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The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.

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Conference Proceedings

A Method for Robust Flexible Design
Christoph Roser, David Kazmer, May 2000

The robust design method aims to seeks to minimize the sensitivity of performance to uncontrolled variation. Product development frequently uses numerical simulations, analytic models and experimental data. However, these underlying predictions may be inaccurate, and include errors that causes the design to be unacceptable and require a design change. This paper presents a method that analyzes the possibility of a design change based on prediction uncertainty, and then estimates possible changes and evaluates the product design flexibility. The results indicate that small changes in design variables to increase robustness may reduce the likelihood and cost of future design changes.

Linking Design to Analysis: The Future of Simulation for Injection Molding
A.R. Thomas, P. Kennedy, May 2000

In recent years designers of injection molded parts have widely adopted solid modeling techniques. The time to derive and prepare an analysis model has become burdensome. This is because conventional CAE analysis of injection molding has made extensive use of the Hele-Shaw approximation to simplify the equations governing the process. A consequence of this simplification is the need to generate a midplane mesh. This example of a technical limit hindering the use of a technology has changed with developments arising from Moldflow's product philosophy of Process Wide Plastics Simulation". PWPS has been enabled by three new technologies. In this paper we discuss these developments and how they will change the way analysis influences the design of injection molded plastic Parts"

Automatic Design Optimization Molding Simulation for Injection Molded Parts
K.S. Barton, Baojiu Lin, Won Gil Ryim, May 2000

The past five years have seen drastic improvements in injection molding simulation. While prior to this period, advanced simulations provided a wealth of information about a part and mold design, a common complaint was that too much time was required to perform an advanced simulation. This is part of the reason for the rise in popularity of desktop" simulations which provide fast useful results though not as detailed as advanced simulations. Besides improving part quality and reducing part costs one of the primary objectives of molding simulation use is to reduce the design cycle and the time to get a mold into production. This paper discusses recently developed molding simulation technology which greatly reduces the time requirement to run an advanced simulation and reduces the overall product development time."

Injection Molding Process Control
R.G. Speight, A.R. Thomas, May 2000

Injection molders require a consistent optimization strategy for machine set-up and production control. The ultimate aim of an injection molding machine is to achieve 100% automatic inspection and quality control of all manufactured parts, where no unacceptable moldings are passed on to the customer. Process monitoring and control offers a key opportunity to the polymer processing industry enabling it to gain an understanding of its processes, to dispel its 'black art' image, and by this provide greater clarity for the machine operators and greater confidence for its expanding and highly competitive markets. The next major development for injection molding machine controllers is the integration of 'industry focussed' expert systems for process optimisation and production control. These expert systems will provide a well documented link between design and process engineering, passing information in both directions.

A Comparative Study of the Melting and Crystallization Behavior for a Metallocene and a Narrow Fraction of Ziegler-Natta Isotactic Polypropylene
Wei Huang, Rufina G. Alamo, May 2000

A comparative study of the melting and crystallization behavior is carried out between a metallocene type isotactic polypropylene and a narrow fraction of a Ziegler-Natta type with the same average defect content. At any crystallization temperature the melting temperature of the Ziegler fraction is ~ 3.5 °C higher than the metallocene. This difference is associated with the thicker lamellae thicknesses found in the fraction. The lamellae thicknesses were obtained by AFM, TEM and SAXS and good agreement was obtained between these techniques. The difference in thicknesses is interpreted as a consequence of a sustained heterogeneity of the intermolecular defect composition distribution in the Ziegler fraction even after fractionation. A second source for this difference could be a different partitioning of the defects present in the metallocene and in the fraction between the crystalline and the non crystalline phases. The product of the interfacial free energies obtained from nucleation theory, is very similar for both isotactic polypropylenes.

Processability and Mechanical Properties of Metallocenic s-PP/Conventional i-PP Blends
Érica Gervasoni Chaves, Maria de Fátima V. Marques, May 2000

Polypropylene with especial properties can be obtained by metallocenic catalysts, which represented the beginning of a new era in the polyolefins technology. In this context, some properties and principally some applications of sindyotatic polypropylene (s-PP) have not been well investigated. In this work, the influence of the metallocenic s-PP addition on the processability and on the mechanical properties of isotatic polypropylene (i-PP) was evaluated. It was observed that an increasing addition of s-PP promoted better processabilility, with an increasing in the impact strength. It was also verified a decreasing in the crystallinity of the blends, resulting in a decreasing in the stress at yield and module.

Interfacial Tensions in Polyolefin Blends
Andy H. Tsou, Michael K. Lyon, May 2000

The interfacial tension between immiscible polymers is difficult to measure due to the high viscosity of molten polymers. Additionally, the lack of optical contrast that exists between two molten polyolefins renders conventional optical methods impractical. Small-amplitude oscillatory shear flow provides an indirect technique for measuring the interfacial stress between immiscible polyolefin binary blends. Based on the model of Palierne, the interfacial contribution to the measured rheological response is governed by the ratio of the interfacial tension to the average radius of the dispersed droplets. In this work we have investigated the use of amplitude oscillatory shear measurements to determine the interfacial tension in binary blends of immiscible polyolefins. The two-dimensional droplet morphology in each blend was characterized using tapping-phase AFM. True dispersion phase radii were obtained after converting the measured two-dimensional size distributions to three-dimensional size distributions through the linear transformation method of Schwartz-Saltykov. Results of measured interfacial tensions in various polyolefin blends are reported. The interfacial tension of a PP/EP blend thus obtained was in agreement with the value calculated from the SANS measurement.

Rheological Properties of in situ Organic Composites
M.-F. Boyaud, A. Aït-Kadi, M. Bousmina, May 2000

A study to evaluate the rheological properties of organic in situ short polymer fibres (poly(butylene terephtalate) (PBT))/high density polyethylene (HDPE) and high density polyethylene/poly(ethylene-co-vinyl acetate) (HDPE/EVA9) composites has been carried out. The in situ compatibilization of the HDPE/EVA9/PBT systems with the Bu2SnO catalyst was performed. The different systems were melt blended in a twin screw extruder, drawn at the die exit and cooled. The results indicate that it is possible to produce such composites using reactive extrusion for compatibilization and post extrusion drawing to control the aspect ratio of the PBT fibres. Morphological analysis allowed evaluation of parameters such as draw ratio, PBT concentration and compatibilization on the size and shape of the fibrils. Their influence on the solid rheological behaviour is discussed.

Anisotropic Properties of Injection-Molded Short-Fiber Thermoplastics
Erwin W. Liang, Gerald G. Trantina, May 2000

As plastics are reinforced with short fibers to increase stiffness and strength and to reduce shrinkage and thermal expansion, fiber motion controlled by the developing flow field during molding leads to a layered microstructure characterized by different fiber orientations through the thickness. The anisotropy of material properties is determined by the fiber orientation and the thickness of each layer which depends on the gating configuration, the part geometry, the rheological properties, and the processing conditions. In this paper we report the directional elastic properties in plaques injection molded with glass fiber reinforced polycarbonate (PC), polybutyleneterephthalate (PBT), and polyamide (PA). Anisotropy plus fiber content and length strongly govern the thermomechanical properties of fiber-reinforced products, which are essential for performing CAE analyses of short-fiber-filled parts.

Effect of Disperse Phase Structure on the Optical Properties of Multicomponent PP Blends
Daniel Ercoli, Graciela Goizueta, Numa Capiati, May 2000

Shipments of plastic packaging materials have strongly increased in recent years. A major reason for the rapid growth of plastics is the versatility of these materials. Blending is a powerful method to create materials with enhanced properties at competitive costs. PP based blends are very promising in these area. This work presents results obtained for ternary blends of polypropylene, linear low-density polyethylene and different ethylene-propylene rubbers. The effect of elastomer viscosity and co-monomer content, blend composition on the phase morphology and optical properties were studied. The particle size distribution of the dispersed phase was studied by TEM. The crystalline structure of the PP matrix was analyzed by DSC and WAXS. Transparency was studied by measuring the light transmitted through specimens of blends placed between polarizers.

Incidence of the Stereoregularity on the Crystalline Modifications of Isotactic Polypropylenes Synthesized with Metallocene Catalysts
Carlos Grande, Ruth Zacur, Graciela Goizueta, Numa Capiati, May 2000

Polypropylene metallocene technology has been growing very fast in the last years. Polypropylene produced in this way is expected to provide competitive properties over the conventional Ziegler-Natta products. This work shows the effect of the regioirregularities content of metallocene based Polypropylene on the % ?-modification of samples isothermally crystallized at different temperatures. The regioirregularities content was determined by 13CNMR and the molecular weights by SEC. The proportion of the different crystalline modifications was determined by WAXS. The thermal behavior of the isothermally crystallized samples was analyzed by DSC. Supermolecular morphologies were observed by Polarized Light Microscopy.

The Use of Benchmarking as a Design Tool
Barbara J. Arnold-Feret, James H. Arnold, May 2000

Benchmarking can be used as a design tool during product development. When used as a design aid, benchmarking reduces costs, increases design reliability, limits liability exposure, and reduces time to market. Benchmarking, typically delegated to a quality function, when integrated into development, reduces design time and cost. Benchmarking is used to establish product critical, major and minor characteristics, and allows design comparison to competitive products. The best of the best" elements from products can be incorporated into the design thus avoiding any mistakes made during the first generation and by competitors in subsequent product. Likewise "worst of the worst" elements can be avoided in new and next generation products thus gaining time money and more profit for the manufacturing sector."

Development of Impact Modified Engineering Polyester Resins for Automotive Applications
M. Lu, S. Nelsen, T. Sinner, S. Leyrer, May 2000

Polyethylene terephthalate (PET) has been successfully used as a fiber, packaging and film material for many years. PET compounds have also been used successfully for injection molding. The use of engineering thermoplastics in the automotive industry continues to expand. A current trend is to replace traditional body panel materials such as metal and SMC with engineering thermoplastics that can be injection molded. The use of the injection molding process to make body panels can save manufacturing time and reduce labor cost. The part made from engineering thermoplastics has to meet the same stringent requirements as traditional materials, including strength, toughness, dimensional stability, weather resistance, and chemical resistance. Recently, Ticona has worked with automotive companies to develop impact modified and reinforced engineering polyester resins to meet these requirements. An early developmental product, Impet® EKX-182, was successfully used in molding the structural body of Chrysler's Composite Concept Vehicle. This material has a good balance of strength and toughness, heat resistance, weatherability and cost effectiveness. Additional application opportunities led to the development of Impet® EKX-215 which has improved strength and toughness. Recently, we have developed a higher modulus, high impact strength material, Impet® EKX-221. In this presentation, we will review the development of these PET based engineering resins. Structure property relationships will also be discussed.

Energy Absorption in Foam Filled Glass Fiber Reinforced Plastic Sections with Light Metal Reinforcement
N. Suresh, Gilbert Chapman II, Craig Patterson, Lawrence J. Oswald, May 2000

The automobile industry is seeing an increased need for the application of plastics and their derivatives in various forms such as fiber reinforced plastics, in the design and manufacture of various automotive structural components, to reduce weight, cost and improve fuel efficiency. A lot of effort is being directed at the development of structural plastics, to meet specific automotive requirements such as stiffness, safety management, strength, durability, environmental standards and recyclability. This paper presents the effect of foam filling on the energy absorption during impact, of typical automotive body sections made up of fiber reinforced thermoplastic material with or without metallic reinforcements. In particular the study compares energy absorption characteristics during impact of typical automotive sections made of fiber reinforced thermoplastic materials without foam filling, with foam filling, with foam and some light metallic reinforcements. An attempt is also made to present results on such energy absorption at varying temperature conditions such as low temperature, ambient and elevated temperatures. In all cases it is found that the inclusion of foam and some lightweight material reinforcement enhances not only the structural integrity of fiber reinforced plastic sections but also improves significantly the energy absorption of such material systems under impact.

Kinetics of Isothermal Crystallization of Syndiotactic Polypropylene: Avrami, Tobin and Malkin Analyses
Pitt Supaphol, May 2000

Various macrokinetic models; namely the Avrami, Tobin, and Malkin macrokinetic models, were applied to describe the kinetics of isothermal crystallization from the melt state of syndiotactic polypropylene (sPP). Data analysis was carried out using a direct data-fitting method, in which the experimental data were directly fitted to each macrokinetic model using a non-linear multi-variable regression program. The results suggested that the experimental data can be best described by the Avrami model, followed by the Malkin and Tobin models, respectively.

The Role of Interfacial Slip in Melt Rheology of Immiscible Polymer Blends
Rui Zhao, Christopher W. Macosko, May 2000

A number of researchers have reported an anomalous lowering of viscosity in immiscible polymer blends. Slip at the interfaces between the polymers has been proposed to explain these observations. Because of the complex morphology developed in melt blends it is difficult to test the slip hypothesis. However, using layer multiplication dies in coextrusion, two or more polymers can be alternatively combined into hundreds or even thousands of continuous layers generating a large amount of well-defined interfacial area. Polypropylene (PP) and polystyrene (PS) with closely matched viscosity were blended in a twin screw extruder and also coextruded into 2, 32, 128 alternating layers. The steady shear and dynamic shear viscosity of the blends was first measured in a capillary rheometer and a rotational shear rheometer using parallel plates geometry. While the steady shear viscosity of the blends was lower than that of both homopolymers, the dynamic shear viscosity of the blends was the same as that of the homopolymers. The pressure drop of the coextruded multilayer melts through a slit die was lower than that of both homopolymers and decreased with an increase in the number of layers. From these results an interfacial slip viscosity was estimated. Addition of diblock copolymer was able to suppress interfacial slip.

Polyamides 4.10 and 4.12: Potentially New Engineering Plastics
Cor Koning, Lilian Teuwen, May 2000

The 1,4-diaminobutane based polyamides 4.8, 4.10 and 4.12 were synthesized and characterized. For comparison, some 1,6-diaminohexane based counterparts were studied as well. PA 4.12, and in particular PA 4.10, proved to have a very beneficial combination of high Tm, high crystallization rate and excellent physical properties, like a relatively low moisture absorption and accordingly good mechanical properties after conditioning. Further, PA 4.12 proved to exhibit an excellent zinkchloride resistance. First indications were obtained, that for aliphatic polyamide isomers, containing 16 carbon atoms in the repeating unit, the melting points are related to the number of ways to make an energetically favourable chain fold upon crystallization: isomers having two possible ways of chain folding have Tm's which are 13-15 °C lower than isomers having only one possible way of chain folding upon crystallization.

The Challenges Facing CAE of Injection Molding as We Enter the Next Millennium
Anne Bernhardt, Giorgio Bertacchi, Natalia Kassa, May 2000

By the end of the 1980s, everyone interested in injection molding had read of the wonders of flow analysis, and of its fabulous capabilities. Since then, nearly everyone engaged in molding projects is likely to have had at least some degree of involvement in one or more applications of molding analysis. As we enter the next millenium, the utility of these techniques is generally accepted. However, the application of CAE technology in the molding industry is still confined to only a small fraction of molding projects. This paper examines the challenges that need to be met to expand CAE of Injection Molding to its full potential in the 22nd century.

Intermittent Extrusion Blow Molding Using a Reciprocating Screw
Nathan A. Mancine, May 2000

The intermittent type of extrusion blow molding is different from continuous blow molding in that it is not a continuous cycle. An intermittent blow molder can be very useful when processing plastics that have a low melt strength, like Polycarbonate. This project began with the donation of a partially finished prototype of a continuous blow molder. This blow molder will use a reciprocating screw injection unit that had been donated. The hydraulic pumps, the clamping system and the frame are still part of the design. This paper will discuss the design and construction of this intermittent extrusion blow molder that will be used in the Penn State University's plastics processing lab in Erie, Pennsylvania.

Sequential Valve Gating for Thin Wall Injection Molding Comparison between Experimental Results and Filling Software
Ronak Shah, May 2000

The objective of this study was to investigate the sequential and concurrent filling patterns of a U-shaped thin walled cavity and to evaluate the weld line location, shifting of weld line location and retention of weld line strength. The experimental results were also compared with the predicted results obtained from a computer filling simulation software. The opening of the gates was sequenced to achieve the desired fill pattern, thereby eliminating hesitation effects which cause the flow front freeze-off and also to control the wall thickness to flow length ratio. The paper discusses the effect of critical processing parameters that affect the shifting of weld line location such as, fill pressure, fill time and gate opening-closing time.

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