Reentanglement Kinetics in Sheared Polybutadiene Solutions

Robertson, Christopher G.; Warren, Sandra; Plazek, D. J.; Roland, C. M.

doi:10.1021/ma048148g

Cited by 53 publications

(56 citation statements)

References 50 publications

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“…26,27 Recently we determined the variation with molecular weight, M, of the time for recovery of the stress overshoot, τ R,η , in interrupted shear flow experiments on entangled 1,4-polybutadiene solutions. 28 In accord with the molecular weight dependence of the linear viscoelastic properties, we found that the recovery kinetics are consistent with a 3.4 power dependence on M. In the present work, we analyze the recovery of the elasticity (from the first normal force data) and the dynamic shear modulus in the rubbery plateau regime. The former reflects chain orientation and the latter is due to the transient entanglement network; thus, both provide a measure of the reentanglement process.…”

Section: Introductionsupporting

confidence: 66%

“…The shear stress recovery data, presented previously 28 and reproduced in Figure 6, are fitted using the exponential function proposed by Stratton and Butcher 23 (4) where A η is a constant, t is the time since cessation of the shearing, and τ R,η quantifies the time scale for the recovery of the overshoot in the transient viscosity. A similar analysis of the normal force data using (5) is included in Figure 6, with the characteristic recovery times plotted in the inset.…”

Section: Non-linear Shear Flowmentioning

confidence: 99%

“…Details of their synthesis can be found in ref. 28. Solutions in an aromatic oil (Sundex 790 from Sun Oil Co.) were prepared by co-dissolution in hexane, with the hexane subsequently removed by evaporation under vacuum.…”

Section: Introductionmentioning

confidence: 99%

“…The entanglement molecular weight, M e = 1.85 kg/mol for neat PB 31 , varies as ϕ -1 for these solutions. 28 The calculated number of entanglements per chain is listed in Table I for each sample. Some experiments were also performed on a more dilute solution (ϕ = 0.15) of the highest molecular weight PB.…”

Section: Introductionmentioning

confidence: 99%

“…The terminal viscosities measured in shear flow 28 are listed in Table I. The recoverable compliance was determined by two methods.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Introductionsupporting

confidence: 66%

Section: Non-linear Shear Flowmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…The terminal viscosities measured in shear flow 28 are listed in Table I. The recoverable compliance was determined by two methods.…”

Section: Introductionmentioning

confidence: 99%

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Recovery of Shear-Modified Polybutadiene Solutions

Roland

Robertson²

2006

Rubber Chemistry and Technology

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Rheological Measurements

2013

Encyclopedia of Polymer Science and Technology

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Rheology is the science to study the flow and deformation of matter. It becomes an important field in material science and engineering, food, biotechnology, and so on. The objects in rheological study are not the ideal solid and ideal fluid, which can be described by the Hookean elastic model and the Newtonian viscous model, respectively. Instead, the rheological study often focuses on materials that can exhibit viscous, elastic, and plastic behavior under different flow conditions. They are often termed as complex fluids or soft matter, which include polymers, gels, suspensions, emulsions, biofluids, foods, inks (1). In contrast to hydrodynamics, which often accounts for the complex flow behavior of simple fluids, simple geometry is utilized in rheological measurements to understand the rather complicated relationship between the mechanical input and output of complex fluids. The real flow fields encountered in many applications (such as polymer extrusion, injection molding, blow molding, fiber spinning, inkjet printing, coating) are rather complicated (2). It becomes a problem whether the rheological measurements that performed under simple flow fields are useful in understanding the complicated flow behaviors of complex fluids. Fortunately, it has been proved in many examples that the properties determined from simple rheological measurements are sufficient to quantify the material parameters in various constitutive equations, which have been used widely and successfully to simulate the flow behaviors in polymer processing (3-11). The most frequently used simple flow fields are simple shear flow and simple extensional flow.The simplest geometry that defines the simple shear is two infinite parallel plates separated by a distance h. The liquid is set between two plates with one plate moving parallel to the other (Fig. 1). In reality, when the length L and the width B are much larger than the gap h, the flow in the center regime resembles the flow between two infinite plates. It means that the edge effects are ignored in most experimental shear geometries. In rheological measurements, the flow between two plates should be laminar. Moreover, it is usually assumed that the velocity across the gap satisfies a linear profile. As shown in Fig. 1, if the bottom plate is fixed and the upper plate moves horizontally with the velocity V, the fluid velocity varies linearly from 0 at the bottom plate to V at the upper plate if the no-slip boundary condition is satisfied. The linear velocity profile generates a constant velocity gradient, which is known as the shear rate. Then, the flow field between two parallel plates is homogeneous in the shear rate. The homogeneous assumption is nontrivial in the rheological tests since the actual velocity

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Yielding during Startup Deformation: From Elastic Deformation to Flow

2017

Nonlinear Polymer Rheology

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Reentanglement Kinetics in Sheared Polybutadiene Solutions

Cited by 53 publications

References 50 publications

Recovery of Shear-Modified Polybutadiene Solutions

Recovery of Shear-Modified Polybutadiene Solutions

Rheological Measurements

Yielding during Startup Deformation: From Elastic Deformation to Flow

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