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Rheological behavior and flow instability in capillary extrusion of ultrahigh‐molecular‐weight polyethylene/high‐density polyethylene/nano‐SiO 2 blends
Author(s) -
Liu Lichao,
Zhao Hang,
Wang Fei,
Xue Ping,
Tian Jing
Publication year - 2019
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.47713
Subject(s) - extrusion , materials science , shear rate , rheometer , rheology , polyethylene , composite material , shear flow , capillary action , rheometry , thermodynamics , physics
Rheological behaviors of ultrahigh‐molecular‐weight polyethylene (PE)/high‐density PE/SiO 2 blends are investigated using parallel‐plate rheometer and capillary rheometer. The molecular chain conformational change mechanism is used to explain flow instabilities during extrusion. The viewpoints are proposed: (1) critical shear rate depends on the relative strength of irreversible viscous loss and reversible elastic orientation for molecular chains in transverse velocity gradient field inside the die and (2) critical shear stress depends on the extent of molecular chain conformational change inside the die, and the ease of conformational recovery after leaving the die. Modified nano‐SiO 2 particles are detected a certain interfacial adhesion in PE matrix. The interfacial interaction limits viscous flow inside the die and conformational recovery after leaving the die, thus causing not only the flow instabilities to occur prematurely on shear rate and delaying sharkskin on shear stress, but also an alternate “sharkskin‐melt fracture” appearance after global extrusion fracture. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136 , 47713.