THE STUDY OF CHEMICAL INDUCED POLYOLEFIN-BASED ION EXCHANGE MEMBRANE FOR ELECTRODIALYSIS APPLICATION

High-performance ion exchange membranes with high ion exchange capacity (IEC), excellent mechanical properties, lower membrane resistance and superior ions conductivity were developed with chemical-induced polymerization in this work. Through a series of synthesizing experiments, structure characterization and properties testing for polyolefin-based cation exchange membrane (CEM) and anion exchange membrane (AEM), LDPE proved to be an optimized backbone material. The CEM with 57.5% styrene, 38.4% LDPE, 3% crosslinking degree and 1% initiator addition yield the highest IEC value (1.72 mol/g) and moderate burst strength. The 10% addition of styrene was found to enhance IEC of 57% to AEM. However, continually increase styrene leaded lower IEC due to the decreasing grafting degree of vinyl benzene chloride (VBC) on polyethylene. The influence of fillers, such as surface-modified glass fiber (GF) and functionalized graphene oxides (GO), on thermal, mechanical and electrochemical properties of ion exchange membrane were investigated in this work by dynamic mechanical analysis, IEC and field emission scanning electron microscopes (FE-SEM), fourier-transform infrared spectroscopy (FT-IR) and electrochemical impedance spectroscopy. The addition of modified GF increases tensile strength, tensile modulus, storage modulus and interfacial adhesion of GF/CEM composite but degraded the strains. The composite with [3-(Methacryloxy) propyl] trimethoxy silane (3-MPS) modified GF obtained superior mechanical properties and interfacial adhesion, whereas the modified effect of triethoxyvinylsilane (TES) was inconspicuous. The addition of unmodified GF even had negative effects on GF/CEM mechanical properties. The FE-SEM showed that the GF treated by 3-MPS and poly(propylene-graft-maleic anhydride) (PP-g-MA) have better compatibility with the CEM matrix than 1,6 bis and TES treated GF. The FT-IR verified the strengthening effects from modified GF were attributed to the formation of Si-O-Si and Si-O-C bonds. The additions of modified GF in CEM positively influence water uptake ability but negatively on IEC. This section provided a way of strengthening GF/CEM composite. The CEM doped with functionalized graphene oxides was verified to be significantly improved in IEC (21% higher) and membrane conductivity (326.7% higher) compare to the pristine CEM. The results also suggested that the improved effects of dual-functionalized GO on CEM properties are superior to the single functionalized GO. The coexistence of -PO3H, -SO3H in GO resulted in CEM possessed 7.8% higher IEC, 77.29% higher membrane conductivity and 43.56% lower activation energy than that with single functionalized GO. This work provides a new strategy for the design of high-performance IEM with excellent mechanical property, high IEC, high conductivity and low membrane resistance for application

Novel radiation grafted membranes based on fluorinated polymers for proton exchange membrane fuel cell

In the first part of this thesis a facile method for preparing poly(vinylidene fluoride) (PVDF)-gpoly( styrene sulfonate acid) (PSSA) membranes by radiation induced graft polymerization is reported. Sodium styrene sulfonate (SSS) monomer has been used for the grafting of SSS from PVDF powder in aqueous dimethyl sulfoxide (DMSO) solution, and it precipitated after synthesis. Later on, the resultant PVDF-g-PSSS graft copolymer membranes were prepared by means of vapor induced phase separation (VIPS) technique at 60% relative humidity (RH), and dried under vacuum at high temperature to achieve PVDF-g-PSSA proton conducting nano-porous membranes. It was found that these membranes exhibit encouraging results in terms of higher conductivity and better mechanical properties compared to Nafion® NR-211. In the second part of thesis, the effect of divinylbenzene (DVB) as a cross-linker on the graft polymerization of 4-vinylpyridine (4-VP) from poly(ethylene-co-tetrafluoroethylene) (ETFE) films was studied. The resulted films were doped with phosphoric acid (PA), and examined for mechanical properties and fuel cell performance. The cross-linked membrane obtained from grafting a mixture of 4- VP with 1% DVB improved the polymerization kinetics, and resulted in 50% graft level (GL). The resulted membrane additionally exhibited proton conductivity as high as 75 mS/cm at 50% relative humidity and 120 °C, besides doubling the power output of fuel cell comparing to a non-cross-linked membrane

Polyethylene-based anion exchange membrane for alkaline fuel cell and electrolyser application : synthesis, characterisation and degradation studies

PhD ThesisAlkaline anion exchange membranes (AAEM) have been fabricated using polyethylene as the base polymer offering a low cost AAEM for electrolyser and fuel cell applications. This study focused on the synthesis and characterisation of AAEM with controlled degree of grafting (DOG) and ion-exchange capacity (IEC) with the following parameters investigated: low density polyethylene (LDPE) film thickness 30-130 μm, gamma radiation dose and monomer concentration. The corresponding IEC, water uptake (WU) and degree of swelling (DS) are reported. The performance of 74.6% DOG membrane in a hydrogen fuel cell showed a high open circuit voltage of 1.06 V, with a peak power density of 608 mW cm-2 at 50 °C under oxygen. The use of a membrane with a high DOG does not impact fuel cross-over significantly and provides improved fuel cell performance due to its high conductivity, water transport and resilience to dehydration. The AAEMs showed long term stability, at 80 °C, exhibiting a conductivity of ca. 0.11 S cm-1 over a period of 3300 h under nitrogen. The membrane showed a degradation rate of 5.7 and 24.3 mS kh-1 under nitrogen and oxygen, respectively. With the membrane lifetime defined as the duration of fuel cell operation until the conductivity of the membrane has reduced to a cut-off value of 0.02 S cm-1, the estimated lifetime of the membrane is 2 years under nitrogen and 5 months under oxygen operating at 80 °C. The fabricated anion exchange membranes were subjected to degradation tests in deionised water for electrolyser/fuel cell operation. After the degradation test, the decrease in ion exchange capacity (IEC) of the AEM, hence decrease in ionic conductivity, was influenced by the applied gamma radiation dose rate. The use of a high radiation dose rate produced membranes with improved stability in terms of % IEC loss due to shorter, more uniformly distributed vinylbenzyl chloride (VBC) grafts. For LDPE-based AEMs, increasing the applied radiation dose rate during grafting from 30 to 2000 Gy h-1 significantly reduced AEM % IEC loss from 38 to 11%, respectively. Analyses of both the aged functionalised membranes and their resulting degradation products confirmed the loss of not only the functional group, but also the VBC group, which has not been reported previously in the literature. Investigation of other amine functional groups revealed similar degradation via the removal of both VBC and head group. Oxidation reactions iii taking place at pH close to neutral are the main contributor to the IEC loss, in contrast to the widely reported E2 or SN2 attack on the head group in high alkalinity solutions. A parallel degradation mechanism is proposed to explain head group loss of AEMs, that involves peroxide radicals which are more dominant in low alkalinity solutions. The investigation of the degradation of a commercially available AEM (A201, Tokuyama Corp.) was performed and compared with the fabricated LDPE AEMs. Using similar membrane thickness, results revealed that the fabricated AEM exhibited superior stability to the commercial A201 membrane in terms of % IEC loss and ionic conductivity, both in fuel cell and electrolyser modes. It is believed that the faster degradation rate of the A201 membrane could possibly be due to the attack of OH- ions on both the head group and on the polymer backbone, the latter of which was not observed on the fabricated AEMs.Engineering and Physical Sciences Research Council (EPSRC)and the Philippine Department of Science and Technology (DOST) through the Engineering Research and Development for Technology Program (ERDT) for funding my PhD fellowship

Perspective Non-Fluorinated and Partially Fluorinated Polymers for Low-Temperature PEM FC

The main requirement to the materials used to make membranes polymer electrolyte membrane fuel cells (PEM FC) is the combination of high proton conductivity and resistance to the FC operation conditions. Thus, the search for inexpensive and high-performance non-fluorinated or partially fluorinated materials for use as FC membranes is an actual task today, since the use of membranes based on perfluorosulfonate acid has a number of disadvantages limiting their application. The aim of this study is the investigation of sulfonated polyimide (SPI) and materials for use as FC membranes. The relevance of research stems from the fact that the use of the SPI will allow to increase the resistance of the membrane to the constantly changing environment in which PEM operates. The objects of research are sulfonated polyimides. SPIs, especially aromatic SPIs, are attractive to researchers, because of the possibility of obtaining a wide variety of chemical structures and also due to their excellent thermal, mechanical properties and high resistance to aggressive media. The results of this study will be methods of obtaining and evaluating the advantages and disadvantages of SPI-based materials. For the first time, special attention will be paid to advanced development based on SPI with the addition of crown-ether fragments

量子ビームを利用したグラフト型フッ素系高分子電解質膜の構造/機能相関に関する研究

学位の種別:課程博士University of Tokyo(東京大学