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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Analysis of Flow in Single Screw Extruders
In the analysis of flow through a single-screw extruder, it is generally assumed that the kinematic condition, rotating barrel around a stationary screw (B), generates the same flow distribution as the kinematic condition, rotating screw inside a stationary barrel (A). Recently this assumption was questioned.This paper addresses the issue of kinematic reversal in detail. The steady state creeping flows in a single-screw extruder under kinematic conditions A and B will be investigated by theoretical analyses, and 3D numerical simulations using the CFD software, POLYFLOW. Both analytical and numerical results indicate that kinematic conditions A and B result in the same flow field. Apparent differences appear only when a flat plate approximation (FPA) is used. However, these differences are solely due to the fact that the FPA does not take channel curvature into account. When channel curvature is properly accounted for by using cylindrical coordinates, conditions A and B produce the same velocity distribution.These results indicate that the FPA should not be used with deep flighted screws because it introduces serious errors. Similarly, the analysis of both kinematic conditions by using the FPA inevitably leads to erroneous results. The error introduced by using the FPA analysis with a moving screw is even greater than with a moving barrel.
Analysis of Low Levels of Polyvinylpyrrolidinone in Polysulfone by FTIR and Pyrolysis GC/MS
FTIR and Pyrolysis GC/MS are two analytical techniques which we used to investigate the detection of polyvinylpyrrolidinone (PVP) as a low level impurity in polysulfone (PSO). These analyses are demonstrated to be convenient and rapid alternatives to time-consuming methods such as solvent extraction, when PVP is thought to be present as an impurity in PSO.FTIR analysis was performed by comparing the intensity of the IR absorption stretches of PVP and PSO. We selected absorbances at 1680 cm-1 and 1586 cm-1 for PVP and PSO, respectively. These absorbances were selected because of their relatively high intensity, and because they are well resolved from each other and from other strong absorbances. It was thus possible to detect and quantitate PVP in PSO to a level of 0.5%, with very good linearity of response. A significant advantage of this method is that it allows for rapid and non-destructive monitoring of the two blended polymers.Pyrolysis GC/MS was also used to investigate low levels of PVP in PSO. Comparison of the levels of certain unique and well resolved pyrolysis products (such as 2- pyrrolidinone from PVP and phenol from PSO) permitted detection and approximate quantitation of PVP in PSO, with a practical detection limit of 0.05%. EI+ ionization was used to produce a mass spectrum of the components of interest, which could be reliably identified by comparison to standard library reference spectra.
Analysis of Melt Instabilities of Poly-(Vinylidene Fluoride) in Shear and Extensional Flows
The melt instabilities of polyvinylidene fluoride (PVDF) were studied in shear and in extension using a capillary rheometer and Rheotens melt tester, respectively. In shear, emphasis was given to wall slip and melt fracture during extrusion in capillary dies. The combined effect of the critical stresses for melt fracture and slip to the appearance of the extruded strands for different die size, and polymer molecular weight were also studied. The results shows that PVDF exhibits a different mechanism of instabilities compared to the those known for polyethylenes. Additionally, wall slip was shown to occur starting at very low shear rates.
Analysis of Parameters Determining the Friction Properties of Thermoplastics in Injection Molding
Frictional forces must be overcome during ejecting of parts molded over deep cores. The friction properties between the molding surface and the part are important for the design of the ejection system. Prototype equipment and test methods were already developed and proposed to characterize the friction properties in as-molding conditions.A factorial design of experiments was devised to establish the hierarchy of the parameters that affect the static friction in ejection. Two thermoplastics (PC and PP) and steel surfaces were considered. The parameters under study included: surface roughness, direction of machining with respect to the test direction and testing temperature.
Analysis of Silicone Polymers at Trace Levels by Pyrolysis Gas Chromatography/Mass Spectroscopy
Silicone polymer release liner surfaces on paper, for self stick stamps and labels, become contaminants in paper recycling. Low print adhesion is one major problem limiting the inclusion of silicone release liners in recycling feed stock. A very sensitive method of analysis of silicone polymer during and after recycling employs pyrolysis GC/MS. The analysis provides a measure of siloxanes, ignoring inorganic silicon compounds such as silicates. The method also distinguishes between linear and branched polysiloxanes by different pyrolysis products. High sensitivity, to ppb, may be possible using single ion monitoring or selected ion data collection of mass spectra.
Analysis of TNPP in LLDPE Formulations: Did the Phosphite Hydrolyze during Processing?
This report describes a simple solvent-based technique for the separation of tris(nonylphenyl) phosphite (TNPP) from a LLDPE (linear-low density polyethylene) resin, as well as subse-quent analysis. The solvent extracts" were ana-lyzed as is using 31P-NMR and/or liquid chroma-tography techniques. The analytical results showed that the main reaction product formed during the compounding step was tris(nonylphenyl) phosphate (PV) by way of phosphite (PIII) oxidation. It was further shown that the phosphite did not undergo any hydrolysis reaction as determined by analyzing for nonyl-phenol and "acid phosphite" levels. Lastly the HPLC method was shown to be viable in the concurrent analysis for both components in typically used phenolic and phosphite antioxidant blends."
Apparent Bulk Modulus as a Measure of Thermodynamic Equilibrium State
Simultaneous volume and enthalpy relaxation behaviour of a-PMMA stimulated a by double-step temperature jump is studied. For both types of relaxation a memory effect following the up-jump can be observed, which is weakened by increasing of preannealing time. A constant relationship between both quantities during the sample expansion has been found. From the dependence of excess enthalpy vs. specific volume, an apparent bulk modulus, Ka, was calculated (Kubat, 1998). Its values increase with pre-annealing time and approach to a maximum value. The modulus can be used for quantification of the thermodynamic equilibrium.
Application and Considerations of Chemiluminescence in Polymer Degradation Studies
Digital electronic imaging using Charge Coupled Devices (CCD) has become popular due to its mass adoption in digital imaging applications. These sensors are moderate in resolution, extremely sensitive, offer wide dynamic range, and compared with photo-multipliers are capable of withstanding exposure to bright light without damage. These characteristics made CCD detectors ideal for chemiluminescence (CL) studies for polymer oxidative degradation.We have adapted a CCD imager with a differential scanning calorimeter (DSC) for simultaneous oxidative induction time (OIT) and CL studies. In addition, these CCD imagers are inherently area detectors, making them easily adapted for multiple sample studies or situations where sample heterogeneity exists. Advantages and considerations of CCD CL technique will be presented.
Application Design Advances through Plastics
Recent developments in plastic materials and processing have opened up product design opportunities that have been heretofore impossible. Designers have utilized plastic materials in a variety of new applications in automotive, consumer, packaging, personal care, electronics, sports and leisure, construction and appliance products.Plastic materials like thermoplastic elastomers, conductive and reinforced products, alloys and blends, etc. have enabled breakthrough designs and new functional products. Process developments like co-extrusion, multi-shot molding, foams and in-mold decorating have accelerated the penetration of plastics into new applications. Design and collaboration tools like CAD (computer-aided design) and rapid prototyping and tooling have contributed to reduction in the product development cycle and time to market.This presentation will review some case studies, which are illustrative and identify the challenges and the opportunities facing thermoplastics today and into the future.
Application of Ultrasound in the Determination of Fundamental Extrusion Performance: Residence Time Distribution Measurement
By means of new probe design and rapid data acquisition of 1,900 Hz repetition rate, we have succeeded in in-line ultrasonic monitoring of residence time distribution (RTD) at the melting, mixing, and pumping zones as well as at the die exit of a W&P 30-mm twin-screw extruder by mounting the ultrasonic probes on the extruder barrel over the screw elements. The experimental systems were LDPE, CaCO3 -filled LDPE and a Kraton/LDPE blend. For the first time the ultrasonic data of each of the extruder functional zones will be presented. The performance of the ultrasonic approach was evaluated against a conventional optical RTD measurement method by using an optical sensor side by side with one ultrasonic probe at the mixing zone of the extruder. Good agreements were obtained. An advantage of the presented ultrasonic technique is that in addition to RTD, it may provide simultaneously other process related information including material composition, filler dispersion, viscosity, etc.
Application of a New Internal Reflection Wave-Guide Coupling Technique to the Study of Polyaniline
Nondestructive three-dimensional refractive index measurements are used for the determination of both crystallinity and orientation in thin polymer films. The prism wave-guide coupler is particularly suited for three-dimensional isotropic and anisotropic thin film studies because of the quantitative character of the information obtained and the ease of data acquisition. It has been limited, however, to measuring the refractive index of transparent or weakly absorbing films. The present study show s that by using a modified prism wave-guide coupler it is possible to determine the complex refractive index over a range from transparent to highly absorbing films from the internally reflected light intensity. Thus both the refractive index, n, and the extinction coefficient coefficient, k, and hence the real, ?1, and imaginary, ?2, parts of the dielectric function, can be obtained. This method is used to determine the anisotropic three-dimensional ?1 and ?2 values of spin coated EB and HCl doped ES polyaniline films at two very different wavelengths.
Application of a Reliability-Based Methodology for Predicting the Outdoor Service Life of Polymers
Organic polymers are a commercially important class of materials that are being increasingly used in outdoor applications such as paints, coatings, sealants, siding and roofing membranes, to name just a few. One of the most damaging elements in the outdoor environment is ultraviolet (UV) radiation, both alone and in conjunction with moisture and temperature. Conventional ways of predicting the weatherability" or service life of a polymer involve either outdoor testing performed in real time or accelerated laboratory testing using artificial UV sources neither of which have proven to be entirely successful.The High Performance Polymeric Building Materials Group at NIST is developing a reliability-based methodology for predicting the service life of a polymeric material in outdoor environments. The NIST approach makes use of methodologies that are well-established in the biological and medical communities. In the course of advancing this new methodology a number of novel instruments for conducting UV exposures have been developed. The basis for the new predictive methodology and the novel instruments used for laboratory UV weathering will be discussed."
Assessing the Interphase in Polypropylene/Glass Composites
The bonding in polypropylene (PP)/glass composites is inherently weak due to the non-reactive polypropylene matrix. Traditional sizings are only useful in increasing the interfacial strength when compatibilizers are added to the matrix. Currently, maleated polypropylene (mPP) is widely used to improve the bonding in PP/glass composites; therefore, the overall properties of the composite are improved.A better understanding of the contributions of the mPP's is desired. This research investigates the interphase in PP/glass composites using in-situ Near-IR fiber optic techniques and glass bead composite mechanical properties.The in-situ infrared technique utilizes a lead doped high refractive index silica glass fiber. The Near-IR source is guided down a single fiber. An evanescent wave is used to concentrate the area of investigation to the interphase. The glass fibers are coated with ??aminopropyltrimethoxy silane (??APS). The results compare several commercial grades of maleated polypropylene blended with a 20 MFI homo-polypropylene. Overall mechanical properties of the injection-molded composites will be analyzed in conjunction with the infrared studies.
Asymmetric Conductive Heat Transfer Resulting from Air Gap Formation during Shrinkage
In injection molding processes, an air gap is formed between the cavity steel and plastic part as shrinkage occurs throughout the cooling phase. Considering the significant difference between the thermal conductivity of P-20 steel (41 W/m·?C) and air (0.0383 W/m·?C), the air gap is a potential medium for creating an asymmetric conductive heat transfer within the plastic part. This assumption of different heat transfer behavior was studied by using finite element analysis and flow simulation packages. The results were contrasted to those of the symmetric behavior. The conclusions made discuss the practical needs of considering the air gap formation in cooling designs and its probable impact on qualities of plastic parts.
At-Process Spectroscopy and Ultrasonic Monitoring of Polymer Melt Processing for Process Monitoring and Control
The use of spectroscopic techniques in the analysis of polymer production processes is becoming more prevalent. At-process methods allow for real-time information on a variety of melt characteristics to be collected. Several analytical techniques are being explored for in-line and on-line use during extrusion processing of polymer melts, with a view to characterising polymers for process monitoring and control.In-line ultrasonic velocity measurements have been made simultaneously with on-line mid- and near- infrared and in-line Raman Spectroscopy during single screw extrusion of a range of blends of an HDPE and a PP. The sensitivity of these techniques to changes in blend composition is being assessed and compared. The techniques show very close agreement in monitoring the dynamics of change from one blend composition to another.
Automated Sheet Die Design
This paper reports on a method of integrating extrusion die design with state-of-the-art computer-aided design programs. The design of a coat hanger extrusion die is automatically optimized using a parametric based three-dimensional polymer flow simulation algorithm. The optimal parameters determined by the optimization algorithm are input to a parametric-based computer-aided-design program to yield tool path for die fabrication. A prototype coat hanger die is fabricated according to the material selection and process conditions specified. Experimental flow distributions match the predicted flow distributions within acceptable experimental error. Because this approach employs three-dimensional flow analysis, it can readily be extended to profile die design.
Automotive Requirements for DuPont Engineering Polymers in Integrated Air Fuel Systems
Automobile companies are looking with increasing frequency at composites (engineering polymers based matrix) to reduce weight, cost and to improve the recyclability of their powertrains.Air Intake Manifolds (AIM's) and Integrated Air/Fuel Systems (IAFS) have emerged as prime candidates for conversion from metal to composites and market penetration in North America is above 80%.This paper will present the state of the art for materials in these applications including real life examples and analysis.Also we will share some of DuPont new offerings in these market that provide significant system cost reduction while performing better in a more demanding environment.
Ballistic Impact Resistance of Composites with Different Fabric Structures and Configurations
Ballistic performance of fiber-reinforced composites with different fabric structures and configurations was studied. Composites with Kevlar-KM2 ripstop fabric performed better against smaller size projectiles due to the effective fiber failure through constraining of the fibers, while hybrid composites constructed from ripstop fabric of Kevlar-KM2 and Spectra-1000 show an advantage with larger projectiles due to the effective strain energy absorption. Hybrid composite configuration of these two structures exhibited overall performance improvement.
Basic Mechanisms of Structural Ordering in Uniaxial Stretching of PLA Using Fully Automated On-Line Birefringence Coupled with True Stress-True Strain Measurement
Fundamental deformation-structure relationships in melt cast amorphous Poly(lactic acid) (PLA) films were investigated using a stretch birefringence apparatus that allows for direct measurement of true stress, true strain, and birefringence at realistic strain rates. The relationships between stress, strain, and birefringence are strongly affected by the processing conditions: temperature, stretch ratio, and stretching rate. The molecular mechanisms of this deformation and the effects of process variables on these are elucidated in this study.
Basic Principles in Materials Selection for Mechanical Fastening of Thermoplastics
In this current paper, we are discussing basic principles in materials selection, which focused on utilization of the light alloys for manufacturing of fasteners for thermoplastics applications.Proposed fastener(s) material replacement (from steel to aluminum) will allow to manage the stiffness considerations, short-term (strength) and long-term (life) performance of the assembled plastic parts for various automotive applications.The results from this investigation provide recommendations on materials pre-selection for the design of fastened thermoplastic components with improved mechanical performance.
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