Physically meaningful discrete relaxation spectrum: Rheological behaviour of monodisperse polymer melts
✍ Scribed by Rachid Smail; Christian Carrot; Jacques Guillet
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 592 KB
- Volume
- 5
- Category
- Article
- ISSN
- 1022-1344
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✦ Synopsis
Abstract
A discrete relaxation spectrum using a small number of modes is derived to describe the relaxation behaviour of monodisperse polystyrene melts. Attention is focused on keeping the physical meaning of the relaxation times. Therefore, molecular dynamics theories are used in the terminal, plateau and transition zones and in the case of entangled melts. The spectrum is divided into three parts corresponding to three assumed different relaxation mechanisms: Rouse mechanism at short times, modified Rouse for tube equilibration and reptation with tube fluctuation in the long time range. This description only requires the knowledge of a limited number of parameters, namely the molecular weight of the polymer under investigation, the scaling law for Newtonian viscosity, the plateau modulus and the molecular weight between entanglements. The method is sucessfully applied to entangled monodisperse polystyrene melts and enables the recovery of final spectra containing only a few relaxation modes.