Cover Picture: Macromol. React. Eng. 2/2016

Saldívar‐Guerra, Enrique; Ordaz-Quintero, Almendra; Infante, Ramiro; Herrera‐Ordóñez, Jorge; Villarreal-Cárdenas, Luis; Wong, Diana Guadalupe Ramirez; Rivera-Rodríguez, Evelia; Flores‐Flores, Rodolfo; Miramontes-Vidal, Luis

doi:10.1002/mren.201670005

Macro Reaction Engineering

2016

DOI: 10.1002/mren.201670005

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Cover Picture: Macromol. React. Eng. 2/2016

Enrique Saldívar‐Guerra

Almendra Ordaz-Quintero

Ramiro Infante

et al.

Abstract: Front Cover: The unique rheological properties of LDPE are a result of its MWD, which is determined by a complex free‐radical kinetic mechanism. The paper illustrated in the cover analyzes some factors that define the MWD in multizone autoclave reactors by using plant data, simulation and mechanistic arguments. Further details can be found in the article by Enrique Saldívar‐Guerra and co‐workers http://doi.wiley.com/10.1002/mren.201500030.

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“…For the kinetic parameters that are closer to the actual reactor operation conditions for LD, one can refer to the other articles. [22,23] The size of the ith tank is represented by…”

mentioning

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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“…For the kinetic parameters that are closer to the actual reactor operation conditions for LD, one can refer to the other articles. [22,23] The size of the ith tank is represented by…”

mentioning

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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Multicompartment Model of an Ethylene–Vinyl Acetate Autoclave Reactor: A Combined Computational Fluid Dynamics and Polymerization Kinetics Model

Lee

Jeon

Cho

et al. 2019

Ind. Eng. Chem. Res.

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In this paper, we present a multicompartment model of an ethylene–vinyl acetate autoclave reactor including the mixing effects of the stirring device analyzed using computational fluid dynamics; the model is simplified by cell aggregation, and the polymerization kinetics is modeled with the method of moments. The proposed model has been verified through comparison of the predicted product properties and locally distributed temperatures with those from an industrial plant. The proposed model, which is capable of simulating a complex system with low computational load, can be applied to maintain consistent product quality, prevent undesired thermal runaway, and optimize the conversion and production rates.

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Cover Picture: Macromol. React. Eng. 2/2016

Cited by 2 publications

References 0 publications

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

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

Multicompartment Model of an Ethylene–Vinyl Acetate Autoclave Reactor: A Combined Computational Fluid Dynamics and Polymerization Kinetics Model

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