Modeling, polymer systems shear viscosity function

The shear thinning behavior, as generally observed with polymer systems, is a typical nonlinear viscoelastic effect, so that by combining the Carreau-Yasuda and the Arrhenius equations a general model for the shear viscosity function can be written as follows ... 

Modeling the shear viscosity function of filled polymer systems by combining two Carreau-Yasuda equations the curve was calculated with the following model parameters Tioj = 8x10 Pa.s X = 500 s Aj = 1.9 = 0.4 rioj = 3x10 Pa.s - O l s = 3 Wj = 0.33. 

A6.2 Modeling the Shear Viscosity Function of Filled Polymer Systems... 

The measurement of yield stress at low shear rates may be necessary for highly filled resins. Doraiswamy et al. (1991) developed the modified Cox-Merz rule and a viscosity model for concentrated suspensions and other materials that exhibit yield stresses. Barnes and Camali (1990) measured yield stress in a Carboxymethylcellulose (CMC) solution and a clay suspension via the use of a vane rheometer, which is treated as a cylindrical bob to monitor steady-shear stress as a function of shear rate. The effects of yield stresses on the rheology of filled polymer systems have been discussed in detail by Metzner (1985) and Malkin and Kulichikin (1991). The appearance of yield stresses in filled thermosets has not been studied extensively. A summary of yield-stress measurements is included in Table 4.6. 

While Eq. (2.33) is valid for monodispersedathermal polymers, in reality polymers are polydispersed and do interact with each other. Consequently, application of the model to a real system requires that the influence of individual molecular weight fractions on the rheological functions is taken into account. For example, in the simplest case of the zero-shear viscosity-composition dependence for entangled systems [194, 195] the prediction is ... 

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