Shear rate effect

The data structure organization described above has been implemented in the BFM as well as in a very efficient off-lattice Monte Carlo algorithm, discussed in detail in the next chapter, which was modified to handle EP and used to study shear rate effects on GM [57]. 

The polymer rheology is modeled by extending the usual power-law equation to include second-order shear-rate effects and temperature dependence assuming Arrhenius type relationship. 

Although shear rate effects are more pronounced in good solvents, the intrinsic viscosity decreases with shear rate even in 0-solvents, where excluded volume is zero (317,318). The Zimm model employs the hydrodynamic interaction coefficients in the mean equilibrium configuration for all shear rates, despite the fact that the mean segment spacings change with coil deformation. Fixman has allowed the interaction matrix to vary in an appropriate way with coil deformation (334). The initial departure from [ ]0 was calculated by a perturbation scheme, and a decrease with increasing shear rate in 0-systems was predicted to take place in the vicinity of / = 1. 

The rheological properties of plastisols generally could not be characterized on the basis of viscosity at some fixed shear rate (effective viscosity). Nevertheless, for practical purposes plastisols are conventionally classified into low-viscous (1-3 Pa s), medium-viscous (10-15 Pa s), and high-viscous (100-1000 Pa s) plastisols. Viscosities are measured at low shear rate y = 1 s l when plastisol flow is Newtonian. 

If it is desired to separate out macroscale and microscale shear rate effects, then a change in the internal geometry of an impeller is necessary to change the relative proportions of these two quantities. 

Figure 2. Calibration curve for shear-rate effect (polystyrene in toluene atSO C)...

Newton s law-conversion factor Shear rate Effective shear rate Fictitious transfer coefficient Collision frequency between drops of sizes a and a for a binary collision process based on number concentration... 

The shear-rate effect on the viscosity of thermosetting resins, r]Jff), is also essential to the determination of the chemoviscosity, r]. The exact relationship will depend on the type of... 

It should be noted that the effects of fillers may be incorporated into the cure and shear-rate effects. The main forms of combined-effects model consist of WLF, power-law or Carreau shear effects, Arrhenius or WLF thermal effects and molecular, conversion or empirical cure effects. Nguyen (1993) and Peters et al. (1993) used a modified Cox-Merz relationship to propose a modified power-law model for highly filled epoxy-resin systems. Nguyen (1993) also questions the validity of the separability of thermal and cure effects in the derivation of combined models. 

Unlike hard, noninteractive particles, however, shear rate affects viscosity as a result of bond breakage of the large fractal aggregates during viscosity measurement [18]. Hence, the viscosity values of this derivation should be considered the true viscosity of solution with negligible shear rate effects. 

By comparing it with the theoretical mixing time, the energetic efficiency of mixing >1 ) can be defined as the ratio between shear rate effectively used for mixing and total shear rate used for the flow ... 

Granular flow behavior extends beyond the critical state as defined by traditional soil mechanics literature. As a result of rapid deformation associated with the flow, inertia as well as shear-rate effects must be considered. 

Flow properties of epoxide oligomers were reported by several workers. Aleman [2,3] discussed shear-rate effects on the shear viscosity measured by an Instron rheometer and found that each epoxide oligomer studied had Newtonian behavior up to the shear rate of 2000 sec Ghijsels et al. [4] reported that the temperature dependence of the zero-shear viscosity was... 

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