Symposium 8 Modeling and Simulation · Polyester coextruded films are coated on a steel laminate...

Section II – Abstracts

Page II.138 PPS-24 – The Polymer Processing Society 24th Annual Meeting – June 15-19, 2008 Salerno – Italy

Symposium 8 Modeling and Simulation


PPS-24 – The Polymer Processing Society 24th Annual Meeting – June 15-19, 2008 Salerno – Italy Page II.139

S08-125

Simulation of Poly-Tetra-Fluoro-Ethylene (PTFE) Paste in Contraction Flows Mitsoulis Evan 1, Hatzikiriakos Savvas G 2

1 NTUA, 2 UBC - Vancouver - Canada [email protected]

A constitutive rheological equation is proposed for the paste extrusion of polytetrafluoroethylene (PTFE) that takes into account the continuous change of the microstructure during flow, through fibril formation. The mechanism of fibrillation is captured through a microscopic model for a structural parameter, χ. This model essentially represents a balance of fibrillated and unfibrillated domains in the PTFE paste through a first order kinetic differential equation. The rate of fibril formation is assumed to be a function of the strain rate and a flow type parameter, which describes the relative strength of straining and rotation in mixed type flows. The proposed constitutive equation consists of a shear-thinning and a shear-thickening terms, the relative contribution of the two being a function of χ. Finite element simulations using the proposed constitutive relation predict correctly the variations of the extrusion pressure with the apparent shear rate and die geometrical parameters.

S08-679

Direct simulation of coextrusion instabilities Agassant Jean-François 1, Merveille Antoine 2, Laure Patrice 3, Mahdaoui Omar 1 1 Ecole des mines de Paris, CEMEF - Sophia antipolis - France, 2 Arcelor Mittal - Maizieres - France, 3 Laboratoire

J.A.Dieudonné - Sophia antipolis - France [email protected]

Polyester coextruded films are coated on a steel laminate for packaging applications. The PET film is composed of two layers: a thin one that insures adhesion to metal and a thick one for mechanical properties and food compatibility.The first PET presents a viscoelastic behaviour as the second one is purely Newtonian.The two polyester resins are first melted in separate single screw extruders, then assembled in a feed block and finally forced in a coat-hanger flat die. The resulting coextruded film is then stretched and coated on the preheated steel laminate.Depending on the relative flow rates and temperatures of the polyesters, marked instabilities may be observed at the interface between the two polymers (they appear just at the die exit) which leads to unacceptable products.First, we performed a 3D computation of a single polymer flow within the complex die geometry. Purely viscous and viscoelastic constitutive equations have been accounted for as well as thermo-mechanical coupling. The computed pressure drop in the die is in agreement with experimental measurements. The 3D computation points out that the velocities take maximum values both in the feeding zone and in the final lip of the die where flow is bidimensionnal. This allows developing 2D time dependant computations in these two zones, using a Newtonian behaviour for the thick layer and a viscoelastic Maxwell multimode behaviour for the thin one.In the feeding zone, all the perturbations will vanish along the feeding section as, in the final part of the die; they will develop or vanish depending on the flow conditions. The numerical results are in quantitative agreement with experiments performed on a lab scale coextrusion packaging machine.These promising results allow now to optimize both processing conditions and die geometry in order to postpone the occurrence of the defect.



S08-739

Numerical simulations of concentrated viscoelastic suspensions in an elongational flow D Avino Gaetano 1, Maffettone Pier Luca 1, Hulsen Martien A 2, Peters Gerrit WM 2

1 Department of Chemical Engineering, University Federico II of Naples - Naples - Italy, 2 Department of Mechanical Engineering, Eindhoven University of Technology - Eindhoven - The Netherlands

[email protected]

Stretching of polymer melts is quite common in several industrial processes like thermoforming, fiber spinning and blow molding. Thus, the elongational viscosity of polymers plays a crucial role in predicting the properties of the final products. The presence of an inclusion locally modifies the imposed elongation flow fields and hydrodynamic interactions between particles arise. Experimental observations showed that, by adding particles into the fluid, the strain hardening phenomenon is partially suppressed. In addition, when the particles are sufficiently large, the hydrodynamic effects dominate.In order to predict the observed features we have developed a numerical model of planar elongational flow accounting for viscoelasticity of the suspending fluid.The numerical scheme is based on recent numerical techniques to improve the convergence and stability of the computations at high Weissenberg numbers. The hydrodinamic interactions are taken into account and a fictitious domain method is implemented, to easily manage the particle motion.The microscopic structure of the suspension has been investigated and the impact of the presence of inclusions on the local fields is analyzed. In particular, for high Weissenberg numbers, highly oriented stretched regions are observed: polymer molecules tend to align along these directions. These predictions give useful insights in processes where the molecule orientation plays a crucial role, such as crystallization. Furthermore, our simulations show an increasing bulk elongational viscosity with the Weissenberg number as well as with particle area fraction. However, the strain hardening decreases if the particle area fraction increases, in qualitative agreement with the behavior seen in experiments.

S08-943

A finite element based methodology for solving moving boundary problems with large deformations in complex geometries:

Applications in polymer processing and rheology Tsamopoulos John 1, Dimakopoulos Ioannis 1 1 University oi Patras - Patras - Greece

[email protected]

We have developed a quasi-elliptic set of PDEs for generating a boundary-fitted discretization mesh that conforms to an entire even multiply connected domain, which is occupied by the fluid that undergoes large deformations. Key ingredients for the success of the proposed transformation are limiting the orthogonality requirements on the mesh and employing an improved node distribution function along the deforming boundary through the penalty method. Then, the physical domain is mapped onto a computational one where a fixed computational mesh is generated. Successive local mesh refinements can be performed, as an interface is approached, by splitting each rectangular element into four using a strip of transition elements. So, a much finer mesh near the deforming interface is generated, while computational time and memory requirements are reduced. The resulting algebraic equations are solved simultaneously using the Newton-Raphson method. The Jacobian matrix in each iteration is stored in Compressed Sparse Row (CSR) format and the linearized system is solved by Gaussian elimination using PARDISO, a direct, sparse-matrix solver,We have applied this method successfully to several complex problems with moving boundaries, but we will present here only the following:1. The transient extension of a viscoelastic filament containing a number of deformable bubbles along its axis of symmetry. Such bubbles (or cavities) are experimentally observed to develop either in the bulk or at the interface with the substrate of a pressure sensitive adhesive, often leading to fibrillation and severely affecting its adhesion properties. 2. The buoyancy-driven steady rise of a bubble in a Viscoplastic fluid using the Papanastasiou model. Unyielded material always exists away from the bubble, and, under certain conditions, either behind it or around its equatorial plane in contact with the bubble. As the Bn number increases, the unyielded domains merge and the bubble gets entrapped.



S08-1234

Finite Element Analysis of Multilayer Coextrusion Rao Rekha R. 1, Baer Thomas A. 2, Schunk P. Randall 1, Lenhart Joseph L. 1, Mondy Lisa A. 1 1 Sandia National Laboratories - New Mexico - USA, 2 Proctor and Gamble - Ohio - USA

[email protected]

Multilayer coextrusion has become a popular commercial process for producing complex polymeric products from soda bottles to reflective coatings, and even ceramic structures where a sintering step is added to burn out the polymer from the ceramic paste. A numerical model of a multilayer coextrusion process is developed based on a finite element discretization and an arbitrary-Lagrangian-Eulerian (ALE) moving mesh implementation to understand the moving boundary problem associated with the polymer-polymer interface. The goal of this work is to have a numerical capability suitable for optimizing and troubleshooting the coextrusion process and circumventing flow instabilities such as ribbing, barring and variable layer thickness. Though these instabilities can be both viscous and elastic in nature, for this work a Newtonian description of the fluid is used. Models of varying degrees of complexity are investigated. A 2D linear stability analysis is undertaken to elucidate possible ribbing instabilities, while a 3D stability of a 2D flow is used to determine if barring instabilities will be a problem. In addition, a full 3D model was built to examine a die design that would allow for offset between the coextruded layers.* Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under Contract DE-AC04-94AL85000.

S08-102

Interplay of Elasticity and Inertia and the Role of Vorticity Type Change in Enhancing Heat Transfer in Tube Flow of Non-Linear

Viscoelastic Fluids Siginer Dennis A. 1, Letelier Mario F. 2 1 Petroleum Institute - Abu Dhabi - United Arab Emirates, 2 Universidad de Santiago de Chile - Santiago - Chile

[email protected]

Heat transfer enhancement in steady pressure gradient driven laminar flow of a class of non-linear viscoelastic fluids in straight tubes of non-circular cross-section at constant temperature is discussed together with the flow structure. The variation of the average Nusselt number Nu with the Weissenberg Wi and Reynolds Re numbers in cross-sections with n axes of symmetry is analyzed. Heat transfer enhancements represented by average Nusselt numbers of an order of magnitude larger as compared to their Newtonian counterparts are predicted as a function of the Reynolds and Weissenberg numbers. The implications on the heat transfer enhancement of the change of type of the vorticity equation is discussed in particular for slight deviations from Newtonian behavior where a rapid rise in enhancement seems to occur as opposed to the behavior for larger values of the Weissenberg number where the rate of increase is much slower. The coupling between viscoelastic and inertial nonlinearities is crucial to enhancement. Fluid vorticity will change type when the velocity in the center of the tube is larger than a critical value defined by the propagation of the shear waves. The physics of the interaction of the effects of the Elasticity E, Viscoelastic Mach M, Reynolds Re and Weissenberg Wi numbers in generating the heat transfer enhancement is discussed.



S08-141

Surface tension effect on micro injection molding Cao Wei 1, Hassager Ole 1, Wang Yanwei 1 1 Danish Polymer Centre - Lyngby - Denmark

[email protected]

We developed a program to investigate the surface tension effect on the filling pattern of micro injection molding. The governing equations are in terms of non-isothermal viscoelastic fluid. The surface tension, defined by Young-Laplace equation, is also accounted in the momentum equation. The conventional FEM is employed to solve the Navier-Stokes problem and thermal problem. The simulated results show that the surface tension plays an important role on the filling of micro scale features (character length ≤20 μm), driving more 50% of the melt volume into the cavity. At the initial filling stage of micro cavity, the pressure driven mode is changed to surface tension driven due to dramatic change of shear rate. Then the flow rate contributed by surface tension drops as the temperature decreases, the melt flow comes back to pressure driven mode. As the melt elongates inside the micro cavity, the velocity profile changes from parabolic to wave shape and then tends to flat as a result of competition between surface tension and pressure. For macro parts (character length ≥ 0.5 mm), on the other hand, the surface tension is considerably smaller than the melt stress and contribution to the flow rate is much less than the pressure gradient, which leads the velocity profile of melt front maintaining the parabolic pattern. Simulations with various process conditions show the value of surface tension closely depends on flow rate, melt and mold temperature.

S08-164

Integrative interconnection of design, calculation and simulation for dimensioning a flow channel in polymer processing Wortberg Johannes 1, Saul Kenny 1, Lupa Norman 1

1 Universität Duisburg-Essen - Nordrhein-Westfalen - Germany [email protected]

Due to the Fact, that currently no continuous software environment to design and optimize a flow-channel for polymer processing is available, this research project was initiated. At present, an optimization process for a flow-channel begins with a CAD-model. This model is the starting geometry to simulate the polymer flow with CFD-tools. Based on the outcomes of this simulation, intelligent appendages for optimization have to be found by the user and transferred into the CAD-model. The Institute for Product Engineering has created a software tool, which enables automatic optimization of the start-geometry by moving the nodes of the mesh to reduce the gradients of physical values such as the flow-rate or the pressure-curve. Actual this solution only in theory leads to an enhancement whereas in practice this “optimization” often causes manufacturing problems. Currently existing integrations of CAD and CFD (Fluent for Catia) only enable accessibility to the mentioned physical values, but in this research project the focus is set on other values like the shear rate or the wall shear stress because of their higher relevance for polymer flow. To realize completely integrated product engineering, a virtual product model has to be coupled fully with a computational fluid dynamic simulation. Therefore, the content of this research project is the development of such a coupling-tool, which is able to determine the optimal flow-geometry by means of defined optimization-criteria, like the shear-rate or the wall shear stress. In this process, the modification of the start-geometry is restricted by limits of the manufacturing technologies. The main advantage of this procedure is, that the geometry keeps its basic origin topology wherein the manufacturing restrictions are considered consequently and which results in an optimized CAD-model. Further, there is no need to change the software environment from CAD to CFD, because the tool assumes this step entirely.



S08-228

Radical-like polymer chain generation of nanostructured copolymers by coarse-grained Molecular Dynamics simulations Leonforte Fabien 1, Perez Michel 1, Lame Olivier 1

1 MATEIS - INSA Lyon - Villeurbanne - France [email protected]

An innovative coarse-grained Molecular Dynamics method is proposed with the principal aim to simulate realistic block copolymers. This method is largely inspired by radical chemical ``polymerization'' experiments. The model consists essentially in a molecular-dynamics algorithm during which relaxation is performed simultaneously while chains are generated. In order to compare static properties of obtained polymer melts with classical generation methods, this generation algorithm is also supplemented by a relaxation part. As a first step, we thus describe the properties of this method by simulating the generation of pure polymers melt containing small to large monomers units. Then, systems are tested according to the well known classical Fast Push Off (FPO) method from Auhl et al. (J. Chem. Phys., 119, 12718 (2003)), validating this new algorithm and pointing out advantages inherent to it. Finally the applicability of this radical-like polymerization technics is discussed for generating nano-structured polymers, namely diblock and triblock copolymers whom which static and dynamical properties are studied to validate our approach. As a last stage, mechanical solicitations are then imposed on such systems in order to study their elastic and plastic response, compared to experiments developed in our research group on oriented PS-PI-PCHD triblock. A particular interest will be attached on the role of binder chains at interface separating each phase, on such mechanical properties.

S08-244

A Dispersed Melting Model with Consideration of the Solids Temperature Profile and its Experimental Verification Potente Helmut 1, Schöppner Volker 1, Kloke Philipp 1, Thümen Anne 2

1 Institut für Kunststofftechnik - University of Paderborn - Germany, 2 BASF Aktiengesellschaft - Ludwigshafen - Germany

[email protected]

Today, several disperse melting models for tightly intermeshing co-rotating twin screw extruders exist. They have in common that they do not consider the temperature profile within the individual pellet. In this paper a melting model is presented that considers the developing temperature profile within the solid particle. The simulation results of the new model are compared to the results of a previous model and as well to experimentally evaluated data.



S08-590

Flow induced polymer crystallisation using concentrated suspension theory Boutaous Mhamed 1, Nadia Brahmia, Matthieu Zinet 1, Bourgin Patrick 2, Zinet Matthieu 1

1 INSA Lyon - Villeurbanne - France, 2 Ecole Centrale Lyon - Lyon - France [email protected]

There are numerous studies devoted to the polymer crystallization under flow - a topic of utmost importance in polymer processing area. One issue is the necessity to improve the modeling of shear/extensional experimental data by relating the crystallization accelerating factors to an easily accessible material related variable. Several authors modeled the effect of the flow on the crystallization kinetics by using the isokinetic approach of Nakamura. Often, the resulting kinetic equations of these models account only for the evolution of the crystalinity fraction a, leaving the influence of crystalline morphology aside. We may quote the work of Guo (2001) which connects the flow influence on the crystallization rate to the increase in the thermodynamic melting temperature in the Nakamura model. In 2005, R.I.Tanner presented a comparison of some models describing the polymer crystallisation at low shear deformation rates under isothermal conditions. Based on Tanner's study, we developed a model of crystallization at low shearing, applied to non-isothermal flows, using only macroscopic measurable parameters. The key features of concentrated suspension theory were used to characterize the effect of crystallization on the viscosity. In addition, we assumed that the flow generates additional crystallization germs via a parameter which combines the deformation and the rate of deformation. The concept of germination-growth is introduced using the fundamentals of the Avrami-Kolmogorov theory, coupled with the Schneider’s approach. The model is applied to a polypropylene, in a cooled Couette flow configuration. The results show the enhancement of the crystallinity due to the shear rates. The competition between to thermal and the flow effect is then presented and discussed: at low cooling rate the shearing effect predominates. Other interesting result show the size distribution of the spherolites as well as the volumes proportion for each crystalline size in the polymer

S08-607

On punsalting Flow of a complex liquid. (Bautista-Manero Model) Herrera Valencia Edtson Emilio 1 1 UNAM - México D,F - México

[email protected]

In this article the rectilinear pipe flow of a complex liquid under a time-dependent pressure drop is considered. The fluctuating component of the pressure drop is asumed to be small amplitude and can be represented by a weakly stationary sthocasthic process. Perturbation solution are developed for a model consisting of the codeformational Maxwell constitutive equation coupled a to a kinetic equation to account for the breaking and reformation of structure. It is shown that the percentage increases in the mean fow rate rises with increasing frequency of fluctuation. Finally, the resonance effect reported in some sets of data by N.Phan-Thien, Mena et al, can be explained by the coupling between the elasticity-structure and the shear-thinning properties of the fluid.



S08-621

Impact and spreading of a droplet on the solid substrate with inertia Jeong Hyun Jun 1, Hwang Wook Ryol 1, Kim Chongyoup 2 1 Gyeongsang National University - Gyeongsangnamdo - South Korea, 2 Korea University - Seoul - South Korea

[email protected]

We present a direct numerical simulation technique for the low inertia impact and spreading of a droplet on the solid substrate. The motivation is industrial inkjet printing that has become an acceptable technology for delivering a small amount of materials to a desired position in the wide variety of applications such as the flat-panel display, PCB and manufacturing DNS chips. The inkjet printing is the process of drop formation and the subsequent impact on a solid or a liquid surface and it is considered complex in nature even for a single homogeneous liquid as an immiscible fluid. In this regard, we consider the impact spreading of a micron-size droplet that just after hits on a flat solid surface. We used a fixed Eulerian mesh for the whole computation. Inertia is applied on an initially stationary droplet just for one time step for acceleration to achieve a certain initial velocity. We used 2nd-order Adams-Bathforth / Crank-Nicholson method (AB2/CN) to solve the Navier-Stokes Equation. We employed the level-set method (LSM) with the continuous surface stress (CSS) for description of droplet spreading with the surface tension. We focus in this work on 2D and axisymmetric droplet problem on a solid surface. We present droplet spreading and rebounding on the solid surface. Reynolds number has been turn out to be important during the spreading and recoiling. We present 2D and axisymmetric results by comparing deformation of shape and/or other quantities such as averaged fluid velocity and averaged shear rate by changing the effect of Reynolds number and the effect of viscous ratio.This work has been supported by 2nd stage of BK21 and NURI project.

S08-734

High Strength Polymers - Finite Element Analysis of Fibre Reinforced Solid Phase Oriented Materials Caton-Rose Fin 1, Alkoles Omar 1, Hine Pete 2, Ward Ian 1

1 University of Bradford - W Yorks - UK, 2 University of Leeds - W Yorks - UK [email protected]

Combining molecular orientation with short glass fibre reinforcement it has been shown that significant improvements in material stiffness in the direction of orientation can be achieved1. Molecular orientation within these studies was achieved by a small scale die drawing process 10 oC below the melt temperature of a composite material. The initial drawing billet being injection moulded so that preferential fibre alignment in the draw direction was achieved during the injection stage. This initial investigation has now been extended to consider the motion of individual fibres during the die drawing process using macroscopic and microscopic finite element models validated via image analysis of actual drawn components. Within this paper we will demonstrate the modelling route to achieve microscale predictions of fibre orientation based on a macroscopic analysis of the complete component using both predicted and measured fibre orientation data.



S08-794

Numerical modelling of dip-coating process Rélot Emmanuelle 1, Bikard Jérôme 1, Navard Patrick 1 1 Ecole des Mines de Paris - CEMEF - Sophia-Antipolis - France

[email protected]

Dip-coating process is a common process, largely used in industry for manufacturing gloves, breast implant, condom, for example. The purpose of this project is to model dip-coating process using a 3D numerical modelling performed on Forge®, software developed by CEMEF and commercialised by Transvalor S.A. A first investigation [1], based on the Enthalpy Method, was carried out using Forge® but due to strong assumptions, non physical results were obtained, consequently this model needed to be developed in order to be usable in the cases studied in this project. Modelling considers a cylindrical mould which is dipped into a liquid polymer bath at a constant speed extracting a thin layer of material. The objective is to predict the thickness of the fluid layer attached on the mould. The mechanical and thermal balance equations are solved in the bath using a Finite Element Lagrangian approach with remeshing technique. A pseudoplastic rheology is used as a first approximation. The interfacial tension liquid/air is taken into account in order to avoid surface instabilities; the method used to implement interfacial tension in the modelling is based on the reformulation of the curvature with Laplace-Beltrami operator. The results show that the thickness is heterogeneous along the mould: maximal at the bottom and minimal at the top. The shape at the tip shows a re-entrance geometry, that is seen when comparing the results with experimental data, performed with a custom-made machine, only in the case of a purely viscous fluid.[1] Bikard J, De Oliveira J., Chaudemanche C., Budtova T. « 3D numerical modelling of a dip-coating process by a multidomain macroscopic approach”, Int. J. of Material forming, 10(3),2007, 337-359

S08-806

Integrative Simulation of blown film formation with interacting cooling airflow Bussmann Markus 1, Wortberg Johannes 1

1 University of Duisburg-Essen - NRW - Germany [email protected]

Increasing the capacity of a blown film line is the major task to gain a more efficient production plant. Still the film cooling system is the device which sets the upper limit for the whole plant. Developments in the recent past have shown that special suited designs of airflow guiding systems have the ability to increase the throughput of the whole extrusion line dramatically. Nowadays the optimization of such systems is only possibly due to a great amount of trials and experiments, which are not suitable for industrial application. Therefore the main aim must be to better understand what causes and influences those regions of negative pressure. Due to this, an integrative computational model to predict the bubble shape has been developed, taking into account the interaction of the cooling air flow and the molten polymer. It is based on an iteration process which contains the linkage between the bubble deformation and its interaction with the air flow. Thus the calculation algorithm has been linked with a CFD-Program in an iteration circle. This iteration calculation is performed until the film contour converges to a final shape. The major goal is to gain a better knowledge of the stretching processes and the interaction between the bubble shape and the airflow. This is intended to lead to parameters and characteristics, which allow the prediction of suitable guiding designs for varying polymers or for example for varying ABVs.



S08-818

Numerical Simulation of Mechanical Properties of Cellular Materials Using Computed Tomography Analysis Fischer Frank 1, Lim Goy Teck 1, Altstädt Volker 1

1 Department of Polymer Engineering - Bayreuth - Germany [email protected]

Foam simulations often suffer significant shortcomings of the over-simplification in the modelling of cell structures and neglecting the inhomogeneity of cell sizes. Hence, there is a strong needs to create finite element (FE) meshes that can realistically describe the cell morphology and the variation in cell sizes. For this, computed tomography (CT) can be aptly applied to generate three-dimensional volumetric data in an accurate but non-destructive manner. This paper presents a novel approach to transfer the cell morphological data obtained by CT to create realistic FE meshes for numerical simulation to predict the mechanical properties of foams. In this integrated approach, CT analysis was first performed to yield a quantitative evaluation of cell structures and the size distribution of the foams. The CT information was then applied to build FE meshes using a tessellation of modified Kelvin cell units or truncated octahedra of various cell sizes as described by the cell size distribution. Furthermore to fully capture the heterogeneous nature of the cell morphology, a coordinate method was proposed herein to directly use the cell coordinates and diameters from the CT analysis to create a “truly realistic” FE mesh, which has the capability to map out cell inhomogeneity like large pores. FE simulations were performed using these meshes to predict the compressive behaviour of polymer foams and the generated numerical results showed a good agreement with experimental data.

S08-981

Simulating injection moulding of micro featured components Tofteberg Terje 1, Andreassen Erik 1 1 SINTEF Materials and Chemistry - Oslo - Norway

[email protected]

In this work we present simulations of the filling phase of injection moulding of products with micro features. The products are typicallycredit card sized with micro features on the size scale 0.1 – 100 µm.These features will in general be too small to be included in afilling simulation of the complete part. We will discuss howsimulations can be coupled between the macroscopic scale of the partand the microscopic scale of the features in order to correctlydescribe the filling pattern, with special emphasis on the microfeatures. The simulations are performed in the framework of ageneralized Newtonian model and we will discuss how the assumptionsmade in this model influence the degree of filling.



S08-1170

A force field for layered silicates and simulation of interfaces with surfactants: Structure, surface energy, and phase transitions Heinz Hendrik 1

1 University of Akron - Ohio - USA [email protected]

The derivation and validation of an all-atom force field for layered silicates (mica, montmorillonite, and pyrophyllite) is presented. Particular challenges to obtain a semiempirical energy model reproducing the crystal structure and surface energy include the assignment of atomic charges and of van-der-Waals parameters, which were addressed by X-Ray measurements of the electron deformation density, an extended Born model to determine atomic charges, and a physically meaningful interpretation of atomic polarizabilities. Experimentally determined surface energies as well as their partition in polar and dispersive contributions are quantitatively reproduced by the force field in molecular dynamics simulation, down from deviations of up to 500% in earlier models. The parameters are implemented/compatible with various energy expressions (PCFF, CVFF, CHARMM, GROMACS). The model has been applied to study the self-assembly of an extensive series of alkylammonium surfactants on montmorillonite and mica surfaces, phase transitions upon heating, as well as the interaction energy between the silicate sheets and surface reconstruction upon separation as relevant for exfoliation in clay/polymer nanocomposites. The simulation aids in the molecular-level interpretation of available XRD, NMR, DSC, IR, and NEXAFS data, and agreement with directly comparable data (basal plane spacings, phase transition temperatures, trans/gauche ratio in chain backbones) will be shown. In particular, the conformational analysis of the surfactant molecules, effects of hydrogen bonding of primary ammonium head groups to the surface, and the process of separation of the clay sheets are explained.A relationship between the packing density and thermal transitions of alkyl chains on layered silicate surfaces was identified on the basis of experimental characterization and simulation, using the ratio of cross-sectional area of the alkyl chains to the available surface area per alkyl chain as parameter.

S08-1224

Evolution of part geometry and temperature during deposition of filaments in Free Form Extrusion Costa Sidonie Fernandes 1, Duarte Fernando Moura 1, Covas José António 1

1 University of Minho - Guimarães - Portugal [email protected]

Free form extrusion, FFE, is a 3D fabrication process which has evolved from rapid prototyping technology, whereby an extruded polymeric filament follows a specific route in the X–Y plane and is deposited onto the previous layer, according to the geometry of the part to be manufactured. After production of this layer, the support moves vertically in order to produce a new layer, the process being repeated until the entire part is obtained. Effective bonding between adjacent filaments is mandatory for making parts with adequate mechanical performance. Thus, upon deposition, each filament must be sufficiently hot. This is supported by keeping the global system in a heated enclosure. Conversely, temperatures may not be too high, otherwise deformation due to gravity may be excessive. The filaments cross-section and their packing mode affects the free space generated, which has to be filled in for the purposes of obtaining a homogeneous part. Given the above, it is important to know the evolution of the part geometry and temperature along the deposition sequence. Such information may be used directly to assess bonding quality and tolerances level, or set the most appropriate operating conditions, namely, oven temperature, extrudate temperature, extrusion rate, deposition sequence, packing mode.This work investigates the effect of the above variables in terms of heat transfer and mechanical deformation. The simulations were performed using the Abaqus software and realistic boundary conditions.



S08-1230

Neural Network-Based Closure Approximation for Short-Fiber Suspension Simulations Smith Douglas Earl 1, Jack David Abram 2

1 University of Missouri at Columbia - Missouri - USA, 2 FSU - FAMU, Tallahassee, FL - Florida - USA [email protected]

Mold filling simulations that predict fiber orientation in short fiber composites employ orientation tensors to reduce the computational burden. Unfortunately, solving any even-order orientation tensor equation requires the next higher even-order tensor to determine a solution. Many closure approximations have been proposed to write, for example, the fourth-order orientation tensor aijkl in terms of the second aij. A few others have appeared that approximate the sixth order tensor. Today it is common to employ an analytical closure such as the Hybrid during a flow simulation due to its computational efficiency, and then use a more accurate, and computationally expensive fitted closure, such as the Orthotropic Fitted or Invariant-Based Fitted, to compute material properties.This paper presents a new class of fitted closure based on Neural Networks (NNET). The NNET closure defines the 9 independent components of aijkl in terms of the 5 independent components of aij through a two layer neural network. This relationship provides a very general representation of the closure function that is computationally efficient due to the linear nature of the functions employed. A brief background of neural networks is provided, followed by the specific form used in this research. The neural network training procedure is described which focuses on the generation of training data and its use in ensuring that the NNET closure is as objective as possible. As with other fitted closures, exact orientation tensors are generated by solving the orientation distribution function evolution equation for multiple homogeneous flows. The NNET closure is then compared to the Hybrid and Orthotropic Fitted closures for various flow conditions which include simple homogenous flows, combined flows, and center-gated disk flows. Overall, the NNET closure is shown to be at least as accurate as the Orthotropic Fitted closure while being only slightly more computationally expensive than the Hybrid.

S08-1232

A Multi-Gauss Point Finite Element Approach for the Predicting Elastic Properties of Short Fiber Composites Smith Douglas Earl 1, Caselman Elijah C. 1

1 University of Missouri at Columbia - Missouri - USA [email protected]

A critical link between short fiber composite melt flow simulations and the evaluation of a product’s mechanical response is the prediction of elastic properties where properties are evaluated from mechanical properties of the fiber and matrix, and the fiber orientation state. Boundary element methods and large scale finite element models have been employed to evaluate the complex micro-structural response of fiber-filled composites. These solution methods, which require specialized programs, large scale computations, and/or complex meshing algorithms, have been shown to give results comparable to established closed-form solutions. This paper presents a new finite element-based approach that employs uniform regular meshes of multi-Gauss point 3-dimensional elastic elements. Our approach defines material properties within each element based on integration point coordinates as referenced to the composite’s microstructure. Spatial fidelity is increased by adding Gauss points in each element rather than increasing the number of degrees-of-freedom in the global system of equations. Special shape functions are defined to allow for a complex deformation field within each of the three-dimensional eight node rectangular brick elements. A representative volume element (RVE) approach is employed with periodic boundary conditions to further reduce the computational domain. Multiple load cases are solved to obtain all normal and shear components of the elasticity tensor. A fitting procedure is developed to define the elasticity tensor as isotropic, transversely isotropic, orthotropic, or anisotropic. Examples are given which illustrate the effectiveness of the calculations which include continuous long fiber, aligned short fiber, and randomly oriented short fiber composites. This approach is shown to provide a good estimate of the elasticity tensor components where computed results are shown to agree well with published data and other more complex finite element calculations.



S08-1351

THE EFFECT OF WALL SLIP IN CONTRACTION FLOWS Ferrás L 1, Carneiro O. S. 1, Pinho F. T. 1, Nóbrega J. M. 1 1 University of Minho, Campus de Azurém - Guimarães - Portugal

[email protected]

It is well known that some fluids exhibit a discontinuity in the velocity field near the flow channel walls, suggesting the existence of slip [1]. In order to account for this issue, a computational rehology code based in the Finite Volume Method was recently modified through the implementation of appropriate boundary conditions. Thus, the usual Dirichlet and Neumann boundary conditions usually applied for the no slip and free slip behaviour were switched by a relationship between the tangent velocity and the tangent stress vector of the fluid near the wall. The validation of this numerical code was done in a previous work [2]. In this work a numerical study is performed in order to evaluate the effect of the wall slip boundary condition in the flow in a 4:1 contraction. The study will be performed both with generalized Newtonian and viscoelastic fluids, employing different slip models. The results obtained will be compared with data published in the literature, for the cases where no-slip is assumed or other slip models are adopted. The runs already performed showed that the occurrence of slip has a huge influence in the vortex growth. The occurrence of wall slip whether increases or decreases the vortex dimensions depending on several factors such as channel dimensions, rheological properties of the fluid and level of slip. References [1]E. Mitsoulis, I.B. Kazatchkov, S.G. Hatzikiriakos, The effect of slip in the flow of a branched PP melt: experiments and simulations. Rheol Acta 44: 418-426, 2005. [2]L. L. Ferrás, J. M. Nóbrega, F. T. Pinho, O. S. Carneiro, “Optimisation of profile extrusion dies: the effect of wall slip”, 23th Annual Meeting of the Polymer Processing Society, PPS-23, Salvador, Brazil, 2007

S08-1399

The optimization of petaloid base dimensions for injection stretch blow moulded PET bottles. Demirel B. 1, Daver F. 1, Kosior E. 2

1 RMIT University, School of Aerospace, Mechanical and Manufacturing Engineering - Bundoora, Victoria - Australia, 2 Nextek Ltd - London - United Kingdom

[email protected]

The base of poly (ethylene terephthalate) (PET) bottles for carbonated soft drink commonly has the so-called petaloid shape, which gives the bottle very good stability. However, petaloid bases are prone to stress cracking particularly during hot summer months. In this study, computational methods are used to optimise the dimensions of the petaloid base with respect to stress cracking resistance and simulation modelling is used to optimise injection stretch blow moulding process parameters.



S08-130

Numerical Investigation of Normal Forces and Die Swell Ratio in Circular Die of Viscoelastic Fluids RAMAZANI S.A. Ahmad 1, Kanvisi Mojtaba 1

1 Sharif University of Technology - Teharn - Iran [email protected]

To determine die swell ratio in circular die, flow of Leonov like conformational rheological models has been solved for creeping flow of theses fluids in this geometry. Distribution of shear rate and the first and the second normal force differences for the mentioned rheological models with different mobility tensors are compared. Using the first and the second normal stresses differences calculated at wall in Tanner’s correlation, die swells for different rheological models have been also obtained. Comparing predicted die swell results with the presented experimental results in the literature shows that model predictions can cover a wide range of die swell behavior generally observed for polymer melts and solutions in circular die steady shear flows. So, it seems that these conformational rheological models in addition to simple shear free flow which already investigated, can predict behavior of polymeric fluids in other shear flow too.

S08-140

Nascent Polymerized Chain Crystallization on Surface Simulated by the Growing Chain Molecular Dynamics Yang Xiao Z 1, Mao Wei 1

1 Institute of Chemistry, CAS - Beijing - China [email protected]

To understand nascent structure of polymerized chain on a catalyst surface, we have developed a code of growing chain molecular dynamics (GCMD), which describes aggregation behavior of growing chain with increase of repeat units during polymerization. This simulation shows that on the surface the growing chain has a nucleation process before certain chain length and an ordered structure growth process. Meantime, chain folding behavior was surprisingly observed.



S08-162

Overview of Free Radical Polymerization of Styrene usingTrifunctional Initiator Ferrareso Lona Liliane Maria 1, Machado Paula Forte de Magalhães Pinheiro B. 1

1 UNICAMP - Campinas- SP - Brazil [email protected]

The study of chemical initiators that have functionality superior than two has been explored in the scientific and industrial field. This type of initiator is able to increase the reaction rate in a free radical polymerization without decrease the molecular weight of the formed polymer. Besides that it can also generates branches in the polymeric chain, changing the polymer structure. Some works in literature show experimental and simulation studies related to free radical polymerization using bifunctional initiators. Machado and Lona (2005) present mathematical models to free radical polymerization of linear (polystyrene) and branched (polyvinyl acetate) polymer using bifunctional initiators. The complexity of the kinetic mechanism increases as the functionality of the initiator increases. There are very few studies presenting models of free radical polymerization using initiators with functionality superior than two (Scorah, 2005 and Scorah et al., 2007). To better understand the behavior of initiators with functionality greater than two, trifunctional initiators were chosen to be studied as the next steps of a free radical polymerization using bifunctional initiator. The trifunctional initiator selected was the TRIGONOX 301 from Akzo Nobel. It is a cyclic triperoxide, very unstable at temperatures greater than 40ºC and it must be kept at room temperature. The objective of this study was to propose a kinetic mechanism and a mathematical model to free radical polymerization using a trifunctional initiator. Styrene was chosen because it is a very well known monomer and there are a lot of data about it. The mathematical model predicts results as conversion, molecular weight, PDI, radical concentration, reaction rate and polymer concentration. An experimental investigation was also explored to validate the simulations results. The experimental part followed the method of polymerization in ampoules. The validation was made to conversion, molecular weigh and PDI datas.

S08-300

THE INFLUENCE OF SIDE REACTIONS ON THE INITIATION OF NITROXIDE MEDIATED LIVING FREE RADICAL POLYMERIZATION Murari André Rodriguez 1, Lona Liliane Maria Ferrareso 1

1 UNICAMP - São Paulo - Brazil [email protected]

Living Free Radical Polimerization (LFRP) has been target of much attention in recent years, it is possible to obtain polymers with a microstructure-a highly controlled, with narrow distribution of average molecular weights and polidispersity (PDI) close a unit. Ionic polymerization also generates controlled microstructures, however the reaction conditions for ionic polymerization require high pureness, what makes it economically unviable its application in industrial processes. Nitroxide Mediated Living Free Radical Polymerization-NMRP is one alternative technique to LFRP, being not sensitive to impurities. Many researchers have developed kinetic models that predict the behavior of LFRP. By using the kinetic model developed by Mesa et al. (2003) and Bonilla et al. (2002) for the NMRP styrene, it was observed that in simulations that model kinetic deviated from experimental data mainly in average molecular weights profiles. George et al (2002) describe irreversible reactions in the initiation stage of the polymerization of styrene between the controller TEMPO (2,2,6,6 - tetramethyl-1-piperidinoxyl) and the initiator BPO (benzyl peroxide). These side reactions exercising that influence on the initial concentration of controller, are not present in the model of kinetic Mesa et al. (2003) and Bonilla et al. (2002). Based on that information, introduced in the model a factor in the efficiency of the controller-fc, and this factor was estimated in order to improve the fit between all profiles of experimental data and the model predicted. And it was possible to note significant improvement in the adjustment in all profiles. Thus, it was shown that lateral irreversible reactions in the stage of initiation exert a significant influence on NMRP kinetic model.



S08-349

Stagnation-Point-Flow of Giesekus Fluids: An Exact Solution Sadeghy Kayvan 1, Mirzadeh Mohammad 1, Sadeghi Soheil 1 1 University of Tehran, Dept. of Mech. Eng. - Tehran - IRAN

[email protected]

Exact solutions are rather rare in fluid mechanics, and this is particularly so for non-Newtonian fluids. This is why the field of computational rheology has become so active in recent years. But computer codes need to be verified first before being of any good in dealing with practical fluid mechanics problems. And, ironically, this can only be done by confronting their output with an exact analytical solution at the first place. Fortunately, exact solutions are available for simple viscoelastic fluid models such as second-order model, Walters’ B model, Maxwell model, and Oldroyd-B model. But the performance of these models is rather poor in extensional flows. Thus computer codes calibrated using such exact solutions cannot necessarily render meaningful results in flows dominated by strong extensional deformation such as those encountered in the extrusion of polymeric melts. More realistic rheological models such as Giesekus model should be relied upon when dealing with such flows. In the present work an exact solution will be reported, to the best of our knowledge for the first time, in a flow in which fluid elements are subject to strong elongational deformations, i.e., the stagnation-point-flow for a fluid obeying the Giesekus model. Numerical results obtained using Keller-Box method suggest that for Giesekus fluids the thickness of the boundary layer becomes thinner the higher the Weissenberg number. A decrease in wall shear stress is also predicted to arise by an increase in the Weissenberg number. In contrast, the first normal stress difference is expected to increase the higher the Weissenberg number. Numerical results obtained in this work can efficiently be used for calibrating current or emerging CFD codes to be used for viscoelastic fluids.

S08-351

Hydromagnetic Instability of Giesekus Fluids in Plane Poiseuille Flow Sadeghy Kayvan 1, Taghavi Seyed-Mohammad 1 1 University of Tehran, Dept. of Mech. Eng. - Tehran - IRAN

[email protected]

The effect of transverse magnetic field is investigated on the instability of Giesekus fluids in plane Poiseuille flow for small magnetic Prandtl numbers. Our approach is a classical one in which stability of flow to small, two-dimensional disturbances will be studied using linearized theory. The system of equations so obtained will be solved using pseudo-spectral method to determine the effect of parameters such as magnetic number, Weissenberg number, mobility factor, and viscosity ratio on the least stable eigenmode. It is found that magnetic field has always a stabilizing effect on plane Poiseuille flow of Giesekus fluids. In contrast, solvent viscosity, fluid’s elasticity, and mobility factor may have a stabilizing or destabilizing effect depending on their magnitude being smaller or larger than a critical value.



S08-385

MEZOSCOPIC RHEOLOGICAL MODEL FOR LINEAR POLYMER MELTS AND SOLUTIONS AND SOME ONE-DIMENSIONAL PROBLEMS

DEVELOPMENT Rybakov Andrey 1, Gusev Alexsey 1, Pyshnograi Grigori 1, Pokrovskii Vladimir 1 1 Altai State Technical University - Barnaul - Russia

[email protected]

To interpret the relaxation behaviour of entangled linear polymers in terms of dynamics of a single macromolecule, we have been developing the approach, which allows one to study systematically deviations from the Rouse dynamics, when adding non-Markovian and anisotropic noise. It was shown earlier, that the introduction of specific form of non-Markovian dynamics leads to emerging of an intermediate length, which has the meaning of a tube radius and/or the length of a macromolecule between adjacent entanglements. The additional introduction of local anisotropy of mobility of particles allows one to get the results of the conventional reptation-tube model for both mobility and relaxation times of macromolecular coil and, beyond it, to estimate a transition point between weakly (the length of macromolecules M < 10 Me, no reptation) and strongly (the length of macromolecules M > 10 Me, reptation) entangled polymer systems. The adequate mesoscopic equation allows us to develop theory of different relaxation phenomena, in particular, a theory of viscoelasticity and to formulate constitutive equations for linear polymers, which, due to the difference of mechanisms of relaxation, appear to be different for the two types of entangled systems.The case of weakly entangled systems are. An advantage of the micro-structural approach is the possibility of studying the relationship between the micro-characteristics of a polymer system (concentration and molecular weight) and macroscopically observed quantities (viscosity, shear and normal stresses). The simple rheological model are obtained. This rheological model where good agreement between the model and the steady flows of solutions and melts of linear polymers of various molecular weights and concentrations in simple shear flow and one-axial elongation flow. Two cases of steady-state flow in a smooth circular tube and between unlimited parallel planes under the action of a constant pressure gradient are considered.

S08-386

Prediction of Heat Capacity of Polymers using ES-SWR and GA-MLR Riahi Siavash 1, Bagherzadeh Kowsar 2 1 Institute of Petroleum Engineering, University of tehran - Tehran - Iran, 2 University of tehran - Tehran - Iran

[email protected]

Heat capacity is the key macroscopic material property which is well understood to permit, when determined over a wide range of temperature, the establishment of connectionto the macroscopic structure and motion. Heat capacity of polymers is normally measured by calorimetry. Detailed discussions about measuring this property are available elsewhere [1].A new quantitative structure-property relationship (QSPR) two-parameter correlation(R2 = 0.847 and s=12.72) of heat capacity jump at glass transition temperature ( ) p g ΔC T for a diverse set of 45 polymers is developed [2]. The descriptors are all calculated directly fromthe chemical structure of repeating units of polymers, and the approach given is applicable,in principle, to all polymers of regular structure. The model was produced by using thestepwise multiple linear regressions, genetic algorithm multiple linear regressions (GAMLR)and artificial neural network. Among the 1664 different structural descriptors thatwere considered as inputs to the model, only two variables (eccentric topological andoctanol/water distribution coefficient) were selected using both the elimination selectionstepwise regression method (ES-SWR) and GA-MLR. The physical meaning of eachdescriptor is discussed in details. In compare of other models, this model has less number ofdescriptors and fits experimental data better than other previous proposed models.References:[1] Godovsky, Y.K., ""Thermophysical Properties of Polymers"", Springer-Verlag, Berlin (1992).[2] Thompson, E.V., ""Thermal Properties"", in Encyclopedia of Polymer Science and Engineering, Vol. 16,Wiley-Interscience, New York (1989).



S08-388

Mixing Analysis of Extensional Flow Mixers, EFM Najafi Mohsen 1, Reza Foudazi 1, Nazokdast Hossein 2 1 Polymer Engineering Department, Islamic Azad University of Mahshahr - Khuzestan - Iran, 2 Polymer Engineering

Department, Amirkabir University of Technology - Tehran - Iran [email protected]

The extensional flow mixers, EFM, were developed by Utracki and due to its great mixing efficiency, have been used as one of the most versatile static mixers in polymer industry. An attempt was made in the present work to analyze the fluid flow and mixing performance in the EFM. For this purpose the velocity field of an isothermal Non-Newtonian viscous flow was simulated based on finite volume method. The role of convergence and divergence of EFM was studied by comparing the flow analysis of EFM and fluid flow in basic geometries such as radial flow between two parallel disks. The results showed that the shear and extensional components of rate of deformation tensor in the EFM increases along streamlines. The results also demonstrated that the sinusoidal changes of extensional components of rate of deformation tensor can be regarded as the most characteristics of EFM which improves the mixing efficiency. Finally, the power consumption per unit volume and volumetric flow rate of EFM and those selected basic geometries in same pressure loss were compared.

S08-396

Measurement of pvT-data at process near cooling rates for injection moulding simulation and comparison of simulation results with

experimental data Lucyshyn Thomas 1, Langecker Guenter Ruediger 1, Fischer Konrad 2 1 University of Leoben - Styria - Austria, 2 Polymer Compentence Center Leoben GmbH - Styria - Austria

[email protected]

At the PPS-22 conference the principle of a new measurement device for the determination of pvT-data at higher cooling rates, which had been developed at the Institute of Plastics Processing at the University of Leoben (Austria), was already presented. Contrary to the standard method, where a cylindrical specimen is cooled under pressure in order to measure the specific volume, the sample of the new measuring apparatus is a flat disc, where the heat can be carried off very fast - comparable to the conditions in an injection mould. The sample thickness can be varied, which has direct influence on the cooling rate and hence also on the pvT-curve. Depending on the sample thickness, average cooling rates of up to 20 K/s were achieved, which is 200 times faster compared to standard measurement methods, where cooling rates are typically in a range of approx. 0,1 K/s.In order to investigate the influence of the pvT-data on the shrinkage and warpage prediction of the commercial injection moulding simulation programme Moldflow Plastics Insight (MPI), several simulation runs with different materials (amorphous as well as semi-crystalline) were performed using standard pvT-data as well as the pvT-data obtained by the new apparatus. For the selected materials, test parts were injection moulded and the geometries of those real parts were digitized using the optical 3D-scanner ATOS II SO (GOM / Germany). After that, the digitized geometries of the deformed real parts were overlaid and compared with the corresponding simulation results, which allows a quantitative evaluation of the influence of the pvT-data on the accuracy of the shrinkage and warpage prediction with MPI.



S08-424

Prediction of the particle size distribution in the shear and elongational flow fields using modified population balance equations behzadfar ehsan 1, salami hosseini mahdi 1, nazockdast hossein 1

1 Amirkabir University of Technology - Tehran - Iran [email protected]

Suspensions and colloids are among important systems which play a significant role in various processes, such as polymerizations, polymer mixing and biological processes. In such systems, the particle size distribution and the mean particle size diameter control the behavior and properties of the system. Studying the parameters affecting the particle size distribution and the mean diameter of particles can make a better understanding of properties of these systems. In the present work, the modified population balance equations (PBEs) were solved using the non-uniform discretization scheme and considering simultaneous breakage and aggregation processes. Additionally, a comparison between the two different flow fields was performed. Furthermore, the effect of the various combinations of the flow fields has been evaluated. By increasing the extent of the elongational flow, the breakage process was hastened. On the other hand, increase of shear flow components leads to increase in both aggregation and breakage. But the breakage process increases more than the aggregation process. Therefore, the mean particle size shifts toward finer particles.

S08-427

Life Prediction of Damaged Polyethylene Gas-Pipes Raos Pero 1, Sercer Mladen 2, Tonkovic Zlatko 3 1 University of Osijek, Mechanical Engineering Faculty - Slavonski Brod - Croatia, 2 University of Zagreb, Faculty of

Mechanical Engineering and Naval Architecture - Zagreb - Croatia, 3 HEP-Plin Ltd. - Osijek - Croatia [email protected]

Keywords: polyethylene pipes, HD-PE, gas-pipelines, pipe failure, life prediction This paper deals with a new approach to life estimation of damaged thick-walled gas-pipes made of high-density polyethylene (PE-HD). The most common approaches to durability prediction of polyethylene gas-pipes rely on methods of fracture mechanics, which involve defining of a stress intensity factor experimentally. However, such tests are carried out on standardized specimens neglecting the influence of real pipe geometry and processing method (e.g. properties anisotropy as a consequence of an extrusion process). On the other hand these data are not always available to gas distributors, which are responsible for the durability of the installed pipelines. Therefore, we have been proposed a new approach aiming to obtain an empirical mathematical model for life prediction of polyethylene gas pipes on the basis of long-term experiments involving three parameters: pressure, length, and depth of crack. First results of the undergoing investigations on PE80 and PE100 pipes will be reported in the paper.



S08-467

SIMULATING CONTROLLED/LIVING FREE RADICAL POLYMERIZATION REACTOR LONA LILIANE FERRARESO 1, XIMENES JULIANA BELINCANTA 1, NOGUEIRA TELMA REGINA 1

1 UNICAMP - SÃO PAULO - BRAZIL [email protected]

Free radical polymerization has been revolutionized in recent years by the introduction of techniques that produce polymers with polydispersity index (PDI) close to 1.0 and controlled molecular weight distribution (MWD) during the polymerization process. One of these so called controlled/living methods is the nitroxide mediated polymerization (NMRP). In this work a kinetic model based on a detailed reaction mechanism for NMRP of styrene with benzoyl peroxide (BPO) as initiator is presented. The mathematical model was based on kinetic rate constants that vary with temperature. The reaction mechanism includes the following reactions: chemical initiation, monomer dimerization, thermal initiation, propagation, reversible monomeric and polymeric alkoxyamine formation (production of dormant species), alkoxyamine decomposition, rate enhancement, transfer to monomer and dimer, as well as conventional termination. The model includes several side reactions which have been found to be relevant to the detailed explanation of MWD features of the polymer formed. Data for two different temperatures (120 and 130ºC) and for a TEMPO/BPO molar ratio equal to 1.1 were obtained for model validation. Additional TEMPO/BPO ratios were tried as well. Detailed sensitivity analyses show how the kinetic constants affect model performance. It was observed that the transfer to dimer affects the molecular weight without affecting conversion. The model performs better when the transfer to dimer is not included in the model. In conclusion, the model proposed is expected to provide useful guidelines towards a better understanding of the NMRP process.

S08-496

A computational and experimental study of the highly selective recognition sites in molecularly imprinted polymer Edris tabrizi Farrin 1, Javanbakht Mehran 1, Riahi Siavash 2, Abdouss Majid 1

1 Department of Chemistry, Amirkabir University of Technology - Tehran - Iran, 2 Institute of Petroleum Engineering, Faculty of Engineerig, University of Tehran - Tehran - Iran

[email protected]

Molecular imprinting technology is a new and revolutionary way of producing recognition sites for specific analytes in synthetic polymers. MIPs are a class of smart materials with a pre-determined selectivity. This is achieved by the copolymerization of a pre-organized complex, formed between functional monomers and the target molecule (the template) with an excess of cross-linker. The polymer selectivity and affinity are related to the strength of this complex. In this work carbamazepine was chosen as the template. A computational design method enables us to select from a virtual library those monomers that interacting strongly with the template. References[1] P.A.G Cormack, A.Z Elorza, Journal of Chromatography B, 804 (2004) 173-182[2] I. Chianella, K. Karim, E. V. Piletska, Ch. Preston, S. A. Piletsky, Analytica Chimica Acta 559 (2006) 73-78[3] W. Dong, M. Yan, M. Zhang, Z. Liu, Y. Li, Analytica Chimica Acta 542 (2005) 186-192



S08-524

Thermal Properties of the P(VDF-TrFE) Copolymer in the Temperature Range from 25Cto 180C Santos Wilson Nunes dos 1, Gregorio Jr. Rinaldo 1, Wallwork Andrew 2

1 Federal University of São Carlos - São Paulo - Brazil, 2 The University of Manchester - Manchester - England [email protected]

The continuous increase in the utilization of polymeric materials in many specific applications has demanded the knowledge of their physical properties both during their processing as raw material, as well as in the overall range of the working temperature of the final polymer product. A typical example is the injection molding process, where the thermal diffusivity plays a fundamental role for the determination of the molding cycle time, while the thermal conductivity and specific heat also have the same importance for the perfect performance of a final product to be used as an insulator, or in a environment subjected to conditions where heat is continuously added or removed. Nowadays, several different techniques for the determination of such properties may be found in the literature. Some specific techniques allow their determination in the same experiment, but in most of the cases they are determined separately. Since considerable differences in properties may occur for a particular polymer as a result of thermomechanical history, crystalline phase, and its general microstructure, materials where phase transitions occur during the heating and cooling process display a non usual dependence of the thermal properties with temperature. In this work, the laser flash technique is employed in the experimental determination of the thermal diffusivity of a vinylidene-trifluoroethylene ferroelectric copolymer P(VDF-TrFE). Specific heat, determined by modulated differential scanning calorimetry, and bulk density determined by ethanol picnometry, are also experimental tasks in this work. Thermal conductivity is then derived from these properties previously determined. Measurements were carried out in the temperature range from 25 to 180oC, including during the melting process and para-ferroelectric phase transition. Keywords: P(VDF-TrFE); Thermal diffusivity; Thermal conductivity; Specific heat; Laser flash technique.

S08-530

Modelling of the Mechanical Properties of Flax Fibre/Polypropylene Composite Elsabbagh Ahmed Mohamed Moneeb 1, Steuernagel Leif 1, Ziegmann Gerhard 1

1 TU-Clausthal, PUK - Clausthal-Zellerfeld - Germany [email protected]

A new modelling approach to calculate the mechanical properties of thermoplastic matrices reinforced with natural fibres is suggested. This model aims to solve the great deviation trends observed in the fibre content out of the range of 10-40%. It considers the transfer of fibre load hand over from fibres pull out to fibre load bearing. Different cases of the matrices are studied. Namely; matrix with either elastic or elastic plastic behaviour, matrix with either brittle or ductile failure strain in comparison with the reinforcing fibre. Length and orientation efficiency factors for stiffness and strength are exploited. Another factor describing the even distribution of the fibres and the amount of corresponding matrix in adhesion is developed. The suggested model is tested against the available experimental data either out of the self made work or out of the literature results. The model shows good matching with the experimental results in a big domain of the fibre weight fraction.



S08-635

A computational investigation of the interaction between the template molecule and the functional monomer used in the molecularly

imprinted polymer and the developed selectivity Riahi Siavash 1, Edris tabrizib Farrin 2, Javanbakht Mehran 2 1 Institute of Petroleum Engineering, Faculty of Engineering, University of Tehran - Tehran - Iran, 2 bDepartment of

chemistry, Amirkabir university of technology - Tehran - Iran [email protected]

Molecularly imprinted polymer (MIP) is a recently developed material which had biomimetic molecular recognition ability. This is achieved by the copolymerization of a pre-organized complex, formed between functional monomers and the target molecule (the template) with an excess of cross-linker. After removing the template molecule, there will be left cavities complementary to the template. Because of its good recognition ability, MIP has a wide range of applications, such as chiral separation [1, 2]. The presented paper is done base on a chlorphenamine–imprinted polymer prepared to selectively separate chlorphenamine from diphenhydramine [3]. In this work, a computational design method was used to optimize and calculate the stabilization energies of the templates and monomer (Methacrylic acid(MAA)) and the complexes formed between the templates and monomer. Finally the binding energies (ΔE) of the complexes were obtained which helps studying types of interactions between the monomer and the templates and also to find out why the MIP is more selective to chlorphenamine. The calculation of ΔE was performed using density functional theory at the B3LYP/6-31+G**. Furthermore, the number of MMAs, (1 MMA or 2MMAs, etc), that simultaneously interact with the template was also investigated. References:[1] P.A.G Cormack, A.Z Elorza, Journal of Chromatography B, 804 (2004) 173-182[2] I. Chianella, K. Karim, E. V. Piletska, Ch. Preston, S. A. Piletsky, Analytica Chimica Acta 559 (2006) 73-78[3] Wen Chen, Feng Liu, Xuemin Zhang, Ke An Li, Shenyang Tong, Talanta 55 (2001) 29–34

S08-724

The Measurement Of The Thermal Conductivity Of Amorphous Polymers Above Glass Transition Temperature Dawson Angela 1

1 National Physical Laboratory - Middlesex - United Kingdom [email protected]

The polymer processing industry is sensitive to low labour cost competition. The industry needs to remain cost effective by improving efficiency when processing polymers into existing and newly developed products. Modelling is used to predict cooling times during injection moulding and to reduce them through improvements in mould design leading to shorter cycle times. For these models to be reliable the data input into the model has to be accurate. Polymers have low thermal conductivities and because of this, heat transfer data is key to predicting accurate cycle times.The thermal conductivity behaviour of amorphous polymers at temperatures above the glass transition temperature (Tg) is not well described. In the literature, different experimental techniques produce data, nominally for the same polymer, describing conflicting trends in thermal conductivity behaviour above Tg. A novel measurement instrument, the heat transfer coefficient (HTC) apparatus, has been designed and built in order to attempt to resolve the measurement issues for thermal conductivity of amorphous polymers above Tg.The repeatability for PMMA tested at a set temperature of 60°C was determined as 1.5 %. The value compares with a repeatability of 8 % for the line-source probe technique. For PMMA at 60°C the mean thermal conductivity value of 0.189 W/(m.K) compares with an accepted standard value for the specimen of 0.192 W/(m.K) differing from the known specimen value by 1.6 %. Therefore the HTC instrument could be used to establish reliable thermal conductivity data for modelling predictions of cooling time during the injection moulding of amorphous polymers.Thermal conductivities of PC and PS were measured from 53°C to 180°C and show an increase in thermal conductivity with temperature above Tg for both polymers. This trend is in agreement with line source probe technique data. A model predicting increasing thermal conductivity with increasing temperature above Tg was reviewed.



S08-752

Structure of poly (acrylic) acid in electrolyte solutions and on surfaces determined from simulations and viscosity measurements Adamczyk Zbigniew 1, Nattich Małgorzata 1, Bratek-Skicki Anna 1, Warszyński Piotr 1

1 Polish Academy of Sciences - Institute of Catalysisi and Surface Chemistry - Poland [email protected]

The structure of poly(acrylic) acid (PAA) molecules in electrolyte solutions obtained from molecular dynamic simulations was compared with experimental data derived from dynamic light scattering (PCS), dynamic viscosity and electrophoretic measurements. Simulations and measurements were carried out for polymers having various molecular weight in the range of 12–140 kD and for various ionic strength and pH. The effect of the ionization degree of the polymer was also studied. It was predicted from simulations that for low electrolyte concentration (10–3 M) and pH=9 the molecule assumed the shape of flexible rod having the effective length comparable with the fully extended polymer chain. For lower ionization degree, a significant folding of the molecule was predicted. These theoretical results were compared with PCS measurements of the diffusion coefficient of PAA, which allowed one to calculate the hydrodynamic radius RH. It was observed that for higher pH, the experimental RH values were in a good agreement with theoretical predictions. On the other hand, significant deviations from the theoretical shape predictions, which occurred at pH =4 were interpreted in the chain hydration effect increasing its stiffness. To obtain additional shape information, the dynamic viscosity of PAA solutions was measured using a capillary viscometer. It was found that the experimental intrinsic viscosity values were in a good agreement with the Brenner’s theory for prolate spheroid suspensions and the molecular dynamic simulations. The bulk structure data of PAA were compared with measurements of the shape and coverage of molecules adsorbed irreversibly on mica surface, using the AFM tapping mode technique in a liquid cell. These measurements were used for a quantitative interpretation of streaming potential measurements of PAA covered surfaces performed in the parallel-plate cell. This work is supported by the MANAR Network, financed by MeiSzW. Cor.author: [email protected]

S08-763

Effects of confined geometries on the flow behavior of dilute suspensions of rigid spheres D Avino Gaetano 1, Cicale Giuseppe 1, Tuccillo Teresa 1, Maffettone Pier Luca 1, Greco Francesco 2, Hulsen Martien A 3

1 Department of Chemical Engineering, University Federico II of Naples - Naples - Italy, 2 Istituto di Ricerche sulla Combustion, IRC-CNR - Naples - Italy, 3 Department of Mechanical Engineering, Eindhoven University of

Technology - Eindhoven - The Netherlands [email protected]

Recently the interest in the use of microdevices for chemical and biochemical processes is increased. Quite often, suspensions are processed in these devices. In such a system, due to the increased surface to volume ratio of using microchannels and microspheres, interfacial effects become more and more important, leading to a completely different particle motion with respect to macrosuspensions.In this work, the effect of a confined geometry surronding a dilute suspension of rigid, non-Brownian, inertialess spheres is studied, through numerical simulations. In particular, both a simple and sinusoidal shear flows are imposed as external flow fields and the impact of the gap between the particle and the wall on the flow fields is investigated.We solve the balance equations by means of a finite elment method in a 3D simulation cell. The particle rigid-body motion is imposed through constraints on the sphere surface. Therefore, the unknown particle rotation is recovered by solving the full system of equations.Preliminary results for a Newtonian suspending liquid show a slowing down of the particle if the gap decreases. For a viscoelastic suspension, this effect is even more pronounced since the nature of the fluid leads itself to a slower rotation, even in unconfined geometries. A significant effect of the confinement on the rheological response of the suspenion is also observed.



S08-774

VERIFICATION OF SIMULATIONS OF CHOSEN PHENOMENA OCCURRING DURING POLYMER INJECTION Nabiałek Jacek 1, Kwiatkowski Dariusz 1, Gnatowski Adam 1

1 Technical University of Czestochowa - Czestochowa - Poland [email protected]

The purpose of present paper was presenting chosen results of investigations on polymer flow during mould cavity filling phase ofinjection process. Advancement in the simulation software make possible to simulate more and more phenomena occurring duringpolymer flow in injection molding process.The results of computer simulations of injection process have been compared with the results of video recording for the plastic flow during filling phase. For the simulating investigations a professional computer software Moldflow Plastics Insight ver. 6.1. has been employed. A specialized injection mould which enables observation and registration of the plastic flow during processing has been employed. The mould enables direct monitoring of the course of phenomena inside ;he mould cavity in two planes. To record the flow, a digital video camera has been employed. As an example the issue of stream flow (jeting) have been described.The results of the investigations enabled documenting of specific phenomena which occur during plastics or their composites injection process. The registered video sequences have been compared with the results of numerical calculations and then it was estimated to what degree the computer simulation of injection process may be useful in practice.The camera enabled to register the flows with the rate of 25 fps. This reduced the scope of the investigations, since at higher plastic flow speeds the registered image became less clear. The investigations were performed on a wide scale, however, only chosen results have been presented.Deep understanding of the phenomena which occur during filling the injection mould may lead to more effective design of the processing tools and shortening of the time for implementation and production time. The transparent sight-glasses have been used, made of a material called Zerodur* which is characterized by the coefficient of thermal expansion close to zero.

S08-860

Optimization of Coathanger melt distributors for a range of different materials. Lebaal Nadhir 1, Puissant Stephan 1, Schmidt Fabrice 2, Schlaefli Daniel 3

1 Institut Supérieur d’Ingénierie de la Conception GIP-InSIC, ERMeP - Saint Diè des Vosges - France, 2 Ecole des mines d’Albi Carmaux ENSTIMAC, CROMeP - ALBI - France, 3 Extrusion Maillefer SA Route du bois 37 - Ecublens -

Switzerland [email protected]

The coat-hanger melt distributor is a device commonly used in the wire coating process. Its task is to distribute the melt around the conductor uniformly. It’s quite common that neither the material nor the flow rate corresponds to what has been specified during the design procedure. This may lead to lack of performances with materials having very different rheological properties from the design material.To avoid this loss of performances, we present in this paper an optimal design approach. This approach involves coupling three-dimensional finite element simulation software and an optimization strategy. The objective is to determine a coat-hanger melt distributor geometry to ensure a homogeneous exit velocities distribution that will best accommodate for a different range of materials and multiple operating conditions.A coat-hanger melt distributor with a manifold of constant width is designed, and a set of experimental measurements is established for two different materials. The results of numerical simulation, obtained by using three-dimensional finite element simulation software, are then validated by comparing them with experimental measurements. The effect of material change is also investigated. After the validation, we use the optimization procedure based on a response surface method in order to improve the exit velocities distribution by adjusting geometrical parameters.



S08-864

Modeling of Deformation Molecular Mechanics of an Oriented Linear Flexible Chain Crystalline Polymer Gafurov Ulmas 1

1 Institute of Nuclear Physics - Ulugbek - Uzbekistan [email protected]

Modelling of molecular processes in plastic deformation of an oriented linear partly crystalline polymer was carried out. Simple cosine periodic potential as in Frenkel-Kontorova’s dislocation model was used for intermolecular interaction and condition of balance of loaded chain in polymer crystallite. The dislocation formation is accompanied molecular chains slippage and local loads relaxation on their amorphous sections as well as by conformation regroupings of these sections in some conditions. In dependence on external load and amorphous region length different cases are realized. The first case takes place when the load is moderate. In this case the load on the amorphous section of a slipped out chain are completely relaxed and this section could change its conformation state. In the another case slipped out amorphous section of a macromolecule is in strained state but its strain is less than one of the macromolecule before its slipping out.The load relaxation value influences on dislocation behavior . This behavior depends except for of macromolecular chain parameters and geometrical configuration mainly from sizes of stressed amorphous section and of initial load on it. Beside of its deformation molecular processes are complexly dependent concentration of chain ends, entanglements and cross –links. According to of the model in polymer deformation the leading elementary process is mechanically stimulation of thermo-fluctuation slippage of passage macromolecules. It is valid at least for flexible chain polymers.

S08-882

Mechanical testing for generating input to numerical simulation of impact response of injection-moulded components Andreassen Erik 1, Daiyan Hamid 1, Grytten Frode 1, Lyngstad Ole Vidar 2, Gaarder Rune H. 1, Hinrichsen Einar L. 1

1 SINTEF - Oslo - Norway, 2 Plastal - Raufoss - Norway [email protected]

Numerical simulation of the impact response of injection-moulded components has gained importance in several industry sectors, in particular in the automotive industry. Recent work [1-4] has demonstrated progress in modelling special features of polymer materials, such as plastic dilatation in tension and sensitivity to hydrostatic stress. However, several experimental challenges remain. Some of these will be addressed in this presentation, based on a study with polypropylene materials. Techniques for compression and shear testing will be one topic. Experience with the new ISO standard for obtaining tensile properties at high strain rates (ISO 18872) will also be summarised. Effects of moulding conditions on the mechanical response will be discussed. Finally, some results with the recent SAMP-1 material model [1] in LS-DYNA will be shown. [1] S. Kolling, A. Haufe, M. Feucht, P.A. Du Bois, “SAMP-1: A semi- analytical model for the simularion of polymers”, Proceedings from LS- DYNA User Meeting, Bamberg, Germany, 2005 [2] J.C. Viana, A.M. Cunha, N. Billon, “Experimental characterization and computational simulations of the impact behavior of injection- molded polymers”, Polym. Eng. Sci., 47, 337 (2007) [3] G. Dean, L. Crocker, “Prediction of impact performance of plastics mouldings - Part 1: Materials models and determination of properties”, Plast. Rubber Comp., 36, 1 (2007) [4] T. Glomsaker, E. Andreassen, M. Polanco-Loria, O.V. Lyngstad, R.H. Gaarder, E.L. Hinrichsen, “Mechanical response of injection- moulded parts at high strain rates”, Proceedings from PPS07ea (Polymer Processing Society), Gothenburg, Sweden, 28.-30. August 2007



S08-933

simulation study on mixing process in twin-screw extruders Tanidono Mami 1, Nakayama Yasuya 1, Tomiyama Hideki 2, Fujino Shigeru 1, Kajiwara Toshihisa 1 1 Kyushu University - Fukuoka - Japan, 2 Japan Steel Works - Hiroshima - Japan

[email protected]

We developed a way to evaluate mixing process in twin-screw extruders. Numerical simulation of melt flow in melt mixing zone of twin-screw extruders was performed. By utilizing the flow simulation data, mixing kinetics was evaluated. From this approach, several measures for mixing performance were discussed to characterize the mixing performance of twin-screw extruders.

S08-999

The effect of operational conditions on the melt flow index (MFI) in Styrene bulk polymerization Shahsavan Hamed 1, Monemian Seyed Ali 2, Goodarzi Vahabodin 3, Torabi Angaji Mahmood 2

1 Sharif University of Technology - Tehran - Iran, 2 University of Tehran - Tehran - Iran, 3 University of Tehran - Tehran - Iran

[email protected]

In this work, industrial bulk polymerization of styrene was investigated. A relation for melt flow index (MFI) was established by a new correlation to polystyrene molecular weight and mineral oil content. Using non-linear regression a new expression for termination to monomer was presented. The effect of operational conditions such as reaction temperature, mineral oil/ styrene and ethyl benzene/ styrene volume ratio on the molecular weight and MFI were analyzed. Also, the polymerization process of styrene was mathematically modeled using moment method. The results show industrial data are comparable with the analytical data.



S08-1023

Performance Modelling and Optimization of Structured-Wall PE Pipes Fuerle Fabian 1, Sienz Johann 1, Innocente Mauro 1, Pittman John FT 1, Samaras Vassilios 2, Thomas Simon 2 1 Swansea University - Wales - UK, 2 Asset International Ltd - Wales - UK

[email protected]

Structured-wall high density polyethylene pipes up to 3m diameter are used extensively in civil engineering applications including storm water attenuation tanks, culverts, surface drainage, inter-process pipe work, sewers etc. The pipes are manufactured by extruding a hollow box section which is spiral wound onto a mandrel with successive turns welded together using PE from an auxiliary extruder. A key quality control measure is the ring stiffness to ISO 9969. The ability to predict this accurately as a function of the pipe wall geometry is a pre-requisite for optimization of the pipe design. The presentation will describe the development and validation of finite element modeling of the ring stiffness test in comparison with experimental results, and consider the relationship between the test results and in-situ performance. Approaches to optimizing the pipe wall structure will be outlined.

S08-1031

Evaluation of the stress-strain behaviour of multigraft copolymers at medium elongations by applying models of rubber elasticity Weidisch Roland 1, Schlegel Ralf 1, Staudinger Ulrike 1, Mays Jimmy W. 2

1 Friedrich-Schiller-Universität Jena - Thuringia - Germany, 2 Department of Chemistry, University of Tennessee, Knoxville, USA - Tennessee - USA

[email protected]

The stress-strain data of multigraft copolymers have been characterized by the application of models of rubber elasticity such as Mooney-Rivlin, Slip-Tube and the None-Affine Tube Model of Kaliske and Heinrich. Multigraft copolymers, consisting of a polyisoprene (PI) backbone and grafted polystyrene (PS) arms, show high strain at break and low residual strain caused by the large amount of physical cross links resulting from several grafted PS-side chains. From the model fits the material parameters Ge and Gc, representing the influence of chemical cross links and entanglements effects, respectively and the ne/Te-value (ne - number of statistical segments between two successive entanglements, Te - Langley trapping factor) are used to describe the tensile behaviour. In this work the PS-content was considered as filler phase taking into account the effect of hydrodynamic amplification and the effect of occluded rubber. In previous work the influence of the functionality and the number of branch points on the strain at break and the tensile strength was shown., which in the present investigations is explained by the model parameters mentioned above describing the stress-strain curve at low (Slip-Tube, Mooney-Rivlin) and medium (None-affine Tube) elongations. It can be seen that for the material with a spherical morphology the modulus Ge representing the amount of physical cross links is increasing with the number of branch points (each branch point consists of a PI-backbone segment and, according to the functionality one, two or four grafted PS-arms), while the amount of chemical cross links remains almost constant. For a lamellar morphology the Ge-value was decreasing with increasing beta, which could be confirmed by applying the None-affine Tube Model. The number of statistical segments ne/Te between two successive entanglements was increasing with increasing number of branch points.



S08-1051

MODELLING TENSILE MODULUS OF CORE-SHELL RUBBER-MODIFIED EPOXIES WITH ANSYS kourki hajir 1

1 tarbiat modares university - 021 - iran [email protected]

Experiments have been carried out to quantify the effects of rubber content on the elastic deformation behaviour of core-shell rubber-modided epoxies.Young's modulus was found to be very sensitive to the volume fraction of rubber particles. Finite element analyses with ansys have also been performed to determine the influences of rubber content on the tensile modulus. By comparing with experimental results, it is found that the Young's modulus of rubber-toughened epoxies can be accurately estimated using the ansys. Agreement with experimental results is good.

S08-1108

Molecular-level Simulation Study of Conformational Behavior of Model Linear Polymers in Aqueous Environment Krejci Jan 1, Nezbeda Ivo 2

1 Department of Physics, University of Jan Evangelista Purkinje - Usti nad Labem - Czech Republic, 2 Department of Chemistry, University of Jan Evangelista Purkinje - Usti nad Labem - Czech Republic

[email protected]

We performed systematic study of conformational behavior and thermodynamics for simple models of linear homonuclear and diblock polymers in aqueous environment on molecular level. A polymer conformation reflects space arrangements of polymer segments resulting from structural and chemical properties of polymers, and from properties of surroundings. The conformational behavior is described by various quantities such as the mean square end-to-end distance and radius of gyration, by the tensor of inertia and by the so-called parameters $\mathfrak{R}$ and $\mathfrak{D}$. The thermodynamic behavior is analyzed using entropic and energetic contributions to the Helmholtz free energy. The polymer model is made up of a flexible chain of tangentially touching hard spheres and/or square-well spheres. The polymer models are studied using the configurational-bias Monte Carlo method combined with the parallel tempering technique.



S08-1136

Functional silica xerogel. Modeling of the metal ions retaining process Curteanu Silvia 1, Cazacu Maria 2, Curteanu Nicolae 3 1 Technical University Iasi - Iasi - Romania, 2 Petru Poni Institute of Macromolecular Chemistry - Iasi - Romania, 3

Institute for Computer Science - Iasi - Romania [email protected]

Functionalized silica xerogels have a great potential of applications, including extraction, recovery and separation of metal ions from aqueous solution. The main pathway to obtain such structure is cohydrolysis in sol-gel system of tetraalkoxysilanes with an appropriate silane coupling agent, (RO)3SiX, where X represents a functional group. Because the available range of functional silanes is limited, it often proceeds with the modification of the X function. A one-pot procedure was applied to obtain silica xerogels containing chelating groups, suitable to be used for retaining metal ions from aqueous solution. In order to find the conditions in which a maximum efficiency in the metal absorption can be reached, a series of experiments have been performed in different conditions. The acquired data were used for process modeling based on artificial intelligence instruments. Neural networks possess the ability to learn what happens in the process without actually modeling the physical and chemical laws that govern the system.A multilayered, feed-forward, fully connected network is chosen in this research to model the dependence of the metal absorption ratio as function of some parameters: chelating group density, metal concentration, pH. The reasons of using this kind of neural network are the simplicity of its theory, ease of programming, and good computational results. This neural network is a universal function, in the sense that, if the topology of the network is allowed to vary freely, it can take the shape of any broken curve. In this study, the topology of the networks was developed by various original methods, following a balance between complexity and performance. The good concordance between experimental data and neural network predictions prove that the considered model renders well the real process.

S08-1169

Influence on Crystallization Process of PET under Different Nucleation Mode Dong Zhi-zhi 1, Chen Li 2, Zhang Zhi-ying 2, Sun Peng 2

1 Key Lab of Fiber Modification and Functional Fiber,Tianjin Polytechnic University - Tianjin - China, 2 Tianjin Polytechnic University,China - Tianjin - China

[email protected]

The crystallization process of poly(ethylene terephthalate) (PET) was studied by the method of the Monte Carlo under the condition of different nucleation. Firstly, the non-isothermal crystallization process of PET was simulated using a self-designed computer program under the predetermined nucleation mode.Secondly, the isothermal crystallization process was simulated under the condition of the sporadic nucleation, which considering the complexity of non-isothermal. The mathematic model of the number of nucleus variation with time can be expressed in following form N(t)=N0[1-exp(-m*t)], where N(t) represents the number of nucleus at t time; N0 , the number of exist nucleus; m is the nuclear vegetal coefficient , that is , the nuclear transformation factors; t is the time. The simulated data of predetermined nucleation mode were analyzed by the Ozawa equation. The values of Avrami exponent n were in agreement with the theory value 3.Under the condition of the sporadic nucleation, the volume of N0 was assumed as 1000,2000,4000 respectively, and m is 0.1, the simulated data were analyzed by the Avrami equation. We had finished the experiments of transformed factors m as 0.5,0.1,0.05,0.01,0.005 with the different value of N0. The results showed that when N0 is the constant, the value of m increased with the time, the early simulation curve deviates theoretical predicting straight line under the condition of isothermal sporadic nucleation. When m is the constant, with the N0 is increased, there have little influence on the values of Avrami exponent n, and the simulation curve deviates theoretical predicting straight line not too. All the results showed that the values of Avrami exponent n were in agreement with the theory value 3 under the condition of non-isothermal predetermined nucleation mode. Sporadic nucleation maybe is one of the reasons that the simulation data of PET deviates theoretical predicting straight line.

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