Screw-extrusion type rheometer

CONSTANT SPEED SCREW EXTRUSION TYPE CAPILLARY RHEOMETERS... 

Figure 3.5 Schematic diagram showing the principal features of a constant speed screw extrusion type capiliary rheometer.

These capillary rheometers are principally the same as those described in Sections 3.2.1 and 3.2.2 except for the melt transport system which is of the screw extrusion type rather than the plunger type discussed earlier. A schematic diagram of an extrusion capillary rheometer is shown in Fig. 3.5. Commercially available extrusion capillary rheometers are the Haake Rheocord (Haake Buchler Instruments, Inc., Saddle Brook, NJ) and the Brabender Plasticorder (Brabender, Duisburg, Germany). The rheological property measurements can be done using a circular or slit orifice, as these are separate attachments for the miniaturized single screw extruder. 

A new type of test methodology for characterizing engineering plastics has been developed. These techniques simulate the extrusion and molding process to show what a polymer would undergo in terms of shear, temperature, pressure, and residence-time deformation. The behavior of a compound can be accurately predicted prior to processing. An online-type rheometer continuously measures the viscosity of the polymer from the die on a real-time basis, and the data is used to make screw speed adjustment to keep the viscosity consistent (10). 

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