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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Effect of Surface Treatment on the Mechanical Properties of Wood-Plastics Composites Produced by Dry-Blending
In this work, wood-plastics composites (WPC) were produced by a simple dry-blending technique. In particular, the effect of wood surface treatment with maleated polyethylene (MAPE) is presented. The effect of wood content was also studied by using different concentrations (0, 10, 20 and 30% wt.) and the samples were mechanically characterized in terms of tensile, torsion, and flexural properties. From the tensile stress-strain curves, modulus, strength, and strain at break are reported, while only shear and flexural moduli were studied for torsion and bending tests. The results show that simple dry-blending can be used to produce homogeneous ultra-high molecular weight polyethylene (UHMWPE)/maple flour composites and that surface treatment can improve the moduli by up to 110%.
Polypropylene and Polypropylene-SEBS Blends for Medical Films
Due to the negative publicity of PVC , polypropylene is attracting increasing attention as an alternative material for flexible medical packaging, such as bottles, films and for disposable medical items. Propylene-ethylene random copolymers are usually the materials of choice as they are suitable for the preparation of transparent films and transparent molded items that can withstand steam sterilization. External elastomers such as stryrene-ethylene/butylene-styrene triblock-copolymers (SEBS) usually need to be added to achieve the desired stiffness (softness) of the final item. In the current study, it was demonstrated that modifying random copolymers with SEBS also improves the toughness and the optical properties of films. The second part of the study investigated whether the use of random-heterophasic polypropylene copolymers instead of random copolymers would allow for a reduction of the costly SEBS elastomers. This study showed that random-heterophasic polypropylenes containing a significantly reduced (30%) amount of SEBS or even containing no SEBS at all can in fact achieve the same performance as SEBS modified propylene-ethylene random copolymers. These results illustrate that random-heterophasic copolymers are an attractive alternative to propylene-ethylene random copolymers as they allow for a reduction of costly SEBS in medical packaging systems.
Artificial Weathering of Materials Used in Collapsible Fuel Storage Tanks
The purpose of this work was to perform a comparative analysis of various candidate nitrile coated fabric materials supplied by potential vendors to be used as fuel storage tanks and compare the results to the currently fielded polyurethane storage tanks. Our strategy is to utilize advanced environmental aging methods to simulate extended weathering conditions. Our results demonstrate that the nitrile coated fabrics performed well in our evaluation. Their breaking strengths are about equal to the currently fielded urethanes and they performed comparably when subjected to environmental aging conditions.
Confounding of Hydrolytic Stability Results by Physical Aging
Determining the correct test method to predict the real-world behavior of a resin can be challenging. For hydrolytic stability, various industries measure a resin’s ability to maintain key properties following exposure to elevated temperature and humidity (hydroaging). One of the properties frequently requested for testing is the notched Izod impact. In this paper, it will be discussed why the results of notched impact testing following hydroaging are actually confounded. Other methods for monitoring a resins hydrostability will be suggested.
Molded-On Mechanical Fastener Ensures Uniform Force Transmission and Sealing of the Joint Surface: Joining Parts Together with the Aid of Self-Tapping Screws
While metal rivet connections have been the subject of widespread research in the past and have since become particularly well-established for use in lightweight structures , the field of plastic rivet fasteners still needs to be researched as it holds significant potential. The fastener system presented here is one possible solution and is seen as a viable alternative to existing connections. The direct molding-on of a boss with an optimized geometry produces a mechanical fastening element, which, in the finished component, produces a sealing undercut due to a uniform force transmission. The method of direct screwing plays an important role in the development of the new fastening solution. The insertion of the thread-forming or self-tapping screw produces the tension needed for compression of the boss, and, together with the necessary pre-load force, thus ensures a reliable connection. The mechanical fastener system was studied in various sizes in order to be able to perform a scale-up of the fastener system. This publication is related to the results of the mechanical fastening element for a nominal screw diameter of 4 mm. The results of the plastic fastener for a nominal screw diameter of 6 mm are presented in .
Influence of Mineral Fillers on the Flame Retardancy of Expandable Graphite / Polypropylene Materials
Halogen-free flame retardant applications attract great interest of industry as well as of research. Most commercial available flame retardants for polypropylene have to be used with high filler loading, which leads to difficulties in processability, poor mechanical properties and unfavorable cost performance. Therefore it is important to gain fundamental knowledge about synergistic combinations of flame retardants and filler to reduce all disadvantages. In this research the combustion and burning behavior of expandable graphite polypropylene compounds with various mineral fillers were investigated. The results of the burning and combustion characterization were different and also partly contradicting. Combined compounds with EG and additional fillers obtain good results for protecting the material against combustion, while compounds filled with expandable graphite, layered silicates or zeolite show good protection against burning.
Morphology and its Influence on Rheological Parameters of Nanocomposites Filled with Layered Silicates Based on Polylactic Acid
In this research work the morphology of polylactic acid (PLA) filled with various types of layered silicates, as well as its influence on the rheological properties regarding melt strength and complex viscosity, were investigated. Thereby the morphology of the produced nanocomposites were examined with small angle X-ray scattering (SAXS) measurements. For the determination of melt strength a Rheotens apparatus, fed by a bypass system during extrusion, was used. Complex viscosities were measured with a rotational rheometer with cone-plate setup. Results show that the different modifications of the layered silicates have a significant impact on the final morphology as well as on the rheological properties of the produced nanocomposites. Beside different achieved interlayer distances and grades of intercalation of the layered silicates inside the polymer matrix, also increased melt strength as well as increased complex viscosities were observed. Thereby a homogenous dispersion and high grade of exfoliation is also preferable for the production of thin products like films.
Scratch Visibility Analysis of Polymer Samples with an Optical Microscope
Determination of scratch and mar performance is important for any application where maintaining surface integrity is important, ranging from coated surfaces to bulk polymers or composites. In this paper we outline a new and systematic empirical method for scratch visibility analysis with an optical microscope. Like many existing methods to quantify the visibility of surface scratches, it relies on differences in the intensity of light reflected off a scratch and an unscratched control area. We show that these differences may not always correlate with perceived scratch visibility and develop a method to overcome this limitation. Our method can be implemented using standard optical microscope technology and delivers reproducible, quantitative results. Results for five proprietary latex coatings are in good agreement with a qualitative scratch visibility assessment.
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.
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