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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Controlled Migration of Antifog from Flexible Polyethylene Films
Antifog (AF) agents are chemicals that prevent the condensation of water as small droplets on hydrophobic surfaces which resemble fog. Antifogs function by minimizing the water surface energy, thus resulting in a continuous film of water rather than single droplets. Inside a greenhouse, the temperature and humidity are usually higher than the outside temperature and fog will thus appear on the inner surface of the PE film. In the present work, a new method of controlled migration of AF is described, by grafting AF molecules to the surface of sub-micron inorganic particles. Glycerides and fatty acids are used as AF. During the grafting reaction two fractions are formed: attached AF fraction to the inorganic particles’ surface, a fraction which cannot be detached by extraction, and an unreacted, thus unattached AF fraction. Aging tests, developed in the present work, have shown a significant decrease of the AF migration rate.
Investigation of Chemically Aged Elastomers Based on Analytical Methods
For over one hundred years, components made of elastomers have been commonly used in practice. However, the knowledge concerning the aging behavior of the material lags behind the existing demands of modern day industries. The property spectrum of elastomeric components extends across a broad range. Areas of application for such materials include aerospace, automotive, and mechanical engineering, plant construction, shipbuilding and civil engineering sectors. When considering the moldability, workability, flexibility and adhesion of elastomers, it is unsurprising that these materials are employed in so many industries. Yet, despite their application in numerous fields, only limited amounts of research has been carried out concerning these materials, and hardly exceeds basic examinations. Hence, intensive studies are necessary in this area. Previous research has already verified that the mechanical properties of elastomers change over time. These scientific findings make intensified research regarding the long-term behavior of elastomers indispensable. Chemical aging studies are highly significant, because the molecular structure and the networking of the material change during the aging process. Due to these changes, various material properties may also alter. In order to be able to make more accurate predictions concerning the life span and durability of elastomeric components, all environmental influences must be intensively researched experimentally. Basic research in the field of chemical aging is essential. In this paper, the aging behavior of natural rubber was tested using the media air, distilled water, and 3%- and 6% de-icing salt solutions.
Using Twin Screw Extrusion Technology to Determine the Effects of Surfactant Concentrations by Melt Blending Organoclays with PET Nanocomposites
The effects of the use of a surfactant for the dispersion of the nanoparticles in a nano-clay/PET composite have been evaluated. An increase in the amount of surfactant improved the dispersion of the particles and consequently led to an enhancement of the mechanical properties of the nanocomposite. The composites were melt-blended using co-rotating intermeshing twin screw extrusion technology and although there was degradation of the surfactant during processing, it did not affect the dispersion of the nano particles in the PET. A range of techniques used to characterise these materials will be discussed, including morphology, differential scanning calorimetry, (DSC), Scanning electron microscopy (SEM), including experimental techniques like mechanical property evaluations.
Biobased Fillers for Polypropylene for Interior Application
Coconut shell and torrefied wood are bio-sourced and renewable materials that can be used as fillers in various polymer matrices. Torrefied wood material can be produced from numerous cellulose based materials, such as wood, sunflower hulls, flax shive, hemp and oat hulls. These bio-fillers would replace talc and glass bubbles which are not a renewable resource. Additionally, the implementation of torrefied wood and coconut would reduce the carbon footprint and improve sustainability of Hyundai and Kia vehicles. In this study, coconut and torrefied wood filled polypropylene properties are tested for a HVAC Case application.
Functional and Design Opportunities Using Physical Vapor Deposition and UV Curable Coatings
Interest in alternatives to electroplated chrome is expanding dramatically. Color and appearance affects are limited with traditional chrome electroplating and successful “paint-on-chrome” applications are expensive and highly proprietary. Collectively the automotive, home appliance and cosmetic market are actively searching for alternatives with the appearance and durability of electroplating, but without the environmental side effects, appearance and functional design limitations, and costs associated with this decades old process. “Chrome look” processes and coatings for decorative and automotive lighting PVD applications have been used in the UV curable coating industry for over twenty years. As development of UV curable coatings for PVD has progressed, so has the understanding of the process and its unique capabilities and applications. This paper will address the advantages of PVD as a chrome alternative to include functional / design capabilities that are either cost prohibitive, or impossible to achieve with electroplated applications, as well as describe some of the tradeoffs associated when using coatings systems as an alternative for chrome electroplating.
Experimental Examination of Gap Bridging in Contour Welding
Because of the many advantages of laser transmission welding such as high-precision energy input and very fine weld seams, the process is used in a wide variety of applications in, for example, medical technology and the automotive industry. To join together large parts, use is frequently made of contour welding because the process combines good flexibility with a considerable amount of freedom regarding the geometry . Contour welding also offers the possibility of producing complex, robot-controlled free-form weld geometries. At the same time, however, the process does have disadvantages. Because the contour welding process involves guiding a beam with relatively high energy density slowly along the seam, the melt pool is very small. In front of the beam, the material is not yet plasticized, and behind it, the melt has cooled down again, making it virtually impossible to produce any meltdown without the parts becoming tilted. Even with complicated clamping devices, perfect contacting conditions are almost impossible to achieve. Especially in the presence of production-related distortion or surface tolerances, air gaps can form between the parts, which act as thermal insulators. In the areas close to the surface of the absorbing part, the laser beam is then converted into heat. This heat is dissipated only into the absorbing part (largely through thermal conductivity) and is not transmitted into the transparent part. This can lead to an undesirable temperature increase, resulting in thermal decomposition of the absorbing part. Knowledge of the relationships between process parameters and the quality of the manufactured part is therefore essential. In the tests described here, the gap-bridging capacity of semi-crystalline (PA 6.6) and amorphous (PC) materials is examined in more detail in relation to the process parameters. For experimental studies a special specimen geometry was used. A result of this study is the high influence of the geometry of the gap, beside
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.
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