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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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.
Compatibilization of Poly(Phenylene Ether) and Polyamide-6,6 Blends by Functionalized Polystyrenes
Polymer blends of Poly(phenylene ether) (PPO) and Polyamide-6,6 (PA-6,6) remain an interesting subject for many researchers. In this paper the compatibilizing effect of a polystyrene, synthesized via controlled free radical polymerization and endcapped with an epoxy function in the immiscible blends of PPO and PA-6,6 was investigated. The properties being examined were notched Izod impact and tensile of injection molded parts. The morphology was also examined by scanning electron microscope. Results had shown that mechanical properties improved with addition of this compatibilizer.
Compounding and Characterisation of Long Fibre Reinforced Composites Based on Flax and Polypropylene
The compounding of long fibre reinforced composites based on flax and a polypropylene matrix has been implemented by a co-rotating, close-intermeshing twin-screw extruder. Extensive experiments have been carried out to optimise the fibre/matrix adhesion and the screw concept. Only short fibre structures could be achieved by the use of conventional screw elements, like kneading blocks or turbine mixing elements. Applying newly developed special screw elements long fibre structures as well as an optimum fibre dispersion could be reached.
Considerations in the Roughness of the Molds Surface and the Molded Parts Utilized in Injection Molding
The methodology of this work is based in the performance of tests to study the influence of the process parameters on the final properties of molded parts (roughness, Ra and Rz).First of all it was necessary to design and manufacture a mold to observe the roughness of different surfaces. EDM and turning were chosen as typical processes for injection mold machining.Finally some preliminary results are included, illustrating the dependence of the average roughness of the molded parts with respect to the machining process and injection molding conditions.
Control of Gas Direction in Gas Assisted Injection Molding; Definition of Resistance to Velocity
Resistance to velocity, rV , should be used as a criterion in the prediction of gas direction in gas assisted injection molding. In addition, melt resin velocity is also used in the prediction. Comparison of the velocity of fluid is especially important for more complex situations. These methods predict the gas flow direction from the knowledge of process variables such as resin flow length, cross section area of cavity, melt temperature, and short shot.
Controlling the 'Color' of Electrochromic and Electroluminescent Polymers and Devices
This lecture provides an overview of a group effort on NIR electroluminescence along with visible and IR electrochromism. Significant advances continue to be made in developing visible light emitting PLED’s and electrochromic polymers with visible color responses. Less effort has been directed to longer wavelengths.
Coprecipitates of Dibasic Lead Phthalate and Tribasic Lead Sulfate
Coprecipitates of dibasic lead phthalate and tribasic lead sulfate tend to crystallize with the latter forming the core of a core/shell structure. The reactivity of this structure towards hydrolysis of ester plasticizers is considerably lower than that of physical blends of the basic lead salts.
Correlations between Orientation and Some Properties of Polymer Films and Sheets
The orientation of biaxially stretched polystyrene (PS) sheets and polyethylene (PE) blown films were investigated. The study mainly focused on the relationships between orientation of amorphous PS and semi-crystalline PE and their shrinkage, tensile properties and tear resistance. For low orientations, it is found that the stress and strain (shrinkage in films) can be simply related to birefringence for both PS and PE. For tear properties of PE films, better correlations were observed with crystalline orientation factors.
Decisions, Judgment and Uncertainty: Psychology and Intuitive Probability
Most decisions in business (and life) are made on the basis of incomplete or estimated information. A wide range of psychological studies conducted over the past thirty years have shown that when forced to deal with uncertainty people fall back on rules of thumb that more often than not violate basic rules of probability and lead to flawed results. By understanding the types of mistakes people typically make, one can avoid these traps and improve the quality of the decisions. This paper discusses several of these, including regression towards the mean, ignoring base rates, and linked events.
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