Some effects of molecular weight distribution on the melt rheology of high density polyethylene

Autor: H. L. Wagner, Kurt F. Wissbrun
Rok vydání: 1962
Předmět:
Zdroj: Polymer Engineering and Science. 2:222-226
ISSN: 1548-2634
0032-3888
DOI: 10.1002/pen.760020309
Popis: Using a high shear rate capillary viscometer, the melt viscosities of a series of high density linear polyethylenes ranging in weight average molecular weight from 70,000 to 160,000 have been measured from shear rates of 2 to 200 sec−1 and from 190° to 240°C. The data, corrected for elastic end effects are described by an empirical relationship except for the temperature term which is fitted to the Williams-Landel-Ferry equation. Over the range measured the viscosity is given approximately by a power law in relation to shear rate with an exponent dependent upon molecular weight. The effects of distribution were examined by measuring the viscosity-shear rate relationships for not only the above series, which varied in Mw/Mn from 23 to 10, but also for blends of polyethylenes of varying molecular weights or of fractions, and other polyethylenes obtained by removal of the high molecular weight tail. In general, the broader the distribution, the more sensitive is the viscosity to the rate of shear. The end correction, a measure of the elastic energy, does not vary much with shear stress or temperature in the case of high density polyethylene.
Databáze: OpenAIRE
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