Extruder diagram

This temperature is affected by the barrel temperature and the heat transfer coefficient, which is influenced again by the screw speed. If viscous dissipation is important, the screw speed also has a direct influence on the material temperature. Finally, the influence of temperature on viscosity completes the extruder diagram. 

By combining the extruder diagram with the reaction diagram an interaction diagram for steady-state operation with single-component bulk polymerizations can be obtained (Fig. 7.3). The coupling between both diagrams is... 

As plastics can have quite different viscosities, they will tend to behave differently during extrusion. Fig. 4.3 shows some typical outputs possible with different plastics in extruders with a variety of barrel diameters. This diagram is to provide a general idea of the ranking of materials - actual outputs may vary 25% from those shown, depending on temperatures, screw speeds, etc. 

Figure 4 Phase diagrams of pectins extracted by water from extruded citrus fibre and by acid from the fibres (upper curve), and of commercial citrus pectins (dm 73%) (lower curve)...

Figure 8 Phase diagrams of the extruded citrus fibres (SME = 250 kWh/t)...

Usually when an extruder is purchased the controls are included. Therefore, they will not be indicated on the control diagram. 

Figure 5.5 shows a schematic diagram of a melt indexer (which is also sometimes referred to as an extrusion plastometer). To determine the melt flow rate of a polymer resin, we place a suitable mass of it into the barrel, which is pre-heated to a standard temperature appropriate to the polymer. We then place a weighted piston on top of the sample. After allowing the polymer to reach the temperature of the barrel we allow it to extrude from the capillary orifice. The melt flow rate is the mass of polymer in grams that extrudes in ten minutes. 

Fig u re 11.1 Schematic diagram show ng the principal components of a single screw polymer extruder... 

Figure 12.5 Schematic diagram showing a continuous mixer feeding a single screw extruder...

Fig. 25. Ko-kneader intensive compounding extruder [Courtesy Buss. AG] (a) Schematic diagrams of slotted screw and barrel pins, (b) ko-kneader with barrel in open position...

Cheletropic reactions, in which a single atom is added or extruded, comprise a special case of cycloaddition reactions. Figure 14.4 displays correlation diagrams for two typical cheletropic reactions, the loss of SO2 from a thiirane dioxide (Figure 14.4a) and the loss of CO from a norbornadienone (Figure 14.4b). The addition of a carbene to an olefin is another example which is discussed below (Figure 14.9a). 

Fig. 12. Tentative flow curves of low-density polyethylene with MFI = 2.0 g/10 min extruded at 170 °C through channels with a two-angle ellipse Wber cross section with a length of 50 (a), 75 (b), and 100 (c) mm with reciprocating-rotary vibration of the element in the zone upstream of the inlet to the channel (according to the diagram given in Fig. 9) ...

Figure 2.32 Schematic diagram of extrudate swell during extrusion.

Schematic diagram of the grooved feed section of a single screw extruder.

Figure 5.10 Schematic diagram of the melt film during melting in extruders.

Fig. 10.73 Schematic of the three-dimensional FEM nonisothermal flow analysis flow diagram employed by the Ishikawa et al. (113). [Reprinted by permission from T. Ishikawa, S. I. Kihara and K. Funatsu, 3-D Numerical Simulations of Nonisothermal Flow in Co-Rotating Twin Screw Extruders, Polym. Eng. Set, 40, 365 (2000).]...

Figure 2. Schematic diagram of mixing in single screw extruder.

An enthalpy diagram also shows that the temperature increase in the example shown is directly linked to the specific energy input. Figure 6.6 gives the specific enthalpies for different products and converts them from kj/kg (left) to kWh/kg (right). In this example, the drive power of the extruder is converted into the dissipative product heat increase . 

Even without software support, the process engineer can still obtain certain predictions by a precise analysis of the processes involved. In this case, process-specific diagrams are very helpful. These illustrate, for example, the specific energy input (Fig. 11.9) or other quality-related characteristics as a function of viscosity, throughput, speed, or discharge pressure. With the aid of enthalpy (Fig. 11.10) as a physical, process-independent value, initial forecasts can be obtained as to the energy that will be required to melt a resin and to extrude at a specified end temperature. 

Melt fracture occurs when the rate of shear exceeds a critical value for the melt concerned at a particular temperature (that is, the critical shear rate ). There is a corresponding critical shear stress and the relevant point on the flow curve (or the shear rate-shear stress diagram) is known as the critical point. It is believed that it is reached in the die entry region (that is, where material is being funnelled from the die reservoir into the capillary of a capillary rheometer)—which, in an extruder, corresponds with the point at which melt moves into the die parallel portion of the die. Some further complicating effects may occur at the wall of the die. 

Figure 1-25 Modified State Diagram Showing Relationship Between Glass Transition Temperature (Tg), Water Activity (GAB isotherm), and Water Content for an Extruded Snack Food Model. Crispness is lost as water plasticization depresses Tg to below 24X2. Plasticization is indicated with critical values for water activity and water content. Source Reprinted with permission from Y.H. Roos, Glass Transition-Related Physico-Chemical Changes in Foods, Food Technology, Vol. 49, No. 10, p. 99, 1995, Institute of Food Technologists.

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