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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Various topics related to sustainability in plastics, including bio-related, environmental issues, green, recycling, renewal, re-use and sustainability.
Failure Analysis of a Cracked Construction Vehicle Grille
Cracking occurred within grilles used on heavy construction equipment, without apparent cause. The cracking was observed to be sporadic and had initiated while the parts were being stored in a warehouse, prior to installation on the vehicles. The cracking was found adjacent to holes used to secure a logo nameplate in conjunction with metal bolts. The focus of this investigation was a timely determination as to the nature and cause of the failures. Of particular interest was whether the failure was primarily associated with material, design, processing, or environmental factors. This paper will document some of the testing performed to characterize the failure mode and identify the root cause of the cracking, in order to illustrate the failure analysis process.
Film Finishing Part I: Commercial and Emerging Thermoplastic Film Based Technologies
The Automotive Finishing Industry, valued at $2.3 billion in North America1, is faced with serious challenges to reduce cost and a growing urgency to meet environmental pressures. The industry is making major progress to reduce emissions but more must be done as requirements are tightened. Concurrently, other technologies are being advanced that may radically change the finishing process in the long term. Finishing plastic parts with film is one of the emerging technologies. Film finishing presents an opportunity for the Plastics Industry to step forward with an all-plastic solution - plastic film finishes on reduced weight plastic body panels.
High Carbon Fly Ash/Mixed Thermoplastic Aggregate for Use in Lightweight Concrete
Synthetic lightweight aggregate has been produced by melt compounding high concentrations of high carbon fly ash into various thermoplastic binders. The composite material is being developed as a synthetic lightweight aggregate for use in applications such as lightweight concrete. In this study, a series of lightweight aggregates have been produced using several fly ash concentrations, and several different thermoplastic binders. The synthetic aggregates have been produced using flexible thermoplastic binders, rigid thermoplastic binders, and a mixed thermoplastic binder formulation. The physical properties of the melt compounded aggregate materials have been evaluated in an effort to determine the relationship between variables, such as the binder stiffness, and the aggregate stiffness. Lightweight concrete test samples have also been prepared and evaluated. The results of the study show that the lightweight aggregate properties are influenced by both the fly ash concentration and the thermoplastic binder composition. However, the effect that the thermoplastic binder has on the physical properties of the aggregate becomes less significant at high fly ash concentrations. At fly ash concentrations of 80%, the physical properties of the aggregate are fairly insensitive" to the composition of the thermoplastic binder. The aggregates produced using a mixed plastic composition had properties that were quite similar to those produced using the individual (control) thermoplastic binders indicating that low value mixed plastic waste may be a candidate binder material for the polymer bound fly ash aggregate."
Interaction in PC/ABS Blends Prepared in a Dynamic Melt Mixer
Polymer blends are more and more important materials in polymer technology. Their role increases due to the recycling processes of mixed plastic waste. One of the key problems of polymer blends is the interaction between the components as they determine the properties. Commercial polycarbonate (PC) and ABS were blended in a dynamic melt mixer in 80/20 and 70/30 ratios. Homogeneity of the blends was characterized by SEM method. Glass transitions of the blends and the pure materials were measured by calorimetric and dynamic mechanical analysis. The interaction and the partial miscibility between the components were determined from the shift of the glass transition temperatures. It was found that the homogeneity of the blends was uniform. The shifts of the glass transition temperatures show some interaction between the components.
Load Oriented One-Step-TWINTEX®-Sandwich-Structure for Large Scale Production of Automotive Semi-Structural Components
In a joint project with the German automotive industry, the Fraunhofer Institute, material suppliers, component-and mold manufacturers, a thermoplastic sandwich material has been developed. The goal is to offer a cost-effective material with increased mechanical properties to combine the advantages of In-Line-Compounded long fiber reinforced thermoplastics (LFT-ILC) or well-established thermoplastic semi-finished products like GMT and advanced thermoplastic TWINTEX® woven fabrics. These requirements are fulfilled by a sandwich which consists of outer layers of woven fabrics and a core layer of recycled material mainly of shredded TWINTEX®, GMT or LFT components or production waste. The foot support for the smart vehicle has been selected to evaluate the sandwich system.
Nanometer-Scale Structural, Tribological, and Optical Properties of Ultrathin Poly(Diacetylene) Films
The ability to create organized ultrathin films using organic molecules provides systems whose chemical, mechanical, and optical properties can be controlled for specific applications. In particular, polymerization of oriented mono- and multi-layer films containing the diacetylene group has produced a variety of robust, highly oriented, and environmentally responsive films with unique chromatic properties . These two-dimensional poly(diacetylene) (PDA) films, where the conjugation runs parallel to the film surface, have previously been prepared in a variety of forms . Of particular interest is the optical absorption of PDA due to its -conjugated backbone. A wide variety of PDA materials, including bulk crystals, thin films, and solutions, exhibit a chromatic transition involving a significant shift in absorption from low to high energy bands of the visible spectrum, thus the PDA appears to transform from a blue to a red color. In addition, the red form is highly fluorescent, while the blue form is not. This transition can be brought about by temperature [3, 4], binding of specific biological targets , and applied stress (mechanochromism) [6, 7]. In this paper, we discuss the Langmuir deposition of ultrathin PDA films and the subsequent measurement of their structural, optical, and mechanical properties at the nanometer scale. By altering the head group functionality, we can choose between mono- and tri-layer PDA film structures . Measurements with the atomic force microscope (AFM) reveal strongly anisotropic friction properties that are correlated with the orientation of the conjugated polymer backbone orientation . Furthermore, we can use the AFM tip or a near field scanning optical microscope (NSOM) tip to locally convert the PDA from the blue form to the red form via applied stress . This represents the first time that mechanochromism has been observed at the nanometer scale. Dramatic structural changes are associated with this mechanochromic tr
Natural Fiber Reinforced Polypropylene Composites – an Approach on Thermoforming Processing
This work has been performed at Mercedes-Benz of Brazil in a partnership with its suppliers aiming the replacement of fiberglass in polypropylene matrix composites by natural fiber reinforcements. The process that has been chosen for this purpose was Vacuum-forming. This choice took into account the large application that this technique represents in the company's commercial products. The results expected for this new material is cost and weight reduction besides the friendly environmental aspect that this change introduces. Jute fiber reinforced polypropylene sheets at constant thickness and fiber content were prepared in order to evaluate the feasibility of the application. The preliminary results have shown that this material has a great potential of application because of the low fiber costs.
Non Woven Textiles from Melt Spun Recycled PET
This study examines the effect of nucleating agents on the physical properties of melt drawn fibres made from post consumer Recycled Polyethylene Terephthalate (RPET). Clear and coloured RPET derived from carbonated soft drink bottles have been used in this study. Titanium dioxide (TiO2) and carbon black (CB) have been added at varied addition rates in a linear low density (LLDPE) and PET carrier. The effect these additives have on the physical properties of the finished textile were evaluated. Evaluations show that reprocessed bottle grade PET is suitable for fibre applications if the intrinsic viscosity and the final fibre properties are carefully controlled. LLDPE masterbatch containing TiO2 and CB at addition rates in the order of one percent were able to improve processing, physical properties and the rate of crystallisation.
Numerical Simulation of Co-Injection Molding
In the co-injection molding process, two (or more) different polymers are injected into the cavity simultaneously or sequentially. Different properties of these two polymers and their distribution in the cavity greatly affect the applications of this molding process. The skin layer can use special polymers to provide good appearance and texture, strength, chemical resistance, EMI shielding and other functions. The core layer can use recycled or inexpensive materials. Together these can improve part quality and lower the cost. However, due to the dynamic interaction of two polymers in the manufacturing process and their difference in properties, process control becomes more complicated and process design becomes a challenge. The rules used for the traditional injection molding process design may not always be useful for co-injection molding any more. An integrated CAE software can be used to simulate the co-injection molding process. In this study, the capability and usefulness of the CAE tool will be shown. The control of polymer distribution will be discussed. The effects of polymer properties and their distribution on part quality will also be studied.
One-Step-Sandwich-SMC: A New Method for the Production of Lightweight Vehicle Parts
In respect of weight reduction an increasing request for light weight materials exists in the automotive industry. The compression molding of sheet molding compounds (SMC) has been established as a cost-efficient and widely applied process for semi-structural automotive components, especially in commercial vehicles. The deficiency of this material is the relatively low Young's modulus, which prevents these materials from being used in loaded structures. Therefore the idea was to increase the performance of these materials by forming a sandwich, but in principle use the same fast and cost-effective process of conventional SMC. The principle of this new technology is based on a one-step process using one sheet containing a blowing agent disposed between two conventional SMC sheets in the mold. By closing the mold the three layers are compressed and heated up until the expansion of the core material starts. The foaming process resulting from the expansion of the core material is controlled by a defined opening motion of the mold according to the requested sandwich height. After the foaming process the curing of the part is completed. The result is a rigid lightweight sandwich structure. The advantages of the One Step Sandwich-SMC in comparison to typical sandwiches are the decrease in production cost and the recycling properties, since no separation of the single layers is required (single material system) and since additionally the core layer may contain a high amount of SMC scrap material. The developing process of this technology was conducted by the simultaneous integration of fundamental research (material development, testing, processing technology) and by the development of the structural part (part conception/design). This demonstrator component is the front hood of a commercial vehicle, the Mercedes-Benz Actros, which was produced with optimized processing parameters. For the demonstrator chosen a cost potential of 30 % and a weight reduction potential of 10-1
Plastic Media as a Mold/Screw Cleaning Alternative
Maintaining molds/screws integrity through regular thorough cleaning is a key factor in producing quality plastic molded parts. The ability to clean quickly and economically (while being aware of environmental issues) is a challenge and a goal for all molders. Non-abrasive blast cleaning utilizing plastic media is the answer to all of the above. Not only is plastic media blasting quick/efficient, it will not alter/damage the mold or screw surface, round/erode corner and edges, or alter tolerances. In addition, all this can be attained with a product that is completely non-hazardous, which makes disposal a non-issue. All of the above has been documented through years of research. Data has been gathered on cleaning times, equipment and material costs with consideration for waste disposal costs comparing hand cleaning, chemical cleaning, and plastic media blast cleaning.
Polyester Polyols for Polyurethanes from Recycled PET
Plastic packaging forms a significant portion of household waste, and PET soft drink bottles represent a major percentage of the waste. Consequently, PET bottle grade material makes up a significant portion of the feedstock in the recycling plant at Visy plastics. The end uses are theoretically many, however, there are few applications for less purified grades of recycled PET. This paper presents the preliminary results of an industry based collaborative research project which aims to investigate the breaking down of recycled PET into its chemical building blocks using glycolysis. The main objective is to produce a polyester polyol for the polyurethane industry from recycled PET and to compare the properties with that of a virgin resin.
Process Optimization for Reactive Blending and Compatibilization of PA 6 and PET in Extrusion
Blends of PA and PET do not have a minor significance in industrial production any more. Especially since the European beverage industry decided to use (multi- and single layer) PET bottles containing PA, the economic and ecological interest in recycling PA and PET is stringently increasing. In former research projects, where IKV has been involved, the compatibilization of PA and PET in extrusion was simply established. New investigations, focussing on the process optimization, enable to correlate the process parameters with the material properties. Therefore an extruder cascade was developed for a one-step-in-situ compatibilization and in addition a new characteristic parameter was constituted which is independent of the type of extruder.
Recovery of Post-Consumer Plastic Waste via Solid State Mechanochemistry
A new solid-state mechanochemical technology is being developed to create value-added materials from post-consumer plastic waste. The process, called solid state shear pulverization (S3P), can recycle various mixtures of ordinarily incompatible plastics, including post-consumer film waste, by subjecting the polymers to high shearing forces in the solid state. This produces uniform, light-colored powders of variable fineness suitable for processing by all conventional plastic fabrication techniques. The resulting materials consistently exhibit high elongation and impact strength. Northwestern University and Material Sciences Corporation are transitioning S3P from the laboratory to the commercial scale.
Recycling of 100% Cross-Linked Rubber Powder by High-Temperature High-Pressure Sintering
Studies estimate there are two billion scrap tires in U.S. landfills with over 270 million tires added yearly. An overview of a simple technique for recycling thermosets will be discussed. In short, it is possible to recycle rubber powders made from scrap tires with the application of only heat and pressure and achieve good mechanical properties. An investigation of the mechanical properties of typical consolidated rubber powders as a function of the molding variables is be shown. To date every type of cross-linked elastomer investigated could be sintered, including silicone rubbers, natural rubbers, ethylene-propylene-diene rubbers, styrene-butadiene rubbers and fluoroleastomers.
Recycling of Crosslinked Multi-Layer Thermoplastic Films - Miscibility Studies
This study was part of a program of work undertaken to develop recycling technology for multi-layer films which are not currently recycled. These multi-layer films comprise barrier layers with surface layers for mechanical strength, and tie layers between. Crosslinking is used to enhance various mechanical properties. The crosslinked layers have a high viscosity which creates processing problems, eg. if the film is recycled, high processing pressures are required. Furthermore, material blend component incompatibilty can result in inferior mechanical properties. Monolayer films of the virgin materials were produced. Multi-layer film with crosslinked EVA/LLDPE and a barrier layer was produced on a blown film line. This multi-layer film was agglomerated" then reprocessed in a twin screw extruder with virgin LDPE and LLDPE and blown into film. The blend miscibility was then determined using a TA Instruments TMDSC. It was found that LDPE blends were initially miscible with the containing scrap whereas LLDPE blends were immiscible. The LDPE miscibility was partly reversible as the blend components phase separated after the second heat treatment during testing in the TMDSC instrument. The initial miscibility was attributed to being induced by high shear during processing."
Recycling of Multilayer and Barrier Coated PET Containers
This paper describes the process for removing barrier layers and coatings (oxygen and carbon dioxide) from polyethylene terephthalate (PET) substrates through a conventional mechanical bottle recycling system. Varied wash chemistry and barrier medium have been examined and the effect on residual multilayer material or coating has been evaluated. Wash chemistry was found to be the controlling factor in improving the external coating removal efficiency. Delamination through mechanical working was found to be the controlling mechanism for separating multilayer materials. The conclusion drawn from our experiments is that the PPG Bairocade coatings were removed most efficiently. Internal deposition techniques may contribute fewer residues to the RPET, however substantiating this is difficult.
Reinforcement of Thermoplastics Using Microcomposite Fillers
Thermoset recyclate fillers are considered as microcomposite reinforcements for polymers. Emphasis is given to glass fibre-reinforced phenolic and polyester waste products as functional fillers for polypropylene, where with appropriate surface modification, significant enhancement in mechanical properties can be achieved. In this respect, the role of a two component treatment package is discussed, in terms of fibre-matrix interfacial bonding, the effect on properties of the host polypropylene matrix, and the failure mechanism induced. Novel integrated compounding technology is described for the cost-effective preparation of polymer composites, containing thermoset recyclate fillers.
Rheology and Crystallization in Fiber Optic Cable Jacket and Conduit Extrusion
Rheological tests measure melt-state polymer flow, delineating molecular structure and predicting extrudability. Rheology of compounds used in fiber optic (FO) cable jackets and in the conduits that contain such cables will be our focus. Polyolefin-based jackets strengthen the FO cable and protect internal components, while the conduit provides long-term strength and protects the cables against environmental stresses. High density polyethylene use in these applications is growing rapidly, spurred by FO cable growth. Important properties in both applications include melt-state processability, stress crack resistance and solid-state stiffness. Melt rheology directly influences processability, combining with crystallization behavior to dictate final solid-state properties.
Solvent Welding of Abs and Hips-A Case Study in Methylene Chloride Substitution
An investigation was conducted to evaluate replacements for methylene chloride in the solvent welding of an acrylonitrile-butadiene-styrene system (ABS) and a high-impact polystyrene (HIPS). Fourteen candidate solvents were experimentally considered. These were divided into three general categories: traditional, green and clean." A relative hazard rating was assigned to each solvent by taking the maximum concentration that the solvent could keep in equilibrium in a specified air space and dividing this value by the threshold limit value (TLV). Solvent welding was tested in both bond-in-tension and single-lap shear geometries. Parameters affecting resultant bond strength that were quantified included time polymer in contact with solvent time after surfaces joined temperature (pre- and post-bonding) contact pressure and vacuum."
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