ISSN:
0021-8995
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
The flow curves of linear polyethylenes are characterized by a set of empirically defined parameters, including the apparent melt viscosity at zero shear stress, the shear stress for onset of non-Newtonian flow, and the slopes of linear sections fitted to data in three shear stress ranges of the flow curve. Not all of these parameters have theoretical significance but all are easily measured and therefore should be useful for broad, practical application. The dependence of the parameters on molecular weight, shape, and breadth of the molecular weight distribution has been demonstrated by using fractions and blends of fractions of linear polyethylenes. The zero shear viscosity and degree of non-Newtonian flow at low shear stress depend primarily on polymer molecular weight. The degree of non-Newtonian flow at higher shear stress can be related quantitatively to molecular weight distribution factors, while the stress for onset of non-Newtonian flow also correlates with molecular weight distribution. Formally, the derived correlations are specific to the apparatus used, but may in fact have much broader validity because of the minor importance in these polymer samples, of elastic effects such as capillary die entry effects.
Additional Material:
10 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/app.1965.070090608
Permalink
