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The rheology for varieties of polyethylene(PE) with
different molecularstructure has been studied. The sample PE''s
possess varying branch structuressuch as different branch length
and short chain branch distribution. The effectof these branch
structures on either the shear and elongation rheology
isdiscussed.
The steady and dynamic shear data was obtained with a rotational
rheometer.The elongation viscosity was acquired by means of the
isothermal fiber spinning.The Cole-Cole plot( log G'' vs. Log G")
was constructed to investigate therelation between the molecular
branch structure and the viscoelasticity forpolymer melts. In
addition, the Phan-Thien-Tanner(PTT) model was applied topredict
their elongation viscosity.
It was revealed from the experimental investigations that both
the shear andthe elongation viscosity, and the viscoelasticity(
seen from the Cole-Cole plot)are strongly affected by the long
chain branching in the polymer materials. Onthe other hand, the
short chain branching shows very little effect. It shouldbe
noted that the narrow short chain branch distribution of
metallocene PE maylessen the viscoelasticity. Finally, the PTT
model can be used to estimate theelongation viscosity of polymer
melt. Limited to a very short range of strainrate, that can fit
the experimental data very well.
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