Browsing by Author "S. Thanawan"

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    Determination of chlorine content in chlorinated, vulcanized natural rubber by XANES
    (2007-11-11) W. Klysubun; S. Thanawan; P. Thamasirianunt; S. Radabutra; P. Sombunchoo; National Synchrotron Research Center, Thailand; The Institute of Science and Technology for Research and Development, Mahidol University; Mahidol University
    The degree of chlorination in chlorinated, vulcanized natural rubber was determined by X-ray absorption near-edge spectroscopy (XANES). The vulcanized natural rubber samples were prepared in film with thickness of 180 μm, approximately. They were treated with chlorination solution with different immersion times ranging from 0.5 to 30 min. Experimental results implied that incorporated chlorine atoms were covalently bonded to carbon atoms in the rubber molecules. The chlorine content increased with the chlorination time up to 10 min before the absorption was saturated. © 2007 Elsevier B.V. All rights reserved.
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    Origin of phase shift in atomic force microscopic investigation of the surface morphology of NR/NBR blend film
    (2009-01-01) S. Thanawan; S. Radabutra; P. Thamasirianunt; T. Amornsakchai; K. Suchiva; The Institute of Science and Technology for Research and Development, Mahidol University; Mahidol University
    Atomic force microscopy (AFM) was used to study the morphology and surface properties of NR/NBR blend. Blends at 1/3, 1/1 and 3/1 weight ratios were prepared in benzene and formed film by casting. AFM phase images of these blends in tapping mode displayed islands in the sea morphology or matrix-dispersed structures. For blend 1/3, NR formed dispersed phase while in blends 1/1 and 3/1 phase inversion was observed. NR showed higher phase shift angle in AFM phase imaging for all blends. This circumstance was governed by adhesion energy hysteresis between the device tip and the rubber surface rather than surface stiffness of the materials, as proved by force distance measurements in the AFM contact mode. © 2008 Elsevier B.V. All rights reserved.
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    Preparation and characterizations of direct methanol fuel cell membrane from sulfonated polystyrene/ poly(vinylidene fluoride) blend compatibilized with pory(styrene)-b-poly(methyl methacrytlate) block copolymer
    (2008-01-15) P. Piboonsatsanasakul; J. Wootthikanokkhan; S. Thanawan; King Mongkuts University of Technology Thonburi; The Institute of Science and Technology for Research and Development, Mahidol University
    This work concerned a development of sulfonated polystyrene (SPS)/poly(vinylidene fluoride) (PVDF) blend membrane for use as an electrolyte in a direct methanol fuel cell. The aim of this work was to investigate effects of the blend ratio on properties of the blend membranes. The partially SPS with various degrees of substitution were prepared by using propionyl sulfate as a sulfonating agent. After that, the optimum SPS was selected for further blending with PVDF, at various blend ratios. Poly(styrene)-poly(methyl methacrytlate) block copolymer (PS-b-PMMA), used as a compatibilizer, was synthesized via a controlled radical polymerization through the use of an iniferter. Thermal behaviors, water uptake, proton conductivity, and methanol permeability of various blend membranes were determine by using TGA,gravimetry, impedance analyzer, and gas chromatography, respectively. From the results, it was found that, water uptake and methanol permeability of the blend membranes tended to increase with the weight ratio of SPS. It was also found that the blend membranes were incompatible, especially those containing more than 40 wt % of the SPS. However, by adding 5 wt % of the block copolymer, the blend became more compatible. Mechanical strength, proton conductivity, and resistance to methanol crossover of the blend membrane remarkably increased after the compatibilization. ©2007 Wiley Periodicals, Inc.