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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A Preliminary Comparison between Long Glass and Carbon Fiber Composites in Shear Flow
Injection molding of fiber composites causes a complex microstructure formed by the intricate flow field created during the molding process. This work aims to understand the transient orientation evolution of long fiber suspensions in a well-defined flow and to ultimately apply the findings to complex flow fields. A sliding plate rheometer is used to measure the shear stress growth created during the startup of shear flow. Preliminary results show that a carbon fiber suspension produces a stress growth response similar to that of higher aspect ratio glass fibers, indicating similar orientation kinetics. Rheological observations are further investigated by experimentally measuring fiber orientation taken at different times during the startup of shear flow experiments.
Newly Improved PCT Compound for LED Reflector Resin
A reflector resin is an important integrated part of LED (light-emitting diode) packaging (PKG), and its properties play a key role in LED PKG reliability and performance. In this paper, selecting a proper reflector resin and important resin properties to LED PKG reliability and performance are discussed. High performance polyester poly(1,4-cyclohexylenedimethylene terephthalate) (PCT) compounds show outstanding reflectance stability under heat and light. A portfolio of Thermx® PCT LED grades is reviewed, and two newly developed PCT compounds are discussed. New PCT compounds show enhanced initial reflectance and reflectance stability. The key application attributes such as silicone adhesion, lead frame compatibility, and surface gloss are investigated and discussed. Overall, Thermx PCT LED compounds are an excellent choice as a LED reflector resin.
Thermoforming of Thermosetting Resins
Thermoforming is defined as a method of processing thermoplastics by applying heat to thermoplastics sheets of different thicknesses and conforming it in to the desirable shape of a final product. The shape and the part configuration is achieved and held by the formation of proportional internal stress due to the sheet stretching and the consequential freezing. The behavior of the thermoplastics sheets and the internal stress cause fatigue and leads to part deformation over time. This mechanism has been a limiting factor of using thermoforming as a production process in applications such as the auto industry, mechanical parts, and the housing industry. Thermosetting resins, particularly polyester and epoxy are the liquid resins with impressive thermal and mechanical properties. Epoxy is considered as the resin of choice in aviation industries and production of aircraft, and vinyl ester, is the material choice for auto industry. Both industries enforce the strictest rules. They require the parts to have a life expectance exceeding a decade. This presentation is aimed to provide the audience with the results of research in thermoforming of thermosetting resins including polystyrene and epoxy and provide them with the impressive mechanical properties of these products.
Radiation-Sterilization of New Medical Resins in Oxygen-Free Packaging
In this work, several medical-grade resins were studied for their color-recovery behavior after sterilization by radiation. Plastic parts irradiated in oxygen-free packaging showed that exclusion of oxygen significantly lengthened the time required for color-recovery, although the final color of samples sterilized in air and oxygen-free atmospheres were almost identical after both were exposed to ambient atmosphere for sufficient time. Newly-introduced Makrolon® Rx2440, a high-flow polycarbonate formulated for radiation-sterilization in oxygen-free packaging completed its color recovery after 14 days when stored in O2-free packaging in the dark.
Failure and Defect Analyses of Polymers via Morphological Investigation
Troubleshooting polymer problems requires a disciplined approach utilizing a variety of analytical tools. Morphological investigation coupled with failure analyses of polyolefin films, injection molded articles and high strength epoxies, are playing key roles in the fundamental understanding and development of these materials. Having the ability to elucidate material morphologies and identify failure mechanisms enables determination of phase size, dispersion, orientation, and component roles during failure. This paper highlights how a combination of analytical tools such as optical, transmission and scanning electron microscopies can be utilized to aid in resin design and process optimization to accelerate product commercialization.
High Temperature Multilayered Poymeric Films for Capacitor Applications
Current state-of-the-art biaxially oriented polypropylene (BOPP) and polyethylene terephthalate (PET) capacitor films are limited by their low energy density, unsatisfactory high temperature and high voltage performance. Recent research combining poly(vinylidene fluoride) (PVDF) with a high breakdown strength linear polymer, such as polycarbonate (PC) or PET, using the multilayer film coextrusion has led to the discovery of novel dielectric films with improved dielectric properties. The study will demonstrate the development of advanced capacitor films for higher temperature applications with enhanced energy storage density and low dielectric loss using the coextrusion technology.
The Feasibility of Using Lignin as Additive and Colorant in Polypropylene
The history of using agricultural base additive and colorant in polymer goes back to the time prior to the introduction of synthetic polymer and plastics materials. The extraction of lignin and the use of lignin in production of natural adhesives can be traced back to the ancient time of Roman, Persian and Egyptian Empire. The human exposures to these materials have proven to have minimal health consequences and minimal precautions. The lignin, as a byproduct of agriculture and paper industry, has a potential of offering a viable natural and sustainable resources as additive and colorant in plastics industry. The application of lignin as a color has a potential of minimizing the use of heavy base colorant to prevent environmental contaminations as well as offering a sustainable, worldwide available and accessible bio-mass. The intention of this investigation has been to study the process-ability, the ease of production as well as the quality of products as a function of the lignin grade and processing technique, and parameters for polypropylene mixed with different amount of lignin.
A Filling Behavior Study in Resin Transfer Molding Process through 3D Simulation and Experimental Visualization
This study focuses on the filling behavior of resin transfer molding (RTM) process. By the visualization system, the flow patterns of resin during transfer molding were observed and the data were used to estimate the permeability tensor. In addition three-dimensional simulation were used to predict the filling behavior in thickness direction and the edge effect of the RTM process. The comparison between simulation and experiment result shows the capability of 3D numerical simulation on the filling behavior of the RTM process. The simulation tool would be helpful to obtain the optimal operating condition to reduce the trial-and-error time and materials.
A Comparison on the Mechanical Properties of Unidirectional Carbon Fiber Reinforced Composites between Thermoplastic and Thermosetting Resins
This paper reports the database of mechanical properties of unidirectional carbon fiber reinforced plastic composites. The unidirectional carbon fiber prepregs which made through hot melt process were used as reinforcement and both polyamind6 (PA6) and epoxy were used as matrix to make CFRP boards through compression process. The mechanical and interfacial properties of 0 and 90 degree CFRP composites were investigated by tensile test and fractured surface observation. Fracture toughness was investigated by compact tension test.
Prediction for Replication Ratio of Microfeatures on Injection-Molded Light Guide Plate Using Finite Element Analysis
A numerical study on the filling behavior of polymer melt into macro- and micro-cavities was performed using the finite element method. The simulation procedure consists of two steps; as the first step, pressure history data were exported from the macroscale flow simulation in which the numerical domain was considered as 7 inch LGP geometry without microfeatures, and next, the microscale flow simulation was performed using pressure data as the boundary conditions. The microscale domain contains single cylindrical microfeatures with a diameter of 30 ?m and a depth of 14 ?m on the nickel stamper with a thickness of 0.5 mm. The numerical results showed that the predicted final height of the microfeatures and the filling time at different positions agreed well with the experimental data.
NIR – Spectroscopy: A Sophisticated Tool for Process and Quality Control
Near infrared spectroscopy was used in-line to determine the residence time distribution of polypropylene with the help of different tracers. Two twin-screw extruders, one single-screw extruder as well as different experiment alignments such as screw speed and their influence on mean residence time and especially residence time distribution have been investigated. It could be seen that with NIR the residence distribution time is easily measureable. Additionally the Young’s moduli and the tensile strength values of different produced polypropylene nanocomposite have been monitored and correlated to the NIR-spectra which have been collected simultaneously during the production on a co-rotating twin screw extruder. The results showed that both mechanical properties can be very well correlated with near infrared spectroscopy so a sophisticated quality control is possible.
Simulation on Warpage and its Mechanism in Co-Injection Molding
With the growing use of co-injection molding process, it becomes essential to understand skin/core material distribution in the cavity for ensuring the quality of final product. In this study, warpage issue will be examined numerically and systematically by process effect and material combination in sequential co-injection development. Specifically, decreasing melt temperature or slowing down flow rate of 1st shot, which makes frozen layer thicker, can improve warpage problem. When the frozen layer is thicker, the core layer is more difficult to penetrate through the thickness direction. Thus, the melt is squeezed to advance in the flow direction, that forces melt go farther and better packing effect can be implemented accordingly. However, warpage becomes worse due to two used different materials with distinct properties mismatching while processing co-injection. To validate our simulation investigation, the experimental study will be performed in the near coming future.
Online Estimation of Local Permeability in Resin Transfer Molding
Resin transfer molding (RTM) is a widely applied manufacturing method of composite materials. In RTM, permeability of fiber reinforcement varies with its geometric formation and affects the property of resin flow. Therefore, effective online estimation is crucial to achieve satisfactory quality product. In this work, a method of online measuring local permeability is proposed, which can deal with variation in local permeability caused by irregular arrangement of fibers. This study is divided into two stages. First, flow visualization was realized and all hardware was integrated to acquire information in resin filling. Second, local pressure and flow front location were substituted into the Darcy’s law, thus making online calculation of local permeability feasible. At the end of this study, the proposed methods are utilized in a trial RTM test to confirm their effectiveness.
Experimental Investigations of the Mechanical Recycling of Offcuts from the Production of Continuous Fiber-Reinforced Thermoplastic Sheets by Injection Molding
This paper examines the recycling of sorted plastic offcuts produced during the manufacture of continuous carbon-fiber-reinforced polyamide 66 sheets. The idea is to process the offcuts so that they can be conveyed to a value adding application. For this study, the offcut is shredded into recyclate and processed by injection molding to produce specimens. The processing properties of the recyclate and the mechanical properties of the specimens are at the focus of the investigations. Good processability of the recyclate is achieved in the tests by using a stuffing device in the hopper of the injection molding machine. With optimum injection molding parameters, an outstanding tensile strength of 293 MPa is obtained in the tests.
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.
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