Simulation & Modeling
Parisa Mohammadzadeh Pakdel; Reza Yegani; Mahdi Salami Hosseini; Elham Shokri
Abstract
In the current study, the flow field and morphology development of a polyethylene (PE) and ethylene vinyl acetate (EVA) blend were investigated numerically during extrusion through a spinneret using Fluent 6.3.26 software. The interface of the two phases was tracked using the volume of fluid (VOF) method. ...
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In the current study, the flow field and morphology development of a polyethylene (PE) and ethylene vinyl acetate (EVA) blend were investigated numerically during extrusion through a spinneret using Fluent 6.3.26 software. The interface of the two phases was tracked using the volume of fluid (VOF) method. In a conventional spinneret, EVA droplets near the walls break up due to the high shear rate, while the central droplet deforms without breaking up. To enhance the breakup of EVA droplets, the effects of device geometry, including the spinneret angle and the presence of one or two lamps, were investigated in detail. The numerical results indicated that a decrease in the spinneret angle from 60° to 45° causes the central droplet to become more elongated in the flow direction. Additionally, the results showed that the presence of one or two lamps in the conical zone of the spinneret causes a portion of the central droplet to break up.
Simulation & Modeling
Utkarsh A. Patil; Pravin Ramchandra Kubade
Abstract
The growing need for enhanced materials has led to the development of nanocomposites, which have shown great potential in various industries. However, optimizing the composition of these materials to achieve the best mechanical performance and cos t-effectiveness remains a challenge. This research addresses ...
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The growing need for enhanced materials has led to the development of nanocomposites, which have shown great potential in various industries. However, optimizing the composition of these materials to achieve the best mechanical performance and cos t-effectiveness remains a challenge. This research addresses this challenge by employing a virtual experimental approach, utilizing Digimat for material modeling and CATIA for design and finite element analysis (FEA). This approach allows for the simulation and analysis of different nanocomposite compositions without the need for costly and time-consuming physical experiments. The study focuses on Polypropylene (PP) and polyvinyl chloride (PVC) based nanocomposites with graphene and carbon black reinforcements. The research investigates the impact of varying the weight percentages of these nanofillers on the mechanical properties of the composites. The PP/PVC blends are created in different weight ratios to provide further compositional control. The material preparation is carried out in Digimat, where the properties of the composites are defined using a micromechanical model. The FEA is then conducted in CATIA, where a standard AS TM D638 tensile specimen is simulated under controlled conditions. The results are validated by varying mesh sizes to optimize deflection and Von Mises s tress predictions. Furthermore, an economic analysis is conducted to evaluate the cos t-effectiveness of the different nanocomposite compositions. The study highlights the importance of virtual experimentation in materials science, as it allows for efficient exploration of various material compositions and reduces the need for physical prototyping. This approach accelerates the material development process and enables the optimization of material design for specific applications. The virtual trials explored alternatives to PVC using PP-based composites reinforced with graphene/carbon black. PP/PVC 40/60 reinforced with 1.5% wt. graphene (P4V6G15) and reinforced with 7.5% wt. carbon black (P4V6C75) showed 31.6% and 31.2% deflection reductions compared to pure PP, respectively. These results show that P4V6 blends, especially those with graphene or high carbon black concentrations, serve as promising alternatives to conventional PVC. Among them, P4V6C75 stands out by offering the best overall mechanical performance. It also provides the lowest production cos t. In terms of economic favorability, P4V6C75 is approximately 2.55 times more cos t-effective than the graphene-based blend P4V6G15. This combination of high performance and low cos t makes P4V6C75 the most suitable candidate for PVC replacement.
Simulation & Modeling
Aamir Mustafa Shaikh; Pravin R. Kubade
Abstract
Polymers can be natural or synthetic and are largely used in several applications due to their versatile properties. Polymers can vary widely in their properties and applications, and they are a fundamental part of our everyday life. Polypropylene (PP) is a thermoplastic polymer from the polyolefin family. ...
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Polymers can be natural or synthetic and are largely used in several applications due to their versatile properties. Polymers can vary widely in their properties and applications, and they are a fundamental part of our everyday life. Polypropylene (PP) is a thermoplastic polymer from the polyolefin family. It is among the most widely used plastics in various automotive and packaging industries. Although PP is widely used in commodity range, still its applications are restricted in niche areas due to lack of toughness which can be improved by incorporation of rubbery materials or fillers. Graphene (G) is one of the nanomaterials used to strengthen polypropylene. Graphene is recognized for its outstanding thermo-mechanical properties, making it a highly desirable material in various fields of science and technology. Benefits gained by incorporation of graphene nanoparticles into polypropylene are studied by researchers. In this study, a finite element analysis is performed which shows the mechanical behaviour of PP and G using ANSYS, which is one of the most powerful finite element analysis (FEA) softwares that can help to perform such simulations to understand stress, strain, deformation of components before actual experimentation. The bending load of 100 N and 1400 N in vertical z-direction are applied for 100% PP model, 100% G model and 50% PP+50% G model and the linear part of stress-strain curve is captured in this analysis.
Simulation & Modeling
Yogeshwar N Thakare; Ajay V Kothari; Saurabh Shinde; Pooja Kadam; Natarajan Venkateswaran; Virendrakumar Gupta
Abstract
MgCl2 supported Ti catalyst is used in commercial propylene polymerization process. Morphology is a key performance determination parameter for polymer resins produced by commercial olefin polymerization process. Higher resin flowability and bulk density (greater than 0.38g/cc) are demonstrated by ‘good’ ...
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MgCl2 supported Ti catalyst is used in commercial propylene polymerization process. Morphology is a key performance determination parameter for polymer resins produced by commercial olefin polymerization process. Higher resin flowability and bulk density (greater than 0.38g/cc) are demonstrated by ‘good’ morphological resins (sphericity close to ‘1’). Polymer resin morphology is controlled by morphology of the catalyst used as well as polymerization conditions. The industrially accepted approaches to control polymer resin morphology are by controlling catalyst morphology through various approaches like pre-polymerization of the catalysts. Morphology of the catalyst is dependent on precursor (support) morphology and process parameters for making the catalyst. In this work, we have developed magnesium alkoxide precursor, a Ziegler-Natta catalyst using the precursor and studied its performance in gas phase propylene polymerization process. Further, morphology of different precursor and catalyst samples is evaluated and correlated it using a “computer vision” based approach. The approach involves modeling the circularity (as an analog of sphericity) of a catalyst and precursor particle. It is observed that the circularity of catalyst particles is lower than that of precursor, due to attrition in the process. It is also reflected in increase in particle size distribution span from 0.83 to 1.32 while synthesis of catalyst from precursor. This approach provides a tool to evaluate and screen the catalysts for using in polymerization.
Simulation & Modeling
Jieqi Wang; Li Zhao; Minju Song; Fenge Hu; Xuelian He
Abstract
The influence of long branches on crystallization behavior has been studied by means of molecular dynamics simulations. Using two systems: polyethylene (PE) with long branches (LCB-PE) and PE without long branches (linear-PE) with the same molecular weight, we have examined the crystallization behavior ...
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The influence of long branches on crystallization behavior has been studied by means of molecular dynamics simulations. Using two systems: polyethylene (PE) with long branches (LCB-PE) and PE without long branches (linear-PE) with the same molecular weight, we have examined the crystallization behavior of the two systems by molecular dynamics simulation. This paper explains the influence of long branches on the isothermal crystallization process and the non-isothermal crystallization process with similar initial interchain contact fraction (ICF) in terms of final ICF, crystal regions, crystallinity, concentration of tie chains and energy. It is found that the crystallization process is classified as two stages: the nucleation stage and the crystal growth stage. The existence of long branches is favorable for the first stage while unfavorable for the second stage. Knots that act as crystalline defects are excluded from the lamella, resulting in decreasing in regularity and crystallinity of molecular chains. From the perspective of potential energy and non-bond energy, LCB-PE has lower energy than linear-PE in the nucleation stage while the energy of linear-PE is lower than that of LCB-PE in the second stage. In short, the long branched chains inhibit the crystallization process.
Simulation & Modeling
Mehrsa Emami; Farzin Hormozi; Hossein Abedini
Abstract
Bulk phase polymerization of propylene with a 4th generation of Ziegler-Natta catalyst was kinetically investigated by means of heat flow calorimetry. The assumptions and modifications on isothermal calorimetric method were demonstrated. Our calibration method showed that heat exchange with the reactor ...
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Bulk phase polymerization of propylene with a 4th generation of Ziegler-Natta catalyst was kinetically investigated by means of heat flow calorimetry. The assumptions and modifications on isothermal calorimetric method were demonstrated. Our calibration method showed that heat exchange with the reactor cover plate is not constant over time. Therefore, the dynamic of cover plate temperature was considered in the calorimetric method. The polymerization rate profiles depending on hydrogen and external electron donor concentration have been investigated. Normalized polymerization profiles (Rp /Rpmax) are plotted and expressed as an exponential function of time. Effects of hydrogen and external electron donor (ED) concentration on Rpmax and polymerization rate were investigated as well. The results showed that by increasing hydrogen concentration, initial polymerization rate (Rpmax) increased. Hydrogen increased productivity by increasing the initial polymerization rate, while it had no negative effect on the rates of decay or its effect was small. The ED concentration was optimized so that the catalyst deactivation rate was at its lowest level. Also, changes in the ratio of activation to inactivation with ED concentration were examined, and a proportional change was observed.
Polymer processing
Moammadreza Nakhaei; Ali Ahmadi; Ghasem Naderi
Abstract
Polyamide 6 / nitrile butadiene rubber / nanoclay (PA6/NBR/clay) nanocomposite has gathered wide acceptance in industry. Laser welding, as a fabrication method, is applied to welding of polymer nanocomposites. In this study, the input parameters (clay (Closite 30B) content, laser power, scan velocity ...
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Polyamide 6 / nitrile butadiene rubber / nanoclay (PA6/NBR/clay) nanocomposite has gathered wide acceptance in industry. Laser welding, as a fabrication method, is applied to welding of polymer nanocomposites. In this study, the input parameters (clay (Closite 30B) content, laser power, scan velocity and stand-off-distance) are varied to achieve the best responses (tensile strength of welds). Response surface methodology (RSM) is utilized to investigate the effect of input parameters on mechanical properties. Morphology and tensile properties of nanocomposites were observed with scan electron microscopy (SEM), transmission electron microscopy (TEM) and tensile test. The results demonstrated that increasing the clay content from 1 to 5%wt and stand-off-distance from 4 to 8 mm decreased tensile strength of welds about 15% and 5%, respectively. The tensile strength of PA6/NBR composite is 25.6, whereas the prediction models showed that under optimal conditions of laser power of 105 W, scan velocity of 300 mm/min and stand-off-distance of 4 mm, the maximum tensile strength of PA6/NBR nanocomposite with 1, 3 and 5 % nanoclay are 27.2 MPa, 27.6 MPa and 24.7 MPa, respectively. These tensile strengths are about 99, 89 and 73% of the strength of these nanocomposites before welding.
Simulation & Modeling
Rezvan Yavari; Hamid Khorsand; Mehran Sardarian
Abstract
During the recent years powder processing technologies have gained much attention due to the less energy consumption and recyclable powders. Manufacturing of complicated parts by the conventional powder metallurgy (PM) method is hard due to the uniaxial pressure, which leads to the low design flexibility. ...
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During the recent years powder processing technologies have gained much attention due to the less energy consumption and recyclable powders. Manufacturing of complicated parts by the conventional powder metallurgy (PM) method is hard due to the uniaxial pressure, which leads to the low design flexibility. In order to prevail these constraints, powder injection molding (PIM) process, which includes powder metallurgy and injection molding processes, is introduced. In powder injection molding, simulations are a very useful tool to predict each step of process and design the mold. By this way, design can already be optimized and mistakes are avoided. In this review a detailed study of simulation of different steps in the powder injection molding process of macro and micro components produced by this method is presented. Simulation investigations of mixing, injection, debinding, and sintering of various researchers are given. The computer simulation tools available for all steps of the PIM process are surveyed and results are presented.
Simulation & Modeling
Hossein Ebrahimi; Ahmad Ramazani S.A.; Seyed Mohammad Davachi
Abstract
Rheological models for polymer solutions and melts based on the finitely extensible non-linear elastic (FENE) dumbbell theory are reviewed in this study. The FENE-P model that is a well-known Peterlin approximation of the FENE model, indicates noticeable deviation from original FENE predictions and also ...
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Rheological models for polymer solutions and melts based on the finitely extensible non-linear elastic (FENE) dumbbell theory are reviewed in this study. The FENE-P model that is a well-known Peterlin approximation of the FENE model, indicates noticeable deviation from original FENE predictions and also experimental results, especially in the transient flow. In addition, both FENE and FENE-P models have some shortcomings from the point of view of theory. To overcome these shortcomings, a new approximation of the FENE spring force has been established. It has been used to develop a modified constitutive rheological model for polymeric fluids. In the procedure of modeling, the effect of non-affine deformation is introduced into the new model. Comparison between the model predictions and experimental data presented in the literature for transient and steady shear flow of polystyrene indicates that this modified model can predict the rheological behavior of polymeric fluids with a great accuracy. The newly developed modified model could predict different slopes that can cover the behavior of most of the polymeric fluids.
Simulation & Modeling
Hafez Maghsoudi
Abstract
In this paper, the performances of potential zeolite membranes were estimated by the Maxwell-Stefan model and then they were placed in Robeson plot of propylene/propane separation. Additionally, the effects of feed pressure and the mole fraction of propylene in the feed on both the propylene ...
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In this paper, the performances of potential zeolite membranes were estimated by the Maxwell-Stefan model and then they were placed in Robeson plot of propylene/propane separation. Additionally, the effects of feed pressure and the mole fraction of propylene in the feed on both the propylene permeabilities and membrane permselectivities were investigated. The results showed that zeolite membranes had better performances than carbon and polymer membranes. However, the performances of carbon membranes were better than those of zeolites 4A and ITQ-3. Also, among various zeolites studied, a DD3R zeolite membrane had the highest propylene permselectivity. According to the minimum requirement needed for membranes (i.e., a minimum selectivity of 35 and a permeability of 1 Barrer) for propylene/propane separation, it was found that the zeolite membranes of DD3R, SAPO-34, Si-CHA and ITQ-12 had this performance requirement. However, DD3R and SAPO-34 zeolite membranes were more preferred than the polymer, carbon and composite membranes due to their higher performances.
Simulation & Modeling
Sara Shahbazi; Yaser Jafari; Fathollah Moztarzadeh; Gity Mir Mohamad Sadeghi
Abstract
Poly (propylene fumarate) (PPF), a linear unsaturated polyester consisting of alternating propylene glycol and fumaric acid units, can be cured in vivo to fill the skeletal defects with minimal surgical intervention. Many different methods have been reported for synthesizing PPF, but none of them gives ...
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Poly (propylene fumarate) (PPF), a linear unsaturated polyester consisting of alternating propylene glycol and fumaric acid units, can be cured in vivo to fill the skeletal defects with minimal surgical intervention. Many different methods have been reported for synthesizing PPF, but none of them gives a clear method. The present paper introduces two new methods in PPF synthesis: Modified reflux system (MRS) and mixed reflux-distillation system (MRDS). Similarly, the effects of applying vacuum (vacuum sequence, time, vacuum applying position, and the distance between vacuum applying position and reactor) as well as nitrogen gas (used continuously or only as an N2 blanket) on the PPF synthesis have been studied. The PPF obtained using optimum reaction condition has been characterized by using NMR, FTIR, and GPC analyses. It is demonstrated that the efficiency of MRDS in synthesizing PPF is higher than that of MRS. Nitrogen gas, vacuum applying position, continuously/stepwise-continuously applying vacuum and other parameters show an important role in the polymerization of PPF in both the MRDS and MRS systems.
Reaction engineering
Mohsen Najafi; Mahmoud Parvazinia; Mir Hamid Reza Ghoreishy
Abstract
A two-dimensional single particle finite element model was used to examine the effects of particle fragmental pattern on the average molecular weights, polymerization rate and particle overheating in heterogeneous Ziegler-Natta olefin polymerization. A two-site catalyst kinetic mechanism was employed ...
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A two-dimensional single particle finite element model was used to examine the effects of particle fragmental pattern on the average molecular weights, polymerization rate and particle overheating in heterogeneous Ziegler-Natta olefin polymerization. A two-site catalyst kinetic mechanism was employed together with a dynamic two-dimensional molecular species in diffusion-reaction equation. The initial catalyst active sites distribution was assumed to be uniform, while the monomer diffusion coefficient was considered to be different inside the fragments and cracks. In other words, the cracks were distinguished from fragments with higher monomer diffusion coefficient. To model the particle temperature a lumped heat transfer model was used. The fragmentation pattern was considered to remain unchanged during the polymerization. A Galerkin finite element method was used to solve the resulting two-dimensional (2-D) moving boundary value, diffusion-reaction problem. A two-dimensional polymeric flow model (PFM) was implemented on the finite element meshes. The simulation results showed that the fragmentation pattern had effects on the molecular properties, reaction rate and the particle temperature at early stages of polymerization.
