Addendum: Rotary Clamp in Uniaxial and Biaxial Extensional Rheometry of Polymer Melts [J. Rheol., <b>25</b> 1 (1981)]

Meissner, J.; Raible, T.; Stephenson, S. E.

doi:10.1122/1.549635

Cited by 27 publications

(23 citation statements)

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“…A maximum in the transient extensional stress of LDPE was observed by several groups [8,9,10]. Steady stress following the stress overshoot was reported firstly by Rasmussen et al [11] and has been experimentally confirmed by comparing the measurements from the filament stretching rheometer and the cross-slot extensional rheometer [12], as well as by comparing the constant stretch rate and constant stress (creep) experiments [13].…”

Section: Introductionmentioning

confidence: 57%

A new look at extensional rheology of low-density polyethylene

et al. 2016

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The nonlinear rheology of three selected commercial low-density polyethylenes (LDPE) is measured in uniaxial extensional flow. The measurements are performed using three different devices including an extensional viscosity fixture (EVF), a home made filament stretching rheometer (DTU-FSR) and a commercial filament stretching rheometer (VADER-1000). We show that the measurements from the EVF are limited by a maximum Hencky strain of 4, while the two filament stretching rheometers are able to probe the nonlinear behavior at larger Hencky strain values where the steady state is reached. With the capability of the filament stretching rheometers, we show that LDPEs with quite different linear viscoelastic properties can have very similar steady extensional viscosity. This points to the potential for independently controlling shear and extensional rheology in certain rate ranges.

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Section: Introductionmentioning

confidence: 57%

A new look at extensional rheology of low-density polyethylene

et al. 2016

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“…elongation. 1,19 It is generally accepted, however, that reliable steady-state elongational data for polymer melts are still missing. Even in cases where steady-state elongational properties ͑especially for some branched polymers, e.g., LDPE͒ have been reported in the literature with advanced rheometers, 22 it is still debatable whether these are true steady-state extensional data or not.…”

Section: Introductionmentioning

confidence: 99%

“…All these explain the intense efforts in the last 40 years to develop accurate elongational rheometers for better quality data over a wide range of stress and strain rates and to increase the maximum extensional strains for which the sample deforms homogenously. [16][17][18][19][20][21] We mention, for example, that it is possible today to obtain quite accurate elongational data up to a Hencky strain of = 7, corresponding to a ratio of final-to-initial sample length of ϳ1100͑ ! ͒, for low-density polyethylene ͑LDPE͒ melts under uniaxial a͒ Authors to whom correspondence should be addressed.…”

Section: Introductionmentioning

confidence: 99%

“…Even in cases where steady-state elongational properties ͑especially for some branched polymers, e.g., LDPE͒ have been reported in the literature with advanced rheometers, 22 it is still debatable whether these are true steady-state extensional data or not. 1,15,19 From a theoretical point of view, recent studies 23,24 have shown that making use of reliable steady-state elongational properties is also essential in evaluating viscoelastic models or in developing new ones.…”

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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“…Until recently, only two special cases of such general tests could be realized [4]. These were equibiaxial and planar elongations performed by means of the following techniques: bubble inflation [5][6][7], rotary clamps [8,13,14] stagnation flow [9][10][11] or simple compression [12].…”

Section: Introductionmentioning

confidence: 99%

Multiaxial elongation of polyisobutylene with various and changing strain rate ratios

Demarmels

Meißner

1985

Rheol Acta

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Abstract:The multiaxial elongational rheometer equipped with rotary clamps is modified such that in addition to simple, equibiaxial and multiaxial elongations also tests with new modes of elongation can be performed. As an example, polyisobutylene is elongated with a ratio of the principal strain rates of m = ka2/kl~ = 0.5 and magnitudes of the maximum strain rate kll = 0.008, 0.04 and 0.08 s-1. As a test result, the first elongational viscosity/~i (t) is obtained which follows closely the linear viscoelastic shear yiscosity 0 (t). In contrast, the second elongational viscosity /~2 (t) remains below 0 (t). By means of a further modification of the rheometer, the test modes can be varied during the deformation period. This allows one to investigate the influence of a well-defined rheological pre-history on the following rheological behaviour. As an example a variation of m = 0.5 --* 2 was performed. The measured normal-stress differences superpose from the single steps of deformation similar to the linear viscoelastic prediction.

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Addendum: Rotary Clamp in Uniaxial and Biaxial Extensional Rheometry of Polymer Melts [J. Rheol., 25 1 (1981)]

Cited by 27 publications

References 0 publications

A new look at extensional rheology of low-density polyethylene

A new look at extensional rheology of low-density polyethylene

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

Multiaxial elongation of polyisobutylene with various and changing strain rate ratios

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