Extensional rheology of linear and branched polymer melts in fast converging flows

Wen, Yu-Ho; Wang, Chen-Chieh; Cyue, Guo-Sian; Kuo, Rong-Hao; Hsu, Chia-Hsiang; Chang, Rong‐Yeu

doi:10.1007/s00397-023-01387-y

Cited by 7 publications

(2 citation statements)

References 77 publications

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“…ε. To correlate with experimental results [46,47], we expressed the applied strain rate in terms of a dimensionless Weissenberg number [48][49][50] defined as Wi = . ετ R , where τ R is the Rouse time, given by τ R = τ e Z 2 , where Z = l/l e is the average number of entanglements per chain and τ e the entanglement time.…”

Section: Methodsmentioning

confidence: 99%

Bead–Spring Simulation of Ionomer Melts—Studying the Effects of Chain-Length and Associating Group Fraction on Equilibrium Structure and Extensional Flow Behavior

Mohottalalage,

Saab,

Maiti

2023

Polymers

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Ionomers are associative polymers with diverse applications ranging from selective membranes and high-performance adhesives to abrasion- and chemical-resistant coatings, insulation layers, vacuum packaging, and foamed sheets. Within equilibrium melt, the ionic or associating groups are known to form thermally reversible, associative clusters whose presence can significantly affect the system’s mechanical, viscoelastic, and transport properties. It is, thus, of great interest to understand how to control such clusters’ size distribution, shape, and stability through the designed choice of polymer architecture and the ionic groups’ fraction, arrangement, and interaction strength. In this work, we represent linear associating polymers using a Kremer–Grest type bead–spring model and perform large-scale MD simulations to explore the effect of polymer chain-length (l) and fraction (fs) of randomly placed associating groups on the size distribution and stability of formed clusters. We consider different chain-lengths (below and above entanglement), varying fractions of associating groups (represented by ‘sticky’ beads) between 5 and 20%, and a fixed sticky–sticky nonbond interaction strength of four times that between regular non-associating beads. For all melts containing associating groups the equilibrium structure factor S(q) displays a signature ionomer peak at low wave vector q whose intensity increases with increasing fs and l. The average cluster size Nc increases with fs. However, the effect of chain-length on Nc appears to be pronounced only at higher values of fs. Under extensional flows, the computed stress (and viscosity) is higher at higher fs and l regardless of strain rate. Beyond a critical strain rate, we observe fragmentation of the associative clusters, which has interesting effects on the stress/viscous response.

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Section: Methodsmentioning

confidence: 99%

Bead–Spring Simulation of Ionomer Melts—Studying the Effects of Chain-Length and Associating Group Fraction on Equilibrium Structure and Extensional Flow Behavior

Mohottalalage,

Saab,

Maiti

2023

Polymers

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“…Therefore, Tseng 35 have sufficiently demonstrated that the GNF-X numerical algorithm can decompose exact shear and extension rates validated in the analytical center-gated disk flow. Significantly, Wen et al 36 performed the non-isothermal GNF-X flow simulations to estimate the extensional viscosity for various polymer melts.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

The importance of extensional viscosity on a peculiar ear-flow front for injection molding simulations of fiber-reinforced composites

Tseng

2023

Journal of Thermoplastic Composite Materials

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An ear-flow front is discovered in the industrial practice of injection molding, especially for fiber-reinforced composites; the advance of the flow front in the center of the cavity is obviously slower than at the edges. To date, such a peculiar flow has not yet been predicted theoretically or computationally and is beyond the predictive capabilities of existing commercial computer aid design (CAE) packages for the injection molding process. Recently, the GNF-X (Generalized Newtonian Fluid eXtended) model of weighted shear/extensional viscosity has been incorporated availably in state-of-the-art predictive engineering software of the 3D-CFD (three-dimensional computational fluid dynamics) framework to show the extension-induced vortex growth in contraction flows of polymer melts. Through 3D-CFD coupled with GNF-X in injection molding simulations, it is significant to demonstrate the importance of extensional viscosity on the ear-flow formation in relation to the weighted viscosity and extension fraction for long-branched and fiber-filled polymer materials. In addition, one can point out that the ear-flow front probably occurs in fast filling conditions for anisotropic fluids.

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The conflicting role of shear thinning and extensional thickening on corner vertex within entry flow for branched and filled polymer melts

Tseng

2023

Korea-Aust. Rheol. J.

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Extensional rheology of linear and branched polymer melts in fast converging flows

Cited by 7 publications

References 77 publications

Bead–Spring Simulation of Ionomer Melts—Studying the Effects of Chain-Length and Associating Group Fraction on Equilibrium Structure and Extensional Flow Behavior

Bead–Spring Simulation of Ionomer Melts—Studying the Effects of Chain-Length and Associating Group Fraction on Equilibrium Structure and Extensional Flow Behavior

The importance of extensional viscosity on a peculiar ear-flow front for injection molding simulations of fiber-reinforced composites

The conflicting role of shear thinning and extensional thickening on corner vertex within entry flow for branched and filled polymer melts

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