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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Polycarbonate for Light Guide Applications
We tried to develop the polycarbonate materials for light guide parts of automotive lamp and liquid crystal display. Common requests in their applications are extra fine optical property and heat aging property, because the light path through the light guide part becomes longer. In addition, the size of light guide plate of liquid crystal display becomes larger and thinner, due to spread of smartphone and tablets, so excellent flow-ability of the material is required. We examined improvement of optical transmission and heat aging property of polycarbonate, maintaining their mechanical and thermal properties. Furthermore, excellent flow-ability polycarbonate was developed with optimizing its molecular weight.
Effect of Surface Treatment on the Properties of Wood-Plastics Composites Produced by Rotomolding
In this work, wood-plastics composites (WPC) were produced by rotomolding to study the effect of wood content and surface treatment on their properties. In particular, wood flour (maple) was dry-blended with linear low-density polyethylene (LLDPE) to produce composites up to 30% wt. From the samples produced, characterization including density, morphology, and mechanical properties (tensile and flexural) was performed. The results show that using a NaOH/MAPE treatment not only increases the mechanical properties of the parts, but also increases the maximum amount of wood that can be introduced in the composites for the range of conditions tested.
New Low Density and Low Hardness Thermoplastic Co-Polyester Elastomers (COPE)
New low hardness (60 Shore A to 75 Shore A) thermoplastic polyester elastomers (TPE-E) deliver excellent performance for a wide variety of automotive and consumer applications. These elastomers have excellent cold temperature impact strength and work well at a broad range of temperature and humidity conditions. These recyclable elastomers can be processed via injection molding, blow molding and extrusion. Various grades with wide range of hardness are suitable for applications requiring excellent elastic properties, controlled flow and compression set. These elastomers shows more than 700% elongation at break combined with the excellent heat aging properties of polyesters. These new highly flexible TPE-E grades fill the property gap between standard thermoplastic polyester urethanes and vulcanized rubbers by providing excellent fatigue strength, chemical resistance and hence an increased operational lifetime. The lower density and higher specific strength of these elastomers contribute to the overall weight reduction of molded parts.
Factors Affecting Thermoformed Trays during Retort
The performance of thermoformed trays during retort is affected by different factors. However, these factors could be grouped into three main sources: material, design, and processing method/conditions. Understanding the individual and cooperative effects of these sources on the performance of the trays during retort is the topic of this article. Optimizing these three sources is key to a successful tray for retort application. Nonetheless, a clever engineer could compensate for a shortcoming of the material by superior design and balanced processing conditions. Similarly, un-optimized processing conditions could be compensated for by choosing a better material coupled with more robust design.
Chemical Resistance Evaluation of Medical Grades Eastman Tritan™ Copolyester and Polycarbonate
Chemical resistance of injection molded articles in medical devices is important in the face of more and more disinfectants being employed to combat hospital acquired infections (HAI). Chemical resistance to common chemicals used for disinfectants and pharmaceutical formulations was investigated for medical grades of copolyester and medical grades of polycarbonate. Chemical resistance of medical grade copolyesters was found to be more robust than chemical resistance of the medical grades of polycarbonate under the recommended injection molding process conditions from each material manufacturer. All tested medical grades of copolyester have excellent clarity, toughness, no break notched Izod. As detailed in this study, they have demonstrated excellent chemical resistance to disinfectants used to combat hospital acquired infections (HAI) and compounds aggressive to polymers used in pharmaceutical formulations.
Properties and Foaming Behavior of Biodegradable Poly(Lactic Acid)/Poly(Butylene Succinate) Blend
Biodegradable poly(lactic acid)/poly(butylene succinate) (PLA/PBS) blends with various blending ratios were prepared by melt mixing for properties and foaming studies. The phase morphology and thermal properties were investigated using scanning electron microscopy and differential scanning calorimetry, respectively. The studies show that PLA/PBS is immiscible blend, and PBS has an effect of plasticizer on PLA, promotes PLA crystallinity with the addition of PBS, meanwhile, decrease the thermal stability of PLA. Supercritical carbon dioxide foaming study shows that the composites foams exhibit larger cell size and smaller cell density compared with neat PLA foam due to lower melt strength of PBS.
Flexible Porous Polyimide Film for Ultra Low-k FPC
Ultralow-k (dielectric constant) films are promising substrates for the next generation of flexible print cables. Recently, we developed a short-cycle process that uses high-pressure CO2 and CO2-tertiary amine zwitterions in a polyimide precursor solution to create 1-3 µm pores with a total porosity greater than 70%. Here, we report a scaled-up process to obtain 10-fold larger ultralow-k porous polyimide films. This process requires a high-intensity UV lamp, a thick quartz window and a hydraulically movable sealing plate to produce 70 × 150 mm2 films, which is the minimum size that is required for the transmission of high-speed data.
Modeling of the Droplet Morphology Evolution in Polymer Blends under Shear by the Pseudo-Potential Lattice Boltzmann Method
In this work, a novel modeling strategy is proposed to simulate the morphology evolution of polymer blends by the inter-particle-potential lattice Boltzmann method. In this model, the binary components of the polymer blends are tracked by two sets of density distribution functions governed by lattice Boltzmann equation. The model is verified by computing the droplet behavior of deformation, breakup and coalescence under shear, and the results are found in good agreement with the theoretical and experimental observations.
Dimension-Dependent Long-Term Properties of Injection Molded Micro Parts
A variety of polymer parts used in microsystems technology is produced by injection molding. For dimensioning and design of these products, both the material properties and their changes during the life cycle have to be taken into account. Due to the smaller dimensions the process and cooling conditions lead to modified material properties, e. g. stiffness. Aging in polymers is affected by process-induced part properties and takes place primarily on the surface layer. Consequently, parts with decreasing dimensions should reveal a modified aging behavior and size-dependent changes in mechanical properties. Within this article the effect of dimension-dependent aging is investigated using differently scaled tensile bars which were aged under varied conditions. The results indicate that a decreasing part size leads to higher physical and chemical aging effects in polymer parts. However, these changes affect the mechanical properties less than expected.
Effects of a Mass Finishing Process on Parts Produced from Ultem*9085 by Fused Deposition Modeling
Parts produced by Fused Deposition Modeling (FDM) tend to have rough and undulating surfaces with staircase effects on rounded and slanting areas of the part. This is due to the characteristics of the process. In many fields of application, high demands are made on the optical quality of the part. An improvement in the surface quality of FDM parts made of Ultem*9085 can be achieved through post-treatment with a mass finishing process. In this paper, FDM specimens are post-treated in a disk finishing unit. Influences of the mass finishing process are analyzed with regard to the dependence of surface quality on the various process parameters and on the finishing medium, grinding time and grinding speed. The finishing efficiency depends on the finishing media and decreases for lower finishing time. For all media a lower disk velocity results a smaller grinding effect, but there are clearly differences between the finishing media. The paper also discusses effects of the grinding process on the mechanical properties of the parts. Especially small part geometries and parts build in z-direction tend to break during the finishing process.
Energy-Saving Based Allocated Generalized Predictive Control (AGPC) in Extrusion Process
Polymer extrusion is an important polymer processing method for turning the raw material into varies of products. Barrel temperature is critical to the end product quality. In this paper, the contradicted property of dual inputs (heating and cooling) has been revealed. For energy-saving, an allocated generalized predictive control (AGPC) is first proposed. The contradicted dual inputs are united as one pseudo manipulated variable, which is obtained and then exclusively allocated to heating or cooling in the framework of GPC. Both the simulation and application to the extrusion temperature process show the effectiveness of the proposed algorithm.
A Mesoscale Simulation Method for Underfill Encapsulation
Underfill process is applied in flip chip encapsulation to prevent interconnection failures caused by the mismatch of CTE between die and substrate. In order to better characterize the capillary flow in underfill process, and otherwise to eliminate the troubles in calculating the capillary force in current underfill simulation methods, i.e., result-based and interface reconstruction, we present a mesoscale underfill simulation method based on three dimensional lattice Boltzmann method. In our method, the improved interparticle-potential model is used to model the fluid-fluid interaction, and Benzi's model is used to model the solid-fluid interaction. A geometric model for underfill simulation is then developed, and allows each surface to have a different wettability by assigning a different mesoscale interaction parameter. For verification purpose, two underfill cases are examined. It has been demonstrated that the proposed method has a good performance in the underfill simulation.
Experimental Analysis of the Material Degradation of PET on a Co-Rotating Twin-Screw Extruder
Plastics, starting from inexpensive mass-produced articles to technical high-end applications, are being used in ever more areas of life. The main drivers are their flexible product properties and the resultant broad application possibilities. To be able to offer plastic products inexpensively and conserve the environment at the same time, more and more attention is being paid to plastics recycling. Polyethylene terephthalate – in short PET – is of particular significance here because of its frequent application in the film and packaging industry and its special material properties. The recycling of PET, however, can only be carried out a limited number of times because it’s processing necessarily results in both thermal and mechanical stresses on the material. This is the basis for the reactions at molecular level, which result in a shortening of the molecule chains (material degradation) and exert a negative effect on the product properties. The aim of this study is to identify the factors that influence the material degradation of PET in twin-screw extrusion. To do this, various screw configurations and different speed and throughput conditions are examined in a series of experiments. Furthermore, material specimens are removed along the length of the screw in order to evaluate the influence of individual screw sections. By determining the intrinsic viscosity of the specimens, it is possible to measure the mean molecular weight and thus the material damage. Based on the test results, guidelines are drawn up for the compounding of PET so as to ensure as little damage as possible to the material.
Morphological Analysis of Natural Fibers and Fiber Orientation Measurements for the Evaluation of Simulation Tools for Injection Molding Materials – NFC-Simulation
Due to environmental and sustainability issues, the request for renewable resources increases. Natural fiber-reinforced injection molded materials are therefore an interesting prospect for the automotive industry. To achieve a broader market launch of this new material in the automotive industry, numerical simulation of this new material is essential. Besides rheological and mechanical properties, the fiber morphology and the fiber orientation are the most important properties for the simulation. To evaluate the simulation results experiments are necessary. The morphology of natural fibers (sisal, hemp and regenerated cellulose fibers) was determined by image analysis of the original fibers and the fibers after the procedures of compounding and injection molding. Therefore the fibers were extracted from the granules and the injection molded components. The size of the fibers was significantly reduced during the compounding process, whereas no further reduction could be observed during the injection molding process. Quantitatively, the same results could be found in simulation based on a mechanistic model. Fiber orientation measurements were done via TeraHertz Spectroscopy to evaluate the simulation of the injection molding process and to be able to predict the mechanical properties of the components.
Influence of Fiber Sizing and Adhesion Promoter on the Mechanical Properties of Inline-Impregnated Polypropylene Laminates
Continuous fiber reinforced thermoplastics are increasingly being used for lightweight construction parts due to their relatively short processing times. Yet, a flexible production of high quality thermoplastic composite parts is still limited due to the limited diversity of thermoplastic prepregs available to the market which are essential for most common forming processes. Therefore, a new process technology for the flexible production of lightweight parts has been developed at the Institute of Plastics Processing (IKV) at RWTH Aachen University. The developed Inline-Impregnation technique allows for processing cost-effective semi-finished products and includes the impregnation and forming in a single process. In combination with a cost-saving mold technology, Inline-Impregnation facilitates an economic production of prototypes and modular series as well as larger series production. This paper presents results of the research on the process technology.
Concept Development and Topology Optimization of Joint Geometries for 5-Point Double-Toggle Clamping Mechanisms
This paper presents an approach for a design systematic development of alternative joint geometries used in heavy-duty mechanisms. The focus is on joints with oscillating motion correlated with high loads and small pivoting angle. The development of the design concept is based on the example of a 5-point double toggle clamping unit which is installed in injection molding machines. Based on a systematic analysis of joints, a new concept is developed and optimized load-conformable by numerical methods. It is investigated, which algorithm is adequate to optimize the joint geometry load conformable.
Compatibilizing Immiscible Blends from Polyethylenes and Polyamide Using Reactive Extrusion
The aim of this work was to investigate the possibilities of compatibilizing immiscible blends of HDPE – PA6 via reactive extrusion. We investigated the influence of the compatibilization on the mechanical and rheological properties, as well as the morphology of the samples was investigated. We found, that it is possible to compatibilize immiscible blends via the in situ production of a compatibilizer from a pre-cursor and a radical generator in the blends. The effectiveness of this method is comparable with the compatibilization via the addition of pre-fabricated, industrially available additives.
Effects of Surface Treatment on Hard to Bond Plastics
Difficult to bond plastics, such as polyolefins and fluoropolymers, are commonly used in various industries for some of the following reasons: the cost of the materials and their inherent chemical and thermal resistance. It can be challenging for manufacturers to find solutions to join these difficult to bond materials together. This paper will provide background information on difficult to bond materials, review techniques for quantifying the surface energy of a plastic, review the latest solutions for surface modification and introduce innovative adhesive solutions to meet the challenges of bonding these specific substrates.
High Melt Strength Polyolfins for Melt Phase Thermoforming and Extrusion Blow Molding via Electron Beam Modification
Product and Applications Development Engineers continually struggle with the task of meeting challenging performance requirements that balance physical properties and processability within even more challenging economic constraints. In this paper, we update the industry with results that will encourage the use of electron beam modification as a means of utilizing materials with desirable physical properties but historically lack melt processability due to their linear structure. It is a continuation of ongoing work with an emphasis on melt phase thermoforming and extrusion blow molding. By inducing long chain branching through high energy electron beam bombardment, dramatic increases in viscosity at low shear are achieved which increase sag time in thermoforming and hang time in blow molding. At higher shear rates, these long chain branched polyolefins exhibit strain hardening which translates into improved material distribution allowing for down gauging. LCB (long chain branched) LLDPE (linear low density polyethylene) is viewed as new polymer altogether as it has not been used as a stand alone polymer in many applications due to its inherently poor melt strength.
An Adaptive Filling to Packing Switchover Method for Injection Molding
The production of technical molded parts requires an extreme high level of efficiency, process- and qualitystability to be competitive in global markets. In manufacturing the isotropy of the internal properties is an important prerequisite for warpage-free moldings. At the same time an accurate impression of the surface and an absolute free orientation of the molecule chains of the polymer are required. Therefore, a cost effective high volume production with consistently high quality requirements can only be guaranteed by a high degree of automation and an optimal process control . It is state of the art to fill the mold cavity velocity-controlled in the injection-phase, and to compensate for shrinkage in a pressure-controlled packing-phase to fill the cavity volumetrically correct to meet quality standards. The properties of the moldings produced depend on the parameters, which are set and modified by the operator of the machine . However, these adjustments are today heavily influenced by the experience of the operator, since an accurate knowledge about the influence of the settings on individual quality features without the knowledge of the details in the process is not possible. Also, the production of plastic moldings is used to process variations which affect the stability of the process and thus the quality of the molded parts. A main problem is under- and overfilling during injection-phase. In this work a method is introduced, which enables an autonomous switch-over, which adjusts the change-over point and adapts the packing pressure based on the condition of the processed resin. Variations in the process and on the material properties are characterized by the flow behavior of the polymer melt, monitored by key ratios and corrected in situ in the same injection-cycle. The result is a significantly increased process- and quality-stability. Frequently interventions by an experienced operator for example, are no longer necessary.
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