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
ON-LINE IN-MOLD TRANSDUCER IN INJECTION MOLDING
Pressure and temperature sensors installed in the injection molding molds have been applied in industry to measure quality related information. However, these sensors allow only the measurement of polymer melt status at the location where the sensors are installed, limiting the generality of information. This paper presents a new transducer technology developed based on the dielectric properties of polymers. The transducer can be installed in the mold with low cost and provide continuous measurement. Plenty of information during the production can be obtained by this transducer. Simulation and experimental results show the effectiveness of the transducer.
DEVELOPMENT OF DIELECTROSTRICTIVE SENSORS FOR ON-LINE SHEAR STRESS MEASUREMENT DURING THE INJECTION MOLDING PROCESS
This study presents the development of a novel sensor
based on dielectrostriction principles. Dielectrostriction
defined as a variation of dielectric properties of material
under deformation detects evolution of molecular orientation
during injection molding and enables on-line shear
stress measurement. To demonstrate the feasibility of this
approach a planar capacitor sensor rosette has been developed
and attached to the surface of an injection mold to
obtain the dielectrostriction signals under various processing
conditions. The calculated shear stresses of polymer
melts based on the dielectrostriction signals were validated
by simulation predictions.
DEVELOPMENT OF DIELECTROSTRICTIVE SENSORS FOR ON-LINE SHEAR STRESS MEASUREMENT
DURING THE INJECTION MOLDING PROCESS
This study presents the development of a novel sensor based on dielectrostriction principles. Dielectrostriction, defined as a variation of dielectric properties of material under deformation, detects evolution of molecular orientation during injection molding and enables on-line shear stress measurement. To demonstrate the feasibility of this approach, a planar capacitor sensor rosette has been developed and attached to the surface of an injection mold to obtain the dielectrostriction signals under various processing conditions. The calculated shear stresses of polymer melts based on the dielectrostriction signals were validated by simulation predictions.
EASTMAN TRITAN' COPOLYESTER FOR HOUSEWARES APPLICATIONS
Housewares applications have frequently made use of clear, tough polymeric materials to enhance visual appeal and functionality while providing durability and light weight versus glass or metal. Eastman Tritan' copolyester was recently introduced into this market and has experienced rapid adoption due to a combination of clarity, toughness and chemical resistance resulting from the unique chemistry of the polymer. Tritan' has improved heat resistance compared to many other copolyesters and can be used successfully at temperatures found in automatic dishwashers. Further, Tritan' provides excellent resistance to stress cracking in the dishwasher environment, and together with its clarity and outstanding toughness finds use in premium housewares applications.
SINK MARK PREDICTION AND OPTIMIZATION ƒ?? A REVIEW
Sink mark is an attribute defect on injection molded components. Study of such attribute defects gained importance due to increased awareness of cost of quality.In the recent past manufacturing community has been concentrating on finding out various techniques and methodologies to address issues related to design and manufacturing processes. Focused attention on these issues can be seen from proliferation of research activities.Recent researches are more technical in nature and objective based. Researches are oriented towards understanding identifying critical factors and possibly in minimizing the effect of sink marks. Researchers are using various approaches like mathematical models software based simulation models and experimental models. This paper presents a detailed review of those researches in the last ten year period (1998-2007) on sink marks. From indepth study three key control mechanisms: Material Product design and Processing variables have been identified. Impacts of the factors related to those three key control mechanisms are discussed. Scope for continued research is also indicated.
DIMENSIONLESS DUROMETRY AND ASTM D2240
Durometry is the measurement of material hardness, such as, plastics, metals, wood, and rubber. ASTM D2240-05 standardizes durometry with 12 hardness scales [1]. These scales employ either conical, round, or flat tipped indentors. Indentation into a solid is governed by linear elastic mechanics, and this paper relates the Young's modulus to ASTM D2240 standardized hardness scale reading. We adimensionalized these indentation mechanics, and uncovered a normalized Young's modulus, ! , and the dimensionless hardness, H . We then discovered a new dimensionless indentor stiffness which we call mechanical indentability, Mi , which can be used to classify the ASTM D2240 standardized hardness scales. The result of our analysis allows practitioners to determine the Young's modulus from measured hardness. Further, our results can be used to convert between any two ASTM D2240 hardness scales.
NEW TECHNOLOGY TO VARY THE RADIAL THICKNESS DISTRIBUTION OF THE PARISON IN EXTRUSION BLOW MOULDING
The optimum parison shows thickness changes over the length and over the circumference to mach the different draw ratios in the final blown part. The thickness variations in direction of the length can be easily achieved by moving the conical mandrel. Now a new technique is available to also dynamically profile the thickness of the parison over the circumference. It can be applied for all die diameters. In many cases the technique can even be easily retrofitted to existing dies to reduce material consumption.The details of the technology will be explained and results achieved as well on pilot machines as also on production machines will be presented.
CONTROL OF THE THICKNESS DISTRIBUTION OF BLOWN FILM BY CHANGING THE FLOW CHANNEL GAP OF THE DIE OVER THE CIRCUMFERENCE
The thickness distribution of blown film is conventionally controlled by either changing the temperature or the velocity of the cooling air. This technique can not be used for the double bubble process where the film is cooled by water before being reheated and blown up in a second step. A new technique to alter the localized gap of the flow channel at the exit of the die has been developed. It can be used to control the thickness over the circumference of the blown film for both the conventional and double bubble process. The technology will be explained and initial test results achieved will be presented.
FEASIBILITY STUDY OF ADDITIVE MANUFACTURING OF THERMALLY CONDUCTIVE PA12 POWDERS BY SELECTIVE MASK SINTERING
Selective mask sintering (SMS) is a new powder-based additive manufacturing technique. Here, the material is molten in laminar direction by broad band infrared radiation. By using this technique, there is a high potential to create three-dimensional thermally conductive parts, layer by layer. In this publication, commercially available PA12 powders are modified by adding thermally conductive fillers such as aluminum grit and copper spheres. Process relevant powder properties were characterized by differential scanning calorimetry, rotational viscosimetry and thermal conductivity measurements. Subsequently, the morphologies, mechanical behaviors as well as thermal conductivities of manufactured specimens were investigated.
VALIDATION OF CRYSTALLINITY MEASUREMENTS OF MEDICAL GRADE PEEK USING SPECULAR REFLECTANCE FTIR-MICROSCOPY
Conventional pipe dies consist of a solid mandrel and a solid outer ring. With such dies the thickness distribution in pipes can only be influenced by centring the die. Two thick regions situated opposite each other can not be fought. This is possible when you retrofit a multiwalled flexring sleeve into the outer ring of a pipe die. Similar to the well proved flex lip technique in flat film production the flexring technology allows for a locally limited adjustment of the flow channel gap. Even the thickness distribution of single layers in coextruded pipes can be fine tuned. The new technology which overcomes by far existing limitations to the pipe production process will be explained and results obtained with the new generation of pipe dies will be presented.
VALIDATION OF CRYSTALLINITY MEASUREMENTS OF MEDICAL GRADE PEEK USING SPECULAR REFLECTANCE FTIR-MICROSCOPY
Characterizing the crystallinity in PEEK is critical, since it dictates the mechanical behavior of the polymer.Wide angle X-ray scattering (WAXS) has been typically employed for this purpose; yet, it is impractical for the measurement of some composite materials. Differential scanning calorimetry (DSC) has also been used but with limited accuracy. Specular Reflectance Fourier transform infrared (R-FTIR) microscopy has been identified as a suitable method to measure the crystallinity of industrial grade PEEK, but its usefulness with medical grade PEEK remains unknown. By comparing R-FTIR, WAXS and DSC for a range of medical PEEK grades, we demonstrate that FTIR can detect changes in crystallinity due to annealing treatments and incorporation of carbon fibers or radiopaque compounds.
ADVANCED INVESTIGATIONS FOR THE NEWLY DEVELOPED SPECIAL INJECTION MOLDING PROCESS: GITBLOW""
GITBlow is an innovative combination of the ƒ??Gas Injection Techniqueƒ? and ƒ??Blow Moldingƒ? processes. A hollow core within the part, which has been created through GIT, is inflated further, enhancing the inflation of GIT. Using this process it is possible to produce very large hollow areas with thin residual walls. In a first step the following paper will show the attainable gas bubble cross-sections and residual wall-thicknesses as well as achievable surface finishes for different types of the GITBlow process. In a second step the influencing factors in order to optimize the wall thickness homogeneity will be identified and analyzed.
EFFECT OF CARBON NANOFIBERS ON THE REACTION KINETICS OF WIND BLADE VINYL ESTER SYSTEM
Wind energy is one of the most promising environmentally friendly renewable sources of energy. Epoxy has been the preferred resin used to manufacture wind blades; however with the increased need to lower costs, vinyl ester resin is gaining importance as a alternative material. The curing of vinyl ester resin in the presence of carbon nanofibers (CNFs) was studied by differential scanning calorimetry (DSC). It was found that the carbon nanofibers have a catalytic effect on the curing kinetics of vinyl ester. However there is a percolation threshold and increasing the amount of CNFs beyond this threshold hinders the reaction. A simple autocatalytic model is used to predict the conversion of the vinyl ester resin.
EVALUATION OF REPLICATION PROPERTIES ON MOLDED SURFACE BY ULTRASONIC INJECTION MOLDING SYSTEM
An ultrasonic injection molding (UIM) system, which applies ultrasonic waves to injection molding, as a precision injection molding technology was developed.The replication properties of microstructure of molded surface were evaluated by UIM system. In particular, the effects of oscillation conditions on replication ratio of molded surface were investigated. As a result, the replication ratio of molded surface was significantly improved in UIM compared with that in conventional molding. The replication ratio increased when the ultrasonic wave was applied immediately after the resin filled in a cavity. Results showed that, by applying ultrasonic waves, oscillatory flow was generated inside the cavity and consequently the surface replication was increased. The surface replication during the packing and holding stages was improved by the oscillatory flow provided by the ultrasonic vibration.
THE INVESTIGATION OF WARPAGE BEHAVIOR BY CONSIDERING THE PROCESS-INDUCED PROPERTY VARIATION IN SEQUENTIAL OVERMOLDING
The crucial factors in multi-component molding(MCM) processes were difficult to identify with theconventional trial-and-error method due to its complicatednature and physical mechanism. Regarding the temperateconduction effect between two shots, we adopt directly atrue 3D simulation tool to investigate. The parttemperature distribution of the first shot is taken intoconsideration and affects the mold filling pattern of thesecond shot. Besides, the mechanical property of the firstshot will also influence the warpage and shrinkagebehavior of the second shot and the final product.Simulations can provide good guidelines to help peopleunderstand the mechanism and make the proper design tofabricate modern MCM products.
THERMAL FEATURE OF VARIOTHERM MOLD IN INJECTION MOLDING PROCESSES
With the development of variotherm mold temperature control, people use this technique to fit the special demands in injection molding. Not only the present mold temperature settings, but also the temperature distribution of the previous state will affect mold temperature. Especially when there are multi-layout of mold temperature controls with different heating sources and cooling sources, whole mold temperature properties would be very sensitive. As a consequence, we study mold temperature control system through CAE simulation, and discuss thermal features of different variotherm processes.
LINEAR VISCOELASTIC PROPERTIES OF N-HEXADECANE UNDER
OSCILLATORY SHEAR VIA NON-MOLECULAR DYNAMICS SIMULATIONS
Small strain amplitude oscillatory shear flows of n-hexadecane fluid are performed using non-molecular dynamics simulations with sinusoidal strain. The features of the oscillatory shear flow regarding velocity profile and phase angle are presented. While the fluid is proved to exhibit linear viscoelastic behavior, its storage and loss moduli have no dependence on strain amplitude. Significantly, at different temperatures, the storage and loss moduli versus frequency curves can discriminate between the solid-like, liquid-like, and gel-like states of the fluid.
IMPROVED COLOR MIXING FOR SHEAR AND THERMALLY SENSITIVE PIGMENTS
Currently, many small twin-screw extruders cannot directly blend specific blue pre-blended composites with temperature and shear sensitive yellow pigments to produce a uniform green color. This research will show a new mixing method, one employing a singlescrew extruder joined directly to a low temperature, low shear, low pressure extensional flow mixer, to develop a 1-pass, mixing process, which creates a superior homogenous, vibrant color from dissimilar, incompatible materials. The challenge was to achieve adequate distribution and dispersion, without generating enough energy from shear, temperature, and pressure which would degrade the sensitive yellow constituent of this mix and turn it brown when degraded.
A THREE-DIMENSIONAL CAE MOLDING OF MICROCHIP ENCAPSULATION
In the packaging of plastic-encapsulated microelectronics (PEM), microchip encapsulation has been the dominant technique for encapsulation processes. With the tendency of the technologies continuously moving toward smaller scale and higher density, the existed defects problems during fabrication become more and more important. Among those problems, wire sweep and paddle shift are the most common. In this study, an integrated CAE technology which gives a comprehensive solution for microchip encapsulation has been developed. By using this technology, wire sweep and paddle shift predictions under different molding conditions can be obtained, and the simulation results also demonstrate the feasibility of our technology for practitioners to analyze their mold designs for microchip encapsulation.
MELT MEMORY AND CORE DEFLECTION
When injection molding long slender hollow parts with closed ends, like test tubes, an unevenly advancing melt front around the cores results in core deflection, a pervasive problem especially when the parts are thinwalled. Accurately predicting core deflection problems is accomplished by considering the distributed load on the core caused by the normal stress distribution acting on the cores. In this paper, the effect of fluid elasticity on core deflection is explored by incorporating melt memory into the prediction of core deflection using the upper convected Maxwell model. The Deborah number is then used to represent the dimensionless amount of elasticity. We find that melt memory significantly worsens core deflection, and we provide a chart to help practitioners predict this.
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