Constitutive Curve and Velocity Profile in Entangled Polymers during Start-Up of Steady Shear Flow
KAUST Grant NumberKUSC1-018-02
Permanent link to this recordhttp://hdl.handle.net/10754/597839
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AbstractTime-dependent shear stress versus shear rate, constitutive curve, and velocity profile measurements are reported in entangled polymer solutions during start-up of steady shear flow. By combining confocal microscopy and particle image velocimetry (PIV), we determine the time-dependent velocity profile in polybutadiene and polystyrene solutions seeded with fluorescent 150 nm silica and 7.5 μm melamine particles. By comparing these profiles with time-dependent constitutive curves obtained from experiment and theory, we explore the connection between transient nonmonotonic regions in the constitutive curve for an entangled polymer and its susceptibility to unstable flow by shear banding [Adams et al. Phys. Rev. Lett. 2009, 102, 067801-4]. Surprisingly, we find that even polymer systems which exhibit transient, nonmonotonic shear stress-shear rate relationships in bulk rheology experiments manifest time-dependent velocity profiles that are decidedly linear and show no evidence of unstable flow. We also report that interfacial slip plays an important role in the steady shear flow behavior of entangled polymers at shear rates above the reciprocal terminal relaxation time but has little, if any, effect on the shape of the velocity profile. © 2010 American Chemical Society.
CitationHayes KA, Buckley MR, Qi H, Cohen I, Archer LA (2010) Constitutive Curve and Velocity Profile in Entangled Polymers during Start-Up of Steady Shear Flow. Macromolecules 43: 4412–4417. Available: http://dx.doi.org/10.1021/ma100162c.
SponsorsThis work was supported by Award No. KUSC1-018-02, made by King Abdullah University of Science and Technology (KAUST) and by the National Science Foundation (Award No. CBET-0756516). We are grateful to Erik Herz and Prof. Ulrich Wiesner for providing the surface-functionalized fluorescent nanoparticle tracers used in the study.
PublisherAmerican Chemical Society (ACS)