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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Keys to Customer Loyalty in the Engineering Plastics Industry
Traditionally, many resources are dedicated to the acquisition of new customers in the engineering plastics industry. While constant replenishment/expansion of the customer base is important, it is critical not to lose sight of the growth potential of existing customers. The costs (and risks) involved in maintaining and growing these accounts are typically much lower than new account acquisition.As a result of over 1000 recent interviews, BRG Townsend has been able to identify, by segment, the attributes that are prerequisites for new account penetration and those which drive existing customer loyalty. By aligning resources with customer loyalty preferences, suppliers can more profitably manage their marketing resources.
Laser Assembly Technology for Planar Microfluidic Devices
The assembly of plastic microfluidic devices, requiring high positioning and welding accuracy in the micrometer range, was successfully achieved using a new technology based on laser transmission welding combined with the mask technique. In this paper we present a high-end laser assembly system for the joining of microfluidic plastic parts with its main related process characteristics and its potential for low-cost and high volume manufacturing. The innovation is a special arrangement of diode laser with a mask to generate micro welding seams with freely definable geometry. A fully automated mask alignment system with a resolution of 2 ?m and a precise, non-contact energy input allows a fast welding of micro structured plastic parts with high reproducibility and excellent welding quality.
LFT-D-ILC - Innovative Process Technology Decreases the Costs of Large-Scale Production of Long-Fiber-Reinforced Thermoplastic Components
In the European industry fiber reinforced thermoplastics have been firmly established for years for the purpose of large-scale production of structural automotive components. In particular, the newly developed LFT direct processing method has increasingly achieved its objectives due to its cost saving potential and excellent material characteristics.As a manufacturer of LFT processing plants Dieffenbacher GmbH & Co. meets the high requirements regarding material quality in order to guarantee a process for safe part production including an acquisition and evaluation system (SPC) of process data.The effect of material quality control will be demonstrated and the process technology will be introduced in this paper. Influences of the in-line compounding on mechanical properties will be discussed.
Load-Carrying Ability of Bolted Connections in Glass Mat Thermoplastics
Compression molded samples of GMT (Azdel R300B01N) were connected to metal steel plates with a bolt M8. No metal inserts were applied. Metal washers were placed between GMT plate and steel plates both at one side and at two sides of the GMT plate. Tests with and without a bold pre-stressing force were carried out. The load-carrying ability was tested with in-plane loading at rates of 1 m/s and 1 mm/s. A nominal bearing stress of 200 MPa seems to be a safe lower bound. Pre-stressing increased the maximum force sometimes with more than 75%. However, it was shown, that it pre-stressing can change the fracture mechanism from bearing fracture into the brittle tensile fracture. Cleavage fracture occurred when a washer with a diameter of 30 mm was used without pre-stressing and a loading rate of 1 m/s was applied.
Long Glass Fiber Composites: Rapid Growth and Change
Long fiber reinforced thermoplastic composites (LFRT) are one of the fastest growing segments in the plastics markets in North America and Europe, experiencing 30% per year growth, over the last decade. Development of new large part applications in the automotive market will continue to drive the growth of these materials.This paper will review the history of the LFRT composite market and give an up-to-date overview. It will also cover the new emerging in-line compounding technologies and what role they will play in this market. An overview of the current technologies will also be covered. The information presented is a brief excerpt from a more detailed study conducted by BRG, at the end of 2001.
Long-Term Creep and Recovery of Polypropylene Impact Copolymer
Effect of temperature on impact PP copolymer was studied during long-term creep and recovery (time duration-840 hrs) at two different stress levels. The experiments were performed at different temperature above glass transition (Tg) to probe the effect of temperature on the entropic nature of the impact PP copolymer due to presence of physical entanglements (networks). The recovery tests were performed in the absence of external forces. This provides accurate information with regard to the effect of temperature on the statistical behavior of the material. Those data were successfully used for finite elements model and packaging applications.
Luster Measurement of Single Textile Fibers by Aspecular Laser Scattering and Image Analysis
Luster is a key appearance attribute of textile fibers that may be defined by how glossy they appear. In textiles made from synthetic polymers, it is typically desirable to have low luster fibers that emulate the appearance of natural fibers such as cotton or wool. Assessment of luster for fibers is often qualitative in nature. A simple quantitative technique based upon laser scattering from a single fiber at an aspecular angle (75 degrees) combined with charge coupled device detection and image analysis was developed. A strong correlation was shown between a defined scattering ratio, obtained from the laser scattering data, and a five level panel luster test. A second correlation based upon fiber standards impregnated with titanium dioxide particles was also made.
Material Challenges in Medical Micromolding Applications
Processors in the medical field are being challenged to mold parts with smaller and smaller features. Many new lab-on-a-chip devices are designed to move biological fluids with micro liter volumes. This requires flow channels and other features that are on the order of microns. Molding parts with features of this size and with the tolerances required for medical applications presents several unique challenges in the selection and processing of the appropriate material. This paper discusses some general principles for material selection in the medical micro-molding field. In addition, several case studies are provided to illustrate solutions on real parts.
Mathematical Modeling of the In-Mold Coating Process for Injection Molded Thermoplastic Parts
In-mold coating (IMC) for thermoplastic parts is employed either to protect products from outdoor exposure or to improve the surface appearance as in automotive applications, or both. The coating material is injected into the closed mold and advances by compressing the thermoplastic substrate. This paper presents a mathematical model for the process. The compressibility of the thermoplastic substrate is taken into account. The corresponding computer code for the coating material filling and packing in a simple geometry has been developed and the results have been verified by experiments.
Measurement of Peroxide Content of Crosslinkable Polyethylene by Differential Scanning Calorimetry
The first rotational molding grades of polyethylene appeared in the 1950's. In subsequent years considerable effort was expended to improve the performance of these polyethylenes through peroxide-initiated crosslinking. Success was achieved due to the availability of peroxides with sufficient stability to be processed at elevated temperatures without significant scorching or pre-curing of the resin. The performance of crosslinkable polyethylene is strongly dependent upon the level of peroxide in the resin. This paper presents data showing that peroxide levels can be quantitatively and reproducibly characterized using differential scanning calorimetry. This method can be used for quality control in determining peroxide loss when grinding the resin into powder for rotational molding.
Measuring Dart Impact Strength of Polyethylene Films
Dart impact strength is widely used by resin manufacturers and film converters for quality control and for selecting the appropriate resin for a desired application. ASTM D 1709, Method A and B are generally used in the industry for dart impact strength measurement. This standard allows a surprising amount of latitude in the details of the test. This paper will describe a systematic study of the dart impact strength measurement technique. Some of the variables that have been explored are the material of construction of the dart head, age of the dart head and the diameter of the incremental weights. Variations of this type, all within the limits set in ASTM procedure D 1709, revealed significant influence on the measured dart impact strength values.
Mechanical Hole Burning Spectroscopy: A Nonlinear Viscoelastic Analysis
A mechanical hole-burning scheme was constructed to compare the analogous observations to those from dielectric non-resonant spectral hole burning (NSHB) for glass forming liquids near their glass transitions. Within the framework of the BKZ nonlinear viscoelastic constitutive equation and without invoking an explicit heterogeneous or homogeneous nature of the relaxation of supercooled materials, the calculated modified shear moduli shift non-uniformly with pump frequency. Mechanical holes were burned in the loss response and exhibited most of the apparent features of those reported from dielectric NSHB.
The Mechanical Testing of Micro Injection Mouldings
Micro-injection moulding is a relatively new technology that is gaining increasing interest in the processing industry. Injection moulded parts weighing less than one milligram are now in production. One of the main issues that has to be addressed with this technology is related to the measurement of the physical properties of the parts. The work in progress at the Wolfson Centre is concerned with the mechanical testing and characterisation of micro-mouldings. We believe that the techniques most suited to this are nanoindentation supported by surface etching, atomic force microscopy and light microscopy, with scope for scanning electron microscopy in the future. The method by which the micro-mouldings are prepared for the nanoindentation testing will be described. Results from proving trials on cut sections of injection mouldings are presented and demonstrate the potential of this technique for the testing of micro injection mouldings.
Mechanical, Thermal and Permeability Properties of PP / Oligopinene Blends
Our interest of study is blending of polyolefins with oligomers from natural and synthetic sources. In this work we show the results on mechanical, thermal and permeability properties of polypropylene (PP) / Oligopinene systems from compression films about 10 microns which were prepared using quenching (liquid nitrogen) from the molten state and permeability was measured using CO2. The addition of oligopinene on PP changes stress-strain curve of the polyolefin. For all oligomer content no more yielding was observed and the elongation at break had an abrupt decrease at a concentration of 10% of oligomer. The thermal analysis revealed that the blend system has two glass transition temperatures. The permeability values changed slightly with the oligomer content in the blends.
Mechanical-Morphology Relationship of PS Foams
The relationship between the morphology and the mechanical behavior of commercial PS foams has been investigated. The foams studied had a closed cell morphology with densities between 25 and 60 kg/m3 and number-average cell sizes between 75 and 230 ?m, and a normal cell size distribution (dv/dn ? 1.20). Mechanical results showed that the compressive strength and modulus could be expressed as a function of the foam morphology, using a unique morphological parameter taking into account the cell size and foam density. Flat sheet impact tests showed that three stages, i.e. initiation, propagation and collapse, could be identified in the impact behavior of the foams, which could be related to the morphological parameter proposed. A transition from a brittle to a ductile behavior could be rationalized using the proposed parameter.
Melt Flow Instability Studies of Metallocene Catalyzed LLDPE in Pelletizing Dies
The capillary flow behavior of metallocene catalyzed LLDPE was studied in the melt flow instability region of the resin. Processing variables, as well as die materials of construction and geometric/design variables of the dies were explored. The extrudate performance variable that this study focused on was the detailed microscopic structures (topographies) of the extrudate surfaces, in order to obtain insights on the die-related origins of the melt instabilities involved. It was speculated that the surface melt fracture of extrudate was similar in nature to other mechanical fracture that is initiated from the formation of small cracks on the extrudate surface, caused by high wall shear stress with increasing flow rate and/or high elongation stress due to exit singularity (or velocity discontinuity). Cohesive failure creating peeling/tearing cracks observed can propagate and evolve into a well-organized structure, depending on the excess stress energy levels on the extrudate surface at the exit and cohesive strength of the polymer melt. Possible methods to mitigate the surface melt fracture in capillary dies were also suggested from the proposed fracture mechanism.
Melt Mixing Improves Hot Runner Balance and Improves Part Quality
One method of balancing multicavity molds is to restore the cross-sectional symmetry of the shear induced hot/cold lamination of the melt before a runner branch. While, this method has been used successfully with H pattern runners it's less compatible with molds including intersections with more than two branches. In this work it is demonstrated that melt homogenizing before critical runner intersections improves the balance of molds independently of their hot runner configuration. In addition, when a mixing nozzle is used to homogenize the melt before delivering it to the cavity, preferential cavity filling can be eliminated and more dimensionally stable parts can be produced with uniform microstructure and mechanical properties.
Melt Processability of Polyethylene with Long Chain Branches
Linear viscoelastic results are presented for several polyethylenes which each exhibit, to varying degree, an increased zero shear viscosity (?0) relative to that observed for a linear polyethylene with the same weight average molecular weight (Mw). This is a well-recognized rheological signature of the presence of long chain branching (LCB). Examination of the small amplitude oscillatory shear data for the branched polyethylenes clearly reveals the presence of two separate relaxations. We examine the utility of considering these polyethylenes as blends of branched and linear species. A unique power-law behavior is observed for the dynamic viscosity in the intermediate frequency region bounded by the distinct relaxations of the linear and long chain branched components. Characterizing these rheological features appears to be a key element in formulating an understanding of the processability of polyethylenes which possess entangled branches.
Melt Processing of Polymers Using Supercritical Fluids
In-line rheometry has been used to study the plasticising effect of sub and supercritical carbon dioxide during polymer melt processing. The extent of the plasticising effect has been investigated using model systems so that theoretical and actual viscosity reductions achieved could be compared. Results will be presented which demonstrate these effects.As a result of this research injection moulding and extrusion processes have been optimised for a selection of polymers and highly filled polymer compositions. This has led to enhanced manufacturing process efficiency and the manufacture of components with preferential foaming.
The Melting Behavior of Amorphous Polyester in a Co-Rotating Twin Screw Extruder
The melting behavior of an amorphous polyester in an intermeshing co-rotating twin screw extruder was examined. It was found that the melting of this low Tg amorphous polyester could happen even in the partially-filled conveying screw section without any kneading or reverse screw elements, if a preformed melt" was created. Barrel heating is more than providing the energy required for melting but to create a layer of "preformed melt". Once this "preformed melt" was created the melting could be sustained with the heaters of the barrel being shut off. The "preformed melt" seems catalytic to this VED (Viscous Energy Dissipation) dominant melting process might also be important to many other melting processes."
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