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Effect of characteristic scale on the extrudate swelling behavior of polypropylene melt in a micro‐extrusion process
Author(s) -
Liu Kui,
Wang Minjie,
Li Hongxia,
Zhao Danyang,
Jin Yifei
Publication year - 2021
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.25707
Subject(s) - die swell , materials science , extrusion , swelling , swell , viscoelasticity , composite material , polypropylene , laminar flow , mechanics , mandrel , thermodynamics , physics
The swelling behavior in micro‐extrusion has a significant effect on the dimensional and shape accuracy of microproducts. In this study, the effect of characteristic scale, defined as the gap of die land in an annular micro‐extrusion die, on the extrudate swelling behavior of viscoelastic melt is analyzed through numerical simulations and micro‐extrusion experiments. The results show that the swelling behavior displays an obvious dependence on the characteristic scale. An increase in the characteristic scale reduces the swell ratio and retards the process to reach the equilibrium state. In contrast, a decrease in the characteristic scale results in a larger magnitude of change in velocity field and faster relaxation development of stress field. The location of the maximum velocity layer for the laminar flow gradually deviates from the geometric center of channel toward the wall of mandrel with the increase in the characteristic scale. Moreover, an increase in the flow rate results in a larger swell ratio for a constant characteristic scale. The elastic effect plays a more dominant role than the viscous effect in determining the viscoelastic swell behavior. It is imperative to consider the complicated swelling behavior and remarkable viscoelastic effect simultaneously in micro‐extrusion process.