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Evaluating screw performance: Extrusion process stability and the degree of mixing from melt rheology data and from measurement on an instrumented extruder
Author(s) -
Plochocki A. P.,
Dey S. K.,
Wilczynski K.
Publication year - 1986
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760261407
Subject(s) - die swell , rheology , extrusion , materials science , plastics extrusion , rheometry , mixing (physics) , viscosity , composite material , extrusion moulding , dimensionless quantity , polyethylene , thermodynamics , physics , quantum mechanics
Abstract A comprehensive study of polyethylene extrusion was carried out with an instrumented extruder on several screws differing in geometry and paralleled with capillary rheometry of the extrudate leading to melt viscosity and elasticity functions. Assuming Oldroyd's constitutive equation for molten polyethylene and the extrudate melt temperature oscillation (Δ T m ) as a measure of the process stability and an indication of melt mixing quality, it was found that the product of the dimensionless numbers (Deborah, De and Brinkman, Br ) correlates well ( r = 0.93) with Δ T m . Since the Br and De groups follow from the rheological characteristics of the melt and the extrusion process parameters, a relationship of type: Δ T m = a + b ( De ) ( Br ) appears useful in designing an extrusion process (for a polymer of known rheology) with respect to its stability, and indirectly, its mixing efficiency.