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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The Effect of Nitrogen Purging on Degradation during Reprocessing in Injection Molding
This study investigated the effect of nitrogen purging in the material hopper on the melt flow index (MFI), residual oxidative induction time (OIT), color and impact strength of impact modified polypropylene copolymer and polycarbonate during repeated reprocessing through an injection molder. Heat history had the expected effect of increasing MFI, changing color and decreasing impact strength for both resins and decreasing OIT in polypropylene. In polypropylene nitrogen purging significantly reduced the changes in MFI and OIT resulting from repeated reprocessing. However, nitrogen purging did not have a significant effect on the properties of polycarbonate, probably due to its inherent resistance to oxidative degradation.
The Effect of Phthalocyanine Pigment on the Microstructural and Mechanical Performance of Propylene-Ethylene Block Copolymer
Injection moulded samples of a commercial propylene-ethylene block copolymer containing 0% - 8% phthalocyanine blue pigment were prepared using a range of mould temperatures (40°C - 80°C). Mechanical and thermal analysis showed progressive increase in tensile modulus, storage modulus (E’) and glass transition temperature (Tg) with increase in pigment loading. However, impact strength of the pigmented copolymer decreased progressively with increase in pigment loading and mould temperature. Thermal analysis of the samples shows that changes in crystalline melting phase ?H, and activation energies Ea for phase relaxations (DMTA) may account for the overall decrease in impact performance of the pigmented copolymer.
Microcellular Nanocomposite Injection Molding Process
This study aims to explore the processing benefits and property improvements of combining nanocomposites with microcellular injection molding. The molded parts produced based on the Design of Experiments (DOE) matrices were subjected to tensile testing, impact testing, and Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Dynamic Mechanical Analysis (DMA), and X-ray Diffraction (XRD) analysis. Effects of processing conditions on the mechanical properties and microstructures have been studied. The results show that the supercritical fluid (N2) helps to further exfoliate and uniformly disperse the nano-clays in the matrix during the course of molding process. Compared to the corresponding base polyamide microcellular parts, the microcellular nanocomposites exhibit better cell structures and cell distributions as well as better mechanical properties.
Applications of Polyamide/Cellulose Fiber/Wollastonite Composites for Microcellular Injection Molding
In this study, a cellulose-fiber-reinforced Polyamide-6 (PA-6) composite, a hybrid composite (PA- 6/cellulose/Wollastonite), and the neat PA-6 resin were injection molded into ASTM test–bar samples with conventional and microcellular injection molding. The impact and tensile strengths of molded samples were measured and the Scanning Electron Microscopy (SEM) images were taken at the fracture surfaces. The effects of filler systems and the introduction of microcellular structure on the impact and tensile strengths were studied. It was found that the cellulose fibers and the cellulose/Wollastonite fillers improve the tensile strength and tensile modulus. In addition, the microcellular injection molded neat resin exhibits a higher impact strength than that of the conventionally molded solid part. However, a reduction in tensile strength was observed with both of the filled composites when molded with microcellular injection molding. This could be attributed to microcells at the interface of cellulose fibers and the polymer matrix.
Fracture Toughness Evaluation of Adjacent Flow Weldline by SENB Method
Fracture toughness of adjacent flow weldline occurring around an obstructive pin was evaluated by single edge notched bend (SENB) method. The fracture toughness near the pin was higher than any other part of the weldline. The fracture toughness decreased drastically along the weldline and then increased gradually toward the end of the specimen. These characteristic features could be explained by flow-induced molecular orientation at the weldline interface. The material flow beside the pin stopped in the middle of the filling process. Molecular orientation parallel to the weldline due to the fountain flow relaxed since no shear stress affected the area, resulting in high molecular entanglement across the weldline. On the contrary, at the downstream side the material kept on flowing during the filling process. This indicated that the molecular orientation could not relax due to flow-induced stress during the process. The magnitude of these two areas was dependent on the position of first collision point (FCP) at which two melt fronts collided first behind the pin. The V-notch depth on the surface of the specimens was also dependent on the distance from FCP.
The Quaterrylimides - Highly Efficient NIR Absorbers for Plastics
A couple of years ago we developed a class of highly efficient organic NIR absorbers based on quaterrylenetetracarboxylic diimides ('quaterrylimides'), which exhibit photo- and thermostabilities at levels hitherto reserved exclusively to inorganic materials. In this paper we want to present models for the explanation of the unique photostability of this class of compounds, as well as recent advances in the synthesis of those materials, and examples for state-of- the-art plastics applications.
An approach to teaching introductory polymers as a new language was considered. A new pedagogy, including complete definitions, novel technical grammar, and the specific roles of symbols and self-correction, was required. In return, the language concept improved student scientific communication skills, problem-solving ability, especially learning from context, and in general accelerated learning. The approach was applied to teach introductory polymer science, resulting in performance substantially equivalent to traditional polymers courses.
Industrial Training Programs for Plastics Manufacturing
The Plastics Institute of America has a long history of training in the polymer/plastics field. Over the past twenty years this training has focused on the shop floor employees and new professionals as compared to research and management types. Successful long term training has been conducted with leading consumer, medical, and electronic manufacturers. The training is offered in a wide range of traditional and cutting-edge areas to help companies and their employees keep pace with the rapid rate of change that has become the cornerstone of today's economy.
Flow-Induced Crystallization and Birefringence in Injection Molding of Semicrystalline Polymers
A novel approach for the numerical simulation of frozen-in birefringence in moldings of semicrystalline polymers was proposed. The approach was based on the calculation of elastic recovery and crystalline orientation function frozen when the stress-induced crystallization occurred. The flow effect on the equilibrium melting temperature elevation due to the entropy reduction between the oriented and unoriented melts was incorporated to model crystallization. To find frozen-in elastic recovery and entropy change, a non-linear viscoelastic constitutive equation was used. The crystalline and amorphous contributions to the overall birefringence were obtained from the crystalline orientation function and the flow birefringence, respectively. The skin layer thickness and birefringence profiles were predicted and measured in moldings of polypropylenes of different molecular weights at various processing conditions.
Adiabatic Splay and Blush in Injection Molded Parts
Most molders are aware of the potential for creating burn marks where air gets trapped in molded parts. What no one seems to consider is blush or splay marks that manifest specifically along knit lines and would otherwise be assumed to be the effect of shear. The only problem is that the shear cannot be accounted for in the tool design. The cause can be traced back to trapped air, predicted with mold filling analysis software (as such), and verified with physical testing. The purpose of this paper is to give proper definition to this defect and distinguish it from burns and short-shots as caused by air entrapment, and thus can be more easily identified and remedied.
Fibre Orientation in Weldline Areas - Investigation of an Air Intake Manifold
The focus of attention is kept on weldline behavior in parts of complex geometry, i.e. the upper part of an air intake manifold. By simulating the filling process using simulation software, the fiber orientation and the filling was calculated and compared to experimental studies. Thereby, a rather inhomogeneous filling behavior was found, caused by an unequally balanced runner system that leads to changes of the flow direction within the cavity during the injection process. These circumstances prevent the weldlines zones from spreading throughout the part. Hence, a distinct control of an uneven flow front pattern could help to reduce the weldline area and therefore minimize zones of optical and mechanical weak points in plastic parts.
3D CAE Simulation and Verification for the Ferrule of MT-RJ Fiber Connector
Because communication and Internet are so popular, light communication will become an efficient way to send message in the next generation. Optical fiber connector becomes an important component that connects, divorces or reunites the fiber, light source, light sensor and the other fiber ferrule connector. Because of the tiny size of products and the demand of precision, the decrease of manufacturing cost and the increase of demanded precision will be a huge obstacle that has to be overcome.This paper presents the study for the molding of ferrule in MT-RJ fiber connectors. The work includes the design of molding configuration with three different gating locations which are used to study the effects for the critical dimensions and precision of fiber holes. In addition, the 3D CAE software are used to simulate and verify the molding results. Moreover, the Taguchi method is used to find optimal processing conditions for resolving the void problems.
Twin Sheet Thermoforming of a Fuel Tank with a Converted Blow Mould
Twin sheet thermoforming has increased in usage over the last ten years, in particular due to its inherent ability to produce hollow parts and consequently challenge blow moulding. Blow moulded automotive fuel tanks are the parts that are the most challenged by twin sheet thermoforming.This work considers the conversion of a fuel tank blow mould for use in twin sheet thermoforming. The added challenge for the project is that the mould needs to maintain a flexibility to return to blow moulding, upon demand. Furthermore, the work includes the use of finite element simulation to reduce the sheet heating times.
Plastics and Polymer-Matrix-Composite Laboratory Activities and Curriculum Options
Central Connecticut State University has developed a multitude of laboratory instructional activities to better prepare students for technological advancements in the plastics and polymer-matrix-composites industries. Engineering and Industrial Technology students can opt for further plastics and composites training through election of laboratory courses in materials, processing, tooling, analysis and design.
Recycling Thermoset Plastics, Can it be Done?
This paper addresses the possibility of using recycled thermoset plastic powder as filler. With budget issues in the academic setting, using recycled thermoset powder as filler could have a positive impact. Recycled powder has been successfully used in a university plastics lab for rotational molding, thermoforming molds, and for composite tooling dough. Three practical lab exercises will be given in the paper.
Globalization has been blamed for the startling loss of US manufacturing jobs over the past several years, particularly in the plastics industry. How can companies survive competition from China and elsewhere in the world? This paper will describe how the problems have come about, what's being done about them and how companies can not merely survive but improve their business.
Plastics Processing: A Changing Environment
The U.S. plastics industry has been hit hard in the past three years. A number of factors have contributed to this changing environment, including globalization, recession and political uncertainty. The premise of this paper is: the market as we knew it in the late 1990s will never return. The world has changed, so has the plastics industry. The question to be addressed is: how can we prosper in this new environment?
On-Line Hybrid Model Based Tuning of Simulation Provides Soft Sensors for the Estimation of Sheet Temperature Distributions in Thermoforming
Some of the main problems to be solved when applying simulation to a process are the discrepancies between the predicted and measured parameters. This can be due to the fact that the actual operating conditions are different from the ones that were input into the simulation due to variations in material properties and errors in the assumptions for the simulation model. This work proposes a technique to tune the results of the simulation to the actual sensor outputs of the machine. The simulation can then be used as a generalized soft sensor for the process: Since the model of the simulation has been fitted to the actual process, the predictions of the simulation for non-readily accessible points will be that much closer to reality. A further advantage is that variations of the process are back-propagated to the input, so that faults that may appear in the system are presented as more easily interpretable variations of the input data.
The Science Based Optimization of Material Heating during Thermoforming Processes
In this paper, the optimized radiative heating of opaque thermoplastic sheet during thermoforming processes has been studied by using a newly developed modeling and optimization approach. The net radiation method has been employed to develop a comprehensive numerical code that can compute the total radiative heat and associated temperature developments locally on the thermoplastic sheet. The resultant simulation model can accommodate full non-symmetric zone heating situations and multi-layered forming materials. A coupled optimization package was then developed to obtain optimized heater pattern solutions that will lead to desired material temperatures during thermoforming processes. This is done by specifying a desired thermoplastic sheet temperature distribution and iteratively solving for the heater setting needed to obtain the desired results
Modeling of the Behavior of Semi-Crystalline Polypropylene at Elevated Strain Rate and Temperature
A non-linear viscoelastic model comprised of two components, a rubber-like hyperelastic component and a viscoelastic time-dependent relaxation spectrum was used to model the behavior of semi-crystalline PP at rates and temperatures close to that found in the thermoforming process. Temperature dependence was introduced through time-temperature-superposition (TTS) using WLF. The hyperelastic constants were identified from equibiaxial tensile experimental tests while the time-dependent relaxation spectrum was characterized through a temperature-frequency sweep analysis from a strain controlled DMTA test. Results show that the developed model is capable of simulating the behavior of semicrystalline PP fairly well.
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