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Computer Simulation of 3D Short Fiber Orientation in Injection Molding
This paper develops a true three-dimensional numerical approach to simulating the melt filling and fiber orientation in injection-molded part of complex geometry. An efficient finite volume method is combined with VOF method to solve the melt flow during molding. The fiber orientation distribution is described by the second-order orientation tensors. The three-dimensional orientation of fibers is determined through the Folgar-Tucker equation, in which an interaction coefficient is introduced to account for the fiber-fiber interaction. Several example cases are simulated to verify the predicted melt front advancement and the corresponding fiber orientation. An industrial case with complex geometry is also studied to illustrate the capability of the proposed methodology.
Three-Dimensional Computer-Aided Mold Cooling Design for Injection Molding
Mold cooling system design in injection molding is of great importance because it is crucial not only to reduce molding cycle time but also to improve part quality. Traditional mold cooling analysis is based on the hybrid finite-difference/ boundary element (FD/BEM) approach. This approach was developed to accommodate the conventional 2.5D Hele-Shaw flow-based shell element model. In this paper, a true three-dimensional mold cooling analysis approach is developed. A fully tree-dimensional numerical analysis faithfully simulates the effects of part geometry, cooling system design, and ambient temperature on the solidification of the part. Finite volume method (FVM) is adopted as the numerical engine of the new approach. This developed approach is proved from numerical experiments to be a cost-effective method for true 3D simulation in injection mold cooling analysis.
Optimization of the Warpage of Fiber Reinforced Thermoplastics by Influencing the Fiber Orientation
This paper describes a new commercial simulation tool to simulate the injection molding process and the warpage of fiber reinforced thermoplastics considering the anisotropic behavior. A full 3D formulation of the Navier-Stokes equations with a VOF algorithm for the description of the free surface motion is used to simulate the filling process. The transport of the fiber orientation is calculated by the Folgar-Tucker equation using a hybrid closure approximation. The resulting fiber orientation tensor is used for the calculation of the anisotropic mechanical behavior. The Halpin-Tsai equations provide the anisotropic material data for the calculation. Through an real-life example it will be shown that the knowledge of the fiber orientation can be used to optimize the runner system in order to change the local fiber orientation and thereby to optimize the warpage of the part.
Effect of Colorant Carriers on Strength of Weld Lines in Polypropylene
In this study, the effects of polyethylene (PE) and polypropylene (PP) colorant carriers for various levels of loading on the short-term strength of weld lines in homopolymer polypropylene are quantified. Tensile bars (“dog bones”) were molded with an intentional weld line in the gauge length of the bars for a variety of material mixes. When tested at room temperature, the colorants with the polyethylene carrier drastically reduced the tensile elongation of the bars when compared with an unpigmented sample. The reduction was so severe that the PE-carrier specimens broke before yielding, thus exhibiting significant loss of strength. Samples of PP having the colorant with the PP carrier, while breaking at significantly lower elongation than their unpigmented counterparts, showed no reduction in weld-line strength because they yielded. Elevated temperature results are less dramatic, the unpigmented and PP-colorant samples yielded and stretched beyond 450%, while three-fifths of the PE-colorant specimens exhibited a yield. A PP co-polymer with PP-based colorant was also studied. In addition, slow strain-rate data is presented for a few compounds, and the rate / temperature dependence is discussed. Finally, several samples were aged at elevated temperature and subsequently tensile tested at room temperature. The results showed reductions in elongation but not weld-line strength.
The Influence of Mould Temperature and Polymer Structure on the Mechanical and Thermal Properties of Metallocene Catalysed LLDPEs
A number of metallocene and conventional LLDPEs, with different material properties, were injection moulded over four different mould temperatures. An assessment of the effect of cooling rate and polymer properties on the mechanical performance of the specimens was conducted to establish any significant correlations. Rheological studies of the materials under high shear rates experienced in injection moulding, was performed to determine flow characteristics of the materials. Differential scanning calorimetry (DSC) and dynamic mechanical thermal Analysis (DMTA) were used to study the influence of the comonomer type and degree of branching on the properties of the materials.
Study of Hue Variation in Different Extrusion Applications
Color Masterbatches are widely used in all types of Applications such as Injection Molding, Blow Molding, Blown-Film Extrusion, Monofilaments, Rafia tapes, etc. This paper is the study done to facilitate faster matching and understand the hue variation in different color with different extrusion applications. Hue variation is studied keeping Injection Molding Application as Standard.
Oxidative Photodegradation of Colored LLDPE
The oxidative photodegradation of colored linear low density Polyethylene (LLDPE) have been studied. Extruded colored films were exposed to natural tropical sunlight for times ranging up to three months simultaneously with control films. Pigment masterbatches had been incorporated into the colored films by means of the now effective masterbatching process. The photooxidized films were analyzed with respect to the pigment effects. Results indicate considerable modifications on the LLDPE properties; the extent of which depends on the nature and composition of the applied pigments.
Effect of the Masterbatch Carrier on the Pigment Dispersion and Mechanical Properties of Colored Polyolefins
Polyethylene and polybutene were used as carriers to produce two color concentrates with a high amount of organic pigments. Different colored plastic products, namely polyethylene film and polypropylene injection molded parts, were produced using both masterbatches. The polybutene masterbatch promotes a better dispersion of the pigment and improves the toughness of injection molded polypropylene.
The Effect of Nitrogen Purging on Degradation during Reprocessing in Injection Molding
This study investigated the effect of nitrogen purging in the material hopper on the melt flow index (MFI), residual oxidative induction time (OIT), color and impact strength of impact modified polypropylene copolymer and polycarbonate during repeated reprocessing through an injection molder. Heat history had the expected effect of increasing MFI, changing color and decreasing impact strength for both resins and decreasing OIT in polypropylene. In polypropylene nitrogen purging significantly reduced the changes in MFI and OIT resulting from repeated reprocessing. However, nitrogen purging did not have a significant effect on the properties of polycarbonate, probably due to its inherent resistance to oxidative degradation.
The Effect of Phthalocyanine Pigment on the Microstructural and Mechanical Performance of Propylene-Ethylene Block Copolymer
Injection moulded samples of a commercial propylene-ethylene block copolymer containing 0% - 8% phthalocyanine blue pigment were prepared using a range of mould temperatures (40°C - 80°C). Mechanical and thermal analysis showed progressive increase in tensile modulus, storage modulus (E’) and glass transition temperature (Tg) with increase in pigment loading. However, impact strength of the pigmented copolymer decreased progressively with increase in pigment loading and mould temperature. Thermal analysis of the samples shows that changes in crystalline melting phase ?H, and activation energies Ea for phase relaxations (DMTA) may account for the overall decrease in impact performance of the pigmented copolymer.
Microcellular Nanocomposite Injection Molding Process
This study aims to explore the processing benefits and property improvements of combining nanocomposites with microcellular injection molding. The molded parts produced based on the Design of Experiments (DOE) matrices were subjected to tensile testing, impact testing, and Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Dynamic Mechanical Analysis (DMA), and X-ray Diffraction (XRD) analysis. Effects of processing conditions on the mechanical properties and microstructures have been studied. The results show that the supercritical fluid (N2) helps to further exfoliate and uniformly disperse the nano-clays in the matrix during the course of molding process. Compared to the corresponding base polyamide microcellular parts, the microcellular nanocomposites exhibit better cell structures and cell distributions as well as better mechanical properties.
Applications of Polyamide/Cellulose Fiber/Wollastonite Composites for Microcellular Injection Molding
In this study, a cellulose-fiber-reinforced Polyamide-6 (PA-6) composite, a hybrid composite (PA- 6/cellulose/Wollastonite), and the neat PA-6 resin were injection molded into ASTM test–bar samples with conventional and microcellular injection molding. The impact and tensile strengths of molded samples were measured and the Scanning Electron Microscopy (SEM) images were taken at the fracture surfaces. The effects of filler systems and the introduction of microcellular structure on the impact and tensile strengths were studied. It was found that the cellulose fibers and the cellulose/Wollastonite fillers improve the tensile strength and tensile modulus. In addition, the microcellular injection molded neat resin exhibits a higher impact strength than that of the conventionally molded solid part. However, a reduction in tensile strength was observed with both of the filled composites when molded with microcellular injection molding. This could be attributed to microcells at the interface of cellulose fibers and the polymer matrix.
Fracture Toughness Evaluation of Adjacent Flow Weldline by SENB Method
Fracture toughness of adjacent flow weldline occurring around an obstructive pin was evaluated by single edge notched bend (SENB) method. The fracture toughness near the pin was higher than any other part of the weldline. The fracture toughness decreased drastically along the weldline and then increased gradually toward the end of the specimen. These characteristic features could be explained by flow-induced molecular orientation at the weldline interface. The material flow beside the pin stopped in the middle of the filling process. Molecular orientation parallel to the weldline due to the fountain flow relaxed since no shear stress affected the area, resulting in high molecular entanglement across the weldline. On the contrary, at the downstream side the material kept on flowing during the filling process. This indicated that the molecular orientation could not relax due to flow-induced stress during the process. The magnitude of these two areas was dependent on the position of first collision point (FCP) at which two melt fronts collided first behind the pin. The V-notch depth on the surface of the specimens was also dependent on the distance from FCP.
The Quaterrylimides - Highly Efficient NIR Absorbers for Plastics
A couple of years ago we developed a class of highly efficient organic NIR absorbers based on quaterrylenetetracarboxylic diimides ('quaterrylimides'), which exhibit photo- and thermostabilities at levels hitherto reserved exclusively to inorganic materials. In this paper we want to present models for the explanation of the unique photostability of this class of compounds, as well as recent advances in the synthesis of those materials, and examples for state-of- the-art plastics applications.
An approach to teaching introductory polymers as a new language was considered. A new pedagogy, including complete definitions, novel technical grammar, and the specific roles of symbols and self-correction, was required. In return, the language concept improved student scientific communication skills, problem-solving ability, especially learning from context, and in general accelerated learning. The approach was applied to teach introductory polymer science, resulting in performance substantially equivalent to traditional polymers courses.
Industrial Training Programs for Plastics Manufacturing
The Plastics Institute of America has a long history of training in the polymer/plastics field. Over the past twenty years this training has focused on the shop floor employees and new professionals as compared to research and management types. Successful long term training has been conducted with leading consumer, medical, and electronic manufacturers. The training is offered in a wide range of traditional and cutting-edge areas to help companies and their employees keep pace with the rapid rate of change that has become the cornerstone of today's economy.
Flow-Induced Crystallization and Birefringence in Injection Molding of Semicrystalline Polymers
A novel approach for the numerical simulation of frozen-in birefringence in moldings of semicrystalline polymers was proposed. The approach was based on the calculation of elastic recovery and crystalline orientation function frozen when the stress-induced crystallization occurred. The flow effect on the equilibrium melting temperature elevation due to the entropy reduction between the oriented and unoriented melts was incorporated to model crystallization. To find frozen-in elastic recovery and entropy change, a non-linear viscoelastic constitutive equation was used. The crystalline and amorphous contributions to the overall birefringence were obtained from the crystalline orientation function and the flow birefringence, respectively. The skin layer thickness and birefringence profiles were predicted and measured in moldings of polypropylenes of different molecular weights at various processing conditions.
Adiabatic Splay and Blush in Injection Molded Parts
Most molders are aware of the potential for creating burn marks where air gets trapped in molded parts. What no one seems to consider is blush or splay marks that manifest specifically along knit lines and would otherwise be assumed to be the effect of shear. The only problem is that the shear cannot be accounted for in the tool design. The cause can be traced back to trapped air, predicted with mold filling analysis software (as such), and verified with physical testing. The purpose of this paper is to give proper definition to this defect and distinguish it from burns and short-shots as caused by air entrapment, and thus can be more easily identified and remedied.
Fibre Orientation in Weldline Areas - Investigation of an Air Intake Manifold
The focus of attention is kept on weldline behavior in parts of complex geometry, i.e. the upper part of an air intake manifold. By simulating the filling process using simulation software, the fiber orientation and the filling was calculated and compared to experimental studies. Thereby, a rather inhomogeneous filling behavior was found, caused by an unequally balanced runner system that leads to changes of the flow direction within the cavity during the injection process. These circumstances prevent the weldlines zones from spreading throughout the part. Hence, a distinct control of an uneven flow front pattern could help to reduce the weldline area and therefore minimize zones of optical and mechanical weak points in plastic parts.
3D CAE Simulation and Verification for the Ferrule of MT-RJ Fiber Connector
Because communication and Internet are so popular, light communication will become an efficient way to send message in the next generation. Optical fiber connector becomes an important component that connects, divorces or reunites the fiber, light source, light sensor and the other fiber ferrule connector. Because of the tiny size of products and the demand of precision, the decrease of manufacturing cost and the increase of demanded precision will be a huge obstacle that has to be overcome.This paper presents the study for the molding of ferrule in MT-RJ fiber connectors. The work includes the design of molding configuration with three different gating locations which are used to study the effects for the critical dimensions and precision of fiber holes. In addition, the 3D CAE software are used to simulate and verify the molding results. Moreover, the Taguchi method is used to find optimal processing conditions for resolving the void problems.
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