Styrene was grafted onto ultrahigh molecular weight polyethylene powder (UHMWPE) by gamma irradiation using a 60 Co source. Compression moulded films of selected pre-irradiated styrene-grafted ultrahigh molecular weight polyethylene (UHMWPE-g-PS) were post-sulfonated to the sulfonic acid derivative (UHMWPE-g-PSSA) for use as proton exchange membranes (PEMs). The sulfonation was confirmed by Xray photoelectron spectroscopy (XPS). The melting and flow properties of UHMWPE and UHMWPE-g-PS are conducive to forming homogeneous pore-free membranes. Both the ion conductivity and methanol permeability coefficient increased with degree of grafting, but the grafted membranes showed comparable or higher ion conductivity and lower methanol permeability than Nafion ® 117 membrane. One UHMWPE-g-PS membrane was fabricated into a membrane-electrode assembly (MEA) and tested as a single cell direct methanol fuel cell (DMFC). Low membrane cost and acceptable fuel cell performance indicate that UHMWPE-g-PSSA membranes could offer an alternative approach to perfluorosulfonic acidtype membranes for DMFC.Crown
Five locally available plant taxa of Solanum nigrum Complex were investigated to resolve the International taxonomic controversy about these plants by analyzing their flavonoid profiles. Total flavonoid contents in the taxa were determined by two complementary colorimetric methods, aluminum chloride method and 2,4-dinitrophenylhydrazine method. Thin layer chromatography was used to detect the glycosides of quercetin. Whereas GC-MS analysis of the hydrolyzed extracts showed the relative percentage of quercetin aglycon in the taxa under study. Statistical analyses of the results were employed for grouping of these taxa into various clusters. The significant distance found between S. americanum, S. chenopodioides, S. nigrum and S. villosum indicated them as distinct species. But S. retroflexum did not show such a marked difference and hence might be regarded as a variety or subspecies of S. nigrum.
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