Rheological properties and associated structural characteristics
of some aromatic polycondensates including liquid-crystalline polyesters
and cellulose derivatives (IUPAC Technical Report)
J. L. White, L. Dong, P. Han, and M.
Laun*
Abstract: A comparative experimental study of shear-flow rheological
properties of thermotropic polymer liquid crystals by eight different
laboratories is described. The materials involved four different liquid-crystalline
polyesters (LCPs), a glass- fiber-filled liquid-crystalline polyester,hydroxypropyl
cellulose (HPC), and two non-liquid-crystalline high-temperature polymers,
a poly(etheretherketone) (PEEK), and a polyarylate (PAR). Studies were
made in both steady shear-flow and dynamic oscillatory experiments.
The data from the various laboratories involved were compared. The level
of agreement in the data was much less for most liquid-crystalline polymers
than for similar isotropic melts. The Cox Merz rule is valid for
PEEK and PAR, but not for the LCPs and HPC. The occurrence of low levels
of extrudate swell and high levels of uniaxial orientation in extrudates
of the LCPs and HPC is described.
* Corresponding author.
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