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Showing 301 to 302 of 302 (0.022 seconds)| 301 |
Blending of Proton Conducting CopolymersWeißbach, Thomas 08 October 2010 (has links)
Highly proton conducting polymers for operation in hydrogen/oxygen proton exchange membrane fuel cells (PEMFCs) provide often a poor mechanical strength due to high water contents. To strengthen the conducting polymers, blends with different ratios of partially fluorinated sulfonic acid graft and diblock copolymers with perfluorinated polymers were prepared. To analyze the effect of the different quantities of the compounds, with regard to water sorption and proton conducting properties, membranes were prepared by dissolving the components and drop casting.
Partially sulfonated poly([vinylidene difluoride-co-chlorotrifluoroethylene]-g-styrene) (P(VDF-co-CTFE)-g-SPS) was blended with polyvinylidene difluoride (PVDF), decreasing the ion exchange capacity (IEC). The blended polymers absorbed less water. However, the by AC impedance spectroscopy determined proton conductivity stayed stable or increased slightly. The effective proton mobility remained constant. Partially sulfonated poly([vinylidene difluoride-co-hexafluoropropylene]-b-styrene) (P(VDF-co-HFP)-b-SPS) with two different PS-block lengths were blended with different amounts of poly(vinylidene difluoride-co-hexafluoropropylene) (P(VDF-co-HFP)). In that case, the polymers absorbed less water and the proton conductivity decreased stepwise by adding more than 20 wt% P(VDF-co-HFP). The results indicate that a blending of P(VDF-co-CTFE)-g-SPS with PVDF inhibits swelling without having an effect on the proton conductivity, though water sorption and IEC are reduced.:1 Introduction
2 Literature Review
2.1 Fuel Cells
2.1.1 Proton Exchange Membrane Fuel Cells
2.1.2 Other Types of Fuel Cells
2.2 Proton Conductivity
2.3 Proton Conducting Polymers
2.4 Impedance Spectroscopy
2.5 Polymers
2.6 Blending
2.7 Synthesis
2.7.1 Atom Transfer Radical Polymerization
2.7.2 Emulsion Polymerization
3 Results
3.1 Synthesis
3.1.1 Polyvinylidene Diuoride (PVDF)
3.1.2 Diblock Copolymers P(VDF-co-HFP)-b-SPS and Blends
3.1.3 Graft Copolymer P(VDF-co-HFP)-b-SPS Blends
3.2 Degree of Sulfonation
3.3 Ionomer Content
3.4 Ion Exchange Capacity
3.5 Water Content and Uptake
3.6 Proton Concentration
3.7 Watermolecules per Ionic Group
3.8 Proton Conductivity
3.9 Proton Mobility
4 Discussion & Conclusion
5 Experimental Part
5.1 Synthesis
5.1.1 Synthesis of PVDF
5.1.2 Synthesis of P(VDF-co-HFP)-b-PS
5.1.3 Sulfonation of the Polystyrene Block
5.2 Polymer Characterization
5.3 Membrane Preparation
5.4 Membrane Characterization
Bibliography
Appendix
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Thermal energy management and chemical reaction investigation of micro-proton exchange membrane fuel cell and fuel cell system using finite element modellingMcGee, Seán January 2015 (has links)
Fuel cell systems are becoming more commonplace as a power generation method and are being researched, developed, and explored for commercial use, including portable fuel cells that appear in laptops, phones, and of course, chargers. This thesis examines a model constructed on inspiration from the myFC PowerTrekk, a portable fuel cell charger, using COMSOL Multiphysics, a finite element analysis software. As an educational tool and in the form of zero-dimensional, two-dimensional, and three-dimensional models, an investigation was completed into the geometric construction, air conditions and compositions, and product materials with a best case scenario completed that summarizes the results identified. On the basis of the results of this research, it can be concluded that polyoximetylen and high-density polyethylene were considered as possible materials for the majority of the product, though a more thorough investigation is needed. Air flow of above 10 m/s, air water vapour mass fraction below 50% and initial temperature between 308K and 298K was considered in this best scenario. Suggestions on future expansions to this project are also given in the conclusion.
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