Scale process monitoring, extrusion

To summarize, while selection and scale-up of extruders is governed by extruder geometry, formulation, and process variables, secondary variables could be used to monitor the process on a continuous basis. Based on the reports thus far in the literature, the variables that seem to play a critical role in scale-up of extrusion are summarized in Table 7. 

Compared to the time scale of their formation, the carbonyl oxides are quite long lived (10 -10 s), and so their subsequent reactions can be monitored kinetically. For most of the carbonyl oxides, the decay is best fit to a second-order rate law, indicating a bimolecular decomposition pathway. For benzophenone oxide, the ketone is the major product at room temperature, and no dimer can be detected. A bimolecular process involving O2 extrusion from two molecules of the oxides is suggested under these conditions. 

A continuous extrusion process was also used to produce foamed sheets. The extrusion line is composed by a lab-scale twin-screw extruder (Haake CTWIOO), a hot heat exchanger, and a capillary system acting as nucleation nozzle. The latter device allowed for a good control of the pressure profile in the extrusion line. Detailed monitoring of the process parameters was obtained by means of four pressure transducers and five melt thermocouples. 

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