Silicones, kinematic viscosity

Fig. 4. Kinematic viscosity—temperature relationship of dimethyl silicone fluids.

We have already discussed the temperature dependence of the kinematic viscosity of silicones with relatively large viscosity values (silicone lubricants). The silicones concerned are chain polymers and in Table XIV the values of their F.V.T.I, is given together with their and x values. 

Figure 36. Effect of oil viscosity on the half-lifetime (r ) of foams formed from 0.06 M sodium dodecyl sulfate in the presence of 200ppm mixed antifoam containing silicone oils [poly(dimethylsiloxane), DMPSJ of various kinematic viscosities and 2.5 wt% hydrophobized silica (T-500).

Seven kinds of silicone oils (dimethyl-polysiloxan) different in viscosity are used ( kinematic viscosity 1.0, 2.0, 10, 30, 100, 1000... 

The carrier liquid of the ferrofluid used in the experiment (APG S lOn, Ferrotec) was a synthetic ester oil which was immiscible in silicone oil. The viscosity rj, density /O, and surface tension a of the ferrofluid at 25 °C were 0.406 kg/ms, 1330 kg/s, and 32xlO N/m, respectively. The saturation magnetization and the initial susceptibility X of this ferrofluid were 44 mT and 1.6, respectively. Two silicone oils with different viscosities were used to investigate the effect of viscous friction [—Si(CH3)20—] , with a kinematic viscosity of V = 50 cSt, and [—C7H80Si—], with a kinematic viscosity of 100 cSt. Both oils had approximately the same surface tension of 2.03 x 10 N/m and a density of 960kg/m. In the experiments, the ferrofluid droplet was surrounded... 

A thin top silicone oil layer was found to significantly affect the first kind of swirl motion in a bottom blown bath with the exception of the swirl period. Although the kinematic viscosity of the silicone oil layer was fixed in this section, the behavior of... 

The original KHI theory [40,41] implies that the critical velocity difference responsible for the onset of mold powder entrapment is influenced by the interfacial tension and the densities of molten steel and mold powder. In addition to these parameters, the kinematic viscosity of mold powder must be taken into consideration. As a first step, particular attention is paid, in the description here, to the effect of the kinematic viscosity of the mold powder on the entrapment, and model experiments carried out using salt water and silicone oils. 

Solid particles having diameters ranging from 75 to 150 p,m were dispersed in the salt water layer as tracers for PIV measurements. The density of the particles was 1,013 kg/m, and accordingly, the density of the salt water was adjusted to the same value. Also, particles having the same density as silicone oil 10 were used as tracers for the measurement of flow velocity in the oil. Each silicone oil type was tagged with a number. For example, silicone oil 10 implies that the kinematic viscosity of the oil is lOmm /s. Adequate tracer particles are available for silicone oil 10 and 100, but nothing exists at present for the other types. 

Figure 8.25 shows the velocity distribution in the vertical cross-section for silicone oil 10. Both the distributions of salt water flow and silicone oil flow are approximately uniform at every time of measurement. On the other hand, the velocity distributions for silicone oil 100 shown in Fig. 8.26 are not uniform because of its high kinematic viscosity. 

Figures 8.27 and 8.28 show the critical velocity differences describing the onset of KHI for silicone oil 10 and 100, respectively. The results shown with open circles were determined by using both the measured values of Vicr and 2, while open triangles were determined by using the measured values of and calculated value of Vicr based on (8.25). For every salt water layer depth, the two sets of results (i.e., the two symbols) agree with each other in Fig. 8.27. As the kinematic viscosity of silicone oil was increased from 10 to lOOmm /s, a discrepancy appears between the two symbols as seen in Fig. 8.28, but it is limited to about 15%. A number of researchers [27, 30, 32] have also observed a critical velocity difference of approximately 20 cm/s for water-siUcone oil systems shown in Fig. 8.17a.

Figure 8.31 demonstrates that all the measured values of the critical salt water velocity can be predicted by (8.27) regardless of the kinematic viscosity of silicone oil. Yamasaki et al. [30] and Komai et al. [42] also observed that the critical velocity difference is a weak function of the kinematic viscosity of silicone oil. 

Figure 8.32 shows that the wavelength decreases with an increase in the salt water layer depth. When the kinematic viscosity of silicone oil is low, say 2 mm /s, the measured values of wavelength A can be approximated by (8.30). As the kinematic viscosity of silicone oil increased, the wavelength increased (see Table 8.5), and (8.30) overestimated the A. Yamasaki et al. [30] observed that the diameter of a liquid paraffin droplet became large with an increase in the kinematic viscosity, which is consistent with the above finding on the wavelength behavior. 

The amplitude of KHI is a function of the depth ratio H2/H1 and the kinematic viscosity of silicone oil, as shown in Table 8.6. Figure 8.33 shows that (8.32) cannot predict the amplitude. 

When the thickness of the silicone oil layer is larger than the amplitude of waves caused by shear flow instability at the silicone oil/salt water interface, the critical salt water velocity is independent of the kinematic viscosity of the oil, vi, in the range of vi from 2 to 350mm /s and satisfactorily predicted by an analytical solution, (8.27), proposed by Milne-Thompson. 

The wavelength X increases with an increase in the kinematic viscosity of silicone oil. The analytical equation for A (8.30) agrees with the measured values of A for vi = 2 mm /s, but overestimates A as vi exceeds lOmm /s. The amplitude of the interfacial instability is also measured. 

Data on diffusion constants of impurity atoms are important to calculate incorporation of dopant impurities in silicon crystals, which control the electronic properties of silicon. However, there are fewer data on impurity diffusion constants except for that reported by Turovskii [85], Kodera [86], Shashkov and Gurevich [87], Gnesin and Raichenko [88], and Keller and Miihlbauer [89]. In the Landholt-Bomstein data book, Miihlbauer recalculated reported data using the kinematic viscosity of molten silicon (v = 3.5 x 10 m /s) [91]. Diffusion constants reported are tabulated in Table 4.3. 

Frictional behaviour was examined under both lubricated and un-lubricated conditions. Distilled water was used as lubricant in the lubricated tests. In addition, silicone oil with a kinematic viscosity of Imm /s and fetal bovine serum were also used as lubricants. Fetal bovine serum was diluted to 30vol% with distilled water to give the similar protein content to synovia, which played a role of lubricant for joint prostheses in vivo, and 0.3wt% sodium azide was added to retard bacterial growth. The viscosities of these lubricants are as small as distilled water. 

Figure 4.12 Influence of kinematic parameter of flow A and viscosity on the dispersion degree of Ti02 agglomerates in silicone oil (trials with a single screw extruder) [151...

Figure 9.11 Degree of disaggregation as a function of the kinematic parameter of flow A and the viscosity of the fluid, measured with Ti02 in silicone oil in a single screw extruder [6, 7]...

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