Oscillating flow behavior of high-density polyethylene melts

✍ Scribed by R. W. Myerholtz

• Publisher: John Wiley and Sons
• Year: 1967
• Tongue: English
• Weight: 589 KB
• Volume: 11
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/app.1967.070110506

✦ Synopsis

The oscillating flow behavior of a variety of highdensity 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 increase 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 LID ratio of the capillary.