Basic parameters, melt rheology, processing and end-use properties of three similar low density polyethylene samples

Meissner, J.

doi:10.1351/pac197542040551

Cited by 223 publications

(97 citation statements)

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“…The shear viscosity, defined as shear ϵ − xy / ␥ , where denotes the stress tensor which is calculated by = ͗͑1 / V͚͒ i ͚ a ͑͑p ia p ia / m ia ͒ + q ia F ia ͒͘, is shown to monotonically decrease with increasing shear rate, indicative of the well-documented shear thinning behavior for practically all polymer melts ͑linear and branched͒. 1,14 We further report ͑results not shown here͒ that the degree of shear thinning for the viscosity and the first-and second-normal stress coefficients of the simulated melt ͑H_78_25͒ was similar to that of linear PE melts simulated in the recent past ͑for example, C 78 H 158 and C 128 H 258 ͒. 40 The branching effect on the shear rheology appears therefore to be relatively minor.…”

Section: Simulation Detailsmentioning

confidence: 94%

“…To this, in addition to knowing the dependence of extensional behavior on external parameters ͑like applied strain rate, time, and temperature͒, one should also know how molecular-level parameters ͑e.g., chemical structure, molecular architecture, molecular weight, branching, and polydispersity͒ affect rheological response. Unfortunately, from an experimental point of view, measuring the ͑steady-state͒ extensional properties of polymers is an extremely difficult task due to a number of issues, 1,14,15 the most important of which being that extensional deformations are inherently unstable due to the formation of a neck in the sample undergoing elongation; furthermore, the material may not deform homogeneously. This significantly limits the range of operation of extensional rheometers and the maximum Hencky strain that can be probed, and much labor is required on the measurements to achieve experimental control; in most of the experiments and tests the material breaks before a ͑'true'͒ steady-state is attained.…”

Section: Introductionmentioning

confidence: 99%

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Tension thickening, molecular shape, and flow birefringence of an H-shaped polymer melt in steady shear and planar extension

Baig

Mavrantzas

2010

The Journal of Chemical Physics

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Articles you may be interested in Nonequilibrium molecular dynamics simulation of dendrimers and hyperbranched polymer melts undergoing planar elongational flow J. Rheol. 58, 281 (2014) Despite recent advances in the design of extensional rheometers optimized for strain and stress controlled operation in steady, dynamic, and transient modes, obtaining reliable steady-state elongational data for macromolecular systems is still a formidable task, limiting today's approach to trial-and-error efforts rather than based on a deep understanding of the deformation processes occurring under elongation. Guided, in particular, by the need to understand the special rheology of branched polymers, we studied a model, unentangled H-shaped polyethylene melt using nonequilibrium molecular dynamics simulations based on a recently developed rigorous statistical mechanics algorithm. The melt has been simulated under steady shear and steady planar extension, over a wide range of deformation rates. In shear, the steady-state shear viscosity is observed to decrease monotonically as the shear rate increases; furthermore, the degree of shear thinning of the viscosity and of the first-and second-normal stress coefficients is observed to be similar to that of a linear analog of the same total chain length. By contrast, in planar extension, the primary steady-state elongational viscosity 1 is observed to exhibit a tension-thickening behavior as the elongation rate increases, which we analyze here in terms of ͑a͒ perturbations in the instantaneous intrinsic chain shape and ͑b͒ differences in the stress distribution along chain contour. The maximum in the plot of 1 with occurs when the arm-stretching mode becomes active and is followed by a rather abrupt tension-thinning behavior. In contrast, the second elongational viscosity 2 shows only a tension-thinning behavior. As an interesting point, the simulations predict the same value for the stress optical coefficient in the two flows, revealing an important rheo-optical characteristic. In agreement with experimental indications on significantly longer systems, our results confirm the importance of chain branching on the unique rheological properties of polymer melts in extension.

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Section: Simulation Detailsmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Tension thickening, molecular shape, and flow birefringence of an H-shaped polymer melt in steady shear and planar extension

Baig

Mavrantzas

2010

The Journal of Chemical Physics

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“…In testing the validity of the model for a system with large L/D, the rheometric and swell data of a pure IUPAC-LDPE standard was used as shown in Figures 1 and 2 [77,78]. The capillary had die diameter 3.00 Dm m  and experiments were carried out at 150℃.…”

Section: Experimental Datamentioning

confidence: 99%

“…Such a capillary is termed a long capillary, in which the effects of the entry flow from the reservoir on the die exit region flow can be neglected. Most theoretical models have been derived for a long capillary [43][44][45][46][47]. However, there have been few quantitative predictions of die swell in actual polymer processing operations in which the ratio of width to length in the die flow channel is relatively short [48][49][50][51][52][53][54][55][56][57][58].…”

Section: Introductionmentioning

confidence: 99%

Die Swell of Complex Polymeric Systems

Wang¹

2012

Viscoelasticity - From Theory to Biological Applications

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“…Fig.3 Prediction of steady shear viscosity and first normal stress difference by using various ε of the PTT model for a LDPE IUPAC-A melt at 150°C. Experimental data are given by Meissner 23) . Determined values are listed in Table 1.…”

Section: Sample Fluid and Determination Of Materials Constantsmentioning

confidence: 99%

Numerical Simulation of Extrudate Swell Problem and Evaluation of Applicability of Viscoelastic Constitutive Models. 1. A Study on Axisymmetric Extrudate Swell from a Straight Die.

Kajiwara

Tomiyama

Sueyoshi

et al. 2001

J. Soc. Rheol., Jpn

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Numerical simulations of axisymmetric extrudate swell for a low density polyethyrene (LDPE IUPAC-A) melt were carried out using the K-BKZ model as an integral type and the PTT and Larson models as a differential type. We employed both the reversible and irreversible models for the K-BKZ and Larson models to investigate the effect of reversing deformation on the extrudate swell from a straight die. First, relaxation spectrum and nonlinear parameters in the constitutive equation were determined from dynamic data of linear viscoelasticity and steady shear flow data by using the nonlinear regression, and then they were applied to the simulation of extrudate swell problem. We evaluated the applicability of these models by comparing experiments and simulation for both rheological data and extrudate swell ratio. For the K-BKZ model, the reversible model over-estimates the swell ratio in high shear rate, whereas the irreversible model predicts the experimental data with high accuracy. The irreversible Larson model also shows the good prediction of swell, on the other hand, the reversible one over-estimates the swell and there exists the multiple solutions.For the PTT model, we carried out the simulation using the models with different values of nonlinear parameter, ε , which has the same steady shear flow properties and the different properties of stress relaxation under reversing double step deformation. The model having the larger stress in the stress relaxation under reversing double step deformation shows the larger swell. From these results, we find that the consideration of reversing deformation characteristics is required for the extrudate swell from the straight die.

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Basic parameters, melt rheology, processing and end-use properties of three similar low density polyethylene samples

Abstract: Abstract

Cited by 223 publications

References 2 publications

Tension thickening, molecular shape, and flow birefringence of an H-shaped polymer melt in steady shear and planar extension

Tension thickening, molecular shape, and flow birefringence of an H-shaped polymer melt in steady shear and planar extension

Die Swell of Complex Polymeric Systems

Numerical Simulation of Extrudate Swell Problem and Evaluation of Applicability of Viscoelastic Constitutive Models. 1. A Study on Axisymmetric Extrudate Swell from a Straight Die.

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