Steady-state modeling of extrusion cast film process, neck-in phenomenon, and related experimental research: A review

Barborik, Tomas; Zatloukal, Martin

doi:10.1063/5.0004589

Cited by 30 publications

(20 citation statements)

References 146 publications

(312 reference statements)

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“…Processability of commercial thermoplastics has always been a key area of research as we continue to work towards more efficient and greener manufacturing. During polymer processing, polymers are subjected to shear and extensional flow [ 1 , 2 ] simultaneously with extensional flow playing a dominant role in processes such as blow molding [ 3 ], fiber spinning [ 4 ], film blowing [ 5 ] and film casting [ 6 , 7 ]. With processing behaviors of polymers being influenced by their molar mass (M w ), polydispersity (PDI), and long-chain branching (LCB) [ 8 ], studying the effects of molecular characteristics and chain architecture on shear and extensional rheological behavior of polyethylene is important in optimizing its processability.…”

Section: Introductionmentioning

confidence: 99%

Modelling of Elongational Flow of HDPE Melts by Hierarchical Multi-Mode Molecular Stress Function Model

2021

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The transient elongational data set obtained by filament-stretching rheometry of four commercial high-density polyethylene (HDPE) melts with different molecular characteristics was reported by Morelly and Alvarez [Rheologica Acta 59, 797–807 (2020)]. We use the Hierarchical Multi-mode Molecular Stress Function (HMMSF) model of Narimissa and Wagner [Rheol. Acta 54, 779–791 (2015), and J. Rheology 60, 625–636 (2016)] for linear and long-chain branched (LCB) polymer melts to analyze the extensional rheological behavior of the four HDPEs with different polydispersity and long-chain branching content. Model predictions based solely on the linear-viscoelastic spectrum and a single nonlinear parameter, the dilution modulus GD for extensional flows reveals good agreement with elongational stress growth data. The relationship of dilution modulus GD to molecular characteristics (e.g., polydispersity index (PDI), long-chain branching index (LCBI), disengagement time τd) of the high-density polyethylene melts are presented in this paper. A new measure of the maximum strain hardening factor (MSHF) is proposed, which allows separation of the effects of orientation and chain stretching.

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Section: Introductionmentioning

confidence: 99%

Modelling of Elongational Flow of HDPE Melts by Hierarchical Multi-Mode Molecular Stress Function Model

2021

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“…, where the constant A is related to the high-strain rate plateau values of the shear and extensional viscosities and f is function evaluating the intensity of stretching during flow. The models handle the differences between highextensional-rate uniaxial, planar and biaxial extensional viscosities compared to others, more advanced constitutive equations (including the molecular-based Pom-Pom model), which unrealistically predict steady-state uniaxial and planar extensional viscosities virtually identical at high extensional strain rates [19,68,74]. These types of GNF models have been successfully tested for polymer melts with linear (mLLDPE [68,71], HDPE [68,69]) and differently branched structures (mLLDPE [68,69,71], mHDPE [68], LDPE [68][69][70]72]) including polymers with star type of the branching (LCB-PP [73]) using steadystate extensional viscosities measured at extensional strain rates typically up to about 10 s -1 , (i.e.…”

Section: Constitutive Equationmentioning

confidence: 99%

“…Knowledge of polymer melt dynamics and stability at very fast flows (i.e. at high speeds and/or in the small channels where orientational and/or stretch Weissenber number is higher than 1 [1,2]) is essential for the optimization and development of new polymeric materials used to produce micro/nano-products via advanced technologies such as additive manufacturing (alias 3D printing) [3][4][5][6][7][8] micromolding [9][10][11][12][13], nano-imprint lithography [14][15][16][17][18], film casting [19][20][21][22][23][24][25], meltblown [26][27][28][29] and electrospinning [30][31][32]. It was found that the flow behavior of polymer melts in highly confined geometries is significantly different from those of the bulk [33][34][35] (i.e.…”

Section: Introductionmentioning

confidence: 99%

Generalized Newtonian fluid constitutive equation for polymer liquids considering chain stretch and monomeric friction reduction for very fast flows modeling

Zatloukal

Drábek

2021

Physics of Fluids

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In this work, the recently proposed frame-invariant Generalized Newtonian Fluid (GNF) constitutive equation [M. Zatloukal, Physics of Fluids 32(9), 091705 (2020)] has been modified to provide uniaxial extensional viscosity at high strain rate limit corresponding to molecular expression for a fully extended Fraenkel chain reported in [G. Ianniruberto, G. Marrucci, and Y. Masubuchi, Macromolecules 53(13), 5023-5033 (2020)]. It uses basic rheological and molecular parameters together with the ratio of monomeric friction coefficients for equilibrium and fully aligned chains. The modified GNF model was successfully tested by using steady-state uniaxial extensional viscosity data for well-characterized entangled polymer melts and solutions (namely linear isotactic polypropylenes, poly(n-butyl acrylate), polyisoprenes and polystyrenes) covering a wide range of strain rates, including those, at which the chain stretch occur. Only two fitting parameters were sufficient to describe all uniaxial extensional viscosity data, one related to the Rouse stretch time and the other controlling the extensional thinning and thickening behavior at medium and high strain rates. The model was compared to five different advanced viscoelastic constitutive equations, which are based on Doi-Edwards theory and include chain stretch along with a number of important additions. The ability of the proposed GNF model to represent steady uniaxial extensional viscosities under fast flow conditions for entangled polymer fluids has been shown to be superior to the predictions of selected advanced viscoelastic constitutive equations. It is believed that the modified GNF model can be used in the stable modeling of non-Newtonian polymer liquids, especially in very fast steady-state flows where chain stretch begins to occur.

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“…Even though polymer processes like extrusion and injection molding are dominated by shear flow, it is a well‐established fact that both extensional and shear flow exist in polymer processes. [ 3‐5 ] Therefore, extensional rheology is an important area of study especially when extensional deformation plays an important role in polymer processing methods such as blow molding, [ 6 ] fiber spinning, [ 7 ] thermoforming, [ 8,9 ] film blowing, [ 8 ] film casting, [ 10,11 ] foaming production, [ 12 ] and paint spray. [ 13 ] The occurrence of strong extensional flow in polymer processing procedures can have a major impact on the properties of the final component as polymer molecules are strongly oriented by extensional flows.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, it is advantageous to be able to measure a wide range of melt viscosities; yet, measurements at the lower limits of extensional viscosities of polymers can be challenging in rheometry. [ 30 ] Extending the viscosity measurements toward the lower limits will be beneficial for polymer processes such as extrusion film casting [ 10,31 ] and injection molding [ 32 ] when polymers with higher melt flow index or lower viscosity are used.…”

Section: Introductionmentioning

confidence: 99%

Modeling of nonlinear extensional and shear rheology of low‐viscosity polymer melts

Poh

et al. 2021

Polymer Engineering & Sci

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The hierarchical multi‐mode molecular stress function (HMMSF) model developed by Narimissa and Wagner [Rheol. Acta 54, 779–791 (2015), and J. Rheol. 60, 625–636 (2016)] for linear and long‐chain branched (LCB) polymer melts were used to analyze the set of transient elongational and shear viscosity data of two LCB low‐density polyethylenes (1840H and 2426 k), and a linear poly‐(ethylene‐co‐α‐butene), PEB A‐780090 as reported by [Li et al. J. Rheol. 64, 177 (2020)], who had developed a new horizontal extensional rheometer to extend the lower limits of elongational viscosity measurements of polymer melts. Comparison between model predictions and elongational stress growth data reveals excellent agreement within the experimental window, and good consistency with shear stress growth data, based exclusively on the linear‐viscoelastic relaxation spectrum and only two nonlinear model parameters, the dilution modulus GD for extensional flows, and in addition a constraint release parameter for shear flow.

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Steady-state modeling of extrusion cast film process, neck-in phenomenon, and related experimental research: A review

Cited by 30 publications

References 146 publications

Modelling of Elongational Flow of HDPE Melts by Hierarchical Multi-Mode Molecular Stress Function Model

Modelling of Elongational Flow of HDPE Melts by Hierarchical Multi-Mode Molecular Stress Function Model

Generalized Newtonian fluid constitutive equation for polymer liquids considering chain stretch and monomeric friction reduction for very fast flows modeling

Modeling of nonlinear extensional and shear rheology of low‐viscosity polymer melts

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