Letter to the Editor: Sufficiently entangled polymers do show shear strain localization at high enough Weissenberg numbers

• Published in: Journal of rheology (New York : 1978) 2014-07, Vol.58 (4), p.1059-1069
• Main Authors: Wang, Shi-Qing, Liu, Gengxin, Cheng, Shiwang, Boukany, Pouyan E., Wang, Yangyang, Li, Xin
• Format: Article
• Language: English
• ISSN: 0148-6055; 1520-8516
• DOI: 10.1122/1.4884361

This Letter concludes that the recent data of Li et al. [J. Rheol. 57, 1411–1428 (2013)] are entirely consistent with the previous observations of the occurrence and absence of shear banding during startup shear and nonquiescent relaxation after large stepwise shear. In other words, based on the linear viscoelastic characteristics of these solutions depicted in Fig. 5(a) of Li et al., we find their results to follow from the previous analysis: One insufficiently entangled solution naturally exhibited homogeneous shear under the explored conditions. The two more entangled solutions did not exhibit shear banding and nonquiescent relaxation, because the samples appear to have significant polydispersity in the molecular weight distribution and because the applied shear rates were much lower than those needed to produce shear banding. Thus, the observations of Li et al. support rather than refute the existing knowledge concerning nonlinear rheological responses of entangled polymer solutions to startup and stepwise shear.