Viscosity three-region

Figure 6 is a plot of specific conductance against mole ratios of methanol to bis(2-ethylhexyl) sodium sulfosuccinate. Like the viscosity data, there are three regions. In the first region, a rapid rise in conductance occurs, which indicates the formation of a microemulsion. It is in this region that the swollen micellar solution and liquid crystalline phase of methanol in bis(2-ethylhexyl) sodium sulfosuccinate is breaking with the formation of microspheres that constitute the microemulsion (13). 

Generally large yield stress effects were dominant in the nematic melts, but they were strongly pre-history dependent. A three region flow curve for 15 mol % modified poly(pheny1-1,4-phenylene terephthalate) was probably due to a not completely molten system. Dynamic viscosity measurements showed strong pseudoplastic behaviour. Strain and time dependence phenomena were not observed. 

The basis for the rheological calculation is the description of the viscosity function of the plastic used with the help of the Carreau model, which describes the viscosity in its dependence on shear rate in the three regions ... 

Some researchers consider the viscosity versus shear rate curve to consist of three regions. At low y, n depends on 7" because of the presence of yield stresses. In region II there is a plateau where n is nearly independent of y. Finally, in region III, n depends on y to some power (n) between -1.0 and 0 which is similar to flexible chain isotropic systems. It is our contention that yield stresses (Oq ) are not common features of pure liquid crystalline fluids. For sey r l different lyotropic systems, values of no are observed at low y. It is possible that only... 

In Section II.B of Chapter 3 the chemical kinetics of the gel effect was considered. However, this effect that is also known as the Trommsdorjf effect has also its implication for the development of the viscosity. Cioffy (9) studied the viscosity development during chain polymerization reactions. Three regions can be distinguished In the first region no entanglements... 

Figure 1 illustrates the curing process as measured by a rheometer. The rheometer follows the development of cure state as a function of time. Vulcanization characteristics such as minimum torque Ml (a measure of compound green viscosity), onset of cure (T1 pt rise), Mh (a measure of maximum cure state reached), and T90% cme (time required to reach 90% cure state) are valuable properties defining cure behavior. Likewise the rheometer cure profile can be broken into three regions of interest, an estimate of scorch safety, an idea of what the cure state development looks like during the cross-linking phase, and how the cross-linked vulcanizate network matures with additional heat. 

LCPs exhibit in simple shear steady-flow several rheological effects, uncommon to polymers with long flexible chains. The first is negative normal stresses observed in some LCPs. The second is the effect of three-region viscosity shown schematically in Figure 11.1. 

In Figure 11.5, the experimental results are shown by dots and the fitting curve by dashed line. Unfortunately, the normal stress data for this polymer were not reported. It is unclear whether the experimental plot is related to the transition from the region I to region II in the general three-region viscosity plot. 

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