Reinforced Composite Membranes

Figure 14. Strain-to-failure versus number of cycles for two types of MEAs one with a reinforced composite membrane (Gore-5510) and the other with regular PFSA membrane (N- 111). The samples are cycled from 30 to 80% RH and from 80 to 120% RH.37...

The main driving force for the development of reinforced composite membranes has been the possibility of increasing both mechanical strength and dimensional stability, leading to the feasible production of very thin membranes. As mentioned in Section 10.2.2, as the cell resistance increases proportionally to the thickness, an improvement in PEMFC performance could easily be achieved by using thin, reinforced composite membranes. From a cost perspective, such thin reinforced composites would contain much less of the expensive ionomer resin than conventional membranes. 

Fibre-reinforced composite materials are relatively new and are of interest for primary constructions. These materials are lightweight and may easily be processed into complex forms. In specifically designed primary constructions, the natural forms of organic membranes may have a counterpart in bionic development such as the technical plant stem , which is formed on a model of giant reeds and horsetail (Milwich et al. 2006). 

Referring to microbial cellulose applications, bacterial nanocellulose has proven to be a remarkably versatile biomaterial with use in paper products, electronics, acoustic membranes, reinforcement of composite materials, membrane filters, hydraulic fracturing fluids, edible food packaging films, and due to its unique nanostructure and properties, in numerous medical and tissue-engineered applications (tissue-engineered constructs, wound healing devices, etc). 

X.B. Zhu, H.M. Zhang, Y.M. Liang, Y. Zhang, Q.T. Luo, C. Bi, B.L. Yi, Challenging reinforced composite polymer electrolyte membranes based on disulfonated poly(arylene ether sulfone)-impregnated expanded PIPE for fuel cell applications, J. Mater. Chem. 17 (4) (2007) 386-397. 

Figure 17. SEM micrographs for the PVA/PAA composite polymer membrane reinforced with sulfonated PP/PE separator (a) top surface and (b) cross-section.

The creation of a dispersion morphology through in situ fibril generation is central to the formation of a microfibril reinforced composite. What is more, this dispersion methodology is also one of the principal methods of barrier property enhancement in many polymer films and membranes. Therefore, it was anticipated that MFCs would be inherently suited to applications in which reduced gas permeability of the matrix polymer was required. 

Tang Y, Kusoglu A, Karlsson AM, Santare MH, Cleghom S, Johnson WB (2008) Mechanical properties of a reinforced composite polymer electrolyte membrane and its simulated performance in PEM fuel cells. J Power Sources 175 817-825... 

Table 12.3 Membrane thickness (L), phosphoric acid dop level (PA op), proton conductivities (tr), and area specific resistances (L/tr) of PBI/fiber reinforced composite membranes...

The biggest application for fiuorinated ionomers currently is as unreinforced membranes for fuel cells, or polytetrafluoroethylene (PTFE) fiber-reinforced composite membranes for electrolytic baths. The membranes can be fabricated by the extrusion method or the solution-cast method. 

Improving the mechanical and thermal strengths of membrane is critical to solve the physical degradation problems, and this has been mainly achieved by reducing the polymer side chain length of PFSA membranes or by using the reinforced/composite membranes. 

Artificial blood vessels and blood vessel coatings, skin implants, artificial heart valves, dialysis membranes, infusion hoses, hose pumps, artificial hearts, balloon catheters, artificial skin replacement Matrix material for carbon fiber-reinforced composite implants, such as osteosynthesis plates and hip joint shafts... 

Matrix material for carbon fiber-reinforced composite implants, such as osteosynthesis plates and hip joint shafts, membranes for dialysis Permanent dressings, ophthalmology... 

Perfluorinated sulfonic acid polymers, such as Nafion membranes, were the most commonly used materials in practical systems for their high proton conductivity and extremely high oxidative stability. However, due to the poor dimensional stability, low mechanical properties of Nafion at high humidity and high temperature, and high cost, an essential need for cost-effective and reinforced substitutes with improved performance arises [193-195]. Nafion blended with the second component could not only reduce the cost, but also improve the mechanical properties and the dimensional stability. Recently, the reinforced composite membranes based on semi-interpenetrating polymer network (semi-IPN) structures of Nafion , polyimidazole (PI) [196-198], polybenzimidazole (PBI) [199], and poly(vinyIidene fluoride) (PVDF) [200] were reported. As shown in Fig. 2.35, the composite membranes with... 

Xu, F., Mu, S., and Pan, M. (2011) Mineral nanofibre reinforced composite polymer electrolyte membranes with enhanced water retention capability in PEM fuel cells, J. Membr. Sci., 377, 134-140. 

Recently, they fabricated the polytetrafluoroethylene (PTFE)-reinforced SPEEK composite membranes to improve their chemical stability and ion selectivity in VRB applications. Compared to pristine SPEEK membranes, the composite membranes exhibited the lower swelling ratio and higher mechanical stability due to the PTFE reinforcement. As expected, the SPEEK/PTFE membranes showed much higher coulombic efficiency and energy efficiency than those of SPEEK membrane. In addition, the composite membranes exhibited much better stability than pristine SPEEK under VRB operating conditions. 

Sang-Yeoul, A., Lee, Y.C., Hab, H.Y., Seong-Ahn, H., and In-Hwan, O. Properties of the reinforced composite membranes formed by melt soluble ion conducting polymer resins for PEMFCs. Electrochimica Acta, 50, 571-575, 2004. 

Perfluorinated membranes reinforced with woven PTFE, such as Nafion 324 or Nafion 417, are used in many industrial electrochemical processes. Unfortunately, the relatively coarse weave of the woven PTFE reinforcement results in membranes that are much too thick for high electrochemical performance. Some non-woven PTFE/perfluorinated ionomer composite membranes have been formulated for ion transport studies and for investigation of other properties relevant to chlor-alkaU and fuel cell applications. Advancements in materials and processing technology have resulted in the introduction of PTFE/perfluorinated ionomer composite membranes claimed by Gore and Associates, Inc. under the Gore Select trademark. Most types of ion exchange membranes contain some type of reinforcement because they are weak and tend to swell substantially as they incorporate a solvent onto their structure. This reinforcement can be a macro reinforcement or a micro reinforcement . 

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