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Relaxation of shear and normal stresses in step‐shear deformation of a polystyrene solution. Comparison with the predictions of the Doi–Edwards theory

1981; Wiley; Volume: 19; Issue: 3 Linguagem: Inglês

10.1002/pol.1981.180190312

1542-9385

Kunihiro Osaki, Shin‐ichi Kimura, Michio Kurata,

Material Dynamics and Properties

Abstract The shear stress σ, two components of birefringence, and extinction angle were measured for a concentrated polystyrene solution in step‐shear deformation of magnitude of shear 0.3 ≤ γ ≤ 4.0. The stress‐optical coefficient did not depend on either γ or time. The first and the second normal‐stress differences v 1 and v 2 were evaluated with the use of the stress‐optical law. Over a certain range of long times, σ could be factored as σ = γ h (γ) G ( t ) and the quantity h (γ) agreed with the prediction of the Doi–Edwards theory based on the de Gennes tube model of entangled polymer chains. At short times the effect of γ on σ/γ was smaller than at long times. The relaxation spectrum became approximately independent of γ at the short‐time end of the rubbery plateau region. The ratios v 1 /σ and v 2 / v 1 were independent of time and were in quantitative agreement with those predicted by the Doi–Edwards theory: v 1 /σ was equal to γ, v 2 / v 1 was negative, and | v 2 / v 1 | decreased with increasing γ.