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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Design Rules for Stereolithography Injection Molding Inserts
The mold life of stereolithography tooling depends upon factors such as material, processing conditions, and geometrical features. With the establishment of limitations for part geometry, the existing Direct AIM process can become a much more reliable method of producing short runs of functional prototype parts in their end-use material. Draft angle is one factor that contributes to mold life. As the draft angle increases, more parts can be manufactured before failure of the feature. Also, a large gate allows the mold to last longer than a small gate due to the decreased injection velocity.
Optimization of Injection-Molding Process with Genetic Algorithms
Injection molding is widely used for mass production of polymer products. One important issue is how to determine the gate location(s) and process conditions to produce parts of the best quality. The objective of this paper is to develop an efficient optimization system that can automatically make such determination. The Genetic Algorithm (GA) will be compared with a functional search method, Simulated Annealing (SA) algorithm. The principle of both algorithms will be described and illustrated with examples. Application of these algorithms to determine gate location and optimal process condition in injection molding will be demonstrated with examples. Gate location is determined based on the principle of balanced flow paths, while the optimal process condition is computed by minimizing the warpage across the entire part. Results show that the Genetic Algorithm is more efficient computationally than the SA algorithm.
Reduce Costs and Get Better Product Using Your Own SPC System on Your Line at Your Profile Extruder's Plant: A Customer's Perspective
SPC (Statistical Process Control) is a powerful tool that can be used to enhance quality and increase productivity in profile extrusion lines, but the number of custom extruders that use SPC is limited. When the right extrusion vendor can be found who is open to new ideas and is willing to work in partnership with a customer with basic SPC skills, it is possible to increase part quality and reduce costs simultaneously. For $3,500 plus a low end laptop and one of the popular spreadsheet programs, a simple, portable and powerful SPC system can be built, assembled, and programmed. All hardware and software is commercially available. Only a limited knowledge of instrumentation, statistics, and the ability to design and use a spreadsheet program is necessary to employ the methods presented. An example is presented wherein a customer brought his own portable SPC system into his profile extrusion company's shop and used it to troubleshoot the process, improve the quality of the customer's product, and decrease manufacturing costs by increasing production rates.
Influence of the HDPE Grade on the Blow Moulding of a Bottle: A Numerical Investigation
A numerical investigation is performed on the influence of the properties of the high density polyethylene properties on the final thickness distribution of a bottle. The K-BKZ integral model with a relaxation spectrum is used for modelling the rheology of the material. A membrane element is used for performing the simulation of the blow moulding of geometrically complex objects, and is combined to a Lagrangian representation for the equations governing the motion. The simulation tool is applied for the production of a bottle with a handle. Numerical predictions on the thickness distribution of the part are compared to available experimental data.
Utilizing an Engineering Resin Supplier's Technical Support
Many molders, designers and resin specifiers do not realize the extent of technical resources available to them by the suppliers of engineering resins. Whether an application is still a concept or currently in production, questions may arise regarding properties or processing of a material. Engineering resin suppliers are generally well equipped to provide guidance in material selection, design, processing and trouble shooting for applications using their materials. This paper will provide an outline of the types of services and data commonly available. Guidelines will be provided for obtaining maximum utilization of the resource for large customers, small customers and even non-customers.
The Six Marketing Secrets for a Profitable Web Site - What Works and What Doesn't
The real secrets to profitable Web Sites are content, content and more good content, along with some interesting tricks, plus understanding the audience. Learn what works to get buyers to visit and then repeatedly come back to your Web Site. Paradigm shifts, although infrequent, change all the rules. Such has been the case with the advent of E-marketing, considered by many to be one of the greatest paradigm shifts of this century. What it has done is enable companies to have dialogues with large numbers of individuals at very little cost; and given companies the ability to keep track of individual habits, estimate individual desires and work to satisfy them.
Polyblends of Polystyrene and High-Impact Polystyrene with Styrene-Ethylene/Butylene-Styrene Thermoplastic Elastomer
Styrene-ethylene/butylene-styrene sandwich block copolymer thermoplastic elastomer was added to polystyrene and to high-impact polystyrene to increase ductility and impact strength. While it decreased modulus, strength, and heat deflection temperature, it did increase the elongation and impact strength of polystyrene greatly, and was superior to conventional rubber-modified polystyrene, both in impact strength and in overall balance of properties. Conversely, addition of polystyrene or high-impact polystyrene to styrene-ethylene/butylene-styrene thermoplastic elastomer did not seriously decrease its rubbery elasticity.
Mistaken Identity: Prevention of Failures Due to Improperly Supplied Resins
Product performance problems are often related to design, molding, or misuse by the end user. However, a more fundamental problem may be a wrongly supplied or inferior resin that can lead to poor performance or failure. Two examples are presented for illustration. Case 1 involved a change in polyolefins supplied for an air filter, which reduced performance. Case 2 was an ergonomic polystyrene chair arm that experienced multiple cracks during shipment in the winter months causing multiple returns to the manufacturer. Methods for material determination in these two cases are shown as well as recommendations for quality control testing to prevent poor products from leaving the factory.
In-House Blending of Polypropylene with EPDM
A custom processor can inventory one hard and one soft resin of good compatibility, and blend them in various ratios to manufacture a wide range of products. In a model study of polypropylene (PP) with ethylene-propylene-diene rubber (EPDM), all ratios from 100/0 to 0/100 showed good practical compatibility. Adding 20% of EPDM to PP increased impact strength 5X; while adding 20% of PP to EPDM doubled tensile yield strength, producing a thermoplastic elastomer. Extrusion pre-blending favored elongation, rebound, recovery, and impact strength; while direct blending during injection molding favored modulus and strength.
Flow-Induced Morphological Changes Inpoly(Styrene-Co-Maleic Anhydride)/Poly(Methyl Methacrylate) Blends
The effects of shear flow on the phase behavior of a polymer blend with high glass transition temperature, Tg, constituents possessing large viscosity difference were investigated in the linear and non-linear regime using shear and capillary rheometry. This was complemented by differential scanning calorimetry and analysis of the extrudates with scanning electron microscopy. The blend is a lower critical solution temperature polymer mixture of a random copolymer of styrene and maleic anhydrite, SMA (Tg=178°C), and poly (methyl methacrylate), PMMA (Tg=105°C). The methodology presented here for the determination of the shear-induced phase diagram should be applicable to any industrial mixture. The activation energy analysis in the phase separated SMA/PMMA(50/50) blends predicted cylindrical domain morphology in the non-linear regime. The latter was confirmed by SEM of the phase separated SMA/PMMA(50/50) extrudates, associated with high shear rates, where fibrillar domain structure was observed in the shear direction.
The Effect of the Boron Mitride Type and Concentration on the Rheology and Processability of Molten Polymers
The influence of a new processing additive (a composition of fine particles of boron nitride) on the rheology and processability of molten polymers is studied. The equipment used includes both an Instron capillary rheometer with special annular dies (Nokia Maillefer wire coating crosshead) attached to the rheometer and a parallel-plate rheometer. A metallocene polyethylene and Teflon FEP with several types of boron nitride varying in particle size distribution are tested at various concentration levels. The additive with the finest particle size has the greatest influence in crosshead dies and tips. As a result, its use eliminates surface melt fracture and postpones the critical shear rate for the onset of gross melt fracture to significantly higher values depending on the additive concentration. The influence of the boron nitride type and its concentration on the polymer rheology is also discussed. It is found that the activation energy for flow of Teflon FEP scales with the BN concentration.
Laser Sintered Short Run Tooling for Injection Molding
Direct prototyping of a mold using a laser sintered (SLSa) polyamide/copper (Cu/PA) compositeb allows the production of a limited number of prototype injection molded parts from production materials such as PP, PE, and ABS. The tooling is produced without doing reverses from patterns typical of prototype tools. The paper details the process including production of the tool, typical parts from such tool, and best use of such parts, tolerances, feature details, and cosmetics. The process is benchmarked against CNC tools and epoxy/composite tooling to compare durability, lead time, and accuracy. Whereas the material is not touted to be a production tooling substitute, the copper/polyamide facing with epoxy based tooling may be an option for parts with low volume, quick turnaround requirements, medium tolerance requirements, and fine detail and feature refinements. However, prior to processing, the Cu/PA tools have several criteria that must be incorporated into the design of the tool in order to effectively utilize the process.
Using Traditional Machine Shops Versus CNC Machining Centers
The paper examines traditional and CNC machining for fabrication of molds and prototypes. Factors examined include: • Delivery • Cost • Equipment • Tolerances • Technical competence • Cosmetics Conventional machined tooling is more appropriate where high finish, extremely high precision and high feature density is required, but CAD data is not available or is not converted easily to CNC cutter paths. Traditional machined prototypes may be more cost effective, delivered faster, and include better feature definition and surfaces for small part volumes. Leaving CNC out of the manufacturing cycle may be beneficial for the OEM, injection molder, and designer in low volume applications and for high precision molds where the feature definition of the part is critical and parts costs must be considered.
High Performance Crosslinkable Thermoplastic Elastomers for Medical and Electronic Applications
A family of thermoplastic elastomers have been developed that when crosslinked by irradiation are shown to have improved thermo- mechanical properties and chemical resistance at elevated temperatures. These materials can be easily injection molded and extruded into thin wall parts and tubing as well as wire and cable coatings. This processing can be performed on conventional thermoplastic processing equipment. They offer design engineers capabilities not previously available. This paper will present an overview of thermoplastic elastomer families and markets where thermoplastic elastomers are used. We will review the advantages of the irradiation crosslinking process and the improvements imparted to plastics and elastomers by this process. We will more specifically introduce the application of the irradiation crosslinking process and its improvements to a specific family of thermoplastic elastomers. That family being the COPA family of thermoplastic.
Decision Diagrams Aided Conceptual Mold Design
The conceptual mold design for injection molding of thermoplastics represents one of the most important phases in mold designing. In practice, the solutions for this phase are often based only on the designer's experience, which may cause severe faults in the finished mold. One of the possibilities in solving this task during the mold design is to apply the decision diagram for a principled selection of the solution for single partial functions of the mold. Such decision diagrams may be very simply checked in practice, the necessary corrections made, and they may be then developed into an adequate computer program - knowledge base, which is of special significance to the less experienced mold designers.
Single Cycle-Twin Sheet Thermoforming for Technical Precision Parts
One feels as we address the dawn of the 21st century that there should be some revolutionary process-something radical-some brilliant new discovery that, as we speak today in the spring of 1999, will create history. Unfortunately, developments as radical are not spawned from the Roman calendar or our individual ambitions to become famous. They are borne of a need, an idea to solve a problem, and so, ultimately, today’s solution is destined to become tomorrow’s technology. I am sure that, being active members of thermoforming and plastics related industries, you are familiar with the simplistic concept of TWIN SHEET thermoforming. The forming of a 3D product from two separate sheets of plastic material is, in broad concept terms, a simple matter. The complexity and technology required too create a similar product of uniform strength and acceptable aesthetic appearance requires much more skill and process technology before it could reach the market. In this presentation we will review the use of single cycle thermoforming machines dedicated to the production of very high precision parts of extreme dimensional accuracy and total quality repeatability.
Hot Fillable Containers Manufactured from New Polymeric Compounds Based on PET/PEN Copolymers and Blends
Copolymers and blends of PET containing NDC units, owing to their favorable combination of properties, may find applications in areas of beverage and food containers of high performance requirements. Copolymer of PET with sizable increase of NDC content has been processed in Injection Stretch Blow Molding (ISBM) in a sort of unique controlled one stage cycle process, which was developed to produce the microstructure necessary to overcome high thermal resistance of hot filling of liquids at up to 95°C accompanied with high barrier properties. PET/PEN blends, which attracted even greater attention, were initially produced and investigated on a scale of experimental system and at later stage produced by an ISBM process into bottle containers. The properties of both type of materials in a form of ISBM produced containers, has found to be depended on their composition and microstructure, which can be tuned by controlling the production parameters. These properties, namely the Tg, the strain induced and the thermal crystallization, were monitored by DSC and DMTA thermal analysis techniques throughout the investigation. The results of this study are promised and may provide the way to a range of new material formulations with a capability of improved properties for ISBM made heat stable containers.
Predicting Flow Length of Spiral Melt Flows in Injection Molds by a Semi-Empirical Model
A spiral-shaped mold of nearly rectangular cross-section with height and width in the order of a few millimeters is often used to classify injection molding materials according to their flowability. The length of the solidified plastic in the spiral, known as flow length, is taken as a measure of the flowability of the resin concerned. The parameters involved in the flow process are, mainly, resin viscosity, melt temperature, mold wall temperature, axial screw speed, injection pressure and geometry of the mold. To minimize the number of experiments required to determine the flow length, a semi-empirical model based on dimensional analysis has been developed. The modified dimensionless numbers used in this model taking non-Newtonian melt flow into account are Graetz number, Reynolds number, Prandtl number, Brinkman number and Euler number. Comparison between experimental data obtained with different thermoplastic resins and the model predictions showed good agreement , confirming the applicability of the approach for any injection molding resin.
Study of the Influence of the Injection Molding Processing Parameters on Molded Part Properties Using the Full Factorial Design
Due to a large number of processing parameters involved in injection molding of thermoplastic melts, a systematic investigation of their main effects and interactions is indispensable in order to achieve the optimum quality of the molding. In this study, the main adjustable influencing factors have been varied, such as melt temperature, injection pressure, cavity wall temperature and coolant rate. The experiments were carried out by applying the factorial design 24 and the following properties were analyzed: weight, dimensions, surface waviness and tensile strength of the molding.
Mechanochemistry Effects in Recycled Polypropylene and its Blends during Solid-State Shear Pulverization (S3P)
On-going research focuses on understanding the mechanochemistry during Solid-State Shear Pulverization (S3P) of recycled polypropylene (PP) and its blends. Free radicals formed during this process act as compatibilizing agents for ordinarily incompatible polyolefin blends. It was observed earlier with Nuclear Magnetic Resonance spectroscopy that each S3P cycle converts a small portion of polypropylene chains from isotactic to atactic stereoregularity. Small amounts of such atactic chain segments impart additional levels of toughness, which offset, in part, the damage associated with the inevitable chain scission. We determined how many processing cycles S3P-made recycled PP can endure without significant loss of mechanical properties.
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