✦ LIBER ✦

Comparison of linear viscoelastic constitutive equations for non-uniform polymer melts

✍ Scribed by J. C. Scanlan; J. Janzen

Publisher: Springer-Verlag
Year: 1992
Tongue: English
Weight: 919 KB
Volume: 31
Category: Article
ISSN: 0035-4511
DOI: 10.1007/bf00373240

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✦ Synopsis

Linear-viscoelastic properties of polydisperse and randomly-branched polymer melts were fit with several proposed relaxation functions by non-linear regression. Three polymer systems were investigated, including 1) crosslinked polyethylenes, 2) polydisperse linear poly(dimethylsiloxane)s, and 3) Marlex polyethylenes, which are polydisperse and probably contain long-chain branching. Four relaxation functions were evaluated, including the Rouse, reptation, stretched-exponential, and stretched-exponential-power-law (SEPL) relaxation functions. The SEPL best described each series of polymers, and therefore may be a general relaxation function for non-uniform polymer melts. The flow activation energy for crosslinked polyethylene may be coupled to a breadthof-relaxation index, indicating that a coupling between a characteristic short relaxation time and longest relaxation time, as suggested by Ngai and Plazek (J. Polym. Sci. Polym. Phys. Ed. 1985, 23:2159-2180), may hold for some nonuniform polymers.

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