Molecular drag–strain coupling in branched polymer melts

Blackwell, Richard J.; McLeish, Tom; Harlen, Oliver G.

doi:10.1122/1.551081

Cited by 142 publications

(126 citation statements)

References 20 publications

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“…Theoretical models of polymer rheology which assume such a partial branch point withdrawal have indeed produced an improved description of branched polymer rheology. 16 This branch point withdrawal is also conjectured to be partially responsible for observed SANS anisotropy. 18 The purpose of the nonlinear shear experiment was to provide some check on the degree of this motion of the branch point when the cross-bar suffers higher stretch than the arms.…”

Section: Rheological Relaxation Processesmentioning

confidence: 99%

“…18 The purpose of the nonlinear shear experiment was to provide some check on the degree of this motion of the branch point when the cross-bar suffers higher stretch than the arms. The motion of the branch point under strain is governed within the theoretical model by the parameter ν* (for details of the calculation, see ref 16). When modeling nonlinear rheology, there is sometimes a discrepancy between parameters used to fit transient shear and extensional data.…”

Section: Rheological Relaxation Processesmentioning

confidence: 99%

“…Recently, a polydisperse version of the theory has been used to account quantitatively for a very wide set of nonlinear rheological data on a standard LDPE. 15,16 To achieve this, it was necessary to invoke a physical consequence of the tube model around the branch points themselves. Termed "branch point withdrawal", it describes the shift of a branch point within a LCB polymer under strain toward the tube containing the strand of greatest tension meeting at the branch point.…”

Section: Introductionmentioning

confidence: 99%

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Arm Relaxation in Deformed H-Polymers in Elongational Flow by SANS

Heinrich¹,

Pyckhout‐Hintzen²,

Allgaier³

et al. 2002

Macromolecules

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We present a small-angle neutron scattering (SANS) investigation of the relaxation process of branched polymer melts under deformation. The selected model polymer is an H-shaped polyisoprene having deuterium-labeled blocks at the dangling tips of the arms. The melt is step strained in a strain rig especially built for that purpose, where the sample temperature and its deformation conditions are precisely controlled. Uniaxial extensions to values of 2 and 3 are performed at a temperature above the polymer glass transition temperature T g. The sample is then allowed to relax during a given time before being quenched to below its Tg in order to freeze the chains conformation to perform the SANS experiments. Very large anisotropies in S(q) develop on time scales corresponding to the relaxation of the dangling arms. The experimental structure function is then compared to theoretical ones obtained by the random phase approximation applied to the tube model. While theory describes well the scattering for short times, it seems not to be able to describe the increase of intensity in the direction parallel to the strain at higher times, even when highly nonaffine processes such as arm retraction and branch point withdrawal are taken into account.

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Section: Rheological Relaxation Processesmentioning

confidence: 99%

Section: Rheological Relaxation Processesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Arm Relaxation in Deformed H-Polymers in Elongational Flow by SANS

Heinrich¹,

Pyckhout‐Hintzen²,

Allgaier³

et al. 2002

Macromolecules

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“…While the motivating applications are important in their own right, we are confident that the underlying ideas have potential for a much wider class of applications. In addition to the areas mentioned in the Introduction, we feel that such an approach will eventually prove relevant in diverse areas such as electromagnetic polarization and conductivity in heterogeneous materials (see [9], [12] and the references cited therein), industrial polymeric melts ( [16], [17], [18], [24]), as well as in other biological applications [4] (e.g., disease pathogenesis, epidemiology, ecological migrations, and genomic to system response modelsbioinformatics!). The fact that the theoretical formulation leads readily to both computationally and theoretically sound approximations significantly enhances the attractiveness of this approach.…”

Section: Discussionmentioning

confidence: 99%

A Probabilistic Multiscale Approach to Hysteresis in Shear Wave Propagation in Biotissue

Banks¹,

Pintér²

2005

Multiscale Model. Simul.

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Motivated by a problem involving wave propagation through viscoelastic biotissue, we present a theoretical framework for treating hysteresis as multiscale phenomena which must be averaged across distributions of internal variables. The resulting systems entail probability measure dependent partial differential equations for which we establish well-posedness in a framework that leads readily to computationally useful approximations.

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“…Blackwell et al 7) , which allows for branch point displacement, is used to overcome the discontinuity in the gradient of the extensional viscosity. The retraction of the arms into the tube has been neglected, and thereby the constraint that the stretch cannot be larger than the number of arms is removed.…”

mentioning

confidence: 99%

Numerical Predictions of Viscoelastic Fluid in Pipe Flow Using Extended Pom-Pom Model

Khorsand

Rashidi

Goharpey

et al. 2011

J. Soc. Rheol., Jpn

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In this study prediction of the steady-state flow of branched polymer melts in pipe geometry with finite volume method is presented. The fluid is modelled using a modification of the Pom-Pom model known as the single eXtended Pom-Pom (XPP) where viscoelastic fluid, is typically a commercial low-density polyethylene. In finite volume method, the operator-integration is used to discretize the governing equations in space or control volume. An iterative solution algorithm that decouples the computation of momentum from that of stress is used to solve the discrete equations. Numerical results are presented; include the profiles of all relevant stresses, the axial velocity, stretch and the viscosity across the gap, demonstrating the performance of the model predictions. The influence of the model parameters on the solution and flow behaviour is described and, in particular, the dependence of velocity and stresses distribution as a function of Weissenberg number is analyzed. Finally, for rectitude and accuracy, the verification of this model is performed with the Gieskus model that shows good conformity between the results.

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Molecular drag–strain coupling in branched polymer melts

Cited by 142 publications

References 20 publications

Arm Relaxation in Deformed H-Polymers in Elongational Flow by SANS

Arm Relaxation in Deformed H-Polymers in Elongational Flow by SANS

A Probabilistic Multiscale Approach to Hysteresis in Shear Wave Propagation in Biotissue

Numerical Predictions of Viscoelastic Fluid in Pipe Flow Using Extended Pom-Pom Model

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