Handbook of Specialty Fluorinated Polymers

Handbook of Specialty Fluorinated Polymers
Author: Susanta Banerjee
Publisher: William Andrew
Total Pages: 341
Release: 2015-04-24
Genre: Technology & Engineering
ISBN: 0323369960

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Fluoropolymers are used in applications demanding service at enhanced temperature while maintaining their structural integrity and have excellent combination of chemical, physical and mechanical properties. Advancements in materials and processing technology mean that a huge amount of research is currently taking place into new, high performance applications for specialty fluorinated polymers. This book is a complete review of the current research in synthesizing new fluorinated high performance polymers and their application in the field of low dielectric constant materials, membrane based separation (gas and liquid) and proton exchange membranes. Special emphasis is given to the preparation of soluble high performance polymers by incorporating fluorine and different structural elements so as to use these classes of polymers in different membrane based applications, including low dielectric constant materials, gas separation, pervaporation, proton exchange membranes in fuel cells, and more. The coverage of processing properties and commercial aspects - as well as a practical assessment of the advantages and disadvantages of specialty fluoropolymers compared to other materials - enables engineers and product designers to apply the latest scientific developments in this area in a practical setting. Thorough coverage of modern applications for specialty fluorinated polymers, including membranes and coatings – giving insight into recent research and the future direction of this technology Brings researchers and engineers up to date with the latest developments in specialty fluoropolymers, to assist in future materials research and part design Includes detailed assessment of the advantages and shortcomings of specialty fluorinated polymers, for ease of comparison with alternative materials

Poly(organophosphazenes) with Azolylmethylphenoxy and Pyridinoxy Side Groups to be Used as Proton Exchange Membranes in Fuel Cells

Poly(organophosphazenes) with Azolylmethylphenoxy and Pyridinoxy Side Groups to be Used as Proton Exchange Membranes in Fuel Cells
Author: Sujeewani K. Ekanayake
Publisher:
Total Pages: 259
Release: 2011
Genre: Azoles
ISBN:

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Proton Exchange Membrane Fuel Cells (PEMFCs) are of great importance to many stationary and portable applications. The development of a more efficient, high-temperature tolerant membrane with a high protonic conductivity has become critical to the better performance of PEMFCs. Consequently, the focus of current research is more focused on synthesizing membranes which can function at a non-humidified high temperature environment. Because N-heterocycles such as azoles substituted on a polyphosphazene backbone have been found to be one of the best polymers in this regard, the focus of this dissertation is primarily on developing PEMs (proton exchange membranes) based on azole and pyridine substituted phosphazenes. In Chapter 1, an overview on PEMFCs as well as PEMs that have been synthesized to date is presented. The first part of the introduction is devoted to sulfonated fluorocarbon-based membrane, Nafion®. Then the focus slowly shifts towards PEMs based on hydrocarbon polymers. The rest of Chapter 1 mainly revolves around polyphosphazene based PEMs. Chapter 2 describes the synthesis of trimeric, small-molecule, model compounds for high polymers. A series of hexakis(azolylmethylphenoxy)cyclotriphosphazenes where the azolyl groups are pyrazol, 1,2,4-triazol and 5-methyltetrazol and all three isomers of hexakis(pyridinoxy)cyclotriphosphazenes have been synthesized and characterized. The focus of Chapter 3 is on the synthesis of poly(dichlorophosphazene) by modifying a literature procedure reported by Wang (Macromolecules 2005, 38, 643-645) via one-pot in situ polycondensation. Chapter 3 also presents a preliminary study on ring opening polymerization. The focus of Chapter 4 is completely on the synthesis and characterization of azole and pyridine substituted polyphosphazenes. Chapter 5 includes film casting studies from both triazolphenol trimer and polymer to obtain corresponding composites and blends by mixing with commercially available poly(PMDA-ODA) amic acid. The cast films were imidized and the degree of imidization was monitored by FTIR. Acid doping studies of each undoped film was performed prior to reporting proton conductivity.

Synthesis of Perfluoroheteroaromatic Polymers for Ion-conducting Membrane Fuel Cells Via Free Radical-based Reactions and Synthesis of Di-cationic Ionic Liquids as Efficient SO2 Absorbents

Synthesis of Perfluoroheteroaromatic Polymers for Ion-conducting Membrane Fuel Cells Via Free Radical-based Reactions and Synthesis of Di-cationic Ionic Liquids as Efficient SO2 Absorbents
Author: Shaoyi Xu
Publisher:
Total Pages: 260
Release: 2016
Genre: Fuel cells
ISBN:

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A novel free radical-based substitution reaction was developed for grafting aromatic/heteroaromatic compounds to perfluorosulfonic acid polymers (PFSAs). Two proton-exchange membranes perfluorobenzoic acid (PFBA) and perfluorobenzenesulfonic acid (PFBSA)—were synthesized for proton-exchange membrane fuel cells via the free radical-based reaction. The physical properties, in-plane ionic conductivities and fuel cell performance of two membranes were investigated. They exhibited different electrochemical and physical properties, possibly due to the formation of unique dimerized/trimerized structure of –CO2H groups in the PFBA membrane. A free radical-based thermolytic reaction under a high temperature (180 oC)/pressure (1000 psi) condition in the presence of TFA and hydrogen peroxide is first demonstrated. A novel perfluorotetrafluoroaniline (PFTFAn) polymer was synthesized from PFSA and 2,3,5,6-tetrafluoroaniline in one step via the thermolytic reaction. After doping H2SO4 in the PFTFAn polymer, a new conjugated acid membrane (H2SO4-doped PFTFAn) was obtained. The H2SO4-doped PFTFAn membrane displayed better chemical stability and mechanical properties than NafionTM due to the removal of –SO3H groups. The second part of this thesis deals with fluoropolymer-based anion-exchange membranes. A new class of coordinated metal/perfluoropolymer type composite membranes were synthesized and characterized for anion-exchange membrane fuel cells (AEMFCs). A membrane comprised of perfluoro(phenyl-2,2’:6’,2”-terpyridine) polymer, ZrO(ClO4)2 nanoclusters, and 2,2’:6’,2”-terpyridine displayed the highest conductivity of 23.1 mS/cm at 60 oC. The chemical stability test of composite membrane showed no conductivity loss after refluxing in 7 M KOH solution at 120 oC for 2,200 h. A H+ coordinated cage-shape molecule with a benzyl group (Bn-proton cage) was designed and synthesized as a base-stable anion-exchange group. By employing the free radical-based reaction, Bn-proton cage was grafted to a fluoropolymer to yield a stable anion-conductive membrane under alkaline conditions. The third part of this thesis is our design, synthesis and test of ionic liquids for reversible SO2 absorption. Novel di-cationic ionic liquids (DILs) were designed and synthesized for SO2 absorption. DILs were found to have better SO2 absorption capabilities than mono-cationic ionic liquids (MILs). A chloride-based DIL comprised of two N-methylimidazolium cations and a PEG9 (HO-(CH2CH2O)9-H) chain could reversibly uptake 3.710 mole SO2 per mole DIL under ambient conditions. The anion, temperature and water impact on SO2 absorption in DILs was investigated. Although replacing chloride with triflate or tosylate groups led to a reduced SO2 absorption for the DILs, a high selectivity against CO2 was observed in CO2 absorption test.

Synthesis of Well Defined, Linear-dendritic, End-functionalised Poly N-vinyl Pyrrolidone Additives Via Reversible Addition-fragmentation Transfer Polymerisation for Use in Polymer Electrolyte Membrane Fuel Cells

Synthesis of Well Defined, Linear-dendritic, End-functionalised Poly N-vinyl Pyrrolidone Additives Via Reversible Addition-fragmentation Transfer Polymerisation for Use in Polymer Electrolyte Membrane Fuel Cells
Author: William Nigel Adam Bergius
Publisher:
Total Pages:
Release: 2012
Genre: Fuel cells
ISBN:

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An ongoing challenge in polymer science is the preparation of materials with specific surface properties that differ from the bulk, whilst retaining the advantageous mechanical properties of the bulk polymer. We have explored the use of multi-end functionalised polymer additives, which undergo rapid spontaneous adsorption to a surface or interface, as an efficient method of modifying surface properties. These materials are of potential use in tailoring the hydrophobicity of the gas diffusion layer (GDL) in a polymer electrolyte membrane fuel cell (PEMFC), and hence optimising fuel cell efficiency. In this research, reversible addition-fragmentation transfer (RAFT) polymerisation has been used to synthesise a range of well-defined, low molecular weight, end-functionalised poly N-vinyl pyrrolidone (PVP) polymer additives bearing aryl-ether end groups containing up to three, low surface energy, C8F17 fluoroalkyl chains. Polymer end-functionality is introduced via the design of functionalised RAFT chain transfer agents (CTAs). Three novel CTAs have been made in addition to their corresponding end-functionalised PVP additives, in a range of molecular weights. Thin films have been prepared comprised of polymer blends of unfunctionalised PVP and varying percentages of each end-functionalised PVP additive, and these films have been analysed by contact angle measurements, ion beam analysis and atomic force microscopy in order to investigate effects of additive concentration, additive molecular weight, matrix molecular weight, design of functional group and annealing. We have shown that modest amounts of additive (

Synthesis of Sulfo-phenylated Terphenylenes

Synthesis of Sulfo-phenylated Terphenylenes
Author: Thomas Skalski
Publisher:
Total Pages: 315
Release: 2019
Genre:
ISBN:

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This thesis reports the synthesis and study of a new class of fluorine-free, acid-bearing polymers for potential usage in proton exchange membrane fuel cells. The polymers were prepared via the synthesis of a pre-sulfonated monomer, followed by homo- and co-polymerization by [4+2] Diels-Alder cycloaddition. Molecular structures were determined by mass spectrometry, infrared spectroscopy, 1H NMR and 2D COSY spectroscopies, and single crystal X-ray diffraction. Disulfonated tetracyclone and tetrasulfonated bistetracyclone molecules were used to synthesize two model compounds to determine the potential isomers present. Tetrasulfonated bistetracyclone was polymerized with 1,4-diethynylbenzene co-monomer. The resultant polymer, sPPP-HNEt3+, was prepared with a high molecular weight and converted into its acid form, prior to casting as a membrane. The membranes possessed a high ion exchange capacity (IEC) of 3.49 meq/g and a proton conductivity of 118 mS/cm at room temperature and at 95% relative humidity (RH), respectively, four and a half time superior as the current benchmark NRE 211®. The polymer film was found to become soluble during exposure to aggressive oxidative solutions no significant chemical changes were observed. The final part of this work focused on increasing the polymer film stability by judiciously tuning the hydrophilic content of the polymer. A family of random-copolymers was prepared based on the above monomers. The parameters for polymerization were studied and the optimal conditions were found using size exclusion chromatography to determine molecular weight. The measured IEC for these copolymers correlated well with the theoretical IEC, ranging from 1.86 to 3.50 meq/g. The conductivity of these polymers at 80°C and 95% RH was found to reach 338 mS/cm. Fuel cell tests were performed using the membranes and provided a peak power density of 770 mW/cm2.

The Design and Synthesis of High Performance Polyolefins for Use in Alkaline Anion Exchange Membrane Fuel Cells

The Design and Synthesis of High Performance Polyolefins for Use in Alkaline Anion Exchange Membrane Fuel Cells
Author: Henry Aloysius Kostalik (IV)
Publisher:
Total Pages: 154
Release: 2011
Genre:
ISBN:

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Fuel cells are devices that convert the chemical energy stored in a fuel directly into electricity and have the potential to serve as a highly efficient and environmentally sustainable power generation technology for stationary and mobile applications. Within a fuel cell, the polymer electrolyte membrane serves as the ion conducting medium between the anode and cathode, making it a central, and often performance-limiting component of the fuel cell. The most common polymer electrolyte membrane fuel cells operate under acidic conditions and are therefore proton conducting. Although proton exchange membrane (PEM) fuel cells are well developed and can offer excellent performance, they rely almost exclusively on platinum, a very expensive and scarce noble metal. This dependence on platinum has severely hindered wide scale commercialization of PEM fuel cell technologies. By comparison, alkaline fuel cells that employ hydroxide conducting alkaline anion exchange membranes (AAEMs) are relatively unexplored. A major advantage of alkaline fuel cells, when compared to acidic fuel cells, is their enhanced reaction kinetics for oxygen reduction, permitting the use of less costly, non-noble metal catalysts (e.g. Ni). Therefore, high performance AAEMs could significantly advance fuel cell technologies. We have been working to develop new polymeric materials that can serve as effective AAEMs. Prior work in this area has mainly focused on re-engineering existing materials to access AAEMs. In contrast, we approached this problem from a synthetic perspective by designing and synthesizing materials from the ground up. Herein, the synthesis of two separate AAEM systems that are synthesized via ring-opening metathesis polymerization are described. The first route involves the copolymerization of a tetraalkylammonium-functionalized norbornene with dicyclopentadiene. The crosslinked thin films generated are mechanically strong and exhibit exceptional methanol tolerance. The second route involves the synthesis of a solvent processable, tetraalkylammonium-functionalized polyethylene for use as an AAEM. The membranes are insoluble in both pure water and aqueous methanol but exhibit excellent solubility in a variety of other aqueous alcohols. These solubility characteristics extend the utility of this system for use as both an AAEM and ionomer electrode material from a single polymer composition. The AAEMs generated are mechanically strong and exhibit high hydroxide conductivities. Lastly, we have developed a standardized procedure for measuring the alkaline stability of a benzyltrimethylammonium (BTMA) model compound and a BTMA functionalized polyethylene. The procedure is broadly applicable and should serve as a testing method to better understand other systems, specifically those based on novel cations. Applying this procedure should facilitate the discovery of AAEMs with increased base stability, thus enabling high temperature AAEM fuel cell operation.

High Temperature Polymer Electrolyte Membrane Fuel Cells

High Temperature Polymer Electrolyte Membrane Fuel Cells
Author: Qingfeng Li
Publisher: Springer
Total Pages: 561
Release: 2015-10-15
Genre: Technology & Engineering
ISBN: 3319170821

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This book is a comprehensive review of high-temperature polymer electrolyte membrane fuel cells (PEMFCs). PEMFCs are the preferred fuel cells for a variety of applications such as automobiles, cogeneration of heat and power units, emergency power and portable electronics. The first 5 chapters of the book describe rationalization and illustration of approaches to high temperature PEM systems. Chapters 6 - 13 are devoted to fabrication, optimization and characterization of phosphoric acid-doped polybenzimidazole membranes, the very first electrolyte system that has demonstrated the concept of and motivated extensive research activity in the field. The last 11 chapters summarize the state-of-the-art of technological development of high temperature-PEMFCs based on acid doped PBI membranes including catalysts, electrodes, MEAs, bipolar plates, modelling, stacking, diagnostics and applications.

Advanced Electrocatalysts for Low-Temperature Fuel Cells

Advanced Electrocatalysts for Low-Temperature Fuel Cells
Author: Francisco Javier Rodríguez-Varela
Publisher: Springer
Total Pages: 318
Release: 2018-10-09
Genre: Science
ISBN: 3319990195

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This book introduces the reader to the state of the art in nanostructured anode and cathode electrocatalysts for low-temperature acid and alkaline fuel cells. It explores the electrocatalysis of anode (oxidation of organic molecules) and cathode (oxygen reduction) reactions. It also offers insights into metal-carbon interactions, correlating them with the catalytic activity of the electrochemical reactions. The book explores the electrocatalytic behaviour of materials based on noble metals and their alloys, as well as metal-metal oxides and metal-free nanostructures. It also discusses the surface and structural modification of carbon supports to enhance the catalytic activity of electrocatalysts for fuel-cell reactions.