Dynamic viscosity data

Steady Shear Viscosity and Dynamic Viscosity Data Neat HDPE rheology data fairly well correspond to each other when obtained by both capillary and rotational rheometers. This actually means that HDPE melt obeys the Cox-Merz rule [26]. The... 

Rigid-rod polymers give much greater values of than flexible-coil polymers. Doi[28] calculated that is equal to 6.0 for the rigid-rod polymers. Kim et al. [29] experimentally found that the value of was 6.7 for the solution of poly(p-phenylene terephthalamide) in sulfuric acid at 30 °C from dynamic viscosity data. This is close to the value predicted by Doi. 

Dynamic viscosity data can be used to approximate the steady shear viscosity by taking advantage of an empirical relationship known as the Cox-Merz rule (Cox and Merz 1958), which relates the magnitude of the complex viscosity at frequency co to the steady shear viscosity at a shear rate y equal to co ... 

TABLE 11 Dynamic viscosity data of different samples of PE... 

Figure 2.17 Comparison of near-critical dynamic viscosity data for CO2 and H2O.

The highly detailed results obtained for the neat ionic liquid [BMIM][PFg] clearly demonstrate the potential of this method for determination of molecular reorienta-tional dynamics in ionic liquids. Further studies should combine the results for the reorientational dynamics with viscosity data in order to compare experimental correlation times with correlation times calculated from hydrodynamic models (cf [14]). It should thus be possible to draw conclusions about the intermolecular structure and interactions in ionic liquids and about the molecular basis of specific properties of ionic liquids. 

In order to reconciliate high-frequency dynamic rheological data with theory, Cerf proposed an additional internal viscosity term which should be mainly molecular weight independent [37] ... 

The scaling results above all pertain to local segmental relaxation, with the exception of the viscosity data in Figure 24.5. Higher temperature and lower times involve the chain dynamics, described, for example, by Rouse and reptation models [22,89]. These chain modes, as discussed above, have different T- and P-dependences than local segmental relaxation. 

Figure 5.5 The dynamic viscosity for a quasi-hard sphere dispersion from the data of Mellema et al.13 The frequency has been normalised to the diffusion time for two different particle radii. The volume fraction is

Mori et al. s results for three PBLG samples in m-cresol. For every sample, Dr decreases monotonically with increasing c, in a way resembling the simulation results shown in Fig. 16b. These Dr data, as well as the dynamic light scattering data, will be compared with Eqs. (50)- (52) in Sect. 8 together with zero-shear viscosity data. 

Fig. 8.1. Dynamic viscosity t] (a>) and steady state viscosity f](y) for undiluted narrow distribution polystyrenes. The data are plotted in reduced form to facilitate comparison. The dimensionless shear rate or frequency is t]0Mwy/gRT >r r/ M co/gRT. [See Eq.(8.3)]. The dynamic viscosities are for Mw = 215000 (O) and Mw = 581000 ( ) at 160° C (312). The steady shear viscosity is for Mw = 411000 (A) at 176° C (313). The shapes in the onset region are similar for the three curves, but the apparent limiting slope for the dynamic...

Fig. 8.3. Dynamic viscosity, absolute complex viscosity, and steady state viscosity for narrow distribution polystyrene. Data obtained at 25° C on a 0.071 gm/ml solution of polystyrene (Mw = 860000) in Aroclor (3/6)...

Viscosity might be described as an internal resistance of a gas or a liquid to flow. Viscosity data are reported as dynamic viscosity, 77, or as kinematic viscosities, v, which are related through density, p, by the following equation ... 

There is a wide-spread literature on methods for temperature-dependent viscosity estimation. Their discussion and further references can be found elsewhere [1,2,17,18,19,20,21], Usually, these methods are based on various input data, such as density, boiling point, and critical point. Dynamic viscosities of most gases increase with increasing temperature. Dynamic viscosities of most liquids, including water, decrease rapidly with increasing temperature [18]. 

Based on our experiments such substitute has been found. The exact specification on the substitute is know-how of the Institute of hydromechanics National Academy of Sciences of the Ukraine at Kiev. The comparison of measured values of dynamic viscosity of the methanol solution substitute and the data available in the literature for real methanol solution are presented in Figure 3 (the value C is the weight concentration of methanol in a solution). Since the measurements were realised within the temperature range T = 18-20°C, a fairly good agreement between methanol and its substitute was proved. Of course, to use the substitute is not limited on this temperature range it should be used also for very low temperatures. The preliminary measurements with the substitute used as the carrier fluid also confirmed results illustrated in Figure 1. 

The table below provides data on the most important properties of pure water under different temperatures. These properties are density (g/ml), molar volume (ml/mol), vapor pressure (in kPa and mmHg), static dielectric constant, and dynamic viscosity (mPa sec). The properties other than the vapor pressure are evaluated at a pressure of 101.325 kPa or the vapor pressure, whichever is higher. 

A study of the flow of a polyhedral foam in a regime of slip at the tube walls has been conducted [39]. It has been established that the rise in the dynamic viscosity of the foaming solution leads to diminishing the flow rate but to a much lesser extent at t0 = 1.25 Pa. Thus, a two fold increase in viscosity causes a 1.3 times decrease in the flow rate, while a 6 times increase in the dynamic viscosity only a 2.23 times decrease. This is probably related to the expanding of the effective thickness of the liquid layer 8 (ca. 3 times). The transition from plug flow (slip regime) to shear flow occurs at To = 9-10 Pa. This value of the shear stress is much smaller than the one obtained from Princen s formula for a two-dimensional foam (Eq. (8.18)) at a given expansion ratio and correlates well with To calculated from Eq. (8.24) and the experimental data of Thondavald and Lemlich [23],... 

Figure 13.5 Dependences of the reduced tensile stress growth coefficient ti (i,t)/ar at 170°C on reduced time fay and reduced strain rate iaj for a SAN resin (wAN = 0.264, Mw = 78 kg/mol, Mw/M = 2.8) during the startup of uniaxial extensions flow. Also illustrated (dashed curve) are dynamic shear viscosity data displayed as 3 r7 (c<, 170°C) versus or7 as suggested by Trouton [64]. Reproduced from L. Li, T. Masuda and M. Takahashi, J.Rheol., 34(1), 103(1990), with permission of the American Institute of Physics...

In addition to relationships between apparent viscosity and dynamic or complex viscosity, those between first normal stress coefficient versus dynamic viscosity or apparent viscosity are also of interest to predict one from another for food processing or product development applications. Such relationships were derived for the quasilinear co-rotational Goddard-Miller model (Abdel-Khalik et al., 1974 Bird et al., 1974, 1977). It should be noted that a first normal stress coefficient in a flow field, V i(y), and another in an oscillatory field, fri(ct>), can be determined. Further, as discussed below, (y) can be estimated from steady shear and dynamic rheological data. 

The rheological properties of the complex network structure of tomato pastes may be assumed to be made up of two contributions (1) one network structure contributed by the solids phase, in proportion to 0s, and (2) another network structure contributed by the liquid (continuous phase), in proportion to 0i = 1 - 0s- However, the effective continuous phase is not the low-viscosity serum itself, but a highly viscous liquid that is an integral part of the tomato paste. Also implicit is that the solids fraction plays a major role in the structure of the TP samples, that is, it can be considered to be the structuring component. These assumptions are also in line with the weak gel behavior indicated by the dynamic shear data. 

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