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Fig. 1. The air spring in bolster type boggy.

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Structural characterization of vulcanized natural rubber was performed by high-resolution latex-state 13 C NMR spectroscopy. The vulcanized natural rubber latex was prepared by vulcanization of high ammonia natural rubber latex with sulfur and sodium di-n-butyldithiocarbamate as vulcanizing agents. High resolution was attained for latex-state 13 C NMR spectroscopy even after vulcanization of the rubber latex, as is evident from no background in spectrum and narrow half width of signals, which were independent of vulcanization time. Small signals at 44 and 58 ppm in the carbon region were assigned by measurements of both distortionless enhancement by polarization transfer (DEPT) and attached proton test (APT) to secondary, tertiary, and quaternary carbons of crosslinking points. The assignment was proved by high-resolution solutionstate NMR spectroscopy of vulcanized liquid cis-1,4-polyisoprene as a model, in which DEPT, APT, 2-dimensional 1 H-13 C correlation (HETCOR), and 2-dimensional heteronuclear multiple bond correlation (HMBC) measurements were applied. V V C 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45:

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