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Isothermal swell of extrudate from annular dies; effects of die geometry, flow rate, and resin characteristics
Author(s) -
Orbey N.,
Dealy J. M.
Publication year - 1984
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.760240710
Subject(s) - die swell , die (integrated circuit) , materials science , isothermal process , composite material , flow (mathematics) , swell , mechanics , extrusion , thermodynamics , physics , nanotechnology
An experimental study was made of the effects of die geometry and extrusion velocity on parison swell for three high‐density‐polyethylene blowmolding resins. Four annular dies were used: a straight, a diverging, and two converging dies. Diameter and thickness swells were measured as functions of time under isothermal conditions and in the absence of drawdown. This was accomplished by extruding into an oil having the same density and temperature as the extrudate. It was observed that 60 to 80 percent of the swell occurs in the first few seconds and that equilibrium swell is attained only after 5 to 8 minutes have elapsed. The diameter and thickness swells appear to be independent phenomena, as the relationship between them depends strongly on die design. The ranking of the resins in terms of the magnitude of the swell was found to be the same for all die geometries and extrusion rates used.