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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Study of the Bond Strength of a Combination Consisting of Composite Sheet and Short-Fiber Thermoplastic
The backmolding of continuous fiber-reinforced thermoplastics – so-called composite sheet – is based on the idea of combining the benefits of injection molding with those of semi-finished composite sheet. In this way it is possible to integrate the forming process for the composite sheet into the injection molding process and not only benefit from the outstanding weight-related strength of the composite sheet but also achieve a high level of stiffness by backmolding the part with rib-like structures. This study investigates the influence of key process parameters on the strength of the bond between the composite sheet and the backmolded thermoplastic component, based on a peel test.
Crystallization and Foaming Behaviors of Poly(Lactic Acid) Using Supercritical Carbon Dioxide as a Foaming Agent
By using supercritical carbon dioxide (Sc-CO2) as a foaming agent, the poly(lactic acid) (PLA) foams were prepared in a batch process using two different temperature modes. The crystallization and foaming behaviors of the PLA were investigated, putting emphasis upon the foaming behavior of spherulites. It is found that by tuning the saturation and foaming temperatures, the spherulites in PLA foams could present various structures, such as circular entities, stamen-like cell structures, and small cells (0.6 µm). Interestingly, a bi-modal cellular structure is observed for the sample foamed at 100°C saturation temperature and 170°C foaming temperature. Using the foaming temperature of 140°C, the samples prepared at 100 and 180°C saturation temperatures exhibit crystallinities of 42.7% and 6.8%, and corresponding expansion ratios of 1.9 and 49.8, respectively.
Developing an Integrated Crash Simulation for Automotive Parts Produced from Natural Fiber Reinforced Plastics (NFC-Simulation)
The interest in renewable materials in car industry is growing dramatically. Natural fiber reinforced plastics (NFC) are an attractive solution, because of their interesting mechanical properties in combination to a good eco balance. One of the main obstacles to being used on a large scale in the car development process is the requirement that all components must proof that they meet product safety requirements and are fit for purpose through using CAE methods. The usage of CAE is a fixed established procedure in the automotive industry to meet today's challenging development times. The project NFC-Simulation, which is described in this paper, established a complete and integrated solution for the simulation of NFC components, from processing to crash simulation. In order to achieve these capabilities, many technical and scientific problems had to be solved in detail and the results integrated to a complete solution.
Computational Fluid Dynamic study of Conformal Heating and Cooling Technology Applied in Injection Molding
This article aims at conducting a detailed Computational Fluid Dynamics study to assess the efficiency of the conformal heating and cooling system associated in an injection molding process. The study involves characterizing the fluid flow and heat transfer behavior in an injection mold designed with conformal heating/cooling circuits. The key result of interest is to obtain uniform temperature distribution over the cavity profile. Further, the study involves identifying the important geometrical as well as flow parameters that have the significant influence on optimizing the heat up and cooling time which promotes uniform temperature distribution on the cavity profile. The formation of uniform temperature distribution, leads to the better quality and aesthetics of the injection molded parts. Importantly, molding defects such as knit lines, flow marks etc., are reduced to a greater extent compared to conventional injection molding processes.
Experimental Investigation of the Mechanical Properties and the Morphology of PA6-MWCNT-Composites Depending on the Melt Compounding Conditions
Melt compounding using a co-rotating intermeshing twin screw extruder is the favored route to prepare polyamide (PA6)-multiwalled carbon nanotube (MWCNT)-composites. The melt compounding conditions influence the final properties of the resulting composites. Thus, this study discusses the influence of the process parameters screw speed, screw configuration, throughput and barrel temperature profile on the mechanical properties and the morphology of PA6-MWCNT-composites. The experimental investigations reveal, that the throughput and thus the residence time has the greatest influence on the mechanical properties, while screw configuration, screw speed and barrel temperature profile have only a minor effect. The area of agglomerates as indicator for the dispersion of the MWCNT shows no direct correlation to the processing parameters.
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.
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