Influence of shearing history on the rheological properties and processability of branched polymers. I
Article first published online: 9 MAR 2003
Copyright © 1979 John Wiley & Sons, Inc.
Journal of Applied Polymer Science
Volume 23, Issue 2, pages 463–471, 15 January 1979
How to Cite
Rokudai, M. (1979), Influence of shearing history on the rheological properties and processability of branched polymers. I. J. Appl. Polym. Sci., 23: 463–471. doi: 10.1002/app.1979.070230216
- Issue published online: 9 MAR 2003
- Article first published online: 9 MAR 2003
- Manuscript Revised: 4 NOV 1977
- Manuscript Received: 26 SEP 1977
The influence of shearing history on the viscoelastic properties of low-density polyethylene (LDPE) is investigated. Swelling of extrudates from a melt indexer is measured for monitoring the variation in viscoelasticity. Continuous shearing of molten LDPE reduces the swelling ratio. The reduction is not due to molecular degradation, as evidenced by constancy of intrinsic viscosity. The rate of the reduction in the swelling ratio depends on the shearing conditions and characteristics of LDPE, but the swelling ratio finally attain a steady value. The swelling ratio reduced by the continuous shearing is completely recovered by solvent or heat treatment. The ratio of the completely reduced swelling ratio to the completely recovered one is defined as a new index representing the viscoelastic variation, the processing index (PI), and the relationship between PI and the primary molecular parameters of LDPE is investigated. It is concluded that the variation in the viscoelastic properties becomes more remarkable with increase in the weight-average molecular weight. The cause of the viscoelastic variation is also discussed from the rheological and thermodynamic points of view.