• Korea-Australia Rheology Journal
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• 제15권2호
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• pp.63-73
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• 2003

An experimental technique was developed to determine the strain-rate in a tensile specimen. Then one can calculate the transient isothermal elongational viscosity. Both shear and elongational viscosities were measured to study the effect of shear and elongational fields on the flow properties. The comparison between these viscosities shows that the onset of rapid viscosity growth as crystallization solidification proceeds occurs at about the same value of time at very small deformation rates (0.0028 and 0.0047 $s^{-1}$). The comparison of these measured viscosities as functions of shear and elongational Hencky strains also reveals that the onset of rapid viscosity growths starts at critical Hencky strain values. The behaviour of steady shear viscosity as function of temperature sweep was also explored at three different low shear rates. Finally, the influence of changing oscillatory frequencies and strain rates was also investigated.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 추계학술발표대회 논문집
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• pp.137-140
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• 2005

Exfoliated nanocomposites of polypropylene/layered silicate were prepared by a melt compounding process using maleic anhydride modified polypropylene (PP-g-MAH) and organoclay. It was found that polypropylene/layered silicate nanocomposites exhibited remarkable reinforcement compared with the pure polypropylene or conventional composite filled with agglomerated organoclay. The polypropylene /layered silicate nanocomposites showed stronger and earlier shear thinning behaviors and outstanding strain hardening behavior than pure polypropylene or other conventional composites in shear and uniaxial elongational flows, respectively. We simulated rheological modeling for the pure polymer matrix and polypropylene/layered silicate nanocomposite in shear and elongational flows using K-BKZ integral constitutive equation. The two types of K-BKZequations have been examined to describe experimental results of shear and uniaxial elongational viscosities of pure polypropylene and polypropylene/layered silicate nanocomposite.

• Korea-Australia Rheology Journal
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• 제17권4호
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• pp.149-156
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• 2005

A simple constitutive model for viscoelastic suspensions is discussed in this paper. The model can be used to predict the rheological properties (relative viscosity and all stresses) for viscoelastic suspensions in shear and elongational flow, and the constitutive equations combine a 'viscoelastic' behaviour component and a 'Newtonian' behaviour component. As expected, the model gives a prediction of positive first normal stress difference and negative second normal stress difference; the dimensionless first normal stress difference strongly depends on the shear rate and decreases with the volume fraction of solid phase, but the dimensionless second normal stress difference (in magnitude) is nearly independent of the shear rate and increases with the volume fraction. The relative viscosities and all the stresses have been tested against available experimental measurements.