Abstract

The mechanical shear degradation of polydisperse Poly isobutene and monodisperse polystyrene in oils of different viscosities in the concentration range of 0.1% to 1% was studied using a high‐shear concentric cylinder viscometer under laminar and uniform well‐defined shear field conditions. Molecular weight distributions (MWDs) were measured by gel permeation chromatography (GPC). Degradation of polydisperse Poly isobutene solutions narrows the distributions principally through the breaking down of large molecules. Degradation of monodisperse polystyrene broadens the distributions at lower shear stress. At higher shear stresses, the distributions do not broaden as much but are still broader than those of the original polymer. The final Mw/Mn ratios are considerably different from the value of 2 expected for random degradation. Hence, the degradation is likely a nonrandom process. It was found that the extent of degradation has a negative concentration dependence coefficient at relatively high molecular weight and a positive concentration dependence at lower molecular weight. Competing mechanisms of "stretching" and "entanglements" for degradation were postulated to explain the results. The degradation data indicate that the shear stress is the controlling parameter, not the shear rate. The shear degradation is independent of initial molecular weight and viscosity of the solvent. Copyright © 1979 John Wiley & Sons, Inc.

Department(s)

Chemical and Biochemical Engineering

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Full Access

International Standard Serial Number (ISSN)

1097-4628; 0021-8995

Document Type

Article - Journal

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Citation

File Type

text

Language(s)

English

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© 2023 Wiley, All rights reserved.

Publication Date

01 Jan 1979

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