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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Plastic Contact Mechanics and its Impact on DEM Simulations of Solds Transport in Extruders
Research work using the Distinct Element Method (DEM) has identified the potential of a discrete approach for more accurately modeling the motion of plastics solids within a single-screw extruder. Experiments of HDPE particles contacting a steel anvil showed a velocity dependency in their impact behavior, which becomes an important consideration when selecting an appropriate force-displacement model for DEM simulations. In addition, Experimental trials have been conducted to examine the bulk motion of solids within an actual single-screw extruder at different screw speeds and barrel temperatures. The implications of velocity-dependency in the contact-displacement models were subsequently examined in 3-D, non-isothermal DEM simulations of the solids-inflow and solids-conveying zones of a single-screw extruder.
The Effects of Mold Closing Speeds and Positions on the Pinch-Off Strength of an Extrusion Blow Molded Bottle
This study will show the effects of mold closing speed and position on the pinch-off strength of an extrusion blow molded bottle. It is important to have an optimal mold closing speed and position so the pinch-off strength is most advantageous to the part integrity. Today, the industry uses past knowledge to process the pinch-off strength. The study will add more scientific knowledge to the industry and improve overall pinch-off strengths. This is needed because simply relying on past experience may not help in new and more difficult situations. Data acquired from the study will give the necessary results to optimize the mold closing speed, position, and pinch-off strength on an extrusion blow molded bottle.It was found that the slower mold closing speed and larger mold closing position created the greatest pinch-off strength and thickness.
Die Balancing: Coupling Flow Simulation, Shape Deformation, & Optimization
The current work demonstrates a novel automatic approach for the die balancing process. The algorithm involves flow simulation through computational fluid dynamics (CFD) and shape change via automatic shape deformation (ASD) to minimize the flow non-uniformity at the die exit. Taking a spiral mandrel die as an example, the combined use of ASD with CFD is highlighted. Using this approach, one baseline simulation was manually set up and two more simulations were automatically created study the effects of helical angle. In the example studied, it was found that changing the helical angle from 315° to 405° had a minor effect on the flow uniformity.
Application of Neural Networks in Prediction of the Microstructure and Mechanical Properties of Microcellular Injection Molded Polyamide Nanocomposites
Back-propagation artificial neural network (ANN) models were constructed to predict the microstructure and mechanical properties of the microcellular injection molded polyamide nanocomposites. Key parameters that affect the evolution of the microstructure, i.e. supercritical content, melt temperature, shot size, melt plastication pressures and injection speed are selected as the artificial neural network inputs, and the outputs are the microstructure defined as the cell size, Weight reduction, and mechanical properties . The results revealed that ANN model offer a favorable method in the optimum design of the nanocomposites and process improvement. This work enhances the systematic understanding of parameters in the optimum design of the nanocomposites and process improvement.
A New Approach for Temperature Measurement Inside an Injection Molding Tool
In the context of lightweight construction and miniaturization, especially in the automotive industry, direct encapsulation of electrical components in injection molded parts gains further in importance. In particular with regard to the processing of temperature sensitive semiconductor devices specific knowledge on the thermal load is required for product-life estimation. In consequence of its mounting points and mass-to-melt-ratio, standard temperature probes are suitable only to a limited extent for this kind of measurement.As this paper shows, semiconductor diodes are well capable of measuring the time-dependent temperature inside an injection molding tool because of their electrothermal properties. During the investigation probes with an edge length less than 200 ?m have been mounted in the cavity of the tool. Due to the low heat capacity of the probe the temperature of the melt is unaffected by its presence and the thermal signal is registered with almost no delay. Using the method presented, the thermal load of directly encapsulated electrical devices can be measured. In particular the thermal degradation of semiconductors can be estimated.
Virtual Simulation of Top Load Performance of Plastic Bottles
A novel analytical computational model was developed to predict Top Load and Side Load performance of light weighted water bottle containers. This approach involves, simulating reheat stretch blow molding of PET containers using Virtual Prototyping™ software to predict the material thickness distribution of the blow molded container and associated mechanical properties derived from estimating the degree of stretch and orientation of different sections of the container. These parameters serve as inputs for Finite Element Analysis involving highly non-linear deformation of the containers under various types of loading. A predictive curve was established to determine the degree of light weighting that can be achieved for a 500mL water bottle by plotting the Top Load Strength as a function of container Sidewall Thickness. The Top Load performance for an empty 14g container was predicted to be about 47 N (10.5 lbs) compared to 86 N (19 lbs) for a 17g bottle and 61 N (14 lbs) for 15g bottle. This analysis has been proven to be effective and accurate for performance analysis without expensive prototyping of the container design and allows a wider number of sample designs and light-weighting options to be explored in a limited amount of time.
Effect of Screw Geometries on Extrusion of Wood-HDPE Blends
This paper investigates the effect of three screw geometries on the extrusion characteristics of 0%, 25%, 36% and 50% wood-filled HDPE blends in a single screw extruder. From the three screw geometries, the effects of feed depths, the compression ratios, and the metering depths were compared. The characteristics included output, pressures and melting profiles. It was found that, due to its partially filled phenomenon, the solid conveying section dominates the extrusion behaviour of the wood-filled resins. A modified solid conveying model based on viscosity was presented, and the solid conveying angles calculated.
Optimization and Analysis of Variability in Injection Molding
Injection Molding (IM) is the most important process for mass-producing plastic products. The difficulty of optimizing an IM process is that the performance measures (PMs), usually show conflicting behavior. The aim of this work is to demonstrate a method utilizing CAE, statistical testing, artificial neural networks (ANNs), and data envelopment analysis (DEA) to find the best compromises between multiple PMs and their variability. Two case studies are presented. A case study based on a virtual part is presented in detail in order to illustrate this method. The second case study is experimentally based, using the American Society of Testing Materials (ASTM) mold, to illustrate how this approach applies when only experimental results are available.
In-Mold Coating for Thermoplastic Parts: Modeling, Rheology and Apparent Slip
In-mold coating (IMC) is carried out by injecting a liquid low viscosity thermoset material onto the surface of the thermoplastic substrate while it is still in the mold. A computer code based on the Control Volume based Finite Element Method (CV/FEM) has been developed to predict the fill pattern and pressure distribution during the coating flow using the Sisko viscosity model and taking apparent slip into account during. Both these factors lead to a better prediction of pressure distribution. The rheological parameters and the apparent slip parameter are ascertained by using a slit rheometer. Simulation and rheology results are presented in this paper.
Mechanical Properties of Rice Hull / Polypropylene Composites
This study attempted to improve the mechanical properties – and impact resistance, in particular – of rice hull/polypropylene composites with the aid of styrene-ethylene/ butylene-styrene (SEBS) and maleated styrene-ethylene/ butylene-styrene (SEBS-MA). The results suggested that both types of additives increased the impact strength of the composites significantly as their content was increased, but only SEBS-MA improved the tensile and flexural strength of the composites. The results also indicated that the SEBS-MA composites consistently showed better mechanical properties – strength and modulus in both tensile and flexural tests and impact strength – than the SEBS counterparts at a given content of additives.
Web-Based Navigating System for Conceptual Design of Plastic Parts
The object of enterprises management is to obtain the competition advantage by better efficiency, quality, innovation, and customer responds. As such, most enterprises implement the product life management (PLM) system to assist design and development, however, the interaction between PLM and CAD is mainly for viewing purpose. Therefore, this research is to develop a web-based conceptual design navigating system which can provide standard and automatic component to shorten the process of conceptual design by seamlessly integrating with CAD system. Furthermore, this system can greatly help the inexperienced designer and provide the collaborative environment of designing process.
Structure and Properties of Thin-Wall Molded with Micro Surface Features
Injection molding of thin-wall parts with micro-scale grooves of polypropylene (PP) and cycloolefin copolymer (COC) were performed to clarify the processability and surface structure of the molded products. Effects of cavity thickness and process conditions on processability and structure of the molded products were evaluated. The replication property and optical anisotropy of molded products were analyzed by polariscope, polarizing microscope, SEM, and confocal laser scanning microscope. The optical anisotropy in the vicinity of the gate was higher than that of any other position, and the optical anisotropy increased with a decrease in cavity thickness. The replication property in the vicinity of the gate also was higher than that of the flow end, and the replication ratio was slightly increased with increasing mold temperature. It was found that the replication properties were correlated closely with skin-shear thickness inside products.
Micro-Scale Disk in Ultra Miniature Injection Molding
Precision micromolding of polypropylene (PP), polyoxymethylene (POM) and polycarbonate (PC) were performed to develop a micro-scale miniature disk and to clarify the mechanism of structure development in micromolded products. Especially effects of process condition and cavity thickness on processability and structure formation in micromolding were evaluated. The processability and high-structures of molded products were also analyzed by polariscope, birefringence, and AFM measurements. In case of PC micro-disk, the molecular orientation in the vicinity of the gate was higher than that of any other position. Birefringence increased with decreasing cavity thickness. Furthermore it was found that the resin flow became unstable in the cavity thickness of 0.1 mm. The molecular orientation of PP products also showed the similar tendency as the case of PC, where birefringences in the vicinity of the gate were higher than any other position.
Modeling of Deformation Processes in Vacuum Thermoforming of a Pre-Stretched Sheet
Modeling of deformation processes in vacuum thermoforming for a preliminary stretched thermoplastic sheet (plug-assist vacuum thermoforming) is investigated in this paper. The model can be used for production of polymeric articles with minor wall-thickness variation. A nonlinear rheological model is implemented for developing the process model. It describes deformation process of a pre-stretched sheet at any phase of vacuum thermoforming process. This process is described by a set of deformation processes that each on them is specified by an appropriate boundary conditions. For model validation, a comparative analysis of the theoretical and experimental data is presented. The wall-thickness distributions obtained from modeling results corresponded well with experiments. The satisfactory result establishes a method for prediction and enhancement of the final products quality in criterion of wall-thickness distribution.
Investigation of Re-Crystallization of Injection Molded TPO Unpainted Plaques
Thermoplastic olefins (TPO) are widely used in the automotive industry as painted exterior plastic parts such as fascias and bumpers. The overall production process includes injection molding of parts, surface treatment, painting and finally baking at 120°C for 30 min. During the injection process, residual stresses are generated by chain orientation and thermal gradients. After the paint process, more stresses and deformations are added. This work focuses mainly on baking conditions and the micro-structural changes as a source of final surface defects. As a first step, we used DSC to simulate the baking process and study the effect of injection molding and baking conditions on unpainted samples. By controlling the scanning rates and the residence time within the DSC furnace, this alternative technique can reveal some interesting results. Samples were also annealed in an oven in the same conditions then analyzed by DSC. The results of both approaches are compared and discussed.
The Effect of Cooling Air Aerodynamics on Bubble Instability in Blown Film
A numerical analysis using a renormalization group (RNG), k-? model and Fluent software was performed to predict the static pressure distribution around the bubble as well as the flow field of cooling air in the film blowing process. Bubble instabilities were experimentally studied using an in-line scanning camera system developed in our laboratory. The combination of experimental measurements and numerical analysis indicated that different bubble shapes led by various cooling rate produced significant differences in dynamics of bubble instability. When the gradient of static pressure along the axis of the bubble is minimized, the stability of the bubble increases.
Volumetric Orientation and Selective Placement of Platelets in Clay Nanocomposites by Chaotic Advection
Following first work reported last year, this paper presents additional information regarding novel polyamide-6/nanoclay nanocomposites having platelets volumetrically oriented and localized within alternating platelet rich and virgin polyamide layers of nano-scale thicknesses. These novel nanocomposites were produced with a continuous chaotic blender (CCB). A variety of structural arrangements among platelets in extruded films are presented. Methods are applicable to other polymer types and additives having platelet shapes. A theoretical permeation model was implemented to assess influences on permeability of structure parameters such as platelet orientation and layer number. By localizing and orienting platelets within multilayers and neglectling crystallinity changes, model results indicate that such nanocomposites may have very low permeabilities. Permeability measurements and evaluations of crystallinity changes are subjects of future work.
Fracture of Polycarbonate in a Medical Device
The fractographic study of a polycarbonate component used in a prototyped medical device is reported of fracture mode, origin and mechanism, based on the examinations of the fracture surface and the interpretation of various fracture markings as observed using scanning electron microscopy (SEM). An explanative kinetics of fracture is given for describing the fracture process and various associated fracture events. The time and temperature effects on the fracture properties and fracture kinetics of polycarbonate are qualitatively considered to explain the causes of material brittleness. It has been noted that under complex long-term loading and varying time-temperature conditions, the fracture origins might be preexisting or newly created in a fracture event. Therefore, caution should be used in assigning the likely causes of material failure for design and manufacturing processes.
Modeling of the Effect of Intercalated Clays on the Tensile Properties of PMMA/Clay Nanocomposite Foams
A constitutive model for tensile behavior of PMMA/clay nanocomposite foams was developed in this paper. The model elucidates the effect of intercalated and agglomerated clays, where the elastic modulus of the nanocomposite foams is affected by the addition of clays to the polymer matrix. A viscoelastic model was adapted for the tensile behavior of the material. The detrimental effect by clay agglomeration was considered on the determination of the elastic modulus. For the verification of the constitutive model, PMMA/clay nanocomposite foams were manufactured by batch process method and their uniaxial tensile test results were compared with theoretical results. The proposed constitutive equation showed agreement with the tensile test results.
Photoelastic Measurement and Numerical Simulation of Residual Stresses
Injection Molded Polycarbonate Parts are extensively employed in optical, optoelectronic and electronic applications. But the molded residual stress can deteriorate the optical properties of the final product. Compared with PMMA, residual stress has more effects on PC injection-molded parts. In this research, the distributions of residual stress of the transparent molded polycarbonate parts have been inspected firstly under polarized light to understand effects of flow-induced and thermal-induced stresses and their interaction. Then based on optical experiment results of photoelasticity, the value of residual stresses was calculated. Flow-induced stress and thermal-induced residual stress of different molding conditions was investigated by numerical methods. A series of multicolored band or fringed pattern and simulation results showed the effect of non-uniform temperature distribution and fill pattern were the causes of residual stresses of thin PC parts.
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