In‐process Measurements for Reactive Extrusion Monitoring and Control

In‐process rheological monitoring of extrusion‐based polymer processes

“…23 depends on the purpose of the data, on the required rate of sensing, on the coupling possibilities accepted by the processing equipment, and on the user friendliness, among others. Designing rheometers for in-process monitoring of extrusion is not trivial, as a number of requirements should be fulfilled: 6 • The device should measure the relevant material response(s) accurately and reliably. • The data should be acquired at a high rate and be insensitive to the mechanical vibrations of the extruder, and to other interferences arising in a typical production environment; quality control requires good sensitivity to changes in material behavior and reasonable time lag between sampling and data, whilst process control demands repetitive quick measurements.…”

“…optical and dielectric spectroscopies, rheometry, light scattering and ultrasound, to follow material morphology, density, viscosity, residence time distribution or to estimate molecular or chemical composition. [4][5][6] This mini-review focuses on in-process rheometry, which is used both in industry and in academia by resorting either to commercial devices or to in-house made prototypes. The motivation for electing rheometry for process monitoring is presented in the next section, which reviews rheological concepts.…”

“…A variety of techniques have been adopted for in‐process monitoring of extrusion, e.g. optical and dielectric spectroscopies, rheometry, light scattering and ultrasound, to follow material morphology, density, viscosity, residence time distribution or to estimate molecular or chemical composition 4–6 . This mini‐review focuses on in‐process rheometry, which is used both in industry and in academia by resorting either to commercial devices or to in‐house made prototypes.…”

“…Selection of the appropriate in‐process technique depends on the purpose of the data, on the required rate of sensing, on the coupling possibilities accepted by the processing equipment, and on the user friendliness, among others. Designing rheometers for in‐process monitoring of extrusion is not trivial, as a number of requirements should be fulfilled: 6 The device should measure the relevant material response(s) accurately and reliably. The data should be acquired at a high rate and be insensitive to the mechanical vibrations of the extruder, and to other interferences arising in a typical production environment; quality control requires good sensitivity to changes in material behavior and reasonable time lag between sampling and data, whilst process control demands repetitive quick measurements. The sample tested should be representative of the material being processed: (i) sampling and eventual thermal equilibration (for on‐line measurements) should not affect the material characteristics; (ii) each measurement should be made on a fresh sample; (iii) samples should be renewed rapidly. Sampling and testing should not interfere with extrusion (e.g. causing secondary flows or stagnation zones) and the main flow should not interfere with the measurement 35,38 …”