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Elastic behavior of LDPE/HEPE blend melts in capillary extrusion
Author(s) -
Liang JiZhao
Publication year - 2000
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 - 10.1002/1097-4628(20001024)78:4<759::aid-app90>3.0.co;2-s
Subject(s) - low density polyethylene , materials science , composite material , shear rate , extrusion , die swell , capillary action , viscoelasticity , polyethylene , pressure drop , polymer blend , high density polyethylene , shear flow , thermodynamics , polymer chemistry , polymer , viscosity , copolymer , physics
Abstract The studies of the elastic behavior in the capillary flow of LDPE/HDPE blend melts were carried out at a test temperature range from 180 to 200°C and at an apparent shear rate of about 25–120 s −1 . The end‐pressure drop (Δ P end ) increased nonlinearly with increasing wall shear stress (τ w ) and achieved a minimum value at a weight fraction (ϕ HD ) of HDPE of 50%. The die‐swell ratio ( B ) increased basically linearly with increasing τ w or Δ P end and achieved a maximum value at ϕ HD of 50%. With the addition of the die length–diameter ratio, the values of B were decreased linearly. At a low shear rate, the temperature sensitivity of the melt die‐swell was more significant than at a high shear rate. With increasing ϕ HD , B increased when ϕ HD < 50%, then decreased. B reached a maximum value at ϕ HD of 50% and a fixed apparent shear rate. This phenomenon may be explained by using the theory of viscoelastic competition between components of polymer blend melts. Furthermore, the first normal stress difference ( N 1 ) of the sample melts was estimated by using an equation published in a previous work. The results showed that B increased linearly with increasing N 1 . © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 759–765, 2000