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Mixing efficiency for polymer blends of very different molecular weights by using a mixing nozzle
Author(s) -
Saeda Shigeru,
Suzaka Yukinori
Publication year - 1995
Publication title -
polymers for advanced technologies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.61
H-Index - 90
eISSN - 1099-1581
pISSN - 1042-7147
DOI - 10.1002/pat.1995.220060802
Subject(s) - nozzle , materials science , body orifice , plastics extrusion , homogeneity (statistics) , composite material , conical surface , polymer , mixing (physics) , polyethylene , mechanical engineering , statistics , physics , mathematics , quantum mechanics , engineering
A way to mix polymer blends of very high and low molecular weights by using a mixing nozzle is presented. An array of blend nozzles with a conical inlet attached to a single screw extruder was used to blend polyethylene homopolymers with very different molecular weights. Using extruders with 30 and 50 mm barrel diameters, the effects of nozzle dimensions and operation conditions with respect to the homogeneity were studied. The device proved useful in obtaining a good macroscopic and molecular homogeneity up to 30 kg/hr by the 50 mm extruder, though care must be taken to avoid the degradation of polymers by heat and shear, especially in the extruder. The key factor ruling the efficiency of blending was found to be the compression ratio, i.e. the ratio of the cross sectional areas of the entrance of the nozzle and that of the orifice, and the shear rate at the orifice. For the nozzle with geometrically similar figure, the critical shear rate at which the homogeneity began to worsen was the same. Scale‐up of the nozzle could be accomplished by enlarging the diameter of the diameter of the orifice, yet maintaining a geometrically similar figure. The maximum output of the nozzle is proportional to the third power of the orifice diameter.