Pressure of extrusion

Particle size and size distribution mixing, amperage, power consumption) Torque or pressure of extrusion... 

Mathematical description of the process of polymer melting in the extrusion channel is complex when ultrasound is used. The description requires firstly, consideration of the mass flow of the polymer, knowledge of the flow characteristics of the melt, the temperature and pressure of extrusion, sizes of the channel and frequency of ultrasonic oscillations. Secondly, coefficient of swelling of the extrudate, effective viscosity of polymer, pressure of melt, and frequency of oscillations. 

The venting works because at a typical extrusion temperature of 250°C the water in the plastic exists as a vapour at a pressure of about 4 MN/m. At this pressure it will easily pass out of the melt and through the exit orifice. Note that since atmospheric pressure is about 0.1 MN/m the application of a vacuum to the exit orifice will have little effect on the removal of volatiles. 

Example 4.4 A blow moulding die has an outside diameter of 30 mm and an inside diameter of 27 mm. The parison is inflated with a pressure of 0.4 MN/m to produce a plastic bottle of diameter 50 mm. If the extrusion rate used causes a thickness swelling ratio of 2, estimate the wall thickness of the bottle. Comment on the suitability of the production conditions if melt fracture occurs at a stress of 6 MN/m. ... 

Mechanical properties of hydrogenated titanium alloys are strongly dependent on the applied stress tensor, especially on its hydrostatic component. This was illustrated by the high-pressure tensile and extrusion tests on the Ti-6Al-2.5Mo-2Cr alloy and the same alloy hydrogenated to a = 0.15 wt.%H. Tests were carried out using the apparatus at the Institute of Metal Physics UD RAS operating at hydrostatic pressures of machine oil to 15 kbax and temperatures to 250°C. 

A French pressure cell can be used to reduce the size of MLV by extrusion under high pressure. Four extrusions of egg PC-MLV at 4°C resulted in the formation of small unilamellar vesicles 94% of the lipid was found in 31- to 52-nm vesicles (Barenholz et al., 1979). 

Empty space in which there are no atoms or molecules. A perfect vacuum cannot be attained in practice and the term denotes a space containing air or other gas at a very low pressure. In industry vacuum is measured in inches of mercury (in Hg) ranging from 0 in at atmospheric pressure to around 30 in at zero absolute pressure. Vacuum Extrusion... 

The 500 mm diameter extrusion problem presented in Section 7.5.1 was simulated using the generalized Newtonian method with and without the iy correction factor. The simulations and the experimentally determined pressure at a position 5.6 diameters downstream are shown in Fig. 7.29. Recall that the generalized Newtonian method over-predicts the pressure by a factor of 1.7 (a 70% over-prediction) at 10.8 MPa. The method with the F, correction factor predicts a pressure of 5.9 MPa, a pressure that is slightly lower than the experimentally determined pressure of... 

The baseline extrusion process was numerically simulated using the processing conditions in Table 9.4 and the method described in Section 9.2.1, that is, with a rate of 77 kg/h, a screw speed of 27 rpm, and a discharge pressure of 10.6 MPa. The iterative calculation process was used to estimate a bulk temperature of 160 °C and a pressure of 13.1 MPa at the entrance to the meter section. The axial pressure and temperature profile for the simulation is shown in Fig. 9.5. 

A plot of the intruded (or extruded) volume of mercury versus pressure is sometimes called a porogram. The authors will use the terms intrusion curve to denote the volume change with increasing pressure and extrusion curve to indicate the volume change with decreasing pressure. Figure 11.1 shows a typical porosimetry curve of cumulative volume plotted versus both pressure (bottom abscissa) and radius (top abscissa). The same data plotted on semilog paper is illustrated in Fig. 11.2. 

At no time along the intrusion curve does the pressure relax. Therefore, no opportunity is provided for a small quantity of extrusion to occur following intrusion. This is a condition which can produce a data point somewhere in the hysteresis region between the intrusion and extrusion curves. 

Figure 25 Integrated thermocouple and pressure transducer to measure temperature as well as pressure during extrusion. Source Photo courtesy of Heaster Industries.

This consists of blocking which involves pressing the mass for several minutes at a pressure of ca. 200 kg/cm2 (3000 lb/in2). The block thus formed is transferred to another press of a type much similar to the extrusion press (Fig. 213). Here the dough is forced through a series of screens and perforated plates. This is referred to as macaroni pressing owing to the shape of the extruded threads. 

Extrusion granulator subclasses primarily are distinguished by the orientation of extrusion surfaces and driving pressure production mechanism. 

Once the emulsifier is well blended into the carbohydrate melt, the flavoring material is added. An emulsion is formed using a flat bladed turbine type agitator (about 4i inches in diameter). The time of agitation is typically about 5 min. The next step involves pressurization of the extrusion vessel with either nitrogen or carbon dioxide. While others have mentioned pressurization of the vessel for extrusion, Miller and Mutka (8) have optimized this parameter for encapsulation efficiency, they found 7-50 psi most suitable for improving encapsulation efficiency. At pressures above 100 psi, they found some emulsions broke and encapsulation efficiency was very poor. 

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