On the Raman spectroscopic determination of phase distribution in polyethylene

A methodological improvement is proposed for increasing the accuracy of the standard Raman spectroscopic method for the determination of the phase distribution in semicrystalline polyethylene (PE). A computer-assisted least-squares decomposition of the overlapping Raman bands, using analytical band shapes, is applied instead of the manual decomposition procedure suggested earlier. Comparison of the results obtained by the two methods shows that the manual decomposition systematically overestimates the amorphous content of PE at the expense of the interfacial content. Sums of 60% Gaussian and 40% Lorentzian functions give the best approximatiion to the measured Raman band shapes of PE. Our conclusion that the interfacial content in semicrystalline PE samples is about twice as high as was suspected before, seems to be supported by the measured densities.

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