ISSN:
0022-3832
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
The apparent viscosities of polyisobutylenes of high molecular weights show extremely high temperature sensitivities in narrow temperature ranges when measured in a capillary viscometer. The temperature at which this anomaly occurs increases as the molecular weight of the polyisobutylene increases. It is higher for a GR-I rubber than for a polyisobutylene of comparable molecular weight. It decreases with decreasing nominal rate of shear and with increasing radius of the capillary tubes through which the polymer is made to flow at a given average linear velocity. It increases with increasing isotropic pressure on the polymer. This effect is similar to one reported previously for colloidal solutions, and discussed by some investigators as “structure turbulence” occurring at Reynolds' numbers as low as one. It is not caused by crystallization or glass transition. An alternative explanation is that on cooling some relaxation time in the polymer molecules become so long that the molecules cannot orient appreciably in the time they take to pass through the capillaries. The relation between the pertinent relaxation time and the transit time cannot be a simple numerical proportion however.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1956.120199203
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