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
Controlling Injection Phase/Packing Phase Switchover Using an Ultrasonic Sensor
An ultrasonic transducer was installed on an injection mold such that a sound pulse would strike a surface of the mold cavity and reflect back to the transducer. A change in the intensity of reflected echoes indicates the presence of polymer at the point where the sound pulse strikes the cavity surface. Detection of the arrival of the polymer at a specific position in the mold cavity is then used to identify the end of the injection phase in a similar fashion to the current cavity pressure based technique. Two important advantages of this technique are that the transducer can be mounted on the external surface of many molds, allowing an installation that requires no machining of the mold and the technique directly senses the position of the polymer in the mold cavity.
Overmolding-Stack-Mold Technology - An Innovative Concept in Multi Component Injection Molding with Many Advantages for the Molder
Turning a part of the mold is the classical, most widely used, method of transporting preforms in multiple component engineering molds. Up until now, turning was carried out exclusively with vertical turntables which were mounted on the moving machine platen and which have a horizontal turning axis. However, because the machine has to provide turning space according to the diagonals of the mold, the problem of a very large machine clamping unit is encountered. In addition to the turning space, a high clamping force is needed for the injection of preform and finished part in one cycle. This situation looks much more advantageous if the over-molding-stack mold system is linked with a horizontal turning device. This process has been developed by Ferromatik Milacron in close co-operation with Foboha GmbH Formenbau, Haslach.
Weathering Effects on Mechanical Properties of Recycled HDPE Based Plastic Lumber
Commingled recycled plastic lumber (RPL) decking was exposed to the environment for eleven years. The weathering effect is examined by performing mechanical property tests on the full size deck boards before and after the exposure. Flexural tests on the weathered deck boards were conducted with the exposed side and the unexposed side tested in tension. The flexural properties after weathering are compared to the original flexural properties. These data show the effect of weathering on recycled high-density polyethylene based RPL. A life cycle cost analysis (LCCA) is also presented to compare the cost of a wood deck versus an all RPL deck. The purchase, maintenance, and disposal costs are included.
Investigation of the Change in Mechanical Properties of Concrete Mixed with Styrene Beads
Judicial mixture of industrial material to produce new properties not inherent in each individual micro constituent has been the subject of an intense scientific and engineering investigation. One such material is a concrete based mixed with styrene (poly-concrete) to change a selected physical and mechanical properties with a reduction in weight. Poly-concrete not only can be used in the construction industries it is also used in plastics industries as well. The need to corrugated materials for production of thermoforming mold has been well sited in the technical literature. Such a material can provide thermoformer with the ability to produce a rapid prototype molds, or molds requires a deep draw ratio at a fraction of cost of more conventional materials. At the present time corrugated aluminum is considered the only material with such a property available in the market. The cost of the corrugated aluminum prohibits more common application of this material in thermoforming industry. The purpose of this study is to investigate the difference between selected properties of traditional concrete as compared to concrete mixed with various amount of expanded polystyrene beads. The investigation was involved with preparation of a concrete mixed with various amounts of expanded Styrofoam beads for evaluation. Five samples of each mixture were produced to the dimensions specified by a predesigned specification. Common concrete mixture as specified by the American Concrete Society was used. A proper curing-time was given to the samples to achieve the optimum mechanical properties. The verification of the uniformity and integrity of the sample was investigated using an imaging system and optical microscope. The result was evaluated using three-point- bending, compression, and impact tests. The expected result was used to establish a correlation between the selected mechanical properties and as a function of the physical composition of the material.
The Effect of Blend Ratio on the Properties of Syndiotactic and Isotactic Polymer Blends
Isotactic polypropylene and syndiotactic polypropylene were random blended and injection molded in various ratios. The blends produced mechanical properties that varied blend composition. Blends with increased i-PP content had higher crystallinity in the isotactic phase, and so exhibited higher moduli and yield strengths and elongation and lower impact properties. As the percent s-PP was increased, overall crystallinity decreased and the impact behavior improved. Since increasing the back pressure during molding enhanced isotactic crystallinity at the expense of syndiotactic, the blends became more rigid. Best clarity was observed in blends with high s-PP contents and lower back pressure.
The Effect of Plastication Variables on Melt Temperature
The affect of back pressure, screw speed, and injection rate on melt temperature of three materials was examined using full factorial designs of experiment. The most significant factor affecting melt temperature of polypropylene and impact modified polystyrene was the screw speed. With these materials, the injection rate also influenced melt temperature, but back pressure and interactions between the primary factors had only minor or insignificant effects. The melt temperature was raised by shear on the polymer and increased soak time. In contrast, the melt temperature of polycarbonate was not significantly affected by back pressure or screw speed; injection rate was not be examined.
Using Process Monitoring as a Method of Preventative Maintenance for Check Ring Wear during Injection Molding
An advantage of collecting process information, after qualifying parts from an injection molding process, is that trends and indicators can be identified that allow you to reject bad parts before they are ejected from the mold. In a similar fashion, it is believed that relationships between some of these indicators can be used to detect long-term deterioration of some elements of the molding process. This study developed a model using a regression analysis that can be used in the monitoring process to identify early indicators of check ring wear, which is a common maintenance item in injection molding.
Crystallization Kinetics of Poly(Ethylene Terephthalate) Based Ionomer Nanocomposite Materials
Cloisite 30A and sodium montmorillonite clays have been added to poly (ethylene terephthalate) and 2, 6, and 10 mol% sulfonated poly (ethylene terephthalate) ionomers in 1,1,1,3,3,3-hexafluoro-2-propanol to form solvent cast nanocomposite materials. Differential scanning calorimetry (DSC) was used to compare and observe differences in crystallization temperatures as well as rates of crystallization for each polymer-clay system. Analysis shows that addition of the clays into poly (ethylene terephthatlate) and sulfonated poly (ethelyene terephthalate) 2 and 6 mol% ionomers increases the crystallization temperatures and decreases crystallization half-times.
The Effects of Regrind Loading Levels and Heat History on the Properties of Selected Engineering Polymers
This study examined the effect regrind levels and heat history on the mechanical properties of polycarbonate. Increasing regrind content and heat history produced no significant change in the tensile and flexural moduli and yield strength of polycarbonate. The Izod impact properties were not greatly affected when the regrind levels were increased, but decreased severely after the fourth heat history. Comparable decreases in transfer (fill) pressure suggest that the molecular weight was reduced. While mixing the single-heat-history regrind with virgin resin produced cloudy samples, increasing the number of thermal cycles caused discoloration of the material.
The Effect of Pack and Hold Parameters on Part Cooling in Injection Molding
This study examined the effects of packing and holding conditions on the cooling of an injection molded part. Increasing packing of molded parts initially resulted in lower surface temperatures of the ejected parts. However, the introduction of more melt into the part increased the overall part temperature, thereby reducing the cooling rate. Thus, highly packed parts exhibited higher surface temperatures at long cooling times. For amorphous materials, the part surface temperature was less dependent on packing pressure. Air gaps measured at part ejection suggested that the time of part surface to mold wall contact was less than five seconds.
The Sensitivity of Notch Radius on the Izod Impact Strength of Polycarbonate and the Effects of Blending with ABS
The notch radius affects the crack propagation rate through polycarbonate upon instantaneous impact loading. The relationship between notch radius and impact strength has been shown to be directly related. Depending on the notch radius, the failures will be either ductile or brittle. Notch sensitivity is a function of impact force divided by the area of the radius. Small radii have less area than a larger radii, thus, an equal force will affect the smaller radii to the greatest degree. Notch radii vary between 0.005 and 1.000 inches. Additionally, ABS, which is not notch sensitive, is added to determine its affect.
Properties of Nanofiber Reinforced Polymer Composites with Intercalated Copper Particles
Polyethylene and Acrylate-Styrene-Acrylonitrile were mixed with carbon nanofibers and copper particles. The composites were mixed with high shear conditions to break-up nanofiber agglomerates and disperse copper. The thermo-physical, electrical and mechanical properties of the composites were analyzed. Electrical measurements showed a drop in resistivity as function of nanofiber concentration. Crystallization temperature of PE composites was not altered; glass transition temperature of ASA was altered. Dynamic mechanical studies showed increases in stiffness for both systems.
Automated CAE Assisted Process Setup Versus Conventional Process Setup Methods
Through the use of a system that reads flow analysis results directly into the injection molding machine controller, it is believed that the process obtained will be better than one obtained using conventional process setup methods. Capability analyses of the automated setup parts and the conventional setup parts will be used to compare the processes. Estimates of the time required for each method will also be made. A part that would be inherently difficult to process was designed with the use of flow simulation software. The part included such processing difficulties as air traps, converging and diverging flow, and thin to thick regions (refer to Figure 2). After the design was complete the mold was designed and built along with a measuring fixture that would be used to evaluate part length and with dimensions (part weights were also measured). A general purpose Acrylonitrile-Butadiene-Styrene was the material of choice to process. The best process was determined by part weight, length, and weight capability studies.
Effects of Particle Size and Solvent Chemicals on the Extractions of Phthalate from Polyvinyl Chloride
Plasticizers are included in many (PVC) polyvinyl chloride formulations. Polyvinyl chloride's soft texture is accomplished using plasticizing chemicals. The plasticizers most commonly used in PVC formulations are a family of chemicals called phthalates. Because of recent concerns regarding implications of chemical leaching and health effects of phthalates on infants, it's important to investigate the methods for measuring phthalates in PVC. Phthalate plasticizers are di-esters of phathalic acid and long chain alcohol and are vegetable oil-like liquids. This study focuses on the effects of three different particle sizes on extraction of phthalates from consumer product formulations. Hexane is the solvent chemical used as the extractor.
The Effect of High Shear Rate and Shear Duration on the Properties of Injection Molded Plastics
Shear rate is an important part design and processing consideration in injection molding. Excessive shear rates can cause polymer chains to break and degrade, but actual limits are currently unknown. Four materials (polycarbonates and polypropylenes) were processed through specially designed runner inserts that varied shear rate. Each material was processed through each insert three times by regrinding and reprocessing. The resulting material was evaluated for mechanical and rheological properties. The mechanical tests showed an insignificant change in properties. Rheological tests showed a progressive decrease in viscosity as shear rate and shear duration was increased.
Effects of Material Height in a Hopper on Part Weight
A hopper is a device whose purpose is to direct the flow of material from a larger cross-sectional area to a smaller cross-sectional area in a uniform fashion. They are used on numerous plastics processing machines, including injection molding machines. Hoppers are constructed in a wide variety of shapes, such as: asymmetric, conical and rectangular. The flow of resin through a gravity-driven hopper has been an area of great study for several years. This paper will discuss research done at the Plastics Lab at the Erie campus of Penn State University to determine if, in fact, height does have an effect on a molding process.
The Effects of Color Additives on Polycarbonate Resins
Polycarbonate resins are utilized in many high tolerance engineering applications and can be purchased with many different fillers. One additive that may not commonly be considered a filler would be the colorant. In going from prototype to production, the resin usually goes from being 'hand-colored' by the manufacturer to 'pre-colored' by the supplier. Generally, the hand-colored resin and the pre-colored resin are considered to be the same. However, in this conversion, some specific properties may not transfer exactly. This research will study the mechanical properties in a typical molding application involving polycarbonate resin, and determine which properties, if any, are subject to significant variances during this material transition to production.
Verifying the Accuracy of Internal Stresses from Blow Molding Simulation Software Used for FEA Stress Analysis
The objective of this study is to use the results of a blow molding simulation package to perform FEA stress analysis of blow molded bottles. The bottle geometry generated from the simulation package will be used for the bottle geometry in the FEA package. The results from this study will be used to develop a correlation between simulated FEA results and actual results from laboratory tests. The study is being done to supply information to the part designer in determining the accuracy of the stress analysis from simulation software. With accurate simulation results a designer can predict the effect of design changes in the blow molded product before hard tooling is cut. Changes in the part design at the CAE level gives the engineer a greater insight in the cause and effect relationship design modifications have on the final part.
Case Study of Simulation Software in the Production Design Phase
This paper is a study to determine the value of BlowView simulation software in the preform design phase of stretch injection blow molding. The software will be used to evaluate different preform designs in an attempt to optimize the design. The blow molding industry will benefit from this study by having an effective design tool to aid in the design phase of a product. This software may be able to reduce design time and reduce production problems. This study will examine one bottle and several different preform designs. The software will be used to evaluate a preform design and determine its efficiency to produce a high-quality bottle. Another preform will then be designed with the intent of improving the previous design and producing a more uniform bottle.
Effects on Physical Properties of Recrystallized Crosslinked Polyethylene on Molded Articles
The final or ultimate mechanical physical properties of a molded plastic article are difficult to determine. As a plastic article will age, it will see several temperature excursions, which can take it momentarily above its crystalline melting point. Upon cooling, the article could possibly recrystallize in a different state that has more or less crystals. Those final properties will be determined by this second more stable crystalline level. The purpose of this paper is to conduct a controlled experiment with crosslinked or potentially crosslinked high-density polyethylene (PEX) and determine the recrystallization long-term stable mechanical properties for these types of molded articles.
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