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Radiation Grafting (radiation + grafting)
Selected AbstractsRadiation Grafted Membranes for Polymer Electrolyte Fuel Cells,FUEL CELLS, Issue 3 2005L. Gubler Abstract The cost of polymer electrolyte fuel cell (PEFC) components is crucial to the commercial viability of the technology. Proton exchange membranes fabricated via the method of radiation grafting offer a cost-competitive option, because starting materials are inexpensive commodity products and the preparation procedure is based on established industrial processes. Radiation grafted membranes have been used with commercial success in membrane separation technology. This review focuses on the application of radiation grafted membranes in fuel cells, in particular the identification of fuel cell relevant membrane properties, aspects of membrane electrode assembly (MEA) fabrication, electrochemical performance and durability obtained in cell or stack tests, and investigation of failure modes and post mortem analysis. The application in hydrogen and methanol fuelled cells is treated separately. Optimized styrene,/,crosslinker grafted and sulfonated membranes show performance comparable to perfluorinated membranes. Some properties, such as methanol permeability, can be tailored to be superior. Durability of several thousand hours at practical operating conditions has been demonstrated. Alternative styrene derived monomers with higher chemical stability offer the prospect of enhanced durability or higher operating temperature. [source] Simultaneous radiation grafting of vinylbenzyl chloride onto poly(tetrafluoroethylene- co -hexafluoropropylene) filmsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2009Junhwa Shin Abstract In this study, we demonstrated that vinylbenzyl chloride (VBC), a versatile monomer with reactive a chloromethyl group could be grafted onto a poly(tetrafluoroethylene- co -hexafluoropropylene) (FEP) film without a degradation of the chloromethyl group during a simultaneous irradiation process. The effects of various irradiation conditions such as the total dose, dose rate, solvent, and VBC concentration on the degree of grafting of VBC onto a FEP film were also investigated. The prepared PVBC-grafted films were characterized using FTIR, TGA, and SEM EDX. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Novel UV-induced photografting process for preparing poly(tetrafluoroethylene)-based proton-conducting membranesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2007Masaharu Asano Abstract A novel process comprising the UV-induced photografting of styrene into poly(tetrafluoroethylene) (PTFE) films and subsequent sulfonation has been developed for preparing proton-conducting membranes. Although under UV irradiation the initial radicals were mainly generated on the surface of the PTFE films by the action of photosensitizers such as xanthone and benzoyl peroxide, the graft chains were readily propagated into the PTFE films. The sulfonation of the grafted films was performed in a chlorosulfonic acid solution. Fourier transform infrared and scanning electron microscopy were used to characterize the grafted and sulfonated membranes. With a view to use in fuel cells, the proton conductivity, water uptake, and mechanical properties of the prepared membranes were measured. Even through the degree of grafting was lower than 10%, the proton conductivity in the thickness direction of the newly prepared membranes could reach a value similar to that of a Nafion membrane. In comparison with ,-ray radiation grafting, UV-induced photografting is very simple and safe and is less damaging to the membranes because significant degradation of the PTFE main chains can be avoided. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2624,2637, 2007 [source] Spectroscopic study of the penetration depth of grafted polystyrene onto poly(tetrafluoroethylene- co -perfluoropropylvinylether) substrates.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2002Abstract This study concerns the radiation grafting of styrene onto poly(tetrafluoroethylene- co -perfluoropropylvinylether) (PFA) substrates and the penetration depth of the graft. Grafting was obtained by the simultaneous irradiation method, and the spectroscopic analysis was made with the micro-Raman technique. Effects of grafting conditions such as the type of solvent, dose rate, and irradiation dose on the grafting yield were investigated. Of the different solvents used, the most efficient in terms of increasing grafting yield were dichloromethane, benzene, and methanol, respectively. A mixture of methanol and dichloromethane used as a solvent for styrene achieved a higher degree of grafting and concentration of grafted polystyrene onto the surface of PFA substrates than solutions of the monomer in the separate solvents. The degree of grafting increased with increasing radiation dose up to 500 kGy, stabilizing above this dose. However, the grafting yield decreased with an increase in the dose rate. The increase in the overall grafting yield was accompanied by a proportional increase in the penetration depth of the grafts into the substrate. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3191,3199, 2002 [source] Comparative study of the radiation-induced grafting of styrene onto poly(tetrafluoroethylene- co -perfluoropropylvinyl ether) and polypropylene substrates.POLYMER INTERNATIONAL, Issue 5 2003I: Kinetics, structural investigation Abstract A comparative study has been made of the radiation grafting of styrene onto poly(tetrafluoroethylene- co -perfluoropropyl vinyl ether) (PFA) and polypropylene (PP) substrates, using the simultaneous irradiation method. Effects of grafting conditions such as monomer concentrations, type of solvent, dose rate and irradiation dose on the grafting yield were investigated. Under the same grafting conditions it was found that a higher degree of grafting of styrene was obtained using a mixture of dichloromethane/methanol solvents for PFA and methanol for PP and the degree of grafting was higher in PP than in PFA at all doses. However, the micro-Raman spectroscopy analysis of the graft revealed that, for the same degree of grafting, the penetration depth of the grafted polystyrene into the substrate was higher in PFA than in PP substrates. In both polymers the crystallinity was hardly affected by the grafting process and the degree of crystallinity decreased slightly with grafting dose. The dependence of the initial rate of grafting on the dose rate and the monomer concentration was found to be 0.6 and 1.4 order for PFA and 0.15 and 2.2 for PP, respectively. The degree of grafting increased with increasing radiation dose in both polymers. However, the grafting yield decreased with an increase in the dose rate. The increase in the overall grafting yield for PFA and PP was accompanied by a proportional increase in the penetration depth of the graft into the substrates. Copyright © 2003 Society of Chemical Industry [source] Preparation of antimicrobial sutures by preirradiation grafting onto polypropylene monofilamentPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 12 2008Bhuvanesh Gupta Abstract Antimicrobial sutures were prepared by the radiation grafting of acrylonitrile monomer onto polypropylene (PP) monofilament. The grafted sutures were subsequently hydrolyzed to transform nitrile groups into carboxylic groups for the immobilization of antimicrobial drug, tetracycline hydrochloride (TC). The modified sutures show continuous release of drug for a period of 4,5 days. The antimicrobial activity of the sutures was determined against both Gram positive and Gram negative bacteria by the zone of inhibition technique. Zone of inhibition was observed around the drug-containing sutures in the plate inoculated with Escherichia coli (E. coli), Klebsiella pneumonea (K. pneumonea), and Staphylococcus aureus (S. aureus). The results of infection studies in albino rats against S. aureus showed no infection even after fourth postoperative day of surgery. This is because of the release of the TC drug at the site of injury, which inhibits the bacterial growth. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||