Melt Flow Index A relatively simple method to provide a general and relative characterization of how a given polymer will flow when melted is a test called the melt flow index (MFI), which is also sometimes called the melt flow rate (MFR) In this test, a small sample of plastic is heated and forced through an orifice by a weighted piston. The results are recorded as the weight of material …

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Pressures inside the Extruder  The pressures inside the extruder reflect the flow that occurs in the extruder. Figure 1.8 shows the flow in a cross section of the screw channel in the metering section of the extruder. At the top of the channel there is a drag flow toward the pushing flight flank and the pressure increases from P4 at the trailing flight flank to P1 at the pushing flight flank. …

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A good understanding of the extrusion process is necessary to solve extrusion problems efficiently. It is recommended for the reader new to extrusion to take classes covering the material characteristics of plastics, typical features of extrusion machinery, instrumentation and operating controls, the inner workings of extruders, and screw and die design. Classes and continuing education short courses on extrusion are available from a variety of colleges and organizations. There are …

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