Small-angle neutron scattering studies of isotropic polypropylene |
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Authors: | D.G.H. Ballard P. Cheshire G.W. Longman J. Schelten |
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Affiliation: | ICI Corporate Laboratory, The Heath, Runcorn, Cheshire, UK;Institut für Festkörperforschung der Kernforschungsanlage Julich, West Germany |
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Abstract: | Small-angle neutron scattering studies have been made of molten and crystalline polypropylene using samples containing small amounts of deuterated polypropylene in a protonated polypropylene matrix. The specimens were characterized by small- and wide-angle X-ray scattering to determine the d-spacing and the degree of crystallinity χ and by gel permeation chromatography to determine molecular weight, Mw, and molecular weight distribution. The degree of crystallinity was varied from 0.5 to 0.7, the d-spacing from 120 to 250 Å and the molecular weight from 34 000 to 1 540 000. Clustering was not observed. The radius of gyration of the tagged molecules was approximately proportional to and almost independent of d and χ. In the melt similar values were obtained which are, within experimental uncertainties, the same as in a θ-solution. For 〈s2〉wk2? 1 the scattering law approaches a k?2 dependence. The results are discussed with reference to the chain-folded model but a fit cannot be obtained over all molecular weights. A simple random coil model fits the neutron scattering data partly but this does not explain the origin of the d-spacing. |
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