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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Avenues of Introducing Chaotic Mixing in Single-Screw Extruders
It is widely known that single screw extruders are poor mixers and improving mixing in single-screw extruders is a challenging task, especially under low shear conditions. In this paper, a methodology based on chaotic mixing sections, spread over almost half of the screw length, is described to improve mixing characteristics of immiscible and miscible polymer systems under low shear conditions.
Balance between Drop Dart and Izod Impact: Predicting Performance in PVC Window Profile Compound
Drop Dart Impact Testing is now widely used to predict the performance needed in window profile fabrication and use. It evaluates formulation effects and strength developed through proper processing. Izod Impact Testing has shown some utility as a predictor of not only strength, but as a better way to differentiate ductility and crack propagation properties of profile compounds, important in the fabrication stage. This paper will discuss the relative merits of both tests, and how they can be used to differentiate additives that contribute to impact and fabrication performance.
Barrier Properties of a Thermotropic Liquid Crystalline Polymer
A developmental Thermotropic Liquid Crystalline Polymer (TLCP) made by Eastman with tradename LN001 was used for barrier property studies. The permeability of methanol and toluene through a membrane of the TLCP was studied using a two-part cell and a Gas Chromatograph to monitor the flux. The membranes of the TLCP and LDPE (as control) were made by compression molding. Both solvents had higher permeability through LDPE than TLCP and that of Toluene was higher than Methanol.
Barrier Screws, Their History and Their Function
This paper will briefly discuss the history of barrier screws and then discuss the design features and resulting performance in single screw extruders. Barrier screw operation in smooth feed and grooved feed machines will be discussed. Comparisons of barrier screw performance to conventional screws will show where the benefits lie and a few examples of where there is less advantage or even disadvantages with barrier screws.
Blend of Polypropylene-G-Poly(Methyl Methacrylate) and Bisphenol-A-Polycarbonate
A novel reactor-made polypropylene-g-poly(methyl methacrylate) (PP-g-PMMA) was used as a component for forming binary blends with bisphenol-a-polycarbonate (PC) and ternary blends with PC and polypropylene (PP). Results showed that the morphology and physical properties of these blends were strongly composition dependent. The compatibility window was determined based on the physical properties and the morphology. The binary blend of PP-g-PMMA/PC shows excellent chemical and stress cracking resitance as compared to PC.
Blending of Immiscible Polymer Systems by Chaotic Mixing
A novel feature of chaotic mixing, that of formation of self-similar mixing structures, is utilized in this study to produce an array of mixing microstructures, such as nested layers, elongated fibrils, droplets and their combinations in the blending of two immiscible polymers, polypropylene (PP) and polyamide-6 (PA6). The effects of initial length scale of segregation, viscosity ratio of the phases, mean shear rate, and the degree of chaotic mixing are studied.
Brittle-To-Ductile Transition Temperatures of Miscible Copolyester/Polycarbonate Blends
The brittle-to-ductile transition temperatures (TBDs) for miscible copolyester/polycarbonate blends are studied using single edge notched bend specimens. The pure copolyester TBD and pure polycarbonate TBD are lower than the TBDs of copolyester/polycarbonate blends. This decrease in toughness is evaluated by examining the yield strength and craze strength as a function of temperature and blend composition.
Capillary Rheometer Pressure Transients for Lubricated Flows through Straight and Semi-Hyperboloidal Dies
Pressure transients in lubricated “skin-core” flow of a long-chain branched polypropylene (PP) are studied in two axisymmetric dies, one a straight die of diameter 1.0 mm and L/D ratio of 10, and the other a semi-hyperboloidal die designed to offer a constant extensional strain rate and a Hencky strain of 4.88. Stable flows are obtained for the melt and flow parameters with which the experiments are conducted. Lubricated flows through straight as well as semi-hyperboloidal dies exhibit longer and non-monotonic pressure transients.
Case Studies Illustrating the Four Primary Causes of Product Failures
Material selection, part design, mold design, and processing must all receive proper attention in order to prevent product failure. This paper will profile case studies of failed products where each one of these fundamentals was neglected. The studies will illustrate the analytical processes used to assign a root cause to each of the problems and will suggest corrections that can prevent costly failures from recurring.
Cast-In-Place (CIP) for Joining and Repairing Live, Polyethylene, Gas Lines - I. Basic Process Description
This paper describes a method for casting a non-leaking sleeve of polyethylene (PE) around the butted ends of PE pipes while the joint is leaking air at pressures up to 388 kPa. The step of casting the sleeve was the critical unknown step in a repair sequence that might be used to repair leaking natural gas pipes. Equipment, parameters, heating profiles, and the effects of mud and water on joint strengths are described.
Cavity Based Ultrasonic Resonance Monitoring in Injection Molding
An ultrasonic transducer was installed on the back of the cavity plate on an injection mold such that the sound vibrations would strike the surface of the mold cavity and reflect back to the transducer. Exciting the transducer in continuous wave mode, a resonant system is produced. When the mold fills with polymer this system is damped and the resonance is changed. By monitoring these changes it is possible to monitor conditions inside the cavity during processing.
Chaotic Mixing in a Free Helix Single Screw Device
Chaotic mixing in the extruder channel, obtained by the periodic motion of top and bottom walls of the channel is considered here. An analytical solution for the flow field in the extruder is used in all the simulations presented here. Using the increased degrees of freedom of the free-helix single-screw extruder, chaotic mixing can be obtained. Experimental evidence for the increased mixing of a dye in an extruder under chaotic flow field is presented.
Closed-Loop Viscosity Control for Injection Molding
This paper describes an automated closed-loop control system that compensates for plastic viscosity variations by directly controlling the machine parameters of an injection molding machine. Viscosity is evaluated using a primary injection pressure integral, and compensated for by changing the temperature profile settings of injection molding machine. The shrinkage changes due to the melt temperature changing are compensated for by adjusting the holding pressure. The paper discusses the theoretical basis of the algorithm and presents experimental results on testing the algorithm.
Co-Injection Molding: Effect of Processing on Material Distribution and Mechanical Properties of Short Glass Fiber Reinforced Polypropylene Test Bars
The co-injection molding process involve injection of two materials sequentially to form a multilayer product with a skin and core structure. Dumbbell test specimens were molded using a 150 ton Engel co-injection machine. The effect of injection speed and skin-core ratio on material distribution was first studied. The mechanical properties of different combinations using virgin polypropylene and polypropylene reinforced with 10, 20, 30 and 40 % (by weight) short glass fiber were measured.
Cold Slug Wells in Injection Molding
Cold slug wells are used on nearly all cold runner molds to prevent potential problems caused by cold slugs that are introduced to the runner from the nozzle tip. However, they are often used without a full understanding of what they do, how they work, were they need to be placed, and how large they must be. This paper quantifies the effectiveness of cold-slug wells and investigates design variations. The effects of location and size are examined to determine the relevance of each. By better understanding the use of cold slug wells, a molder can design and use them more successfully to help minimize related problems.
Comarative Study of Polystyrene Foam Degradation in the Open-Air and Artificial Weathering Exposure
Polystyrene foam(PS foam) both without and with 1% Benzoyl peroxide coated were found to be exponentially degraded within 6 months under the open-air and artificial weathering exposure. The reaction mechanism of this foam was identified as chain scission. The peroxide was effectively used as photo accelerator. The experimental data and also the statistical hypothesizes analysis using t-test with the 95% degree of confidence suggested that the data obtained from the open-air and the ones from artificial weathering exposure were analogous.
Comparing Cavity Pressure Sensor Technologies Using In-Mold Data
Three cavity pressure sensor configurations were used to compare data from direct and indirect, piezoelectric and strain gage sensors. The indirect button style sensors tended to read slightly lower peaks than direct flush mount sensors, and data decayed slightly later. Also, the piezoelectric sensors tended to respond approximately 5 ms faster than the strain gage sensors. However, data from all sensor types correlated very well with one another. For all practical purposes, there is no distinguishable difference in the data utility between one sensor type and another.
Comparing Mechanical Properties of Hot Water Piping Using Electron Beam Cross-Linking to Chemically Cross-Linked Water Piping Using a Silane Reactant
The two main methods of cross-linking commercial hot water piping used in industry today are the electron beam method and the chemical method using a silane reactant. Piping cross-linked using both methods will be compared in order to determine which method produces better mechanical properties.
Comparing the Tensile/Yielding Behaviors of the New Isotactic and Syndiotactic Polypropylenes
PP product design and application possibilities have expanded significantly with developments in metallocene catalysis. With the large number of structural and compositional differences these resins bring to the plastics consumer, processing effects require an improved scientific understanding. A variety of isotactic and syndiotactic PP’s are described in detail regarding their tensile and (specifically) yielding behaviors, useful to predict performance characteristics, in property evaluations and as an aid for orientation processing in film and fiber applications.
Comparison of Conventional Gate Freeze Techniques to Process Control Software
This paper presents the results of a study that was conducted to show whether process control software works as well or better than the part weight or cavity pressure methods in determining gate freeze.The study was done with three different molds using two materials for each mold. The molds utilized all had cavity pressure transducers close to the gate. The materials used were nylon and ABS, in order to contrast semi-crystalline and amorphous behaviors.
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