bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of Mechanical Properties of Rubber Products Molded by Transfer and Compression Methods**
Authors: Dinzburg B. N. , Bond R. 
Published: December 2013

Abstract
This paper compares the differences developed in rubber properties between compression and transfer molding methods for various types of polymers. It has been shown that the two molding methods produce distinctly different rubber properties for the same elastomer. Acrylonitrile butadiene rubber (NBR) shows little difference in durability between molding methods. Transfer molding (TM) reduces modulus and hardness of NBR, but improves compression set. The crosslink density of rubbers made with TM is higher than those made with compression molding (CM). Highly saturated acrylonitrile butadiene rubber (HNBR) properties are significantly different between the two molding methods. As for NBR rubbers, the TM method reduces modulus and hardness, but improves compression set. The crosslink density of rubbers made by TM is higher that those made with CM. Silicone rubber (VMQ) that does not require post cure shows the same rubber properties change as NBR. Transfer molding yields low tensile and modulus but better compression set. Polyacrylic rubber (ACM) molded with the TM method shows reduced tensile, elongation, modulus and hardness; but after post cure, modulus and hardness did not show substantial differences. The compression set was lower with TM both before and after post cure. Crosslink density is significantly higher with TM, but the difference diminishes after post cure. Ethylene acrylic rubber (EAM) and fluoroelastomer rubber (FKM) exhibit property changes similar to acrylic rubber when molded either with compression or transfer molding methods. Rubbers molded with TM methods showed a higher degree of anisotropy in rubber properties than with CM. With enlarged extension ratio, the coefficient of anisotropy increased, with the exception of ACM.
Numerical Simulation of the Advancing Front in Injection Molding
Authors: Fauchon D. , Dannelongue H. H. , Tanguy P. A. 
Published: December 2013

Abstract
A 2D finite element model is presented for the prediction of the advancing front in the thickness of a part during mold filling in the polymer injection molding process. The full Navier-Stokes equations are considered for the determination of the velocity and the pressure. The computation of the flow front uses the Arbitrary Lagrangian-Eulerian approach and is coupled with an automatic remeshing technique triggered only when the mesh becomes distorted. Three series of numerical tests with a Newtonian fluid are presented. The first one deals with the fountain-flow in a flat gap and a tube and allows for validation of the code. The second example in a 90° bend illustrates the capability of the proposed method to deal with multiple fronts, and the third one deals with jetting.
Material and Numerical Aspects of Mathematical Modeling of Blow Molding**
Authors: Cohen A. , Seitz J. T. 
Published: December 2013

Abstract
The work describes an approach to simulation of a blow molding process. The development originated from the need to reduce the amount of experimentation through a screening of processing conditions and preform configurations. The simulation uses a standard finite element software capable of handling large deformations and an interaction with rigid surfaces, which are encountered in blow molding. The developed constitutive equation for a general purpose polystyrene in the rubbery state was incorporated into the model. Temperature and rate dependencies, typical for plastic materials, are accounted for in this model. The application of the developed model for analysis of the preform's deformations is illustrated here on a number of examples.
Finite Element Analysis of Polymer Melt Flow in Profile Extrusion Coating Die
Authors: Matsuoka T. , Takahashi H. 
Published: December 2013

Abstract
Automotive side protection moldings, which consist of polymer and an inserted metal core, are produced by profile extrusion coating. The molding process is similar to wire coating process except using a cross-head profile die because the cross-sectional shape of the side protection molding is complex. The polymer is extruded from the profile die covering the metal core, which is fed to the die simultaneously. Then, there are two flow regions within the profile die. One is pressure flow region where the polymer is flowed by pressure gradient. Another is drag flow region including pressure flow. The drag flow appears in the area where the polymer contacts the moving metal core in the die. Finite element analysis was developed for simulating the combined pressure and drag flow in a complex profile die. The flow is assumed to be isothermal planner flow for a non-Newtonian fluid. Power law model is used to represent viscosity of the polymer. Distributions of pressure and velocity are simulated by the analysis. Polymer melt flow through a flow channel of a die for producing the side protection molding was analyzed to achieve uniform velocity at the outlet of the die. A suitable shape of the flow channel was designed by several iterative simulations.
Study on the Formation of β-Crystalline from Isotactic Polypropylene Fiber
Authors: Chen X. , Wang Y. , Wang X. , Wu Z. 
Published: December 2013

Abstract
In this paper the conditions for the manufacture of high content β-form crystal isotactic polypropylene fiber in the presence of β nucleation and the β to α form transition during processing were studied. The results showed that the melt temperature had little effect on the relative content of β-form (K value) presented in as-spun fibers within a certain temperature range (210 to 230°C) while the cooling rate and cooling medium had a significant effect on it. In the case of a constant pump deliver (Q), the K value in the as-spun fiber decreased from 0.95 to 0 as the spinning speed increased from 3.25 m/min to 70 m/min. The smaller the thermal conductivity of cooling medium, the greater was the K value. After stretching the β-form PP fiber, there were many crevices at the fiber surface. It was confirmed by the mercury porosimetry that the drawn fiber possessed microvoid structure. The size and quantity of microvoids were closely related to the K value, stretching temperature and stretching ratio. Compared with PP fiber without nucleating agent, the drawn fiber had a lower apparent density and its moisture absorption was improved.
Predicting the Skin-Core Boundary Location in Injection Moldings
Authors: Brito A. M. , Cunha A. M. , Pouzada A. S. , Crawford R. J. 
Published: December 2013

Abstract
Over the past few years a technique for relating the quality and properties of sub-components to those of real injection moldings has been developed. A major aspect of this is the correlation of microstructure in the two situations. This paper describes the computer prediction of structure development in injection molded polypropylene. This is done on a personal computer using a finite difference method and it is shown that accurate predictions can be made in relatively low computing time. The characteristic skin in polypropylene moldings is shown to be controlled by the filling phase and is dependent on the shear stress and temperature. The computer model is able to predict the onset of skin formation and hence the skin thickness. These predictions have been shown to agree well with experimental observations. The skin-core boundary which has been found to have a major effect on the mechanical properties of molded polypropylene has also been shown to lie between the no-flow isothermal and the maximum shear rate locus. This has important implications for computer simulations of the injection molding process.
Optical Properties and Orientation Development in Uniaxially Stretched Syndiotactic Polystyrene from Amorphous Precursors
Authors: Hsiung C. M. , Cakmak M. 
Published: December 2013

Abstract
On-line uniaxial deformation behavior and deformation induced crystallization characteristics of initially amorphous syndiotactic polystyrene (s-PS) sheets were studied using an Iwamoto biaxial stretcher operated in the uniaxial mode. The stress strain curves obtained under various conditions indicate that this polymer can be stretched uniformly at 110°C which is between its glass transition temperature and cold crystallization temperature. The principal refractive indices were determined as a function of deformation conditions. Because of the negative intrinsic birefringence in the s-PS polymer chains the refractive indices in stretching direction decrease and those in the transverse direction increase with deformation.
Process for Improvement in Toughness of Unsaturated Polyester with Elastomer
Authors: Sakai T. , Nakamura K. , Inoue S. 
Published: December 2013

Abstract
By combined usage of a high speed intermeshing twin screw extruder and an injection molding press, a direct reactive extrusion and injection molding process has been developed for improving toughness of the thermoset unsaturated polyester (UP) by blending with an elastomer.
The unsaturated polyester and elastomer were homogenously kneaded with each other and a radical initiator dissolved in a liquid monomer was added to the molten mixture. This was carried out at a relatively low temperature from the final feeding port of the twin screw extruder to allow not the curing reaction to proceed during the twin screw extrusion stage.
The molten UP-elastomer alloy was accumulated, injected into the hot mold, and cured. The products obtained from these experiments were evaluated with regards to their physical properties and their morphologies. The elastomer, NBR produced the greatest improvement in toughness. The physical properties of the UP-NBR alloy obtained by this reactive extrusion process were generally equivalent to those of polypropylene except for thermal characteristics.
Skew Stretched Polycarbonate Films
Authors: Wu J. P. , White J. L. 
Published: December 2013

Abstract
The formation and characterization of complex chain orientation of polycarbonate skew stretched films is described. The directions of symmetry axes of orientation are represented in the form of refractive index and infrared absorption ellipsoids. The chain orientation is evaluated in terms of White-Spruiell biaxial orientation factors based on the principal axes of orientation. The anisotropic mechanical properties of skew stretched films are correlated with their orientation states. The major symmetry axes of skew stretched polycarbonate films tend to move toward the second stretching direction as increasing second stretching ratio. The chain orientation behavior of these films exhibit increasing uniaxial orientation character at high second stretching ratio. The anisotropic characters of tensile modulus and yield stress of skew stretched films follow a linear relation with the magnitude of chain orientation within our stretching range.
In-cycle Deterministic and Stochastic Dynamics of Extrusion Blow Molding
Authors: DiRaddo R. W. , Garcia-Rejon A. 
Published: December 2013

Abstract
Optimization of the thickness distribution in extrusion blow molded parts is crucial to minimize cycle times and resin usage. Closed-loop parison programming can be cycle-to-cycle or in-cycle. Corrective action occurs between cycles for the case of cycle-to-cycle control. However, this control scheme does not correct for high frequency disturbances that enter the system, such as periodic flowrate changes, noise from the gap position transducer, uneven melting and compression of the polymer and uneven inflation.
Corrective action occurs during the cycle for in-cycle control. This allows for regulation of the high frequency disturbances. Deterministic in-cycle model identification was performed by obtaining the impulse responses of the bottle thickness distribution to pulses in the die gap input during the extrusion cycle. The response was found to be time variant along the individual cycle. Stochastic identification was also performed in order to ascertain a noise model for the system. A first order ARMA noise model was found to adequately describe the process.
Control simulations were performed to determine the feasibility of in-cycle control. A minimum variance controller with a constraint for minimizing of manipulated variable movement was found to adequately regulate both a deterministic and a stochastic disturbance input during the extrusion cycle.
Simulating Polymer Mixing Processes Using the Boundary Element Method
Authors: Gramann P. J. , Osswald T. A. 
Published: December 2013

Abstract
The mixing of plastic into filled and unfilled polymer blends has been an important issue in the polymer industry. Processing difficulties with these polymers have been encountered in the mixing quality as well as in the thermal degradation due to viscous heating. Mixing often occurs as an element of the processing step, e.g., inside single and twin screw extruders used in the fabrication of final parts or sheets, and inside internal mixers such as the Banbury type mixer. Quantifying the mixing inside an extruder or an internal mixer and predicting the thermal degradation due to viscous heating is an extremely difficult task. A better understanding of the mixing process and control of viscous heating will lead to optimal parts and may eventually allow us to increase the relative amount of fillers within the material. This paper presents a boundary element simulation of the flow of filled and unfilled polymer blends inside extruders and internal mixers. First, the general equations that govern such flows are shown. The boundary integral equation and the fundamental solutions are then formulated followed by the numerical implementation and logistics of the simulation. After the theoretical background is presented, a numerical example is given. The paper then shows how the simulation was used to analyze the flow inside a single screw extruder and internal batch mixers. Such a simulation can be used to eliminate some of the tedious trial-and-error tasks that are typically performed in the early stages of material synthesis and can also be used by manufacturers of mixing equipment when optimizing the geometries of cavities and mixing heads to achieve optimum mixing with reduced viscous heating. This research will significantly increase our knowledge of the behavior of filled and unfilled polymer blends and expand our understanding of the complex phenomena that take place during their mixing process.
Crystalline Orientation in Injection Molded Polyethylene Parts
Authors: Wu J.-P. , White J. L. 
Published: December 2013

Abstract
The complex crystalline orientation character of injection molded high density polyethylene was examined. The principal axes and level of orientation along these axes were evaluated using wide angle x-ray diffraction pole figure analyses for various injection molding conditions. The principal axes of each layer were determined by means of ellipsoidal representations from wide angle x-ray diffraction pole figure data. It has been found that the principal axes of crystalline orientation do not exactly coincide with the flow direction. The crystalline orientation state for each layer was evaluated in terms of biaxial orientation factors with appropriate principal axes of orientation. The general behavior of crystalline orientation indicates b-axis orientation normal to the wall and perpendicular to the flow and width directions and c, a-axes biaxial orientation in the plane of the flow and width directions. A mechanism leading to this distribution of crystalline axes is discussed.
Orientation Development of Mixed Anisotropic Particles in Compounds
Authors: Lim S. , White J. L. 
Published: December 2013

Abstract
An experimental study of the development of orientation of mixed fiber and flake polymer compounds in polymer processing operation including extrusion and molding is discussed. Aramid fiber and talc and mica flakes are studied. The orientation of the particles is determined using wide angle x-ray diffraction. It is found that mixed particle systems lead to lower orientation of both fibers and flakes. The fibers tend to orient in the primary machine direction, while the flakes tend to orient perpendicular to the fibers. This is distinct from fiber compounds and flake compounds where fibers orient in the plane of the machine and transverse directions and flakes orient parallel to machine surfaces.
An In-line Rheometer for Molten Plastics
Authors: Broadhead T. O. , Nelson B. I. , Dealy J. M. 
Published: December 2013

Abstract
A novel in-line rheometer for use with molten plastics has been developed and evaluated. It is a process sensor designed to be installed in a melt flow stream, for example at the exit of an extruder. The entire process stream flows through the rheometer, so there is no output signal delay due to the flow of melt in a sampling line and gear pump. A small fraction of the melt entering the rheometer is drawn into a small gap between a rotating drum and an outer cylindrical wall. The shear stress acting on a small area of the outer wall is monitored by a shear stress transducer. A technique for taking into account the small pressure flow that is superposed on the drag flow in the shearing gap is described. The major problems that must be addressed in designing an in-line sensor arise from the fact that the temperature, pressure and flow rate of melt entering the rheometer are subject to the fluctuations and upsets that are ubiquitous in industrial processes. The new rheometer is able to operate in this environment and yield reliable viscosity values. However, the output signal of the shear stress transducer was found to be affected by the pressure and contained a low frequency noise component that limited its accuracy. An improved version of this transducer is currently under development.
Heat Transfer in Single and Twin Screw Extruders
Authors: Domschke T. , Justus C. 
Published: December 2013

Abstract
The elementary processes during heat transfer in screw extruders are described by a simulation model. The balance equations are solved numerically with a personal computer. By contrast with known computational approaches, consideration is given to the non-stationary processes in the melt layer between the screw flight and the barrel wall. This is guaranteed by incorporating the “pulsating shear” in this layer into the model as a dissipative energy source. The computational results are used to demonstrate, in an exemplary fashion for one extruder series, the influence of all the relevant machine and process parameters on the internal heat transfer.
The Gas-assisted Injection Molding Process
Authors: Potente H. , Hansen M. 
Published: December 2013

Abstract
This paper presents an application example for the modelling of a mold used for the gas-assisted injection molding process. The simulation software used allows the computation of the distribution of the thickness-fraction of skin material all over the part depending on the process conditions. The illustrations are shown in connection with an industrial mold and the simulation results are compared with experimental data showing a reasonable agreement. The influence of variations of different operation point parameters is shown. Some effects occurring due to the gas flow into the cavity are described.
Flow Mechanisms, Material Distributions and Phase Morphology Development in a Modular Intermeshing Counter-Rotating Twin Screw Extruder of Leistritz Design
Authors: Lim S. , White J. L. 
Published: December 2013

Abstract
An experimental study is presented of the mixing of polyamide-6 and polyethylene in a Leistritz modular counter-rotating twin screw extruder. Seven different screw configurations were investigated and the material distributions and phase morphology developments along the axis of the screw were characterized. The behavior of different modular elements was determined including screw flights of varying thickness, Kiesskalt compression elements and shearing elements.
Flow and Fiber Orientation Calculations in Reinforced Thermoplastic Extruded Tubes
Authors: Ausias G. , Agassant J. F. , Vincent M. 
Published: December 2013

Abstract
A calculation of fiber orientation of reinforced thermoplastics in two tube die geometries is presented. The flow field and fiber motion are calculated using coupled anisotropic constitutive equation and equation of change for fiber orientation. A finite element method is used for the flow field computation, and a simplified characteristic method for the fiber orientation. Results show that fibers orient parallel to the tube axis in a classical die of constant radius in the final land whereas fibers have a more isotropic orientation in a die with a final divergent land. Experimental observations and quantification of fiber orientation in reinforced thermoplastic tubes extruded with the two dies are presented. Results of the calculation agree well with the experimental data for the classical die. For the diverging die, the agreement is good at the tube surface, but the calculation underestimates the degree of orientation perpendicular to the tube axis in the core of the tube.
Tubular Film Blowing
Authors: Liu C.-C. , Bogue D. C. , Spruiell J. E. 
Published: December 2013

Abstract
A theoretical model for tubular film blowing, based on treating the bubble as “quasi-cylindrical” at each point and incorporating a deformation-thinning viscosity equation, explained all of the essential features of the experimental data. The viscosity function required to fit the blown film data was in plausible agreement with viscosity data (complex viscosity data) measured independently. Under most conditions the model predicts an “intuitive” effect of inflation pressure on blow-up ratio; that is, increasing the pressure causes the final radius (the blow-up ratio) to increase. The predicted passage from an “intuitive” regime to a “counterintuitive” regime, which occurs at high blow-up ratios, results from the thinning behavior of the viscosity model. Comparisons with the earlier model of Pearson and Petrie are also made. This model, based on thin-shell theory, disagrees with the data in several essential ways: it predicts counterintuitive results as regards the effect of inflation pressure and melt viscosity on bubble radius. These effects come about from an axial curvature term in thin-shell theory. The differences between the two models are discussed in detail.
Melting and Blending in a Modular Co-Rotating/Counter-Rotating Twin Screw Extruder
Authors: Cho J. W. , White J. L. 
Published: December 2013

Abstract
A comparative experimental study of blending polyethylene and polystyrene in a modular self wiping co-rotating and intermeshing counter-rotating twin screw extruder is described with similar modular screw configurations. Comparisons are made using different screw configurations possessing different numbers and placement of kneading disc blocks. Generally the intermeshing counter-rotating mode melts and mixes more rapidly than the co-rotating mode. The phase morphology in each machine seems to similarly from mixtures of pellets to polyethylene lamellae surrounding polystyrene pellets to a co-continuous morphology. Kneading disc blocks greatly enhance the rate of melting and mixing and are most effective when placed near the feed port rather than near the die. At 160°C, where the polystyrene has a much higher viscosity a co-continuous morphology develops. At 260°C where the polystyrene has a lower viscosity first a co-continuous and then a disperse phase morphology evolves.