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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Improving Thermoplastic Foam Stability in the Molten State by Interfacially-Adsorbed Particles
Addition of particles of low surface energy is shown to have a strong stabilizing effect on polymer foams. We examine two high melt index polymers, polystyrene and polylactic acid, foamed by chemical blowing agent. Both polymers show extensive coalescence and collapse when held in the melt state for extended periods. Addition of 5-10 wt% PTFE particles almost completely eliminates collapse, and greatly reduces coalescence. SEM shows that particles adsorb on the inner surface of the foam cells and creates a particulate shell that protects against coalescence. This appears to be a promising route to foam polymers with poor melt strength, especially in processing operations which involve slow cooling.
Automatic Optimization of Preform Geometry and Process Parameters in Two-Stage Stretch-Blow Moulding Process
The total production costs of PET bottles are significantly affected by the costs of raw material. Therefore, stretch blow moulding industry intends to reduce the total production costs by an optimized material efficiency. The key factor is seen in a product specific preform design and well adapted process parameters. Due to a multitude of complex boundary conditions, the design process of new stretch-blow moulded products is still a challenging task and often based on empirical knowledge. Application of current CAE-tools can support the design process by reducing development time and costs. This paper describes an approach to determine optimized preform geometry and process parameters iteratively. The wall thickness distribution and the local stretch ratios of the blown bottle are calculated by a three-dimensional process simulation. Thereby, the wall thickness distribution is correlated with an objective function and preform geometry as well as process parameters are varied by an optimization algorithm. The approach is applied on an 0.5 litre PET bottle of Krones AG, Neutraubling, Germany. The investigations point out that the design process can be supported by applying the simulative optimization approach.
Microcellular Foaming Behavior of Poly(butylene succinate)/Nanosized Calcium Carbonate Composites
In this paper, the foaming behavior and thermal property of biodegradable poly(butylene succinate) (PBS)/nanosized calcium carbonate(nanoCaCO3) composites were investigated. This article focused on the study of the effect of nanoCaCO3 on foam morphology of PBS using supercritical CO2 as the foaming agent. The presence of nanoCaCO3 acted as nucleation site to facilitate the crystallization of PBS that results in the increase of PBS crystallization up to 63.63%. The effect of incorporation of the nanoCaCO3 particles on the thermal stability was quantified by the temperature at 5% and 10% weight loss. Along with the addition of nanoCaCO3, the temperatures at 5% and 10% weight loss of PBS/nanoCaCO3 composites are higher than pure PBS. The SEM results shows that with the addition of nanoCaCO3, the foam samples cell size decreased and cell density increased greatly.
A Prediction Model for the Numerical Optimization of a Novel Blown Film Cooling System
In a prior work, a process model for the numerical optimization of blown film cooling systems was developed. This model is able to compute a realistic bubble film behavior depending on the cooling configuration. However, the optimization of a new cooling system requires proper initialization data to minimize the calculation period. In this paper, a prediction model is presented that can offer these data in a pre-optimization loop. The model is able to calculate an optimal cooling configuration with the corresponding film contour that is qualified for a detail process simulation. Furthermore, a novel cooling approach is optimized, using this model.
Processing and Manufacturing of Natural Fiber Reinforced Plastics to Specimens for Generating Simulation Data (NFC-Simulation)
Generating basic material data information for natural fiber composites (NFC) for simulation requires uniform process parameters. This study is primarily concerned with the technical implementation of the uniform processing of different natural fibers (NF) such as sisal, wheat straw, hemp pellets, cellulose fibers and man-made fibers in extrusion and injection molding process. We were able to prove the possibility of compounding very different types of natural fibers and plastics under the same conditions by using optimized process parameters and by using a specialized extruder screw configuration.
Autosterile Injection Molding (AIM): A New Manufacturing Approach for Medical Single Use Products
An autosterile injection molding (AIM) process meets the requirement of sterility for medical single use products with the advantage to avoid additional sterilization procedures. However, autosterile injection molding is not yet common use within the polymer manufacturing industry. In contrast, autosterile manufacturing can be considered as state of the art within the pharmaceutical industry for many years. Therefore, injection molding within clean rooms is examined with regard to possible implementation as an autosterile manufacturing process. Sterility of polyoxymethylene melts are investigated in addition with the sterility of the injection mold during the manufacturing cycle and the contamination probability during the packaging period.
Sustainable Plastics: Life Cycle Assessment of Biobased and Recycled Plastics
Plastic materials and products produced today should not deplete resources or abilities of future generations to produce plastic materials or products. Sustainable plastics can be sustainable by producing products with reduced greenhouse gas emissions, reduced solid waste, and reduced pollution as compared to conventional plastics. Based on cradle-to-grave life-cycle assessments (LCA), PLA plastic containers had lower greenhouse gases, lower waste generation, and lower pollution than virgin and recycled PET containers. The PLA clamshells had 86% and 79% lower overall environmental impacts than recycled PET and virgin PET containers, respectively, as measured with a Greene Sustainability Index (GSI).
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.
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