Morphological Structure Of Membrane Research Articles

Nano-fiber/net structured PVA membrane: Effects of formic acid as solvent and crosslinking agent on solution properties and membrane morphological structures

A technique of electro-spinning/netting (ESN) has been investigated to prepare poly(vinyl alcohol) (PVA) nanofibrous membrane with unique morphological structure of nano-fiber/net (NFN). The prepared NFN membrane consists of both common electrospun nanofibers (with diameters in hundreds of nanometers) and two-dimensional nano-nets (with nanofibril diameters smaller than 50nm). It is revealed that formic acid has dual effects (i.e., as solvent and crosslinking agent) on solution properties and membrane morphological structures, and systematic analyses on rheological properties of three different 10wt% PVA solutions with solvents being water, formic acid, and their 1/1 (wt./wt.) mixture have been conducted. Results indicate that the molecular interactions (particularly hydrogen bonding) among water, formic acid, and PVA macromolecular chains, as well as the acetal formation (i.e., chemical crosslinking), have significant influences on macromolecular conformation, solution rheological properties, and morphological structure of membranes. The acetal formation, which leads to improved tensile strength of PVA NFN membrane, has been verified by FT-IR and DSC. Additionally, the PVA NFN membrane has been assembled into a gravity-driven filtration device; and the membrane exhibits high rejection ratio (>99%) for polystyrene microspheres (with diameters of ~0.2μm) and high water flux (3773L/m2∙h) under the pressure of 40kPa.

Preparation of Hydrophilic and Antifouling PVC/PAN Hollow fiber Membrane

Poly (vinyl chloride) /poly (acrylonitrile) (PVC/PAN) hollow fiber membrane was prepared by phase inversion method and it was hydrolyzed in different NaOH solution concentration. After hydrolysis modified, the change of surface characteristic of the PVC/PAN hollow fiber membrane was described by Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR) and water contact angle. Morphological structures of membranes were observed by field-emission scanning electron microscope (FESEM). Protein filtration was employed to evaluate the antifouling performance of the membrane. All these results demonstrated that PVC/PAN hollow fiber membrane modified by hydrolysis showed high permeation flux, good hydrophilicity and antifouling.

Synthesis of Nonfluorinated Amphiphilic Rod−Coil Block Copolymer and Its Application to Proton Exchange Membrane

New amphiphilic block copolymers composed of thermally and chemically stable poly(arylene sulfone ether ketone) and sulfonated poly(styrene-co-acrylonitrile) were successfully synthesized through two-step polymerization, condensation polymerization followed by controlled radical polymerization, for application to proton exchange membrane fuel cells. The morphological structures of membranes were investigated as functions of the hydrophilic chain length and the degree of sulfonation (DS), and were related to the proton conductivity of the membranes. Because of their inherent high thermal stability and well-connected hydrophilic channel, the newly synthesized membranes show high proton conductivity at relatively low DS and a continuous increase in proton conductivity above 90 °C. They also exhibit good thermal and oxidative stability.

UV curable sulfonated hybrid materials and their performance as proton exchange membranes

In this study 2-acrylamido-2-methylpropanesulfonic acid (AMPS) containing UV curable nanocomposite membranes were prepared by using the sol–gel method. Tetraethylorthosilicate (TEOS), and 3-(methacryloyloxy)propyl trimethoxysilane (MAPTMS) were used, respectively as an inorganic precursor and coupling agent. Cross linking agents such as poly(ethylene glycol diacrylate) (PEGMA) and ethylene glycol dimethacrylate (EGDMA) were used to arrange the mechanical and physical properties of the resulting hybrid membrane. The hybrid formulation polymerized under UV irradiation and the gel percentage, water uptake of the membranes were calculated. The polymerization conversion of the organic part was investigated by using photo-differential scanning calorimetry (photo-DSC). The thermal and mechanical properties of the membranes indicated good stability. The morphological structure of membranes was investigated by scanning electron microscopy (SEM). In addition proton conductivity and methanol selectivity measurements were performed. The proton conductivity of the AMPS20–SOLGEL30 nanocomposite membrane is about 0.138 S cm −1 at 50 °C. Selectivity toward methanol for the same membrane is very low with a selectivity factor of α = 0.032, which satisfies the requirements for DMFC applications.

Molecular and Morphological Designs of High Performance Polymeric Membranes

Currently, membrane separation techniques, such as reverse osmosis and ultrafiltration, play an important role in industrial separation technology. To develop high performance polymeric membranes, it is essential to design the molecular and morphological structures of the membranes for their specific applications. In the reverse osmosis field, we have developed several kinds of composite membranes for specific uses. Applications include ultrapure water production, seawater desalination, softening and desalination of brackish water, and recovery of valuable substances. In the course of development, thin-film composite membrane materials and membrane morphology have been analyzed intensively and are becoming clearer. These results enable us to control membrane performance by an optimum combination of membrane materials and membrane morphology. The morphological structure and chemical structure of the composite membranes were designed to optimize the performance of both the ultrathin layer and the supporting...