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Special Issue "Computational Modeling and Simulation in Polymer"

A special issue of Polymers (ISSN 2073-4360).

Deadline for manuscript submissions: closed (20 October 2016)

Special Issue Editors

Guest Editor
Dr. Xianqiao Wang

College of Engineering, University of Georgia, Athens, GA 30602, USA
Website | E-Mail
Phone: 1-706-5426251
Interests: computational nanomechanics, computational nanomaterials. bio/inorganic interfaces, modeling and simulations.
Guest Editor
Dr. Ying Li

Department of Mechanical Engineering, University of Connecticut, Storrs CT, USA
Website | E-Mail
Phone: +1-860-486-7110
Interests: multiscale modeling; computational material design; mechanics and physics of soft matter; design of mechanical metamaterials and targeted drug delivery
Co-Guest Editor
Dr. Yingjie Xu

Engineering Simulation and Aerospace Computing (ESAC), Northwestern Polytechnical University, Xi’an 710072, China
Website | E-Mail
Phone: +86-29-8849-3914 (ext. 1225)
Fax: +86-29-8849-5774
Interests: mechanics of polymeric materials and composites; computational modeling of processing and mechanical behaviors of polymers; computational modeling of composites; optimal design of advanced materials and structures
Co-Guest Editor
Prof. Dr. Weihong Zhang

Engineering Simulation and Aerospace Computing (ESAC), Northwestern Polytechnical University, Xi’an 710072, China
Website | E-Mail
Phone: +86-29-8849-5774
Fax: +86-29-88495774
Interests: computational mechanics of solids and structures; optimal design of advanced materials and structures
Co-Guest Editor
Prof. Dr. Sofiane Guessasma

Research unit Biopolymers, French Institute for Agricultural Research (INRA), 44300 Nantes, France
Website | E-Mail
Phone: +33-240675036
Fax: +33-240675167
Interests: computational mechanics of materials (polymers, biomaterials, ceramics, metals, alloys); polymer 3D printing; materials design
Co-Guest Editor
Prof. Dr. Chuntai Liu

National Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou 450002, China
Website | E-Mail
Phone: +86-371-6388-7969
Fax: +86-371-6388-7570
Interests: computer aided engineering for polymer processing; polymer processing-microstructure-properties; conductive polymer composites; polymer degradation and stability

Special Issue Information

Dear Colleagues,

Computational modeling and simulation has been emerging as an indispensable tool, nowadays, to complement and/or guide experiments in every field. The complex and intriguing mechanical/physical properties of polymeric materials, originating from the multiple spatial and temporal scales, call for the advanced multiscale computational techniques in order to account for all-important mechanisms in polymers.

Since more and more accurate interatomic potentials for a wide range of materials have been developed based on quantum-mechanical calculations, all-atomistic molecular dynamics simulations have become a powerful tool for analyzing complex physical phenomena, i.e., bond vibrations, diffusion, and rheology of polymeric materials. However, the length and time scales that can be probed using all-atomistic molecular dynamics simulations are still fairly limited, since all the atoms are explicitly considered and their electrostatic interactions are long-ranged. This special issue is dedicated to the recent research advances in computational modeling and theoretical analysis in the polymeric materials from nano to macro scales, irrespective of the properties of interest, more specifically, to (1) molecular dynamics methods, (2) coarse-grained methods, finite element methods, and (3) multiscale computational methods in polymer science.

In this Special Issue, a special discussion on “Computational Modeling in Injection Molding Process and Service Life of Thermoplastic Polymers” will be introduced, which would be our special session.

Due to the favorable combination of easy processability and attractive mechanical properties, thermoplastic polymers have been widely used in structural applications over recent decades. Injection molding is one of the most widely employed methods for manufacturing thermoplastic polymer products. To ensure proper operation under heavy-duty conditions, these polymer products have to meet two primary requirements: the molding quality during the injection molding process and the mechanical performance during the service life. It is, thus, important to accurately predict and optimize the molding defects under various processing conditions and the mechanical behaviors in different loadings. Considering the large amount of parameters involved (processing, geometry, material properties and loading conditions), it is virtually impossible to realize this in a purely experimental setting. A promising way to simplify this problem is the employment of computational modeling from injection molding process to service life.

The objective of this Special Session is to provide an opportunity for scientists, engineers, and practitioners to present their latest computational modeling achievements in injection molding process and mechanical performance of thermoplastic polymers. All the submissions are expected to have original ideas and new approaches. Potential topics include, but are not limited to: (1)simulation of the flow of polymer melts during an injection molding process; (2)prediction of the molding defects; (3)optimization of the injection molding process to improve the molding quality; (4)constitutive modeling of thermoplastic polymers; (5)modeling of the influence of molding process on the mechanical behaviors of polymers; (6)computation of the mechanical performance of polymer products under complicated loading conditions; (7)simulation of the low or high velocity impact behavior of polymer products.

Dr. Xianqiao(XQ) Wang
Dr. Ying Li
Dr. Yingjie Xu
Prof. Dr. Weihong Zhang
Prof. Dr. Sofiane Guessasma
Prof. Dr. Chuntai Liu
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Molecular dynamics in polymers
  • Coarse-grained molecular dynamics in polymers
  • Multiscale modeling in polymers
  • Finite element analysis in polymers

Published Papers (16 papers)

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Research

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Open AccessArticle Effect of Cyclic Loading on Surface Instability of Silicone Rubber under Compression
Polymers 2017, 9(4), 148; doi:10.3390/polym9040148
Received: 12 March 2017 / Revised: 11 April 2017 / Accepted: 14 April 2017 / Published: 21 April 2017
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Abstract
This work combines experiments and finite element simulations to study the effect of pre-imposed cyclic loading on surface instability of silicon rubber under compression. We first fabricate cuboid blocks of silicon rubber and pinch them cyclicly a few times. Then, an in-house apparatus
[...] Read more.
This work combines experiments and finite element simulations to study the effect of pre-imposed cyclic loading on surface instability of silicon rubber under compression. We first fabricate cuboid blocks of silicon rubber and pinch them cyclicly a few times. Then, an in-house apparatus is set to apply uniaxial compression on the silicon rubber under exact plane strain conditions. Surprisingly, we find multiple creases on the surface of silicone rubber, significantly different from what have been observed on the samples without the cyclic pinching. To reveal the underlying physics for these experimentally observed multiple creases, we perform detailed nanoindentation experiments to measure the material properties at different locations of the silicon rubber. The modulus is found to be nonuniform and varies along the thickness direction after the cyclic pinching. According to these experimental results, three-layer and multilayer finite element models are built with different materials properties informed by experiments. The three-layer finite element model can excellently explain the nucleation and pattern of multiple surface creases on the surface of compressed silicone rubber, in good agreement with experiments. Counterintuitively, the multilayer model with gradient modulus cannot be used to explain the multiple creases observed in our experiments. According to these simulations, the experimentally observed multiple creases should be attributed to a thin and stiff layer formed on the surface of silicon rubber after the pre-imposed cyclic loading. Full article
(This article belongs to the Special Issue Computational Modeling and Simulation in Polymer)
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Open AccessArticle Mechanical Performance of Graphene-Based Artificial Nacres under Impact Loads: A Coarse-Grained Molecular Dynamic Study
Polymers 2017, 9(4), 134; doi:10.3390/polym9040134
Received: 10 March 2017 / Revised: 2 April 2017 / Accepted: 5 April 2017 / Published: 7 April 2017
PDF Full-text (4931 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Inspired by the hierarchical structure and outstanding mechanical performance of biological nacre, we propose a similar multi-layered graphene–polyethylene nanocomposite as a possible lightweight material with energy-absorbing characteristics. Through coarse-grained molecular dynamics simulations, we study the mechanical performance of the nanocomposite under spall loading.
[...] Read more.
Inspired by the hierarchical structure and outstanding mechanical performance of biological nacre, we propose a similar multi-layered graphene–polyethylene nanocomposite as a possible lightweight material with energy-absorbing characteristics. Through coarse-grained molecular dynamics simulations, we study the mechanical performance of the nanocomposite under spall loading. Results indicate that the polymer phase can serve as a cushion upon impact, which substantially decreases maximum contact forces and thus inhibits the breakage of covalent bonds in the graphene flakes. In addition, as the overlap distance in graphene layers increases, the energy absorption capacity of the model increases. Furthermore, the polymer phase can serve as a shield upon impact to protect the graphene phase from aggregation. The dependence of mechanical response on the size of impactors is also explored. Results indicate that the maximum contact force during the impact depends on the external surface area of impactors rather than the density of impactors and that the energy absorption for all model impactors is very similar. Overall, our findings can provide a systematic understanding of the mechanical responses on graphene–polyethylene nanocomposites under spall loads. Full article
(This article belongs to the Special Issue Computational Modeling and Simulation in Polymer)
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Open AccessArticle Pressure Analysis of Dynamic Injection Molding and Process Parameter Optimization for Reducing Warpage of Injection Molded Products
Polymers 2017, 9(3), 85; doi:10.3390/polym9030085
Received: 19 October 2016 / Revised: 24 January 2017 / Accepted: 23 February 2017 / Published: 7 March 2017
PDF Full-text (7995 KB) | HTML Full-text | XML Full-text
Abstract
Plastic injection molding technology is one of the important technologies for the manufacturing industry. In this paper, a numerical dynamic injection molding technology (DIMT) is presented, which is based on the finite element (FE) method. This numerical simulation method introduces a vibrational force
[...] Read more.
Plastic injection molding technology is one of the important technologies for the manufacturing industry. In this paper, a numerical dynamic injection molding technology (DIMT) is presented, which is based on the finite element (FE) method. This numerical simulation method introduces a vibrational force into the conventional injection molding technology (CIMT). Some meaningful work has been executed for investigating the mechanical evolution behavior of DIMT. As the basis for illustrating the mechanism in warpage optimization results, dynamic parameter analysis on the rule of pressure response is performed in detail. In the warpage optimization work, three kinds of structure with different molding materials are selected as the comparison. The final warpage of each product is efficiently minimized by using a Gaussian process-based sequential optimization method. From the further discussions, the features of DIMT in improving the molding quality are revealed, indicating that it may not be appropriate for geometrically large structures. This study has significant meaning for the actual injection molding industry. Full article
(This article belongs to the Special Issue Computational Modeling and Simulation in Polymer)
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Open AccessArticle Multi-Objective Optimizations of Biodegradable Polymer Stent Structure and Stent Microinjection Molding Process
Polymers 2017, 9(1), 20; doi:10.3390/polym9010020
Received: 18 October 2016 / Revised: 26 December 2016 / Accepted: 30 December 2016 / Published: 17 January 2017
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Abstract
Biodegradable stents made of poly-l-lactic acid (PLLA) have a promising prospect thanks to high biocompatibility and a favorable biodegradation period. However, due to the low stiffness of PLLA, polymeric stents have a lower radial stiffness and larger foreshortening. Furthermore, a stent
[...] Read more.
Biodegradable stents made of poly-l-lactic acid (PLLA) have a promising prospect thanks to high biocompatibility and a favorable biodegradation period. However, due to the low stiffness of PLLA, polymeric stents have a lower radial stiffness and larger foreshortening. Furthermore, a stent is a tiny meshed tube, hence, it is difficult to make a polymeric stent. In the present study, a finite element analysis-based optimization method combined with Kriging surrogate modeling is firstly proposed to optimize the stent structure and stent microinjection molding process, so as to improve the stent mechanical properties and microinjection molding quality, respectively. The Kriging surrogate models are constructed to formulate the approximate mathematical relationships between the design variables and design objectives. Expected improvement is employed to balance local and global search to find the global optimal design. As an example, the polymeric ART18Z stent was investigated. The mechanical properties of stent expansion in a stenotic artery and the molding quality were improved after optimization. Numerical results demonstrate the proposed optimization method can be used for the computationally measurable optimality of stent structure design and stent microinjection molding process. Full article
(This article belongs to the Special Issue Computational Modeling and Simulation in Polymer)
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Open AccessArticle Hydrodynamic Interactions and Entanglements of Polymer Solutions in Many-Body Dissipative Particle Dynamics
Polymers 2016, 8(12), 426; doi:10.3390/polym8120426
Received: 16 November 2016 / Revised: 5 December 2016 / Accepted: 6 December 2016 / Published: 9 December 2016
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Abstract
Using many-body dissipative particle dynamics (MDPD), polymer solutions with concentrations spanning dilute and semidilute regimes are modeled. The parameterization of MDPD interactions for systems with liquid–vapor coexistence is established by mapping to the mean-field Flory–Huggins theory. The characterization of static and dynamic properties
[...] Read more.
Using many-body dissipative particle dynamics (MDPD), polymer solutions with concentrations spanning dilute and semidilute regimes are modeled. The parameterization of MDPD interactions for systems with liquid–vapor coexistence is established by mapping to the mean-field Flory–Huggins theory. The characterization of static and dynamic properties of polymer chains is focused on the effects of hydrodynamic interactions and entanglements. The coil–globule transition of polymer chains in dilute solutions is probed by varying solvent quality and measuring the radius of gyration and end-to-end distance. Both static and dynamic scaling relations for polymer chains in poor, theta, and good solvents are in good agreement with the Zimm theory with hydrodynamic interactions considered. Semidilute solutions with polymer volume fractions up to 0.7 exhibit the screening of excluded volume interactions and subsequent shrinking of polymer coils. Furthermore, entanglements become dominant in the semidilute solutions, which inhibit diffusion and relaxation of chains. Quantitative analysis of topology violation confirms that entanglements are correctly captured in the MDPD simulations. Full article
(This article belongs to the Special Issue Computational Modeling and Simulation in Polymer)
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Open AccessArticle Atomistic Modelling of Confined Polypropylene Chains between Ferric Oxide Substrates at Melt Temperature
Polymers 2016, 8(10), 361; doi:10.3390/polym8100361
Received: 6 September 2016 / Revised: 7 October 2016 / Accepted: 11 October 2016 / Published: 14 October 2016
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Abstract
The interactions and conformational characteristics of confined molten polypropylene (PP) chains between ferric oxide (Fe2O3) substrates were investigated by molecular dynamics (MD) simulations. A comparative analysis of the adsorbed amount shows strong adsorption of the chains on the high-energy
[...] Read more.
The interactions and conformational characteristics of confined molten polypropylene (PP) chains between ferric oxide (Fe2O3) substrates were investigated by molecular dynamics (MD) simulations. A comparative analysis of the adsorbed amount shows strong adsorption of the chains on the high-energy surface of Fe2O3. Local structures formed in the polymer film were studied utilizing density profiles, orientation of bonds, and end-to-end distance of chains. At interfacial regions, the backbone carbon-carbon bonds of the chains preferably orient in the direction parallel to the surface while the carbon-carbon bonds with the side groups show a slight tendency to orient normal to the surface. Based on the conformation tensor data, the chains are compressed in the normal direction to the substrates in the interfacial regions while they tend to flatten in parallel planes with respect to the surfaces. The orientation of the bonds as well as the overall flattening of the chains in planes parallel to the solid surfaces are almost identical to that of the unconfined PP chains. Also, the local pressure tensor is anisotropic closer to the solid surfaces of Fe2O3 indicating the influence of the confinement on the buildup imbalance of normal and tangential pressures. Full article
(This article belongs to the Special Issue Computational Modeling and Simulation in Polymer)
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Open AccessArticle Tailoring the Static and Dynamic Mechanical Properties of Tri-Block Copolymers through Molecular Dynamics Simulation
Polymers 2016, 8(9), 335; doi:10.3390/polym8090335
Received: 8 June 2016 / Revised: 22 August 2016 / Accepted: 31 August 2016 / Published: 19 September 2016
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Abstract
Although the research of the self-assembly of tri-block copolymers has been carried out widely, little attention has been paid to study the mechanical properties and to establish its structure-property relation, which is of utmost significance for its practical applications. Here, we adopt molecular
[...] Read more.
Although the research of the self-assembly of tri-block copolymers has been carried out widely, little attention has been paid to study the mechanical properties and to establish its structure-property relation, which is of utmost significance for its practical applications. Here, we adopt molecular dynamics simulation to study the static and dynamic mechanical properties of the ABA tri-block copolymer, by systematically varying the morphology, the interaction strength between A-A blocks, the temperature, the dynamic shear amplitude and frequency. In our simulation, we set the self-assembled structure formed by A-blocks to be in the glassy state, with the B-blocks in the rubbery state. With the increase of the content of A-blocks, the spherical, cylindrical and lamellar domains are formed, respectively, exhibiting a gradual increase of the stress-strain behavior. During the self-assembly process, the stress-strain curve is as well enhanced. The increase of the interaction strength between A-A blocks improves the stress-strain behavior and reduces the dynamic hysteresis loss. Since the cylindrical domains are randomly dispersed, the stress-strain behavior exhibits the isotropic mechanical property; while for the lamellar domains, the mechanical property seems to be better along the direction perpendicular to than parallel to the lamellar direction. In addition, we observe that with the increase of the dynamic shear amplitude and frequency, the self-assembled domains become broken up, resulting in the decrease of the storage modulus and the increase of the hysteresis loss, which holds the same conclusion for the increase of the temperature. Our work provides some valuable guidance to tune the static and dynamic mechanical properties of ABA tri-block copolymer in the field of various applications. Full article
(This article belongs to the Special Issue Computational Modeling and Simulation in Polymer)
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Open AccessArticle On the Orientation-Induced Crystallization of Polymers
Polymers 2016, 8(6), 229; doi:10.3390/polym8060229
Received: 1 April 2016 / Revised: 1 June 2016 / Accepted: 3 June 2016 / Published: 8 June 2016
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Abstract
In order to understand orientation-induced crystallization of polymers, we introduced an intermolecular interaction between polymer chains based on quantum mechanics. We therefore considered a pair of perfectly extended chains where the intermolecular interaction is assumed to be based on the hydrogen interaction with
[...] Read more.
In order to understand orientation-induced crystallization of polymers, we introduced an intermolecular interaction between polymer chains based on quantum mechanics. We therefore considered a pair of perfectly extended chains where the intermolecular interaction is assumed to be based on the hydrogen interaction with a single chain. When two protons of each extended chain become closer together under tension, the attractive force between the extended chains is caused by the interaction between hydrogen atoms surrounding the main chains based on the hydrogen molecule ion H 2 + . The energy is split into the ground and excited states, and the spontaneous process leading to the ground state is the origin for orientation-induced crystallization. Full article
(This article belongs to the Special Issue Computational Modeling and Simulation in Polymer)
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Open AccessArticle A Phase Field Technique for Modeling and Predicting Flow Induced Crystallization Morphology of Semi-Crystalline Polymers
Polymers 2016, 8(6), 230; doi:10.3390/polym8060230
Received: 21 April 2016 / Revised: 27 May 2016 / Accepted: 2 June 2016 / Published: 8 June 2016
Cited by 1 | PDF Full-text (3681 KB) | HTML Full-text | XML Full-text
Abstract
Flow induced crystallization of semi-crystalline polymers is an important issue in polymer science and engineering because the changes in morphology strongly affect the properties of polymer materials. In this study, a phase field technique considering polymer characteristics was established for modeling and predicting
[...] Read more.
Flow induced crystallization of semi-crystalline polymers is an important issue in polymer science and engineering because the changes in morphology strongly affect the properties of polymer materials. In this study, a phase field technique considering polymer characteristics was established for modeling and predicting the resulting morphologies. The considered crystallization process can be divided into two stages, which are nucleation upon the flow induced structures and subsequent crystal growth after the cessation of flow. Accordingly, the proposed technique consists of two parts which are a flow induced nucleation model based on the calculated information of molecular orientation and stretch, and a phase field crystal growth model upon the oriented nuclei. Two-dimensional simulations are carried out to predict the crystallization morphology of isotactic polystyrene under an injection molding process. The results of these simulations demonstrate that flow affects crystallization morphology mainly by producing oriented nuclei. Specifically, the typical skin-core structures along the thickness direction can be successfully predicted. More importantly, the results reveal that flow plays a dominant part in generating oriented crystal morphologies compared to other parameters, such as anisotropy strength, crystallization temperature, and physical noise. Full article
(This article belongs to the Special Issue Computational Modeling and Simulation in Polymer)
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Open AccessArticle Numerical Simulation and Experimental Investigation of the Viscoelastic Heating Mechanism in Ultrasonic Plasticizing of Amorphous Polymers for Micro Injection Molding
Polymers 2016, 8(5), 199; doi:10.3390/polym8050199
Received: 24 March 2016 / Revised: 25 April 2016 / Accepted: 10 May 2016 / Published: 17 May 2016
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Abstract
Ultrasonic plasticizing of polymers for micro-injection molding has been proposed and studied for its unique potential in materials and energy-saving. In our previous work, we have demonstrated the characteristics of the interfacial friction heating mechanism in ultrasonic plasticizing of polymer granulates. In this
[...] Read more.
Ultrasonic plasticizing of polymers for micro-injection molding has been proposed and studied for its unique potential in materials and energy-saving. In our previous work, we have demonstrated the characteristics of the interfacial friction heating mechanism in ultrasonic plasticizing of polymer granulates. In this paper, the other important heating mechanism in ultrasonic plasticizing, i.e., viscoelastic heating for amorphous polymer, was studied by both theoretical modeling and experimentation. The influence mechanism of several parameters, such as the initial temperature of the polymer, the ultrasonic frequency, and the ultrasonic amplitude, was investigated. The results from both numerical simulation and experimentation indicate that the heat generation rate of viscoelastic heating can be significantly influenced by the initial temperature of polymer. The glass transition temperature was found to be a significant shifting point in viscoelastic heating. The heat generation rate is relatively low at the beginning and can have a steep increase after reaching glass transition temperature. In comparison with the ultrasonic frequency, the ultrasonic amplitude has much greater influence on the heat generation rate. In light of the quantitative difference in the viscoelastic heating rate, the limitation of the numerical simulation was discussed in the aspect of the assumptions and the applied mathematical models. Full article
(This article belongs to the Special Issue Computational Modeling and Simulation in Polymer)
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Open AccessArticle Simulation of Jetting in Injection Molding Using a Finite Volume Method
Polymers 2016, 8(5), 172; doi:10.3390/polym8050172
Received: 16 March 2016 / Revised: 18 April 2016 / Accepted: 22 April 2016 / Published: 4 May 2016
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Abstract
In order to predict the jetting and the subsequent buckling flow more accurately, a three dimensional melt flow model was established on a viscous, incompressible, and non-isothermal fluid, and a control volume-based finite volume method was employed to discretize the governing equations. A
[...] Read more.
In order to predict the jetting and the subsequent buckling flow more accurately, a three dimensional melt flow model was established on a viscous, incompressible, and non-isothermal fluid, and a control volume-based finite volume method was employed to discretize the governing equations. A two-fold iterative method was proposed to decouple the dependence among pressure, velocity, and temperature so as to reduce the computation and improve the numerical stability. Based on the proposed theoretical model and numerical method, a program code was developed to simulate melt front progress and flow fields. The numerical simulations for different injection speeds, melt temperatures, and gate locations were carried out to explore the jetting mechanism. The results indicate the filling pattern depends on the competition between inertial and viscous forces. When inertial force exceeds the viscous force jetting occurs, then it changes to a buckling flow as the viscous force competes over the inertial force. Once the melt contacts with the mold wall, the melt filling switches to conventional sequential filling mode. Numerical results also indicate jetting length increases with injection speed but changes little with melt temperature. The reasonable agreements between simulated and experimental jetting length and buckling frequency imply the proposed method is valid for jetting simulation. Full article
(This article belongs to the Special Issue Computational Modeling and Simulation in Polymer)
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Open AccessArticle Modelling and Validation of Synthesis of Poly Lactic Acid Using an Alternative Energy Source through a Continuous Reactive Extrusion Process
Polymers 2016, 8(4), 164; doi:10.3390/polym8040164
Received: 14 January 2016 / Revised: 12 April 2016 / Accepted: 14 April 2016 / Published: 22 April 2016
Cited by 2 | PDF Full-text (5061 KB) | HTML Full-text | XML Full-text
Abstract
PLA is one of the most promising bio-compostable and bio-degradable thermoplastic polymers made from renewable sources. PLA is generally produced by ring opening polymerization (ROP) of lactide using the metallic/bimetallic catalyst (Sn, Zn, and Al) or other organic catalysts in a suitable solvent.
[...] Read more.
PLA is one of the most promising bio-compostable and bio-degradable thermoplastic polymers made from renewable sources. PLA is generally produced by ring opening polymerization (ROP) of lactide using the metallic/bimetallic catalyst (Sn, Zn, and Al) or other organic catalysts in a suitable solvent. In this work, reactive extrusion experiments using stannous octoate Sn(Oct)2 and tri-phenyl phosphine (PPh)3 were considered to perform ROP of lactide. Ultrasound energy source was used for activating and/or boosting the polymerization as an alternative energy (AE) source. Ludovic® software, designed for simulation of the extrusion process, had to be modified in order to simulate the reactive extrusion of lactide and for the application of an AE source in an extruder. A mathematical model for the ROP of lactide reaction was developed to estimate the kinetics of the polymerization process. The isothermal curves generated through this model were then used by Ludovic software to simulate the “reactive” extrusion process of ROP of lactide. Results from the experiments and simulations were compared to validate the simulation methodology. It was observed that the application of an AE source boosts the polymerization of lactide monomers. However, it was also observed that the predicted residence time was shorter than the experimental one. There is potentially a case for reducing the residence time distribution (RTD) in Ludovic® due to the ‘liquid’ monomer flow in the extruder. Although this change in parameters resulted in validation of the simulation, it was concluded that further research is needed to validate this assumption. Full article
(This article belongs to the Special Issue Computational Modeling and Simulation in Polymer)
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Open AccessArticle Density Functional Theory of Polymer Structure and Conformations
Polymers 2016, 8(4), 121; doi:10.3390/polym8040121
Received: 8 March 2016 / Revised: 26 March 2016 / Accepted: 30 March 2016 / Published: 15 April 2016
Cited by 1 | PDF Full-text (1832 KB) | HTML Full-text | XML Full-text
Abstract
We present a density functional approach to quantitatively evaluate the microscopic conformations of polymer chains with consideration of the effects of chain stiffness, polymer concentration, and short chain molecules. For polystyrene (PS), poly(ethylene oxide) (PEO), and poly(methyl methacrylate) (PMMA) melts with low-polymerization degree,
[...] Read more.
We present a density functional approach to quantitatively evaluate the microscopic conformations of polymer chains with consideration of the effects of chain stiffness, polymer concentration, and short chain molecules. For polystyrene (PS), poly(ethylene oxide) (PEO), and poly(methyl methacrylate) (PMMA) melts with low-polymerization degree, as chain length increases, they display different stretching ratios and show non-universal scaling exponents due to their different chain stiffnesses. In good solvent, increase of PS concentration induces the decline of gyration radius. For PS blends containing short (m1 = 1 100) and long (m = 100) chains, the expansion of long chains becomes unobvious once m 1 is larger than 40, which is also different to the scaling properties of ideal chain blends. Full article
(This article belongs to the Special Issue Computational Modeling and Simulation in Polymer)
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Open AccessArticle Experimentation and Modeling of the Tension Behavior of Polycarbonate at High Strain Rates
Polymers 2016, 8(3), 63; doi:10.3390/polym8030063
Received: 28 January 2016 / Revised: 23 February 2016 / Accepted: 24 February 2016 / Published: 29 February 2016
Cited by 2 | PDF Full-text (13541 KB) | HTML Full-text | XML Full-text
Abstract
A comprehensive understanding of the mechanical behavior of polycarbonate (PC) under high-rate loadings is essential for better design of PC products. In this work, the mechanical behavior of PC is studied during tensile loading at high strain rates, using a split Hopkinson tension
[...] Read more.
A comprehensive understanding of the mechanical behavior of polycarbonate (PC) under high-rate loadings is essential for better design of PC products. In this work, the mechanical behavior of PC is studied during tensile loading at high strain rates, using a split Hopkinson tension bar (SHTB). A modified experimental technique based on the SHTB is proposed to perform the tension testing on PC at rates exceeding 1000 s−1. The effect of strain rates on the tension stress–strain law of PC is investigated over a wide range of strain rates (0.0005–4500 s−1). Based on the experiments, a physically based constitutive model is developed to describe the strain rate dependent tensile stress–strain law. The high rate tensile deformation mechanics of PC are further studied via finite element simulations using the LSDYNA code together with the developed constitutive model. Full article
(This article belongs to the Special Issue Computational Modeling and Simulation in Polymer)
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Review

Jump to: Research

Open AccessReview A Review of Multiscale Computational Methods in Polymeric Materials
Polymers 2017, 9(1), 16; doi:10.3390/polym9010016
Received: 20 October 2016 / Revised: 7 December 2016 / Accepted: 22 December 2016 / Published: 9 January 2017
Cited by 1 | PDF Full-text (7798 KB) | HTML Full-text | XML Full-text
Abstract
Polymeric materials display distinguished characteristics which stem from the interplay of phenomena at various length and time scales. Further development of polymer systems critically relies on a comprehensive understanding of the fundamentals of their hierarchical structure and behaviors. As such, the inherent multiscale
[...] Read more.
Polymeric materials display distinguished characteristics which stem from the interplay of phenomena at various length and time scales. Further development of polymer systems critically relies on a comprehensive understanding of the fundamentals of their hierarchical structure and behaviors. As such, the inherent multiscale nature of polymer systems is only reflected by a multiscale analysis which accounts for all important mechanisms. Since multiscale modelling is a rapidly growing multidisciplinary field, the emerging possibilities and challenges can be of a truly diverse nature. The present review attempts to provide a rather comprehensive overview of the recent developments in the field of multiscale modelling and simulation of polymeric materials. In order to understand the characteristics of the building blocks of multiscale methods, first a brief review of some significant computational methods at individual length and time scales is provided. These methods cover quantum mechanical scale, atomistic domain (Monte Carlo and molecular dynamics), mesoscopic scale (Brownian dynamics, dissipative particle dynamics, and lattice Boltzmann method), and finally macroscopic realm (finite element and volume methods). Afterwards, different prescriptions to envelope these methods in a multiscale strategy are discussed in details. Sequential, concurrent, and adaptive resolution schemes are presented along with the latest updates and ongoing challenges in research. In sequential methods, various systematic coarse-graining and backmapping approaches are addressed. For the concurrent strategy, we aimed to introduce the fundamentals and significant methods including the handshaking concept, energy-based, and force-based coupling approaches. Although such methods are very popular in metals and carbon nanomaterials, their use in polymeric materials is still limited. We have illustrated their applications in polymer science by several examples hoping for raising attention towards the existing possibilities. The relatively new adaptive resolution schemes are then covered including their advantages and shortcomings. Finally, some novel ideas in order to extend the reaches of atomistic techniques are reviewed. We conclude the review by outlining the existing challenges and possibilities for future research. Full article
(This article belongs to the Special Issue Computational Modeling and Simulation in Polymer)
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Open AccessFeature PaperReview Decorating Nanoparticle Surface for Targeted Drug Delivery: Opportunities and Challenges
Polymers 2016, 8(3), 83; doi:10.3390/polym8030083
Received: 31 January 2016 / Revised: 25 February 2016 / Accepted: 1 March 2016 / Published: 17 March 2016
Cited by 5 | PDF Full-text (41203 KB) | HTML Full-text | XML Full-text
Abstract
The size, shape, stiffness (composition) and surface properties of nanoparticles (NPs) have been recognized as key design parameters for NP-mediated drug delivery platforms. Among them, the surface functionalization of NPs is of great significance for targeted drug delivery. For instance, targeting moieties are
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The size, shape, stiffness (composition) and surface properties of nanoparticles (NPs) have been recognized as key design parameters for NP-mediated drug delivery platforms. Among them, the surface functionalization of NPs is of great significance for targeted drug delivery. For instance, targeting moieties are covalently coated on the surface of NPs to improve their selectively and affinity to cancer cells. However, due to a broad range of possible choices of surface decorating molecules, it is difficult to choose the proper one for targeted functions. In this work, we will review several representative experimental and computational studies in selecting the proper surface functional groups. Experimental studies reveal that: (1) the NPs with surface decorated amphiphilic polymers can enter the cell interior through penetrating pathway; (2) the NPs with tunable stiffness and identical surface chemistry can be selectively accepted by the diseased cells according to their stiffness; and (3) the NPs grafted with pH-responsive polymers can be accepted or rejected by the cells due to the local pH environment. In addition, we show that computer simulations could be useful to understand the detailed physical mechanisms behind these phenomena and guide the design of next-generation NP-based drug carriers with high selectivity, affinity, and low toxicity. For example, the detailed free energy analysis and molecular dynamics simulation reveals that amphiphilic polymer-decorated NPs can penetrate into the cell membrane through the “snorkeling” mechanism, by maximizing the interaction energy between the hydrophobic ligands and lipid tails. We anticipate that this work will inspire future studies in the design of environment-responsive NPs for targeted drug delivery. Full article
(This article belongs to the Special Issue Computational Modeling and Simulation in Polymer)
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