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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High Strain Rate Testing of Polymers for Impact Simulations
The increased use of polymeric materials in impact and high strain rate applications is motivating the use of impact simulations during design. Simulation of polymer impacts however requires difficult-to-measure stress-strain behavior at high strain rates. Complicating the measurement task further is the need to establish failure criteria associated with high strain rate deformations. Even when appropriate data is collected, appropriate high strain rate constitutive models need to be fit to the data before being incorporated into a simulation code. This article presents a testing and constitutive modeling process to achieve accurate impact simulations using polyether ether ketone (PEEK) as the example material. High and low strain rate data is presented over a large strain rate range. The resulting data and material model is used simulate a drop test which is then compared with an actual drop test data to validate the model.
The Study of Dynamic Behaviors and Optical Quality for Fisheye Lens Using Injection Compression Molding
Injection compression molding (ICM) process can bring a lot of advantages to enhance the product quality. Meanwhile, ICM also introduces more parameters increasing the complexity of molding. In this study, conventional injection molding (CIM) and ICM processes on the fisheye lens development through numerical simulation are compared. Results show that ICM process can provide better geometrical shape accuracy, and better optical properties with lower retardation and fringe order. Furthermore, we also examine various compression gap and compression speed effects on geometrical shape accuracy and optical quality. It shows that different compression gap and compression speed have no significant effect on geometrical shape accuracy control. However, under constant compression speed, if the compression gap is too large, optical property will become worse.
Troubleshooting Gear Pump Assisted Single-Screw Extrusion Processes
Gear pumps are often used in tandem with singlescrew extruders to increase rate, decrease resin consumption, improve process stability, decrease extruder discharge pressure, and decrease the extrudate temperature. When a process is unstable, it is often not obvious if the extruder is unstable and the gear pump is operating well, or the extruder is operating well and the gear pump operation is unstable. This paper will describe a few operations where gear pumps improved a process, how they are used in unstable processes, and approaches to troubleshooting lines using gear pumps.
An Innovative Food Packaging Design for Can Replacement: A Product Development Story at Printpack
This paper demonstrates an innovative approach on how to develop a new package design for food industry. Unlike traditional customer-oriented product development, this approach engaged our final consumers at the first stage, which helped us develop and confirm the ideas of this package design. Then, iterations of prototypes were made, tested, and modified to evolve into a viable solution for large-scale manufacturing. In addition, a comprehensive study on heat penetration during thermal processing was conducted to facilitate its commercialization by providing our customers with certain guidance on how to utilize this package design in an appropriate way.
Comparison of Mesh Partitioning Technique and Level-Set Method for Coextrusion Simulation
Multilayer flow is simulated in five different coextrusion dies using the mesh partitioning technique as well as by the level-set method. These simulations show that depending upon the layer structure in the die, one of the two techniques may be more suitable for the coextrusion simulation. In general, the layer structure predicted by the mesh partitioning technique is found to be more accurate than the corresponding predictions from the level-set method. Level-set method requires that the layers should be arranged in a sequential manner, which is not necessary if the mesh partitioning technique is used. The mesh partitioning technique cannot simulate a multilayer flow if an interface between the polymer layers splits into two interfaces, or if two interfaces, which start separately, merge into a single interface in the die.
Dynamics and Hysteresis in Capillary Rheometry
Several sets of experiments were conducted to investigate the dynamics and hysteresis in capillary rheometry. Experimental data indicate that the imposed flow rate history can vary the apparent viscosity by a factor of 10, a magnitude as significant as a change between the minimum and maximum recommended processing temperatures. Contributing factors that were investigated and found insignificant included the capillary length:diameter ratio, viscous heating of the polymer melt, rheometer transmission, and instrumentation. Other contributing factors to be analyzed further include polymer compressibility and viscoelasticity.
Structure-Property Relationship of Biaxially Oriented Polyethylene (BOPE) Films Made via Double Bubble Film Fabrication Process
Mechanical and optical properties were compared between a double bubble biaxially oriented polyethylene (BOPE) film and a blown film. The double bubble film exhibited higher modulus, higher tensile strength, better optical properties, but lower tear strength. Morphological differences between the double bubble film and the blown film were investigated with differential scanning calorimetry (DSC), wide angle X-ray scattering (WAXS) and small angle X-ray scattering (SAXS). It was found that in the double bubble process the large crystals were broken up into smaller fibrillar crystals with a larger long spacing. C-axis of the fibrillar crystals preferentially lay in the plane of machine direction and cross direction (MD-CD). The lower tear strength for double bubble films has been proposed to be due to the fibrillar crystal morphology. A sample with a larger low temperature melting peak showed a better tear strength with a similar stiffness.
New Effect Pigment Preparations – New Products Are Driving the Efficiency in Masterbatch Production and Enable Plastic Processors to Enter New Markets
Effect Pigments are widely used in plastic materials to achieve gold, silver or pearlescent colours. The main aspect is to achieve a differentiation and to upgrade the value of the end user product. The first part of the presentation describes the production, processing, optical aspects and the special features of aluminium-, gold bronze-, and pearlescentpigments. This will be followed by the introduction of new effect pigments such as the platinum dollar aluminium pigments which enable spray coated like" silver effects in mass coloured plastics. In addition a new generation of pearl pigment on the basis of artificial glass substrates will be highlighted. Today's key success factor for pigment manufacturers is the ability to provide easy to use product forms with high and consistent qualities such as Eckart's Micropellets. These products enable significant cost reductions compared to regular pigment powders or pastes in masterbatch production as they enable higher production speeds and easy dispersion. They also significantly reduce cleaning times in production. Finally a short outline on use of aluminium pigments to improve insulation properties of plastics will be given. Energy saving is Megatrend especially at today's crude oil prices. Aluminium pigments reflect IR light and therefore can be used to improve the insulation and help to keep the heat inside (winter) or outside (summer)."
Thermoforming of Biodegradable Sheets Obtained from a Thermoplastic Starch and Polylactic Acid Blend
This paper describes the blending and the thermoforming performance of a thermoplastic starch (TPS) and polylactic acid (PLA) compound. A twin screw extruder (TSE) was used for corn starch plasticizing and blending with the plasticized PLA. A single screw extruder was used to melt, functionalize and feed the plasticized PLA into the TSE. Extruded pellets were used to make sheets through extrusion calendering, which were ultimately thermoformed in a parallelepiped shape. Thermoformability of the sheets was evaluated by the area ratio, the maximum uniaxial deformation, and the thickness measurement in the machine direction (MD) and transversal direction (TD). The operating window was defined using DMA techniques. The compound showed good thermoformability characteristics.
Experimental Study of Fiber Attrition within a Long Fiber Glass-Reinforced PP under Controlled Conditions
The effect of the process/material conditions over the fiber damage was studied. In this experimental study, a controlled shear flow was generated by using a Couette device. Two Polypropylene (PP) resins with 30 and 40 % glass fiber concentration by weight, respectively, were used. The measurement of the fiber length distribution was done using the STAMAXTAT SABIC® method and it was observed that the melt temperature, rotational speed, residence time and fiber concentration greatly affect the fiber length distribution. Furthermore, comparing the damage occurred during the injection molding and purged with those generated in a Couette device, it was found that an additional reduction in fiber length occurs during injection molding because the fibers are forced to pass through narrow channels.
Pressure-Rise Tests for Detecting Particles in Polymers
A pressure-rise test method was developed and qualified to detect undesired particles in polymers. The feasibility of this method was confirmed by a polymer with a large number of particles, and the key parameters for defining pressure-rise were characterized as the initial pressure, initial slope and pressure-rise per hour. The theoretical simulations of initial pressure and pressure-rise due to screen blockage were demonstrated and validated with experimental data. This test method is useful for resin quality assurance, screen life determination, and new formulation development of polymers for many extrusion processes.
Device for Measuring Microscale Viscosity in a Self-Aligned Microgap
A novel rheometer for measuring shear viscosity in a self-aligned microgap was developed. Drag flow of simple linear motion was created inside two self-aligned parallel plates. A ball-bearing contact between the loading and moving parts was employed to facilitate self-alignment so that gap thickness smaller than those in standard rheometers can be obtained. Analysis based on the lubrication approximation indicated that a self-balancing liquid film can be generated between the two plates during rheological measurement. The new device was successfully used to measure the viscosity of selected fluids.
Crystallization Characteristic and Heat Seal Properties of Biodegradable Films
Biodegradable polymer film was prepared from poly(lactic acid)/thermoplastic starch (PLA/TPS) blend by cast film process at 0, 5 and 10 wt% of TPS. The PLA and PLA/TPS blend films were heat sealed at heat sealed temperature of 90 and 100 °C. The heat seal time was varied from 0.5 to 2.0 s with a pressure of 0.2 MPa. The effect of heat sealed conditions on heat seal properties of PLA and PLA/TPS films was investigated. Heat sealed strength of PLA/TPS blend films decreased when increasing the heat sealed times. PLA/TPS heat sealed films exhibited greater crystallinity than the PLA heat sealed film, which characterized by crystallization kinetic study.
Acoustic Process Analysis of Rubber Compounding
Properties of rubber compounds differ batch-wise. This can lead to waste and, thus, it is desirable to reduce these variations. One reason for quality variations of rubber compounds is the discontinuous way of compounding in internal mixers. Mixing effects make it difficult to adjust the process parameters of internal mixers in order to guarantee constant qualities. Experienced operators of internal mixers observe that characteristic noises during the mixing process can be correlated with the state of mixing. Thus, a project has been started to use these mixing noises for the development of a control system for internal mixers, which is able to characterize the state of the rubber compound. First, a measurement system has been implemented which allows the online visualization and recording of the mixing noise. It is systematically analyzed how the mixing noise is related to the state of mixing and the resulting elastomeric properties. The results show a correlation between filler incorporation and the characteristic sounds.
An Interconnected Porous Poly(?-Caprolactone) Structure Fabricated by Micro-Cellular Injection Molding Combined with Chemical Foaming and Particulate Leaching
In tissue engineering applications, a scaffold containing an interconnected porous structure is often highly desired, since these interconnected pores allow nutrients and signaling molecules to rapidly diffuse into the material. A mass production method of fabricating a porous structure, microcellular injection molding, was combined with chemical foaming and particulate leaching methods to fabricate an interconnected porous structure made of poly(?-caprolactone) (PCL). Sodium bicarbonate (SB) was employed as the chemical foaming agent. The results showed that the interconnected porous structures of poly(?-caprolactone) were successfully obtained based on different material compositions. Sodium bicarbonate not only generated carbon dioxide as a gas blowing agent, but also served as the heterogeneous nuclei for the gas bubbles. Sodium bicarbonate and its byproduct, sodium carbonate, also became the porogens in the subsequent particulate leaching process. The morphology of the pores and interconnectivity were discussed in this paper. These interconnected porous structures have the potential to be used for tissue engineering scaffolds.
Application of Visual Mold for the Effect of Counter Pressure Mechanism on Gas-Assisted Injection Molding Process
Gas assisted injection molding refers to injecting gas into the short shot melt in the packing stage. Compressed gas is used as the medium to push melt and maintain pressure. Cost is saved by hollowed core. Therefore, the hollow rate and penetration length are required in end product quality. This study visualizes molding flow and uses a gas counter pressure mechanism in the gas assisted molding process. The melt flow behavior is influenced by controlling the counter pressure, making it possible to discuss the effect of a counter pressure mechanism on the hollow rate of gas assisted molded articles. This study designs an in-mold visible mold and uses a clip-shape cavity for an experiment on gas assisted injection molding with a counter pressure mechanism. The flow field of two-phase fluid and the fountain effect under different counter pressure conditions are observed by high-speed photography and adding particles. The relationships among the penetration length of the finished product, the hollowed evenness and the molding parameters are analyzed, and a database of gas assisted injection molding under counter pressure mechanism is created. The experimental results show that when the gas counter-pressure is applied to the gas-assisted molding, although the hollow area is reduced, the penetration length of the finished product can be increased, so as to make the hollow quality uniform. In addition, it is observed in the fiber orientation that the interlayer structural orientation is made uniform as the counter pressure increases, meaning the counter pressure can reduce the shrinkage of a finished product.
UV Curing Behavior of Polydimethylsiloxane Toughened Acrylate
Ultraviolet (UV) curing characteristics of polydimethylsiloxane(PDMS) toughened acrylate was investigated by photo DSC. PDMS was introduced as a rubber toughening phase in the acrylate coating on plastic film to avoid the crack formation. It was found that the crack formation in acrylate coated thin film was disappeared by adding PDMS but PDMS interrupted UV curing of acrylate. The lowering of UV curing by PDMS could be minimized when PDMS having higher methylvinylsiloxane content in PDMS was mixed with acrylate due to the UV curing between methylvinylsiloxane and acrylate.
Surface Modification of Polymeric Surfaces Using Reactive Gas Technology
Traditional methods to activate surfaces include corona and plasma treatment, which have some drawbacks. This presentation describes a technology for modifying polymeric substrates, which has proven effective for improving the performance of existing products and for facilitating activation of “difficult to modify” materials such as PP and PE. The treatment involves using Inhance Technologies’ proprietary reactive gas atmosphere technology that creates permanent high surface energy. The treatment can be carried out on 3 dimensional as well as 2 dimensional structures. The treatment gives tenacious adhesion and allows use of a broad array of continuous phase systems including epoxies, polyester, polyurethane, concrete, water based coatings and others. The surface modification chemistry can be very rapid, often a few seconds, which enables processing to be done continuously and on-line.
Novel Melt Filtration Technology for Challenging Recyclate
The American market for recycled plastic offers both enormous economic potential and strategic challenges. Especially in light of the domestic shale oil boom, recyclers must find ways to maintain competitive advantage in the market. Tackling increasingly contaminated, wet and hard-to-process materials offers a path to this end. Co-rotating twin screw extruders are well suited for accepting plastic regrind of different shapes, bulk densities and contamination levels. Energy extensive drying steps after the washing process can be eliminated, when steam and moisture is removed in special venting barrels. In this paper, process experiences with a novel continuous melt filter are presented, which offers superior processing and flexibility for recyclers to capture untapped value. The functionality and processing potential of this filter in combination with the twin screw extruder is explained by using examples from the post- industrial recycling market, the automotive recycling effort and as well as the post-consumer recycling sources.
Investigating the Full-Face Joining of Polymer-Metal Hybrid Structures
Hybrid structures consisting of metal inserts and injection molded ribbing offer both a cost-efficient production technique and an excellent ratio of mechanical performance to weight. Thus, this technique has found its use a million times over for the fabrication of lightweight parts, especially in automotive applications. Currently, joining both families of materials is achieved by form-fit and frictional joints due to its easy process integration. This paper presents a new approach by joining both materials adhesively in the process of the In-Mold- Assembly and shows the lightweight potential to be additionally tapped.
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