Contraction flow of ionomers and their corresponding copolymers: Ionic and hydrogen bonding effects

Tomković, Tanja; Mitsoulis, Evan; Hatzikiriakos, Savvas G.

doi:10.1063/1.5088453

Cited by 21 publications

(7 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The lifetime of these ionic bridges depends on their ionic environment and appears to shorten with increasing monovalent cation (mainly potassium) concentration. Usually, the sticker lifetime is described using an empirical Arrhenius form

, where the activation energy is determined from the linear rheology using Van ’t Hoff plots [ 13 , 23 , 26 , 40 , 51 , 52 , 53 ]. In this section, we argue that this activation energy might not be the one that is of importance to the non-linear rheology, because a different mechanism of sticker opening takes over.…”

Section: Experimental and Modelling Methodsmentioning

confidence: 99%

Stretching of Bombyx mori Silk Protein in Flow

et al. 2021

View full text Add to dashboard Cite

The flow-induced self-assembly of entangled Bombyx mori silk proteins is hypothesised to be aided by the ‘registration’ of aligned protein chains using intermolecularly interacting ‘sticky’ patches. This suggests that upon chain alignment, a hierarchical network forms that collectively stretches and induces nucleation in a precisely controlled way. Through the lens of polymer physics, we argue that if all chains would stretch to a similar extent, a clear correlation length of the stickers in the direction of the flow emerges, which may indeed favour such a registration effect. Through simulations in both extensional flow and shear, we show that there is, on the other hand, a very broad distribution of protein–chain stretch, which suggests the registration of proteins is not directly coupled to the applied strain, but may be a slow statistical process. This qualitative prediction seems to be consistent with the large strains (i.e., at long time scales) required to induce gelation in our rheological measurements under constant shear. We discuss our perspective of how the flow-induced self-assembly of silk may be addressed by new experiments and model development.

show abstract

Section: Experimental and Modelling Methodsmentioning

confidence: 99%

Stretching of Bombyx mori Silk Protein in Flow

et al. 2021

View full text Add to dashboard Cite

show abstract

“…25,27 Among them, the integral KBKZ model and the differential PTT model seem suited due to the possibility of describing the shear and elongational properties of polymer melts independently. 14,[28][29][30]…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional flow simulations for polymer extrudate swell out of slit dies from low to high aspect ratios

et al. 2019

View full text Add to dashboard Cite

The impact of the slit die geometry and the polymer melt flow characteristics on the extrudate swell behavior, which is a key extrusion operating parameter, is highlighted. Three-dimensional (3D) numerical simulations based on the finite element method are compared with their conventional two-dimensional (2D) counterparts at the same apparent shear rates using ANSYS Polyflow software. The rheological behavior is described by the differential multimode Phan-Thien-Tanner constitutive model, with polypropylene as a reference. It is shown that increasing the aspect ratio of the die geometry (width/height ratio variation from 1 to 20) contributes to a significant change in the 3D extrudate deformation (relative changes of 10% in several directions; absolute changes up to 30%) and delays the equilibrium axial position (up to a factor 10). High aspect ratios induce a switch to contract flow (swell ratio <1) for the edge height swell. The 3D extrudate swell strongly deviates from the 2D simplified case due to the die effect near the wall, even for higher aspect ratios. Also a different relation with the material parameters is recorded. The initially large swell behavior is followed by a small shrinkage flow in the middle height direction which cannot be captured by the 2D counterpart. The findings are supported by a comprehensive analysis of the velocity and stress fields in and out of the slit dies.

show abstract

“…The importance of the extensional viscosity on the entry pressure was studied extensively for the case of ionomers [ 40 , 41 , 42 , 43 ]. Results are presented in Figure 3 for two polymers, one ionomer (19.2-Na65) and its corresponding copolymer (19.2-Na65).…”

Section: Capillary Rheometrymentioning

confidence: 99%

“…Unlike Newtonian fluids, polymer melts slip over solid surfaces when the wall shear stress exceeds a critical value [ 13 , 14 , 15 , 16 , 17 , 18 ]. In particular, slip effects have been reported in the capillary flow of molten polyethylenes [ 44 , 45 , 46 , 47 , 48 , 49 ], polydimethylsiloxanes [ 50 ], polystyrenes [ 51 , 52 , 53 ], polybutadienes [ 54 , 55 ], polypropylenes [ 56 , 57 , 58 ], fluoropolymers [ 59 ], polylactides [ 60 ], polyisobutylenes [ 61 ], ionomers [ 40 , 41 ] and other viscoelastic fluids [ 62 , 63 ]. Thus, in a comprehensive study of any melt, possible slip effects should be studied to be used as boundary conditions in high shear rate flows.…”

Section: Slip Effectsmentioning

confidence: 99%

“…On the other hand, the use of the K-BKZ model is capturing adequately well the entrance pressure as a function of the contraction angle for all three polymers. As the con- The importance of the extensional viscosity on the entry pressure was studied exten-162 sively for the case of ionomers [40][41][42][43]. Results are presented in Fig.…”

Section: Entrance Pressure Significancementioning

confidence: 99%

See 1 more Smart Citation

Rheological Properties Related to Extrusion of Polyolefins

Mitsoulis

Hatzikiriakos

2021

Polymers

Self Cite

View full text Add to dashboard Cite

Rheological properties related to the extrusion of polyolefins are the shear viscosity, the elongational viscosity, the slip velocity and their temperature- and pressure-dependencies. These properties are measured in the rheology lab mainly via a parallel-plate rheometer and a capillary rheometer. Then appropriate rheological models have to be used to account for all these properties. Such models are either viscous (e.g, the Cross model) or viscoelastic (e.g, the K-BKZ model). The latter gives the best fitting of the experimental data and offers excellent results in numerical simulations, especially in extrusion flows. Wall slip effects are also found and measured by rheometric flows. Modeling of extrusion flows should make use of appropriate slip models that take into effect the various slip parameters, including the effects of shear stress, molecular characteristics, temperature and pressure on the slip velocity. In this paper the importance of these properties in extrusion are discussed.

show abstract

Contraction flow of ionomers and their corresponding copolymers: Ionic and hydrogen bonding effects

Cited by 21 publications

References 48 publications

Stretching of Bombyx mori Silk Protein in Flow

Stretching of Bombyx mori Silk Protein in Flow

Three-dimensional flow simulations for polymer extrudate swell out of slit dies from low to high aspect ratios

Rheological Properties Related to Extrusion of Polyolefins

Contact Info

Product

Resources

About