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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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.
Design of an Integrated Crash Energy Absorber for Compression Molded Bumper Beams
Due to upcoming demands from insurance companies, there is an increasing need for bumper beams that take care of minimum repair costs after collision. The compression molding technique offers excellent possibilities to integrate crash absorbers into the bumper beam design. Experiments were carried out on six types of reinforced polypropylene cans. The difference in crush energy absorption of these materials was studied. The tests were carried out at crosshead speeds of 50 and 2000 mm/min.
Design, Material and Processing Effects on the Tensile Properties of Filled Polypropylene
A statistical evaluation was performed to evaluate the effects of design, material and processing conditions on the tensile properties of a filled polypropylene. Coupons were machined from injection molded plaques at different orientations and evaluated using the common tensile test. The results were compared using an analysis of variance (ANOVA). The following effects were found to be of significance in decreasing order: the type of filler, the level of filler and orientation.
Designing Runners to Control Gas Distribution in Gas-Assist Injection Molding
This paper presents a study about the ways in which shear, developed in the perimeter of the runner, affects the distribution of gas in gas-assisted injection molding. High-shear regions in the perimeter of the runner can be traced and followed into a part-forming cavity. The high-shear regions create variations in the melt viscosity within the cavity. Once gas is injected, the gas flow is significantly influenced by these viscosity variations. A method is investigated which controls the position of these high-shear laminates and thereby the distribution of gas within the mold.
Determining Cause of Failure in Plastic Parts through Microscopic Analysis
A critical first step in analyzing a plastic part failure is the examination of the cracking and the fracture surfaces. Important clues in understanding the failure mechanism are revealed by the recognition of distinctive crack pattern and characteristic fracture surface features. Several actual field failure case histories are described to illustrate the microscopic techniques and how the interaction of mechanical stresses and service environment produce unexpected failures.
Developing a Method for Rapid Design and Manufacture of Tooling
Following is the development of a method for the rapid design of bridge or short production tooling for injection molding. Starting with a product definition, part was modeled in a solid modeler. The part model was analyzed by the finite element method for performance under load and by flow analysis software to determine molding characteristics.Once the design was proven, NC code was generated to cut the cavity and runner system. The mold was commissioned and the mold cycle parameters were verified.
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