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Transient Stress and Strain Responses Predicted by the Internal Viscosity Model in Shear Flow

 

作者: Charles W. Manke,   Michael C. Williams,  

 

期刊: Journal of Rheology  (AIP Available online 1989)
卷期: Volume 33, issue 6  

页码: 949-978

 

ISSN:0148-6055

 

年代: 1989

 

DOI:10.1122/1.550069

 

出版商: The Society of Rheology

 

数据来源: AIP

 

摘要:

Predictions are made for the shear‐flow transient rheological properties of the dilute solution internal viscosity (IV) model developed earlier by Bazua and Williams. Properties considered are: the viscosityη+(t),first and second normal stress coefficientsψ1+(t)andψ2+(t),and submolecule and coil extension following abrupt imposition of a constant shear rate γ̇; the analogous relaxation propertiesη−,ψ1−,ψ2−following abrupt cessation of flow at constant γ̇; the creep complianceJ+(t)following abrupt imposition of a constant stress σ; and the constrained elastic recoilJ−(t)following abrupt removal of σ after attainment of steady flow. Most predictions are displayed for hydrodynamic interaction coefficienth*=0and comparisons therefore made with the Rouse model (no IV, andh*=0), but some variation ofh*is included. Calculations are made primarily for a fixed molecular weight, corresponding toN=100(whereNis the number of submolecules per chain), and also for a fixed IV coefficient φ corresponding to a critical (and large) valueφ0(N)equal to400f(wherefis bead friction coefficient). However, results for some variation ofNand φ are also shown. The major role of IV is to cause the following changes relative to the Rouse model: (1) abrupt jumps att=0forη+,η−,ψ1−,ψ2−;(2) oscillating approaches to steady state forη+,ψ1+,ψ2+;(3) non‐zero values ofψ2+andψ2−,although the steady‐state values areψ2=0as for Rouse; (4) general time‐retardance of response; and (5) suppression of coil extension at high γ̇ so that Gaussian statistics remain valid. The behavior ofη+(t)at high γ̇, using the large IV valueφ=φ0,shows a multipeaked pattern remarkably similar to data on solutions of liquid‐crystal polymers.

 

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