A MODEL FOR FOAM DEVOLATILIZATION IN AN EXTRUDER

A model is developed for the design of the devolatilization section in an extruder, which is optimized with respect to foam growth and proce ss parameters. The previously developed bimodal/film model for polymer devolatilization is used to design L-c, the distance from the melt se al to the vacuum port for completion of foaming and breakup in the ext ruder. The model requires one free parameter, the number of stripper b ubbles as a function of important process parameters. A statistical re gression method and a backpropagation neural network are used to devel op the correlations. The developed correlation along with the bimodal/ film model is applied to design a distance, L-c, prior to the vacuum p ort for completion of foaming and breakup in an extruder. Polyethylene /acrylic acid devolatilization in a 28-mm co-rotating twin-screw extru der is used as a case study for model demonstration.