Prediction of the Viscoelastic Behavior of Low‐Density Polyethylene Produced in High‐Pressure Tubular Reactors

Pladis, Prokopis; Meimaroglou, Dimitrios; Kiparissides, Costas

doi:10.1002/mren.201500008

Cited by 20 publications

(24 citation statements)

References 52 publications

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“…Therefore, a higher processing temperature induces a higher stress relaxation rate of polymer chains, resulting in a decrease of the swelling ratio. As a branched polymer melt possesses a higher activation energy than its linear counterpart, [83] the temperature effect on extrudate swell is related to the molecular thus material parameters as covered in the following subsection. Indeed, Liang et al [33,65,66] found that an increasing processing temperature decreased the extrudate swelling at a given shear stress for polymer melts.…”

Section: Effect Of Processing Parametersmentioning

confidence: 99%

State of the‐Art for Extrudate Swell of Molten Polymers: From Fundamental Understanding at Molecular Scale toward Optimal Die Design at Final Product Scale

Tang

Marchesini

Cardon

et al. 2020

Macro Materials & Eng

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Exit velocity profiles for parallel die and die optimized using conical widening or narrowing. Reproduced permission. [164] Copyright 2010, Elsevier Ltd. c) Average velocity of each outflow subsection of the slit die (width = 100 mm and height = 1.5 mm), Reproduced with permission. [173] Copyright 2012, Elsevier Ltd. d,e) The geometry profiles of the Catheter cross section covered as case study. f) The velocity distribution at the die outflow for different trials-T0: the original die profile; T1: r 2 varies from 0.9 to 0.95 mm; T2: r 2 varies from 0.95 to 0.9 mm, θ 2 varies from 45° to 43°; T3: r 2 varies from 0.9 to 0.95 mm; T4: θ 2 varies from 43° to 40°; T5: r 3 varies from 0.7 to 0.65 mm. Reproduced with permission. [166] Copyright 2013, Elsevier. g) The corresponding objective function evolution in consecutive trials. Reproduced with permission. [166] Copyright 2013, Elsevier Ltd.

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Section: Effect Of Processing Parametersmentioning

confidence: 99%

State of the‐Art for Extrudate Swell of Molten Polymers: From Fundamental Understanding at Molecular Scale toward Optimal Die Design at Final Product Scale

Tang

Marchesini

Cardon

et al. 2020

Macro Materials & Eng

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“…As a result, a little less than 2000 branched chains were extracted and transferred in a polyconf.dat file. The number of molecules is quite lower than that reported by Pladis et al., [ 24 ] so the BoB‐rheology calculations were performed for the plural polyconf.dat files generated by repeating the MC simulation several times for one condition, and the averaged values thereof were used. The polymer molecules with a degree of polymerization larger than 500 000 (molecular weight 14 × 10 6 ) generated in the MC simulation were excluded as they are practically considered to be a gel.…”

Section: Methodsmentioning

confidence: 99%

Relationship between Branched Structure and Viscoelastic Properties of Highly Branched Polyethylene Derived by Monte Carlo Molecular Simulation and the BoB‐Rheology Simulation Methods

Kitade¹,

Yokomizo²,

Hattori

et al. 2020

Macro Theory & Simulations

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However, in some special applications, such as high-speed laminate molding where extremely high MS is desired, a special grade of LD manufactured by the autoclave process is preferred and the tubular's grade are often unusable. The reason is considered that there is a difference in the long-chain branched (LCB) structure of LD produced by these two manufacturing processes.An experimental report on the differences in the structural and the viscoelastic properties of autoclave and tubular process LD was made by Yamaguchi and Takahashi. [2] They concluded that LD by the autoclave process (autoclave LD) had more complex branched structure than LD by the tubular process (tubular LD). They discussed the complexity of branched structure by using the g′-factor (the ratio of the intrinsic viscosity of branched molecule to linear molecule with the same molecular weight in a dilute solution) and the rate dependence of extensional viscosity. However, only with these factors, it is impossible to quantitatively discuss the specific differences in the branched structure.Modeling and simulation is another approach to investigate the effects of reactor types used for the production. LD is produced through the free-radical polymerization that involves chain transfer to polymer, leading to simultaneous long-chain branching and scission. When the random scission process of the formed branched polymer molecules is involved, simple population balance differential equations cannot be applied, because the number of possible scission points to obtain a polymer with a designated molecular weight depends on the complex branched architecture. [3][4][5] Note that all of the deterministic models that employ the closure methods for the moment equations are not exact, because they need the assumption of the distribution type before calculating the molecular weight distribution.The problem of random scission of the branched polymer was solved by using the Monte Carlo (MC) simulation method in 1996. [4] Combining this technique with the theory proposed for the free-radical polymerization that involves chain transfer to polymer, [6] Tobita proposed an appropriate way to account for the simultaneous long-chain branching and scission during In this report, it is verified by the simulation what kind of difference can be caused in the molecular structure and the viscoelastic property by the difference in the manufacturing process of the high-pressure low density polyethylene, that is, autoclave (or vessel) process and tubular process. The Monte Carlo simulation developed by Tobita is used as the molecular structure simulation. The molecular simulation is performed assuming a five tanks-in-series model, which allows one to investigate a wide variety of reactor operations, from the condition closer to the tubular process to the autoclave processes systematically. The branched structure is quantitatively evaluated by the parameter known as priority and seniority (segment depth). The viscoelastic simulation is based on the branch-on-branch rheology (BoB-...

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“…One of the key components of this relationship is the connection between the synthesis conditions and the bivariate MWD-LCBD of the polymer. The latter is an input to advanced rheological models that can predict the melt flow properties of the resin (Pladis et al, 2015).…”

Section: Modeling Of Bivariate Distributions In Polymer Systemsmentioning

confidence: 99%

Improved numerical inversion methods for the recovery of bivariate distributions of polymer properties from 2D probability generating function domains

Brandolin

Balbueno

Asteasuain

2016

Computers & Chemical Engineering

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Please cite this article as: Brandolin, Adriana., Balbueno, Ayslane Assini., & Asteasuain, Mariano., Improved numerical inversion methods for the recovery of bivariate distributions of polymer properties from 2D probability generating function domains.Computers and Chemical Engineering http://dx. GRAPHICAL ABSTRACTIn this work two 2D pgf inversion methods are developed, for which the pgf is regarded as a complex variable. These methods provide an outstanding accuracy in the inversion, thus allowing extending the 2D pgf technique for modeling bivariate distributions without restrictions in the range of values of its independent domains HIGHLIGHTS  Advanced modeling of polymer processes.  Prediction of bivariate (2D) distributions of polymer molecular properties.  Improvement of the pgf modeling method.  Development of new pgf inversion methods that use complex and/or real pgf.  Accurate modeling of 2D distributions with domains of different orders of magnitude. AbstractThe 2D probability-generating function technique is a powerful method for modeling bivariate distributions of polymer properties. It is based on the transformation of bivariate population balance equations using 2D probability generating functions (pgf) followed by a recovery of the distributions from the transform domain by numerical inversion. A key step of this method is the inversion of the pgf transforms. Available numerical inversion methods yield excellent results for pgf transforms of distributions with independent dimensions with similar orders of magnitude, for example bivariate molecular weight distributions in copolymerization systems.However, numerical problems are found for 2D distributions in which the independent dimensions have very different ranges of values, such as the molecular weight distributionbranching distribution in branched polymers. In this work, two new 2D pgf inversion methods are developed, which regard the pgf as a complex variable. The superior accuracy of these innovative methods makes them suitable for recovering any type of bivariate distribution. This enhances the capabilities of the 2D pgf modeling technique for simulation and optimization of polymer processes. An application example of the technique in a polymeric system of industrial interest is presented.

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Prediction of the Viscoelastic Behavior of Low‐Density Polyethylene Produced in High‐Pressure Tubular Reactors

Cited by 20 publications

References 52 publications

State of the‐Art for Extrudate Swell of Molten Polymers: From Fundamental Understanding at Molecular Scale toward Optimal Die Design at Final Product Scale

State of the‐Art for Extrudate Swell of Molten Polymers: From Fundamental Understanding at Molecular Scale toward Optimal Die Design at Final Product Scale

Relationship between Branched Structure and Viscoelastic Properties of Highly Branched Polyethylene Derived by Monte Carlo Molecular Simulation and the BoB‐Rheology Simulation Methods

Improved numerical inversion methods for the recovery of bivariate distributions of polymer properties from 2D probability generating function domains

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