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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Advances in Fusible Core Technique
Fusible core technology allows the production of injection molded parts which cannot be manufactured by conventional mold technology because of undercuts and internal geometries. The production sequence consists of several process steps. The reliability and economy of the process depend on each process operation as well as on the correct design of the interfaces between the steps. This paper presents sample applications, production methods and potentials for future applications. Moreover, current R+D work is described which mainly focuses on improved process engineering, a better understanding of the boundary conditions of product design and a wider range of applicable polymers.
Scale-Up Rules for Blow Heads
Alongside time-intensive flow analyses, requiring extensive calculations, the use of dimensional analysis is an alternative strategy for the design of blow heads. Selected blow heads are broken down into their basic geometrical elements and subsequently transfer formulas are established. Assuming for reasons of simplification that the material flow is isothermal, stationary and laminar and that wall adherence is prevailing, the concept of representative quantities is used to take into account the non-Newtonian behavior of the melt. The combination of the basic elements produce the full-scale device which -compared to the model - display both identical processing times and loss of pressure as well as unchanging shear velocity and wall shear stress, but will achieve different levels of material throughput.
The Processing of Renewable Resources Using a Short Single Screw Extruder with a Combined Section for Solid Conveying and Plastification
Due to the growing awareness of the necessity to protect the environment, the substitution of conventional plastic materials by biodegradable materials is gaining an ever increasing importance. An application that makes sense especially with regard to economic aspects is the processing of non-modified crop on plastics processing machines. This is made possible by the concept of a single-screw extruder equipped with a metering unit with which the total amount of energy required to plasticize the material is generated exploiting the friction occuring in the solid matter. As opposed to conventional extruder designs which exhibit separate areas for conveying the material and for plasticizing the same, these two tasks are united in one section of the extruder. The concept is based on specific geometries of screw and cylinder which secure that the entire mass flow passes a shear zone situated in the material conveying zone, warranting a very efficient transmutation of energy.
Transcription of Small Surface Structures in Injection Molding - An Experimental Study
The ability to replicate the surface roughness from mold wall to the plastic part in injection molding has many functional and cosmetic important implications from medical use to designer products. Generally the understanding of surface transcription, i.e. the replication of the surface structure from mold to plastic part, also relates to micro injection molding and molding of parts with specific micro structures on the surface such as optical parts. The present study concerns transcription of surface roughness as a function of process parameters. The study is carried out with a polystyrene part, process parameters at typical levels and a rough spark eroded mold surface with Ra = 12.6 ?m.
Influence of Molecular Weight Distribution on LLDPE Blown Film Processing Conditions and Property Sensitivity
The effect of key blown film processing parameters on linear low density polyethylene (LLDPE) film properties was investigated. The processing parameters studied were frost line height, blow up ratio, output rate and melt temperature. Statistically designed experiments were conducted with three high alpha olefins (HAO) copolymers of similar melt index, density and short chain branching distribution (SCBD) but of different molecular weight distribution (MWD). Film impact strength variations with processing conditions were found to depend strongly on polymer MWD.
The Relations between the Composition and the Permeation Resistance of the Polyethylene/Compatibilizer Precursor/Modified Polyamide Blends
The effects of compatibilizer precursor (CP) and modified polyamide (MPA) contents on the permeation rate of unleaded gasoline and on the morphology of polyethylene/modified polyamide (PE/MPA) blends are investigated. The optimal composition of PE/MPA for the lowest gasoline permeation rate is PE70/MPA15, which blended 30% of MPA (compounded 15% of CP with 85% of PA) with 70% of PE. The barrier properties improvement of PE/MPA blown tubes against unleaded gasoline reach a maximum (367 times at 25°C) comparing with genetic PE.
Color Mixing Performance in Injection Molding: Comparing a Conventional Screw and Non-Return Valve to Those Designed for Improved Mixing
A competitive global economy requires processors to consider every available option to reduce their costs. One popular approach is to convert to in-house coloring, the blending of natural resin with color concentrate at the injection molding machine. With this approach, the greatest cost savings can be realized by using the highest letdown ratio of color concentrate possible. However, to successfully realize this cost savings, good mixing performance in the barrel is essential. This study will show that a mixing screw provides better mixing than a conventional screw and that a sleeve mixer non-return valve significantly improves mixing when it is used with either screw. Thus, the improved productivity of in-house coloring can be realized by applying this technology.
Modeling of the Mechanical Behavior of Nonlinear Viscoelastic Materials under Multidimensional State of Stress
The mechanical behavior of nonlinear viscoelastic materials depends on time, temperature, loading rate and height of load. A model is presented that allows the simulation of nonlinear viscoelastic materials under multidimensional state of stress and load history. This 3-dimensional deformation model is built by parallel arrangement of a certain number of basic elements. Each basic element consists of an elastic Hookean element and a damper system (3D damper) to describe the viscous properties. The model is calibrated by isothermal strain controlled tensile tests at different temperatures. Along with suitable calculation algorithms this model offers the ability to simulate any multidimensional load history caused by direct stresses. The model allows the simulation both of quasi-static and dynamic loading at different temperatures.
Compatibilizers for Thermotropic Liquid Crystalline Polymer/Polyolefin Blends Prepared by Reactive Mixing: The Effect of Processing Conditions
The effect of processing conditions on the melt formation of a graft-copolymer compatibilizer for blends of a thermotropic liquid crystalline polymer (TLCP) and polyolefins was investigated. The compatibilizer was formed by an melt acidolysis reaction of a 50/50 (w/w) blend of TLCP and the sodium salt of a poly(ethylene-co-acrylic acid) ionomer. The effect of various processing conditions in a batch mixer and a single screw extruder on the extent of reaction were assessed. The extent of graft-copolymer formation and the efficacy of the product as a compatibilizer for TLCP/polyethylene blends was affected by the processing temperature and the rate screw (or rotor) speed.
Investigative Analysis of the Influence Reprocessing Has on the CIEL*a*b* Tristimulus Color Values of Special Effect Thermochromic Polypropylene
The intent of this investigation is to determine the feasibility of achieving optimal color quality when reprocessing special effect" thermochromic polypropylene. The investigation involves blending extruding and molding samples of virgin and reprocessed "special effect" thermochromic polypropylene. All samples undergo visual as well as CIEL*a*b* Tristimulus color value testing. Analysis of the visual and numeric data will determine whether the color values of the reprocessed material remain within the color space established by the standard. If the investigation proves that the color values are within the acceptable color range then recycling of the material would be both economically and environmentally beneficial."
Impact of Fines Separation on Reinforced Thermoplastic Regrind
The process of regrinding thermoplastic resin is associated with a series of handling, feeding, contamination, and melting problems. Some have suggested that removal of fines from reinforced resin can have an adverse effect on certain material characteristics and processing conditions. A dedicated system employing special grinding techniques, aspiration of fines, and static abatement was used to study the impact of fines removal through a number of generations of process history. The system once optimized allowed a detailed study of the relative viscosity, glass content, and tensile properties of the material conditions. The results provide a foundation for molders seeking to incorporate thermoplastic regrind into current production settings.
Understanding Wear Mechanisms: The Key to Mold Life
Molders and mold builders have been puzzled by unanticipated wear in the injection mold. For instance, sometimes hard components fail, and adjacent softer components last. A thorough investigation has been conducted on the types of wear that occur in a mold, as part of the long-term wear studies on copper alloys. Three very distinct mechanisms exist: abrasive, erosive, and adhesive wear. Characteristics of these three wear mechanisms have been isolated as they relate to injection molds. Certain design features in a mold are linked to each of these mechanisms. Understanding this relationship makes mold wear more predictable, avoidable, and correctable.
Use of Copper Alloys to Reduce Mold Condensation Problems
Hot days with high dew points, and their high relative humidity, invariably lead to a host of molding problems. The molder is faced with either substantially altering the process or coping with the effects of sweating molds and equipment. A steel core in an injection mold was replaced using a copper alloy. Process conditions for the mold were established to accommodate operating conditions with a high dew point. Controlled testing was performed under adverse weather conditions. Results of these tests prove the efficacy of correctly applied copper alloy components for the reduction or elimination of problems caused by condensation on molding components.
Wall-Liquid Heat Transfer Coefficients in Batch Intensive Mixers
An empirical correlation that predicts the wall-liquid heat transfer coefficient, h, in batch intensive mixers for neat polymers and polymer blend systems has been tested and verified. The correlation predicts the heat transfer coefficient using the Nusselt number, Nu, the Reynolds number, Re, the Prandtl number, Pr and the viscosity ratio, ?r. The correlation takes the form Nu = ?(Re)?(Pr)?(?r)? Experiments were carried out with ten different amorphous and semicrystalline neat polymers over different operating conditions including different processing temperatures, degrees of fill and shear rates. Polymer blend systems were also studied. Further testing of the polymers with different blade geometries also yielded heat transfer coefficients predicted by the correlation.
Three-Dimensional Simulation of the Rubber Injection Molding Process
Conventional shell element based simulation programs, usually referred to as 2½-dimensional, reach their limits for thick rubber parts as well as in critical molding areas like sudden wall thickness changes or at ribs. Three-dimensional programs for the simulation of the rubber injection molding process have been developed at IKV and in co-operation with industrial partners. These programs allow the three-dimensional, non-stationary, non-isothermal flow calculation for shear-thinning and incompressible rubber compounds during the filling stage and the calculation of the curing stage as well. Simulation and experiment show a good correspondence. By consideration of inertial forces, even the prediction of jetting is possible. In comparison to a 2½-dimensional simulation, the flow front progress is predicted more accurately.
Improved Processing of Highly Filled Calcium Carbonate Compounds
Calcium carbonate treated with an interfacial agent, such as stearic acid or stearate, will typically wet or lubricate its surface resulting in lower viscosity than untreated calcium carbonate. In this paper, the effects of fatty acid derivatives on highly filled calcium carbonate both treated and untreated, in polypropylene compounds will be discussed. The use of fatty acid derivatives can be effective for lowering extrusion pressure, leading to throughput increases. The overall effect on filler addition, viscosity, mixing and processing properties will be shown for one class of fatty acid derivative.
INDEX™ Interpolymers: New Materials for the Wire and Cable Industry
INDEX Interpolymers, including ethylene/styrene Interpolymers, are a new family of polymeric materials that are being utilized in a variety of durable applications. Unique structural parameters, material characteristics, and property combinations, including processibility, that make these new polymers ideal candidates for a variety of wire and cable applications are described. Materials engineering possibilities, including the incorporation of specific filler types and loadings, allow the formulation of materials with property balances of benefit to the industry, including applications that require low smoke generation. A variety of wire and cable applications are summarized and the benefits of the Interpolymer formulations highlighted.
Evolution of Structural Hierarchy in Uniaxially Deformed Branched Poly Lactic Acid Films as Followed by Spectral Birefringence Technique and Others
Over the past two decades, the lactic acid homo and copolymers have been extensively investigated for a variety of medical and pharmaceutical applications; including wound closure1, dental repairs2, fracture fixation (bone plates, screws, pins, and splits)3, ligament reconstruction, vascular grafts4, nerve repairs5 and drug delivery6,7. They are also extensively used in controlled drug release area6-8. With the recent developments in the technologies for purification of the raw materials, the large scale usage of these lactic acid based polymers became quite feasible. This, in turn, is opening the door for application particularly in the biodegradable packaging.
The Effect of Titanium Dioxide Particles on the Deformation Behavior and Orientation Development in PET Films
The effect of TiO2 particles on the stress-strain behavior of PET films from amorphous precursors at a series of compositions and deformation temperatures were investigated. TiO2 particles act as a nucleation agent and enhance the thermally induced crystallization of the PET chains. However, when stretched from the amorphous state, the TiO2 concentration levels as low as 0.35wt% was found to reduce the overall stress and retard strain hardening and accompanying strain induced crystallization. As a result, under the same stretching conditions, the films containing TiO2 were found to possess lower crystallinity and orientation levels. This was attributed to the reduction of chain entanglements in the presence of these small amounts of TiO2 particles in the stretching process. The results on the structural hierarchy developed in stretched and heat-set films will be presented.
The Effect of Deformation and Composition on the Structure Evolution in the Pre-Oriented PET/PEI Blend Films during the Heat Setting Process
The objective of this research is to affect the deformation and thermal behavior PET through synergistic blending strategies. For this purpose, a series of crystallizable compositions of PET (Tg=70°C) and PEI (Tg=215°C) were prepared. The structure evolution during uniaxial deformation was investigated. The very fast structural rearrangement processes that take place during the heat setting process were investigated using the newly developed Spectral Birefringence Technique. In 100/0 PET/PEI samples, above the onset of strain hardening the birefringence rapidly increases with time. The total increase in birefringence decreases with the increased levels of orientation and crystallinity imparted during the stretching stage. The introduction of PEI and the increase of its concentration tend to dilute the crystallizable PET chains. This, in turn, introduces a relaxation step at the early stages of heat setting at 180°C even in samples that were stretched to high stretch ratios. We also demonstrated that our Spectral Birefringence Technique is fast enough to keep up with the very rapid changes that take place at 180°C where the fastest crystallization is experienced.
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