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The shear viscosity of a latex which is ordered at rest is studied as a function of the shear rate and volume fraction. At low shear rates and for moderate to high volume fractions, the flow curves show dynamic yield behavior which disappears below a volume fraction of 8%. At high shear rates, the onset to the high shear rate plateau of the viscosity can be observed. A new model for the shear viscosity for lattices at high volume fractions is described. This model is based upon theories for the shear viscosity of dilute lattices of Blachford et al. ͓J. Phys. Chem. 73, 1062 ͑1969͔͒ and Russel ͓J. Fluid Mech. 85, 673 ͑1978͔͒. In terms of this model, the ordered latex is broken down under shear flow into ordered domains suspended in a disordered fluid. The larger the shear rate, the smaller the volume fraction of ordered domains. The experimental results can be described reasonably well with the model discussed here. ͓S1063-651X͑97͒12808-2͔ PACS number͑s͒: 82.70.Ϫy

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