Continuous-flow capillary rheometer

Figure 3.2 Plots of log versus logy and loglVj versus logy for a low-density polyethylene at various temperatures ( C) (O, ) 180, (A, A) 200, and ( , ) 220. The data with open symbols were obtained using the cone-and-plate fixture of a rotational-type rheometer, and the data with filled symbols were obtained using a continuous-flow capillary rheometer. Refer to Chapter 5 for details of the experimental methods employed to obtain the data. (Reprinted from Han et ah. Journal of Applied Polymer Science 28 3435. Copyright 1983, with permission from John Wiley Sons.)...

Another experimental method that is as important as continuous-flow capillary rheometry is slit rheometry. The basic idea of slit rheometry is the same as that of continuous-flow capillary rheometry insofar as the measurement of wall normal stress along the die axis is concerned. But, there is a significant theoretical difference between the two methods, as we will make clear, and also in the die design. The slit rheometer has some advantages over the continuous-flow capillary rheometer in the way that transducers can be mounted on the die wall, but there are also some disadvantages. 

Figure 5.20 gives log versus log a plots for an LDPE (NPE 952) from three different sources from Han et al. (1983b), who employed a continuous-flow capillary rheometer from Baird et al. (1986), who employed a slit rheometer from Lodge and de Vargas (1983), who also employed a slit rheometer. It should be pointed out that a comparison of the data displayed in Figure 5.20 from three different sources... 

Table 5.6 gives the experimental data obtained for an HDPE (melt density of 0.745 gm/cm ) at 200 °C using a continuous-flow capillary rheometer for three different UD ratios. 

Table 5.7 gives experimental data obtained using a continuous-flow capillary rheometer for an LDPE. 

In a paper by Han et al. (1983b), data were not presented and only a log Nj versus log ff plot was presented. The values of in the log IVj versus log continuous-flow capillary rheometer. 

When using a continuous-flow capillary or slit rheometer, one must first make certain that the pressure gradients are constant (i.e., -dT ldz = dp/dz = constant in a capillary die or -dT ldz = dp/dz = constant in a slit die) in the region where wall normal stresses are measured. Nonlinear wall normal stress profiles of Tyy(b, z) may be observed in a slit die when pressure transducers are mounted in the die area that includes the entrance region (Eswaran et al. 1963, Leblanc 1976, Rauwendaal and Fernandez 1985). Nonlinear profiles of Tyy(b, z) in a slit die may also be observed... 

When using a continuous-flow capillary or slit rheometer, a number of design considerations must be taken into account. (1) Pressure transducers must be mounted... 

What is the alternative The answer clearly lies in the use of a continuous-flow capillary (or slit) rheometer, which makes use of wall normal stress measurements in the fully developed region of a capillary (or slit) die (see Chapter 5). That is, as long as the wall normal stresses along the axis of a die are linear (i.e., in the fully developed region), a can be calculated from... 

Another method is to use continuous-flow capillary (or slit) rheometry, as discussed in Chapter 5. Han and coworkers (Han and Ma 1983a, 1983b Han and Villamizar 1978 Han et al. 1976) were the first to use a continuous-flow capillary (or slit) rheometer to determine the viscosity of polymer melts with solubilized gaseous components. Later, other investigators (Elkovitch et al. 1999 Lee et al. 1999 Royer et al. 2000, 2001) employed the same method. 

HVA 6 Automated CapiUary/Sht Viscometer MFM Melt Flow Rheometer Automatic Melt Flow Indexer AK Continuous Capillary Rheometer Han Slit Rheometer... 

Regrind 11 (recalled boards, brittle, weak) 0.28 (No continuous flow in a capillary rheometer, n could not be determined, estimate gave n is close to zero) 4.35... 

Fluids flowing in a capillary rheometer see a shearing mode of deformation. Since fluids are always in motion and cannot hold a shape, a static measure of the strain is not useful a continuous deformation rate must be determined. Dilferentiating the shear strain with respect to time gives the shear strain rate or shear rate ... 

The reasons for the continuing use of melt flow indexers are low cost (about 10% the price of a capillary rheometer), simplicity and speed of use. Improved PID heating controls and more precise linear barrel-bore machined from a nitride-hardened steel or specially engineered ceramic has led, with recent models, to more reproducible results. Melt indexers can be obtained in a range... 

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