry. Developing new membrane morphologies are required to improve the gas permeation properties of the membranes. Mixed matrix membranes composing of polymer matrices and distributed inorganic/organic particles are among the promising, developing membrane materials. In this study, the effect of low molecular weight additive (LMWA) type and concentration on the gas separation performance of neat polyethersulfone (PES) membranes and zeolite SAPO-34 containing PES based mixed matrix membranes was investigated. Membranes were prepared by solvent evaporation method and annealed above the glass transition temperature (Tg) of PES in order to remove the residual solvent and erase the thermal history. They were characterized by single gas permeability measurements of H2, CO2, and CH4 as well as scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC). Various LMWAs were added to the neat PES membrane at a concentration of 4 wt %. Regardless of the type, all of the LMWAs had an anti-plasticization effect on PES gas permeation properties. 2-Hydroxy 5-Methyl Aniline, HMA, was selected among the other LMWAs for parametric study on the concentration effect of this additive. The incorporation of SAPO-34 to PES membranes increased the permeabilities of all gases with a slight loss in selectivities. However, the addition of HMA to PES/SAPO-34 membranes increased the ideal selectivities well above the ideal selectivities of PES/HMA membranes, while keeping the permeabilities of all the gases above the permeabilities of both pure PES and PES/HMA membranes.