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:
Existing viscosity data on polyethylenes were studied as a function of temperature and molecular weight. New measurements were made on low density polyethylenes which had molecular weights useful for the test of theory. Viscosities of normal alkanes, considered as a lower extension of polyethylenes, were also correlated. The equation, log η = A log (M) - B (where η is absolute viscosity, M is molecular weight, and A and B are constants), is applicable over a wide range of Newtonian viscosities. Bueche's theory postulates that A approaches unity for chain lengths up to a critical molecular weight, Mc, where molecular entanglement abruptly becomes important. Above Mc, the theory requires A to be 3.4. Values of A for normal alkanes are shown to approach unity below Mc. The entanglement point, Mc, is temperature dependent and occurs at relatively low molecular weights. Above Mc, A for linear polyethylenes is near 3.4. However, certain polyethylene data give higher values for A. Activation energies for viscous flow, ΔE*, were obtained for polyethylenes and normal alkanes. They were found to be internally consistent and to vary as a linear function of the log of molecular weight. The change of ΔE* with less general functions of molecular weights shows a maximum curvature near Mc. Results are considered in terms of flow theory.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/app.1960.070030808
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