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Measurement and simulation of low‐density polyethylene extrudate swell through a circular die
Author(s) -
Mu Yue,
Zhao Guoqun,
Li Huiping,
Liu Jie,
Xu Xingming,
Mu Wenbo,
Chen Anbiao
Publication year - 2009
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.2551
Subject(s) - die swell , low density polyethylene , swell , materials science , mechanics , viscoelasticity , rheology , flow (mathematics) , die (integrated circuit) , melt flow index , rheometer , swelling , composite material , polyethylene , polymer , thermodynamics , extrusion , physics , copolymer , nanotechnology
Abstract BACKGROUND: Extrudate swell is a common phenomenon in polymer processing. The investigation of its mechanism is of both scientific and industrial interest. RESULTS: The rheological parameters of a material described by the viscoelastic PTT (Phan‐Thien–Tanner) constitutive model are obtained by fitting the distributions of material functions detected with a strain‐controlled rheometer. The swelling ratios of low‐density polyethylene (LDPE) under different volume flow rates are indirectly obtained using a photographic technique. A mathematical model of extrudate swell is established and its finite element model is derived. A penalty method is employed to solve the extrudate swell problem with a decoupled algorithm. Computation stability is improved by using the discrete elastic‐viscous split stress algorithm incorporating the inconsistent streamline‐upwind scheme. CONCLUSION: The swell phenomenon of LDPE through a circular die is investigated using both experimental measurement and numerical simulation. The swelling ratios obtained from the simulation are compared with those measured: they agree well with each other. The essential flow characteristics of polymer melts are predicted and the mechanism of the swell phenomenon is further discussed. Copyright © 2009 Society of Chemical Industry