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Compression creep of molten low‐density polyethylene
Author(s) -
Aleman J. V.
Publication year - 1992
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.1992.070440611
Subject(s) - creep , materials science , viscoelasticity , low density polyethylene , volume (thermodynamics) , viscosity , activation energy , composite material , compression (physics) , polyethylene , extrusion , die swell , deformation (meteorology) , thermodynamics , chemistry , physics
Viscoelastic parameters of low‐density polyethylene melt (LDPE) in compression creep have been measured. Volume deformation ( k %) increases as pressure ( P ) increases and temperature ( T ) decreases. Plots of the bulk creep compliance B(t) vs. time ( t ) may be shifted to provide master curves. As the pressure and the temperature increase, the pressure shift factors ( b p and a p ) increase almost linearly [activation volumes (Δ V * ) varying from 1.0 to 15.0 cm 3 mol], while the temperature‐shift factors ( b T and a T ) decrease. The steady‐state creep compliance ( B s ) describes the recoverable storage of elastic energy ( Be ) and seems to be related to the extrusion die‐swell ( B s c / B s d ). Volume viscosity (η K ) decreases with increasing stress ( P ) and increasing temperature ( T ).