Macroporous hydrophobic membran

Kunz W, Benhabiles A, and Ben-Aim R. Osmotic evaporation through macroporous hydrophobic membranes a survey of current research and appUcations. J. Membr. Sci. 1996 121 25-36. 

In MD, a macroporous hydrophobic membrane is in contact with an aqueous heated solution on one side (feed or retentate) (Figure 4.9). The hydrophobic nature of the... 

Porous affinity membranes based on hydrolyzed poly(GMA-co-EDMA) grafted with glicidyl methacrylates oligomers were also reported [2,60]. Tennikova et al. [2] prepared functionalized macroporous poly(GMA-co-EDMA) membranes by reaction with propane sulfone, diethylamine, or water, leading to the formation of corresponding sulfonic acid, diethylamino or diol-derivatized stationary chromatographic phases. Unfortunately, the poly(GMA-co-EDMA) membranes are mechanically weak and due to their hydrophobic character may cause nonspecific adsorption of proteins. 

The GDL of PEM fuel cells connects between the bipolar plate/flow channel and catalyst layer. It provides the pathways for mass, heat, and electron transport, and also acts as the physical support of CL and membrane. The present state-of-the-art GDL consists of both a macroporous substrate and a micropo-rous layer (MPL). The macroporous substrate is a porous network of graphite fibers, which is usually carbon paper, carbon felt or carbon cloth. The substrate is often coated with hydrophobic materials such as PTFE for better liquid water removal. The MPL is coated on one side of the substrate which faces the catalyst layer. A typical MPL is a composite layer mixed by carbon particles and PTFE. The MPL usually has lower porosity and permeability but higher hydrophobicity and electrical/thermal conductivity than its substrate layer. The MPL enhances the water management and thermal/electricity connection between the substrate layer and CL to better cell performance. Unlike the membrane and catalyst layer, researches focusing on developing new materials and/or revolutionary design are scarce. Therefore, this subsection only focuses on the macroporous substrate/MPL GDL. 

The Clark sensor is equipped with a gas-permeable membrane located in direct contact with the working electrode surface (Fig. 7.20). The membrane separates the sensor from the sample solution. In this way the electrode surface is protected. Selectivity is increased since only gaseous components can reach the active area. Membranes of macroporous polytetrafluorethylene (PTFE) are used preferably. The material is strongly hydrophobic. Water in liquid state is unable to permeate the membrane pores. Unlike liquid water, gases easily diffuse through the pores. Membranes of silicon rubber have also been used with the Clark sensor. They are permeable for oxygen since it is dissolved homogeneously in the matrix. 

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