SPE Library
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
Applications and Developments of Color Laser Marking of Thermoplastic Components
Designers of thermoplastic products have always striven to find faster, more cost-effective and durable methods for marking plastic parts. Manufacturers are also looking for systems that allow the reduction of paint and eliminate VOC issues. With new quality mandates, permanent marks on parts must be durable, legible, and traceable to provide information for the lifecycle of the product. Color laser marking thermoplastics is a new marking method that meets these criteria. There are a number of factors to be considered when introducing laser marking into a manufacturing operation. First, is to plan for laser marking at the earliest stage of product development. Second, is to understand the physics and chemistries involved when the laser beam hits the plastic surface. Last, is the impact of using a computer-controlled laser for faster marking and rapid design changeover. Current commercial product case histories are included to illustrate this new technology. These issues and others will be discussed in this paper.
Time Dependent Crack Growth in Polyethylene: Characterizing the K vs. da/dt Dependence and the Effects of Igepal
Testing of newly developed pipe is both time consuming and costly. Hydrostatic creep-rupture tests that measure hoop stress vs. time to failure can be used to rank systems and predict service lifetimes. This paper presents a fracture mechanics approach to ranking polymers and predicting lifetimes for long-term, slow crack-growth rate failures. Constant load three point bend tests have been performed on notched specimens to produce displacement vs. time data and calculate stress intensity (K1) vs. crack growth rate (da/dt) relationships. Very good repeatability has been demonstrated and da/dt has been found to be a unique function of K1 independent of the combination of load and crack length used to obtain it.
Molecular Modeling of Nanocomposite Systems
Most polymer/clay nanocomposites require the surface modification of the clay in order to render the clay compatible with the polymer. Two main methods for surface modification of smectites have been described in the literature. These methods include the more traditional ion exchange method utilizing onium ions and the more recently described ion-dipole method. With the large number of surface modifying agents available and the great variety of polymers, a rapid method of screening was needed. Computational modeling has proven to be just such a tool. A computational method has been developed that can predict very accurately the type of intercalate that will form with a given molecule but also yield quantitative x-ray d-spacings for the intercalated clay complex. The method also can be utilized to predict the energetics of exfoliation into a polymer to form a nanocomposite. This modeling method, as well as, specific examples will be described in detail.
Saving Costs and Time by Means of Gas-Assisted Powder Injection Molding
Powder injection molding (PIM) is well established for net shape production of ceramic parts. However, the size of the molding is limited by economic efficiency due to the expensive powder. Moreover the wall thickness defines not only cooling time but rather the time required for debinding and sintering. For this reason the combination of PIM and gas-assisted injection molding is of interest. It provides more cost effectiveness through considerable savings for debinding and sintering time. The aim of IKV's investigations is to realize gas-assisted PIM" and to provide comprehensive knowledge about the spreading of the gas bubble."
Enhanced Automatic Sortation of Post-Consumer Bottles
The selection of an automatic sortation system for separation of post-consumer bottles is of high importance for today’s recycler. The configuration of a modern recycling plant also needs to be carefully assessed, as different configurations in plant equipment have their own advantages and disadvantages and this can make the difference between a successful operation and a failure. This article examines the performance of spectroscopic sorting equipment in a recycling environment, which has to be viable at high speeds, problems associated with this technique as well as possible solutions to improve performance.
The Dependence of Cooling Channels System Geometry Parameters on Product Quality as a Result of Uniform Mold Cooling
The design and geometry of a cooling-channel system are significant factors for the injection molding process, as an optimized cooling system presumes high-quality molded parts at minimum cooling time. Significant quality characteristics of the molded part, depend on the geometry of the cooling system and on how heat is taken away by the cooling system per production cycle. A proper cooling system design results in a rapid but uniform and balanced cooling, and therefore decreases shrinkage, warpage, thermal residual stresses and maintains dimensional accuracy and stability. In the present paper the C-MOLD cooling analysis software is used to investigate systematically, based on the design of experiments" method the effect of the basic cooling system geometry parameters (diameter depth pitchnumber of cooling channels per manifold) on mold cooling quality. The mathematical model obtained from the above analysis can then be used to optimize the injection molding quality."
The Dependence of Cooling Channels System Geometry Parameters on Product Quality as a Result of Uniform Mold Cooling
The design and geometry of a cooling-channel system are significant factors for the injection molding process, as an optimized cooling system presumes high-quality molded parts at minimum cooling time. Significant quality characteristics of the molded part, depend on the geometry of the cooling system and on how heat is taken away by the cooling system per production cycle. A proper cooling system design results in a rapid but uniform and balanced cooling, and therefore decreases shrinkage, warpage, thermal residual stresses and maintains dimensional accuracy and stability. In the present paper the C-MOLD cooling analysis software is used to investigate systematically, based on the design of experiments" method the effect of the basic cooling system geometry parameters (diameter depth pitch number of cooling channels per manifold) on mold cooling quality. The mathematical model obtained from the above analysis can then be used to optimize the injection molding quality."
A Comparison of Different Strategies for Injection Filling Velocity Control
Injection velocity during filling stage was experimentally controlled using different control algorithms, from simple open-loop control and Proportional-Integral (PI) closed-loop control, to more advanced strategies such as Self-Tuning Regulator (STR), fuzzy control and Generalized Predictive Control (GPC). It is shown that the advanced control can effectively overcome the non-linear and time-varying characteristics of the filling velocity. The advantages and drawbacks of each strategy are presented and experimentally illustrated. The use of advanced control strategies is shown to be necessary for accurate control of the injection velocity with good repeatability.
Reduced Time to Market Using Blow Molding Simulation Software
Speed to Market. The cliché is well entrenched in today’s business jargon. When spoken, we nod our heads fully cognizant of the relentless pressures the concept conjures up. To deliver fresh new products in lightning strike fashion. That directive is the paramount force driving engineers and designers to endlessly search for the latest tool that will circumvent time, provide greater precision and produce that widget with less cost. Technical Blow molding is considered by many as much a black art as either science or engineering and rightfully so. We often look to the technician who runs the machine day in and day out for advice. Perhaps we consult a fellow employee who knows the most about what did or didn’t work in their world of experience. In both cases, we’re trying to get a feel of whether or not that new design is moldable. More often than not, we fall back to what is safe because we no longer have the luxury of additional time to debug or break in a truly new idea on the molding floor. A new tool has arrived that will change how we approach blow molding. This paper will examine an actual case study on how Fisher-Price, Inc. was able to drastically reduce product debug time by utilizing BlowView® Blow Mold Simulation Software developed by the Industrial Materials Institute of the Canadian National Research Council.
Effects of Molecular Structure on the Rheology and Processability of High Density Pokyethylene Blow Molding Resins
The influence of molecular structure on the rheology and processability of HDPE blow molding resins is studied. Experiments were conducted using capillary and extensional rheometers, a melt indexer and a blow molder unit. Twenty four resins were analyzed in terms of their shear flow and extensional properties, extrudate swell characteristics, and melt strength. The studied samples were produced using a variety of manufacturing technologies and had varying molecular weight characteristics. From the results, the influence of molecular structure on the rheological properties was determined. Furthermore, to assess resin processability, pillow mold (blow molding) experiments were performed. The implications of rheology on processability (parison sag and weight swell) are also discussed.
Determining Etch Compensation Factors for Printed Circuit Boards
A model has been developed to simulate the progression of material properties and residual stress development during the processing and etching of metal-clad, multi-layered, fiber mat reinforced, thermoset resins used in the printed circuit board industry. The simulation predicts the dimensional movement of the laminates during the manufacturing stages. This information can then be used to prescribe compensation factors to the artwork during the etching process. Predicting the residual stress, shrinkage, and warpage of these systems can lead to a minimization of the size of the circuit patters while decreasing the number of failures.
Modeling and Simulation of Mechanical Properties of PP According to the Thermal History Imparted
The object of this investigation is to design software, along with the corresponding experimental methodology, that allows characterizing and/or predicting the mechanical behavior of semicrystalline plastic materials, such PP, based on the crystallinity developed during the manufacturing process used. The experimental temperature and crystallinity profiles are theoretically reproducible by means of the simulation program developed. The curves obtained for the various properties indicate that there is a high degree of proportionality between crystallinity and mechanical properties.
Composite Material for Rapid Tooling Produced by High Speed CNC Machinery
Rapid Prototyping (RP) and Rapid Tooling (RT) have become increasingly important processes for fast to market" product development. Two RT approaches are to produce molds from (1) RP patterns and (2) CAD data using additive or subtractive methods. This paper discusses the second approach based on a new moldmaking material that can be CNC machined at very high speeds. The new composite material demonstrates the compressive strength thermal resistance and thermal diffusivity required for the injection molding of production grade thermoplastics to produce hundreds of dimensionally accurate prototypes under normal injection pressures and temperatures."
DOE & Decoupled Molding Part I: Process Centering and Validation from the Plastic's Point of View
Frequently, injection molders approach experimental designs from the perspective of the settings on the molding machine, sometimes resulting in sub-optimal or misleading results. Further, when the resulting process is validated, it is typically done under short term sources of variation. This frequently proves to be a poor evaluation of the true long-term capability of the process. A new approach to centering and validating processes is proposed and a model study is presented for illustration. Here, the experiment is conducted around the fundamental variables that affect the part inside the mold, using a physical model" that acknowledges the unique physics of the injection molding process. Next the data is correlated with fundamental process variables allowing causal relationships to be established. Finally during validation primary sources of long-term variation are introduced into the capability study."
DOE & Decoupled Molding Part I: Process Centering and Validation from the Plastic's Point of View
Frequently, injection molders approach experimental designs from the perspective of the settings on the molding machine, sometimes resulting in sub-optimal or misleading results. Further, when the resulting process is validated, it is typically done under short term sources of variation. This frequently proves to be a poor evaluation of the true long-term capability of the process. A new approach to centering and validating processes is proposed and a model study is presented for illustration. Here, the experiment is conducted around the fundamental variables that affect the part inside the mold, using a physical model" that acknowledges the unique physics of the injection molding process. Next the data is correlated with fundamental process variables allowing causal relationships to be established. Finally during validation primary sources of long-term variation are introduced into the capability study."
DOE & Decoupled Molding Part II: Correlation of Cavity Pressure with Part Characteristcs for Automated Parts Containment
As more molders face pressure to reduce costs of quality, many are turning to cavity pressure monitoring to automate part segregation. Here, abnormal parts are automatically rejected in real time using alarm levels placed around key cavity pressure measures. However, few techniques are available to determine which measures to monitor and what alarm levels to set for each of them. A new, systematic technique has been developed to assist molders in the selection of appropriate measures and alarm levels. Using data taken during a DOE based tryout, correlations are made between cavity pressures and key part characteristics. For metrics which show the best correlations, alarm limits are set based on part specifications. In this paper, a model study is presented to illustrate the application of these techniques.
Dramatic Changes in Glass Filled Polyphenylene Sulfide (PPS) via Variations in Maximum Fill and Packing Pressures, Injection Rate and Melt Temperature
Process conditions in injection molding can dramatically change the mechanical properties of glass filled PPS. The parameters studied included maximum cavity-fill pressure, packing pressure, injection velocity, and melt temperature. This study utilized advancements in cavity pressure measurement and switching by cavity pressure to control the injection fill stage. Also, an easy designed experiment was used that allows for practical, quick, and reliable testing of part properties that can be applied to future part performance studies. Due to many mechanical variables, this study focused on tensile properties.
New Methodology for Determining the Blow Mouldability of Engineering Resins for Automotive Applications
For a resin to be successful in a blow moulding application, it has to comply with a set of characteristics known as a whole as the material's blow mouldability". This concept includes the parison swelling behaviour (both in diameter and thickness) and the resistance of the melt to extension (melt strength). This paper outlines a new methodology geared towards the establishment of relationships between relevant rheological properties and key processing material behaviour parameters (swell and sag) governing the blow moulding process. The technique has been applied to the intermittent extrusion of a PC/ABS blend (PULSE™). Several processing parameters such as drop time extrusion temperature and die gap were studied."
Injection/Stretch Blow Moulding of PET/LCP Blends for Better Product Performance
PET plastic containers are mainly manufactured by the injection stretch blow moulding process. Their main advantages compared to glass containers, are their low cost of production, lighter weight and high impact resistance. However, the growing demands on beverage containers regarding barrier properties and hotfill ability have surpassed the PET limits in applications such as beer bottles, fruit juice containers, etc. The aim of this work is to examine if PET/LCP blends moulded on a one-step injection stretch blow moulding can produce bottles that fulfill the requirements of barrier and mechanical properties and hotfill ability. The results are interpreted based on the flow behaviour and microstructure characteristics of the materials.
Microstructure Development during the Injection Moulding of PET/LCP Blends
For several years, plastics processors have been blending two or more generally incompatible materials in order to improve physical or mechanical properties. Depending on the degree of compatibility and thermomechanical history during processing, various goals may be attained: easier processing, improved mechanical (modulus, impact strength), thermal and barrier properties. Polyethylene terephthalate (PET) enjoys wide success in industrial applications because of its outstanding mechanical, optical and barrier properties. However, the growing demands of the electronics and automotive sectors have surpassed the PET performance limits. With its outstanding barrier properties as well as mechanical properties even at high temperatures, LCP's are potential candidates as a blend component.
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