Issue 14, 1990

Flow of ordered latex suspensions: yielding and catastrophic shear thinning

Abstract

The flow properties of ordered latex suspensions are investigated using a constant-stress rheometer. The suspensions, studied over a volume-fraction range 0.38–0.62 and at ionic strength 10–2, 10–3 and 10–4 mol dm–3, show four distinct responses to increasing stress. At low stresses the suspensions behave like elastic solids holding a strain for times greater than 104 s and displaying complete strain recovery upon release of stress. At higher stresses, the suspensions show non-recoverable strain upon application of the stress, but steady-state rates of deformation are not reached for times greater than 104 s. Over a narrow stress range, the suspensions begin to flow reaching a steady-state rate of deformation in times less than 500 s. The stress becomes independent of steady-state shear rate in this region suggesting the onset of flow occurs at a dynamic yield stress which marks the onset of the low-stress, shear-thinning region. The high-stress, shear-thinning region is entered at a critical stress where the steady-state viscosity drops 1–3 orders of magnitude. Scaling of the long-time zero-stress modulus, yield stress and critical stress on volume fraction and suspending medium ionic strength are discussed in light of structural studies reported in the literature.

Article information

Article type
Paper

J. Chem. Soc., Faraday Trans., 1990,86, 2629-2639

Flow of ordered latex suspensions: yielding and catastrophic shear thinning

L. Chen and C. F. Zukoski, J. Chem. Soc., Faraday Trans., 1990, 86, 2629 DOI: 10.1039/FT9908602629

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