Dynamic modulus of polyisobutylene solutions in superposed steady shear flow

Simmons, J. M.

doi:10.1007/bf01982380

Cited by 60 publications

(26 citation statements)

References 7 publications

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“…Until now, only few experimental data associated with the dynamic viscosity and storage modulus measurement in the orthogonal superposition are available. Tanner and Simmons [4,5] were perhaps pioneers in the study of orthogonal superposition and they showed that the dynamic viscosity and storage modulus decrease with an increase of steady shear rate. This observation is the same as that in the parallel superposition.…”

Section: Introductionmentioning

confidence: 98%

“…Later, K-BKZ theory used by Tanner and Williams [6] is found to be in agreement with the experimental results. Further, Shroff and Shida [12] examined the applicability of Yamamoto's integral constitutive equation [11] to the data obtained in the orthogonal superposition by Simmons [5] on a 8.54% polyisobutylene solution in cetane. They compared the theoretical results with experimental data for the dynamic viscosity and found that the theoretical results do not agree with the experimental data.…”

Section: Introductionmentioning

confidence: 98%

“…However, the reduction of the dynamic viscosity and storage modulus is less pronounced when the same steady shear rate is considered. Later, Tanner and Williams [6] modified the instrument designed by Simmons [5] to do further experimental investigations. The main modifications are made in the sample cell and the air bearing arrangements.…”

Section: Introductionmentioning

confidence: 99%

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Orthogonal superposition of small and large amplitude oscillations upon steady shear flow of polymer fluids

Wong

Isayev

1989

Rheol Acta

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Abstract:The orthogonal superposition of small and large amplitude oscillations upon steady shear flow of elastic fluids has been considered. Theoretical results, obtained by numerical methods, are based on the Leonov viscoelastic constitutive equation. Steady-state components, amplitudes and phase angles of the oscillatory components of the shear stress, the first and second normal stress differences as functions of shear rate, deformation amplitude and frequency have been calculated. These oscillatory components include the first and third harmonic of the shear stresses and the second harmonic of the normal stresses. In the case of small amplitude superposition, the effect of the steady shear flow upon the frequency-dependent storage modulus and dynamic viscosity has been determined and compared with experimental data available in literature for polymeric solutions. The predicted results have been found to be in fair agreement with the experimental data at low shear rates and only in qualitative agreement at high shear rates and low frequencies. A comparison of the present theoretical results has also been made with the predictions of other theories.In the case of large amplitude superposition, the effect of oscillations upon the steady shear flow characteristics has been determined, indicating that the orthogonal superposition has less influence on the steady state shear stresses and the first difference of normal stresses than the parallel superposition. However, in the orthogonal superposition a more pronounced influence has been observed for the second difference of normal stresses.

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 98%

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Orthogonal superposition of small and large amplitude oscillations upon steady shear flow of polymer fluids

Wong

Isayev

1989

Rheol Acta

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“…The shear thinning is ascribed to a loss of entanglements, resulting from the flow-induced orientation of the chains. [1][2][3][4][5][6][7] Although this loss is reversible, the time scale for entanglement recovery can be very slow. This allows advantage to be taken of the "shearmodified" state during polymer processing; for example, elastic effects such as die swell are much weaker for some time after the shearing.…”

Section: Introductionmentioning

confidence: 99%

“…All rheological measurements were done at 25 °C. 32 The crossover from Newtonian flow to shear thinning behavior occurs at a shear rate given by 33 (2) This is the approximate value of the minimum shear rate necessary to ensure disentanglement by flow.…”

Section: Introductionmentioning

confidence: 99%

Recovery of Shear-Modified Polybutadiene Solutions

Roland

Robertson²

2006

Rubber Chemistry and Technology

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We have investigated the recovery of the overshoot in the transient viscosity, the first normal stress coefficient, and the dynamic modulus for entangled polybutadiene solutions subjected to nonlinear shear flow. The molecular-weight dependences of the various time scales (linear viscoelastic relaxation time, entanglement recovery time, and timescale for decay of stress following cessation of shearing) are all consistent with the usual 3.4 power law. Nevertheless, the time for recovery of the stress overshoot and plateau value of the dynamic modulus were substantially longer (by as much as two orders of magnitude) than the linear viscoelastic relaxation time calculated from the Newtonian viscosity and the equilibrium recoverable compliance. These results indicate that complete entanglement recovery requires cooperative chain motions over a length scale exceeding that associated with linear relaxation. This persistence of a disentangled state means that a state of low viscosity and reduced elasticity is retained for an extended time, suggesting that shear modification can be used to facilitate the processing of polymers.

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Experimental Methods

2017

Nonlinear Polymer Rheology

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Dynamic modulus of polyisobutylene solutions in superposed steady shear flow

Cited by 60 publications

References 7 publications

Orthogonal superposition of small and large amplitude oscillations upon steady shear flow of polymer fluids

Orthogonal superposition of small and large amplitude oscillations upon steady shear flow of polymer fluids

Recovery of Shear-Modified Polybutadiene Solutions

Experimental Methods

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