首页   按字顺浏览 期刊浏览 卷期浏览 Time and Shear‐Rate Scaling Laws for Liquid Crystal Polymers
Time and Shear‐Rate Scaling Laws for Liquid Crystal Polymers

 

作者: R. G. Larson,   D. W. Mead,  

 

期刊: Journal of Rheology  (AIP Available online 1989)
卷期: Volume 33, issue 8  

页码: 1251-1281

 

ISSN:0148-6055

 

年代: 1989

 

DOI:10.1122/1.550072

 

出版商: The Society of Rheology

 

数据来源: AIP

 

摘要:

Recoverable strains were measured on isotropic and liquid crystalline solutions of PBLG [poly(γ‐benzyl‐L‐glutamate)] and HPC [hydroxypropylcellulose]. For isotropic PBLG, the strain recovery approaches the expected linear viscoelastic behavior in which the recovery is proportional toγ̇0,asγ̇0—the shear rate prior to recovery—becomes small. In the nonlinear regime for isotropic PBLG, the magnitude and shear‐rate dependence of the recoverable strain are qualitatively consistent with the Doi theory. In the liquid crystalline state, neither PBLG nor HPC show a regime of linear viscoelasticity even at strain rates low enough that the viscosity is nearly independent ofγ̇0.Instead, the total strain recovery is independent ofγ̇0,although the time over which this recovery occurs is inversely proportional toγ̇0.Plots of recoverable strain versus the product of timetandγ̇0for various values ofγ̇0nearly superpose. This scaling of recovery time withγ̇0−1is similar to a result obtained with PBLG by Moldenaers and Mewis and confirmed here in measurements ofG′andG″after cessation of steady‐state shearing. Remarkably, not only do plots of recovered strain versusγ̇0tfor variousγ̇0superpose for each of the three liquid crystalline PBLG and HPC samples, but even curves for the three different materials come fairly close to superposing. Extending an idea of Marrucci, a simple phenomenological scaling equation for the evolution of domain size and domain distortion is proposed that can account for these phenomena.

 

点击下载:  PDF (1424KB)



返 回