Gas permeation property of polyaniline films

The sol-gel method was employed to synthesize an inorganic-organic photosensitive composite material, silica/polyimide. Silica was covalently bonded to polyimide by introduction of 1,4-aminophenol as a coupling agent. A photosensitive cross-linking agent, 2-(dimethylamino) ethyl methacrylate, was used to engender UV sensitivity to the composite. Using field emission scanning electron microscope imaging at very high magnifications, the composite film was found to exhibit a porous crosssectional structure. The pores were interconnected to form numerous continuous channels within the matrix and silica particles were attached to the pore wall of the polyimide host. Depending on the preparation conditions, the size of the silica particles could vary from 20 nm to a few lm. The thermal degradation temperatures, dynamic mechanical properties, glass transition temperatures, thermal expansion coefficients, and dielectric constants of various silica/polyimide composites were measured, and the results indicated that incorporation of silica could improve the thermal and dimensional stabilities of the polyimide. Also, because the silica/polyimide composite had a porous interior structure, it had a rather low dielectric constant with the lowest achievable value being 1.82.

Section: Resultsmentioning

confidence: 99%

Porous structure and thermal stability of photosensitive silica/polyimide composites prepared by sol‐gel process

Huang

Don

Lai

et al. 2009

“…Therefore, hyperthin skin layer with hardly any defects is possibly formed by solidification at their sharp interface. Such solvent properties might depend on dielectric constant and dipole moment 21. After coating, oxygen:nitrogen selectivity of 6FDA–BAAF polyimide membranes was found to be 4.3 for 7.1 × 10 −5 cm 3 (STP) cm ‐2 s ‐1 cmHg ‐1 of oxygen flux.…”

Section: Evolution and Developmentmentioning

confidence: 99%

“…Recently, a new type of asymmetric membrane developed by Hachisuka et al at Nitto Denko Corporation having an almost defect‐free hyperthin skin layer (40–60 nm) was wet‐cast from a solution with 18 wt % polyimide synthesized by 2,2‐bis(3,4‐dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 2,2‐bis(4‐amino phenyl)hexafluoropropane (BAAF) in diethylene glycol dimethyl ether 16, 21, 22. Solvents such as diethylene glycol dimethyl ether are miscible in water, but a sharp interface exists between diethylene glycol dimethyl ether and water for a while.…”

Section: Evolution and Developmentmentioning

confidence: 99%

Review on the development of defect‐free and ultrathin‐skinned asymmetric membranes for gas separation through manipulation of phase inversion and rheological factors

Ismail

Yean

2003

102

Development of high-performance asymmetric membranes is a major breakthrough in membrane technology. A comprehensive study on original concepts and new advances in membrane formation process is necessary to generate defect-free and ultrathin-skinned asymmetric membranes with superior performance for gas separation process. Correlation of rheological factors with primary-phase inversion process is a novel approach in membrane research that provides a potential platform to improve membrane performance. The former controls general morphology of membrane, whereas the latter further affects molecular orientation in membrane.

“…A particular additive can either suppress or induce macrovoid formation, depending on its concentration in the casting solution. Following systems were found to suppress macrovoid formation (upon increasing the additive concentration in the casting solution): CA/1,4‐dioxane (DIO)/water, PI/NMP/THF/water, PI/NMP/THF/IPA, PI/NMP/THF/AC, and PI/NMP/THF/1‐hexanol, PI/DMF/DIO, polyetherimide (PEI)/NMP/diethylene glycol dimethyl ether (DGDE) and PI/NMP/DGDE . On the other hand, addition of DIO, DGDE, AC, and GBL to PSf/NMP solutions promoted macrovoid formation .…”

Section: The Process Of Phase Inversionmentioning

confidence: 99%

Understanding and guiding the phase inversion process for synthesis of solvent resistant nanofiltration membranes

Hołda

Vankelecom

2015

367

268

Since its introduction in membrane technology in the 1960's, phase inversion by means of immersion precipitation has been widely studied for the preparation of membranes to be applied in the fields of microfiltration (MF) and ultrafiltration (UF). However, much less knowledge is available about this process in terms of integrally skinned asymmetric nanofiltration membranes, especially for more hydrophobic polymers applied in solvent resistant nanofiltration (SRNF). This review focuses on the preparation aspects of integrally skinned asymmetric membranes to be applied in the field of SRNF via phase inversion. It starts with the explanation of the basic principles of the phase inversion process, covering both thermodynamic and kinetic aspects. Further, it summarizes the parameters that significantly influence final membrane performance and morphology, including polymer type and concentration, casting solvent, additives, evaporation time, and temperature, humidity, membrane thickness, composition, and temperature of coagulation bath and post-treatment. Literature contained within this review constitutes the core references in the field of SRNF, but also several references on preparation of MF, UF, aqueous NF, and reverse osmosis (RO) membranes have been included to better clarify or illustrate certain aspects of the process.