Relation between extrudate swelling of polypropylene and molecular weight |
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Authors: | D. Romanini G. Pezzin |
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Affiliation: | (1) Centro Ricerche G. Natta della Montepolimeri S.p.A., I-44100 Ferrara, Italy;(2) Centro di Studio per la Fisica delle Macromolecole del C.N.R., Via Selmi, 2, I-40126 Bologna, Italy |
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Abstract: | Six samples of polypropylene produced by Montepolimeri were carefully characterized in dilute solution and studied, with a capillary extrusion rheometer, in large ranges of shear and temperature. The extrudate swelling behaviour is found to be regular as far as its shear stress and temperature dependence is concerned, but the influence of molecular weight is abnormal. With increasing molecular weight the amount of elastic recovery (as measured by the extrudate swell) decreases markedly and the shear modulusG (obtained from the data by making use of simplifying assumptions) appears to be an increasing function ofMw at all the shear stress investigated. No similar results appear to be reported in the literature.Presented in part at the VIIIth Intern. Congress on Rheology, Naples, September 1–5, 1980. |
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Keywords: | Extrudate swelling elastic recovery polymer melt polypropylene |
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