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Oscillating flow behavior of high‐density polyethylene melts
Author(s) -
Myerholtz R. W.
Publication year - 1967
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.1967.070110506
Subject(s) - materials science , polyethylene , shear rate , rheometer , molar mass distribution , flow (mathematics) , capillary action , shear flow , shear (geology) , mechanics , volumetric flow rate , melt flow index , thermodynamics , composite material , rheology , copolymer , physics , polymer
The oscillating flow behavior of a variety of high‐density polyethylene and copolymer samples was studied in a constant displacement rate rheometer. At any plunger velocity, the period of the oscillations decreases linearly with melt depth, suggesting a resonance phenomenon. As plunger velocity is increased, the load waveform changes in a regular manner that indicates a progressive increases in the proportion of each cycle spent on the right‐hand branch of the flow curve. Little difference was found in the shear stress at which oscillating flow began for samples differing in molecular weight, molecular weight distribution, and manufacturing process. However, the shear rate at which oscillating flow begins depends, strongly on both molecular weight and distribution. Oscillating flow is shifted to higher shear rates by broadening distribution, reducing molecular weight, increasing temperature, or decreasing the L / D ratio of the capillary.