Viscose applications

High Viscosity Applications Turbine Propeller Paddle 1. Volume Circulation 2. Law Ve loci 1 y 1.5 1 lo25 i 1 2 to 2 1 Slngl or Multiple... 

Talc is also often used as an extender in epoxy adhesives and sealants, but it also has flow control properties. Talc is used in higher-solids, high-viscosity applications such as caulking compounds, automotive putties, mastics, and sealants. Talc is a hydrophobic and organophilic material. 

C - C " 8 11 L911P, L810P Linear and semi-linear phthalates for low viscosity applications Low temperature... 

Viscosity, Applicable to both gas and liquid systems when there is a change in specific viscosity with extent of reaction. (Used frequently in studying polymerization.)... 

Attritors In the Attritor (Union Process Inc.) a single vertical armature rotates several long radial arms. The rotation speeds are much slower than with other stirred media mills, and the grinding behavior in these mills tends to be more like that in tumbling mills than in other stirred media mills. They can be used for higher-viscosity applications. These are available in batch, continuous, and circulation t es. 

For high-viscosity applications, lack of turbulence adjacent to the bubble, and the general difficulty in pumping around the draft tube (riser), prevent the use of simple pneumatically agitated airlift fermenters. Stirred tank fermenters are typically used for media with a viscosity exceeding 100 cP. As noted before, an... 

Proximity and nonproximity impellers are the two major designs used in mixing applications. Proximity relates to distance from the vessel wall. Figure 9.50(a) shows a nonproximity impeller typically used for turbulent conditions. Its blades are not close to the vessel wall. Close proximity agitators like anchors and helical ribbons, illustrated in Figures 9.50(b, c), are typically used for high-viscosity applications. 

Spalding [89] defined a simple expression for the eddy viscosity applicable to the entire law of the wall region as... 

Mixing in a vessel can be achieved for low-viscosity applications by the use of a submerged nozzle from which a high-velocity jet of liquid emerges. A pump is used to withdraw part of the liquid from the vessel and recycle it via the nozzle to the vessel. The momentum transferred from the high-velocity jet to the liquid in the vessel causes the mixing action and circulation within the tank (see Figure 7.6). 

Wide formulation possibilities to suit individual requirements (e.g., color, viscosity, application temperature, and performance characteristics)... 

Coating materials composed of resins suspended in a hydrocarbon liquid. An organosol is plastisol with an added solvent, which swells the resin particles, thereby increasing viscosity. Applications include spray coating, dipping, and coatings for aluminum, fabrics, and paper. 

NH2—CH2—CH2—NH2). Dendrimers are ideal macromolecular standards for use in size exclusion chromatography, membrane porosity evaluation, Newtonian viscosity applications, and electron microscopy. Unique, high surface functionality (Z may range from 2,3, or 4 to several thousand) provides nanoscopic building blocks for complex nanoconstructions based on either covalent bonding or self assembly-type processes. In the biomedical field. 

Viscous Liquids. Fluids with viscosities up to 50.000 centipoise can be processed in a standard thin-layer evaporator. "Zero-clearance" rotors do not exhibit the range of viscosity application that "fixed-clearance" rotors exhibit. Some firms manufacture "thin-film" vertical extruders" for the 50,000 to 20,000,000 centipoise range where fluids cease to flow under the influence of gravity alone. Thin-film evaporators, inherently low-pressure-drop devices, have mechanical turbulence and therefore relatively good heat transfer properties over a wide range of viscosities. 

Two types of silicone are available. Each is formulated to conform as the generic name implies by following the circuit contours without leaving sharp solder points or other obtrusions uncovered. Their general properties are also shown in Table 3.3. The first of these (4) is a solventless, viscous fluid elastomer which can be applied directly to a circuit board by flow coating, but is usually diluted by solvent to reduce its viscosity. Application may then be by dipping, spraying or flow... 

Low viscosity mixing applications can usually be handled efficiently with impeller systems consisting of one or more turbines. To obtain adequate mixing under the laminar flow conditions encountered in high viscosity applications, on the other hand, close-clearance impellers such as anchors and helical ribbons are required. These impellers sweep the whole wall surface of the vessel and agitate most of the fluid batch through physical contact. Helical ribbon impellers are typically used for industrial applications where the viscosity is in the range 20 000 to 25 000 Pa s. Wall scrapers can be mounted on the impeller blades to improve heat transfer. 

In this section we describe turbine impellers used in transitional and turbulent flow apphcations. High viscosity applications and appropriate impeller types are discussed in Section 6-6. Further discussions of impellers may be found in Chapter 21 and in Dickey et al. (2001). A number of video clips illustrating the effects of impeller selection are included on the Visual Mixing CD. 

The planetary dual disperser (PDDM) is reportedly ideal for the powerful mixing of high-viscosity applications requiring ultra-fine dispersion quality. The PDDM features four agitators—two planetary stirrers and two high-speed shafts—all rotating on their own axes while orbiting the mix vessel on a common axis. Pictured is a 40-gal model equipped with built-in vacuum pump assembly for operation up to 29.5" Hg. 

This formula takes into account the diameter of the vessel (D), the velocity of the fluid (v), the density (p) and the viscosity ((i). The Reynolds number has no dimensions. For high viscosity applications one can see that we need large scale diameter agitator and low speed. On the other hand for low viscosity fluids the diameter of the agitator may be as low as one third the vessel diameter and the speed high. In scale-up the ratio of impeller diameter to vessel diameter is an important factor. 

For syringe applications, programmable time/pressure controllers are used to produce beads and dots. An adjustable vacuum also can be used to control drips between dispense cycles. Pressure options relate to material viscosity with zero to one bar specified for low-viscosity applications, for example. Shot duration can typically be controlled between 0.01 and 99.99 s. 

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