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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Comparison of Aluminum, Wood, and Epoxy as Thermoforming Mold Materials
There are many different types of materials used in the thermoforming industry for the molds used to form plastic products. The most commonly used are aluminum-alloys, soft and hard woods, and epoxy. Each of these materials has distinct characteristics that make them useful under certain design conditions and manufacturing production processes. The following addresses the qualifying factors for each of the commonly used materials based on their characteristics and manufacturing requirements.
Effects of Processing Parameter on Pinch-Off Designs
This study examines the effects of process changes on weld line strength using different pinch-off designs. Mold closing speed and melt temperature were varied with four different pinch-offs. To determine the effect of these process changes on weld line strength, 4 D.O.E.'s were used. Five specimens were taken from each D.O.E. run and tested for tensile strength at the weld.
Attachment Design Analysis of a Plastic Housing Joined with Snap-Fits
Consumer product manufacturers continually desire to make their plastic components more inexpensive by such methods as reducing part count, reducing wall thickness, eliminating tools, and reducing assembly time. Integral fasteners, or snap-fits, can be used to achieve some of these goals, but must be carefully incorporated into a product design. Many of these products, especially portable or hand-held electronic items, need to meet rigorous test requirements, including drop testing. Many common attachment designs that use snap-fits can fail under these conditions. This paper covers the investigation of a desktop telephone housing to ensure that snap-fit disengagement did not occur under drop impacts. First, a failure tree analysis of the product was performed to determine likely scenarios for disengagement. Then tests were conducted to determine impact force magnitudes. Drop testing of prototypes was conducted to determine under what conditions disengagement occurred. From these results, design changes were suggested and prototypes constructed to test the suggested changes. The results of this analysis and testing suggest some general design guidelines to make products attached with snap-fits more robust against the conditions found in typical drop tests.
Effect of Glass Fiber Sizing Molecular Weight on Interphase Durability of Glass Fiber-Vinyl Ester Composites
Model multi-component glass fiber sizings, with formulations based upon current patent disclosures, were prepared to model the full coating packages used in commercial glass fiber manufacture. The sizings consisted of silane coupling agent, film former, and emulsifying surfactant in water, and were applied to glass fibers prepared directly from molten glass. Sizing formulations were extended to vary component reactivity and molecular weight. Unidirectional multi-fiber composites were prepared with Dow Derakane 411-C-50, a vinyl ester / styrene resin system. Interphase durability was characterized by measuring interlaminar shear strength (ILSS), before and after hygrothermal exposure.
Novel Ionomer for Nylon Blow Molding Applications
A novel ionomer is being developed to modify nylon for blow-molding applications. The new ionomer that contains reactive functional groups attains excellent compatibility with nylon by a combination of physical and chemical interaction. The modifier can be dispersed in small particle size as low as 50 nm in nylon 6. This report discusses the melt rheology, blow-molding evaluation and weldline strength of the nylon modified with the novel ionomer. The particle size of the ionomer dispersed in nylon is discussed to explain the unique properties of the new modifier. For comparison, a maleated ethylene polymer (EP) and a conventional ionomer are included in the study.
Use of Polyolefin Additives in Inert Gas Extrusion Foaming of Polystyrene
Polystyrene was blended with small quantities of PP, HDPE, and LDPE and foamed using carbon dioxide as a blowing agent in a twin screw extruder to obtain low density foams. The effectiveness of these additives on the bubble nucleation, density and mechanical properties of the foams was studied. The results show that addition of PP in small quantity improves density, cell size, and surface properties of the foam drastically. The improvement is attributed to crystallization of PP before foam cell expansion; this results in bubble nucleation from the formed crystal sites that also act as gas barrier for individual cells.
Ultrasonic Monitoring of Nozzle and Cavity during Injection Moulding
Ultrasonic techniques are recognised as powerful sources of process information. Transducers are applied directly, are non-invasive, yet interrogate the entire melt cross-section, while data are available real-time. During injection moulding, two zones are considered: nozzle and cavity. In the nozzle, ultrasonic velocity measurement provides temperature and pressure information. Mean temperatures not observed by other techniques are detected. Previous extrusion based experience is used to address issues of high temperature transducer operation. In the cavity, changes in reflection coefficient and ultrasonic velocity provide information on mould filling and part cooling. Various mould geometries are monitored using a number of ultrasonic transducers.
Shearing of Plastic in Runners Causes Property Differences in Parts
This paper presents a study of the effect of shear variations, developed in a runner of a multi-cavity mold, on the impact properties of molded parts. The study has found that impact strength can vary by as much as 2:1. The effect of runner designs are also presented.
The Effects of Pulse Cooling on The Molding Cycle and Part Variation
A design of experiments study was performed that analyzed the effect of pulsed heating and cooling on warpage of an injection molded part. The study involved the following factors: inlet water temperature, melt temperature, mold temperature, and cooling time. The critical dimension was measured by an optical coordinate measuring scope with a repeatable process determined by an R&R study. The gathered data determined that, within the range of the factors study, the inlet water temperature was the only one that did not effect warpage.
Characterizing Scrap Vinyl Flooring to Determine Feasible Reuse Options
The manufacturing waste generated during the production of vinyl floor tiles is typically sent to landfills, rather than recycled, because of a lack of reuse options for this material. This waste is typically PVC loaded with approximately 80% limestone. The goals of this research are to characterize this material to determine the feasibility of reprocessing it and to measure the mechanical properties of the processed material. This study will also attempt to suggest an injection molding or extrusion application for the mixture.
A Method to Characterize the Impact Properties of Hand Tools
There does not currently exist a method for the characterization of the impact properties of hand tools, specifically screwdrivers. Without a scientific method of collecting data for various designs, it is difficult for manufacturers to determine the effect of material or design changes on the impact properties of the product. The most demanding application for these hand tools can often be a hammer blow to the handle of the product, and therefore this abuse must be strongly considered in the design criteria.
Applications of Thermal Analysis in the Design of a Bulk Continuous Acrylic Copolymerization Process
DSC analysis is conducted to obtain kinetic information of the chain addition copolymerization in bulk of a quad-monomer acrylic system. The experimental variables include reaction temperature, type of peroxide and peroxide concentration. By assuming that the copolymerization is a simple reaction, the approximate apparent order of the reaction can be identified; and along with the heat of reaction information, it is demonstrated that the DSC analysis is very useful in facilitating the parametric design process of a continuous stirred tank reactor (CSTR) operation. Selected results of conversion and cumulative copolymer composition of the CSTR samples are included. A more rigorous approach of analyzing the reaction kinetics of the copolymerization is also briefly addressed.
Non-Isothermal Modeling of Co-Rotating and Contra-Rotating Twin Screw Extruders
The quality of the mixing of different raw materials, i.e. the uniformity of the mixture, is a key issue that will determine the morphology and the specific product properties of the resulting compound [1, 2]. Numerical simulation of flow in extruder components provides a new insight, both qualitative and quantitative, into those features. 3-D transient numerical simulations of twin screw extruder (TSE) configurations are presented. A special method, the mesh superposition technique (MST), has been introduced to provide a convenient way to model intermeshing TSEs without involving any remeshing complexity . It has been validated in previous work for isothermal cases . To account for the important non-isothermal effects, the method is compared against numerical and experimental results for additional, non-isothermal validation . We present an analysis of different non-isothermal features that characterize the flow induced by a co-rotating as well as a contra-rotating configuration. Both cases are compared in terms of pressure profiles, temperature fields, resulting torque imposed on the screws and from a mixing point of view to illustrate a typical analysis of different TSEs and provide objective information to select the most appropriate configuration for specific process requirements.
Branching of Polypropylene with a Polyfunctional Monomer for Extrusion Foaming and Thermoforming Applications
Melt strength of polymers is one of the primary criteria for the success of low-density extrusion foaming and thermoforming processes. In this paper, branching of PP using polyfunctional monomer was studied in a batch mixer and a small scale co-rotating twin screw extruder as a function of modifier concentration and process conditions. Melt viscoelastic properties of the products, related to melt strength/elasticity, including die swell and recoil, were investigated to examine the degree of long chain branching, which could lead to improve foaming and thermoforming processability. The melt strength of those materials was compared with that of a commercial high melt strength PP and an unmodified general purpose PP.
Small Angle X-Ray Scattering Study of EACE Processed Semicrystalline PET
Semi-crystalline poly(ethylene terephthalate) (PET) was shear orientated by the novel Equal Channel Angular Extrusion (ECAE) process. Small angle X-ray scattering indicates that extrusion induces preferred orientation of the lamellar structure. Before passing the shear plane, the material has a weak orientation. But after passing the shear plane two preferred orientations are formed in the extruded region; one perpendicular to the shear plane; the other 45° from the shear plane. The physical and mechanical properties of the extruded PET were also investigated and found to correlate well with the ECAE-induced shear orientation.
Experimental Determination and Numerical Modeling of Morphological Development during Injection Molding of Self-Reinforcing Composites
The correlation between structure development during injection molding, and the tensile modulus of injection molded PET/LCP blends were studied, through experimentation and numerical simulation. Process parameters were varied to determine their effects on the tensile modulus and structure development of the blends. A combined numerical simulation and analytical calculations, has been used to model the experimental results. A model that establishes the relationship between the aspect ratio of LCP fiber, the elongational strain, and the tensile modulus, enables us to predict the processing dependent morphology and tensile modulus of injection molded blends.
Predicting Creep in Bottle Design
Experimental creep is data collected to drive an FEA program, ultimately used to predict bottle deformation caused by an internal pressure. The results indicate that it is possible to predict bottle deformation using existing creep data, but it is a highly manual process. The FEA program is beneficial in determining stresses caused by internal pressures, which can then be used to calculate deformations. True deformations can be calculated for segments of a bottle using FEA, but a new approach has been suggested, which will allow the FEA program to calculate the deformations along the entire sidewall of the bottle.
A Study of the Tensile Creep Behavior of Wood Flour Filled HDPE in Aqueous Mediums
Wood flour filled polyethylene can be used as a replacement for conventional lumber in the waterfront structure industry. The effect of large amounts of moisture and submersion in fresh and salt water on the long term mechanical properties of these materials is important to understand. This study will examine the tensile creep behavior of wood flour filled high density polyethylene in air, fresh lake water, and salt water. An apparatus for aqueous tensile creep testing has been designed and built, and will be used to gather data for this study.
Modeling Gate Freeze in Hot Runners Using CAE
When using computer flow simulation software to predict gate freeze time in hot runners it is hard to know how to correctly model the hot drop tip to accurately correlate the gate freeze time. This study will attempt to use computer flow simulation to correlate the gate freeze time of hot runners predicted by the simulation to actual gate freeze times. This will be done by changing a model to make the gate freeze prediction match an actual molded part, and observing how these changes affect the rest of the model.
A Biodegradation Study of Co-Extruded Nanocomposites Consisting of Polycaprolactone and Organically Modified Clay
Nanocomposites containing biodegradable polymers and clays were investigated to improve biodegradable properties. Polycaprolactone (PCL) (83,000 and 43,000 g/mol molecular weight) was mixed with additions of either 2 or 5% of synthetically modified montmorillonite clay. A twin screw extruder was used to produce the pellets. The pellets were then co-extruded with multilayering technology to produce 15-inch wide films from a 256 and 1024 layer die multiplier configuration. This study focuses on the biodegradation studies in compost, soil, and marine environment with results showing improved biodegradation rates in selective nanocomposites and environments.
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