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A study of bicomponent coextrusion of molten polymers
Author(s) -
Han Chang Dae
Publication year - 1973
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1973.070170422
Subject(s) - die swell , polystyrene , materials science , polyethylene , composite material , extrusion , die (integrated circuit) , low density polyethylene , high density polyethylene , capillary action , viscosity , polymer , nanotechnology
An experimental study has been carried out of coextruding polystyrene with lowdensity polyethylene and polystyrene with high‐density polyethylene, using both slit and circular dies. Two melt streams were separately fed to the die entrance and forced to flow side by side through a die. When using the slit die, wall normal stresses were measured with three melt pressure transducers flush‐mounted on each of the rectangle's long sides, directly opposite each other. When using the capillary die, three different capillary length‐to‐diameter ( L / D ) ratios were employed: 4, 11, and 18. Wall normal stresses were measured for dies having L / D ratioes of 11 and 18 only. The measurements of wall normal stresses permitted one to determine the pressure gradient, and hence the viscous property. For each set of extrusion conditions ( L / D ratio, flow rate, and component ratio), extrudate samples were collected. These were later carefully cross sectioned and photographed in order to examine the shape of the interface between the two components. At the phase interface of the polystyrene/low‐density polyethylene system, it has been observed that the polystyrene, which is more viscous and yet less elastic than the low‐density polyethylene, has a convex surface. However, at the phase interface of the polystyrene/high‐density polyethylene system, the high‐density polyethylene, which is more viscous and also more elastic than polystyrene, is seen to be convex. This then appears to indicate that the viscosity ratio of two components is primarily responsible for the final shape of the interface.