SPE Library

The torque rheometer has been an essential instrument for a wide spectrum of research and development and quality control testing laboratories throughout the years. The torque rheometer has evolved just as quickly as advances in material chemistry. Highly sophisticated software and hardware technologies have now been introduced to better serve the needs of a modern laboratory. New challenges in such areas as plastics recycling and environmentally friendly fillers for plastics are some of the needs being met by using this multifunctional instrument. This paper intends to discuss how these changes have made the instrument more relevant than ever.

The use of polymeric materials for transparent, lightweight armor has been of great interest to the U.S. Army for a number of years. Field items such as goggles, lens, face and windshields are currently manufactured using advanced polymeric plastics. These items are designed with polymers that provide excellent optical clarity, rugged abrasion resistance, and high ballistic impact strength. However, as with any organic polymer system, these materials are susceptible to degradation over time when exposed to various environmental (i.e. sunlight, moisture, temperature) conditions. This structural degradation (1-4) will eventually comprise the original integrity of the materials' desired properties. In this study, the impact of accelerated weathering upon newly developed polyurethane based thermoplastic materials was investigated. A fluorescent ultraviolet (UV)/condensation weathering tester was selected for the exposure study. The materials were characterized by UV/VIS spectroscopy and FT-IR spectroscopy. The results reveal that the urethane linkages undergo a scission reaction upon UV exposure drastically affecting the mechanical properties of the material. Furthermore, these urethane scissions produce a yellowing of the polyurethane which can inhibit its use where optical clarity in important.

Dairy and fruit juice bottles are a major source of post consumer recycled high density polyethylene (PCR HDPE). The recycled HDPE has limited post-consumer applications due to its poor stress crack resistance (SCR). This paper presents a review of a test method for SCR and some preliminary results of the development of recycled HDPE blends with improved SCR. The improvement has been achieved with the addition of a modifier, and results indicate that there is a potential to incorporate the use of recycled HDPE in non-pressure pipe applications. These customised blends have been tested for SCR according to the Notched Constant Ligament Stress (NCLS) test. The NCLS test is a new test method (ASTM F17.40) which is currently under development. The NCLS test will be used to determine the susceptibility of HDPE resins to slow crack growth (SCG) under a constant ligament stress in an accelerated environment. The results from the test will subsequently be correlated with field performance results.

Annually, the United Kingdom deposits around 20 million tonnes(1) and the United States around 2 billion tonnes(2) of waste into landfill. To protect the environment from the harmful effects of leachate from the waste, landfill sites are protected using a system of thermoplastic liners, typically made from polyethylene. Due to manufacturing limitations on the size of the lining sheets, welding is employed to join adjacent sheets at the landfill site. This paper reviews current welding practices, the industry approach to quality, and discusses the moves towards certification of welding personnel in order to raise standards across the industry.

The environmental stress cracking (ESC) behavior of some plastics is very well examined. Especially for polyethylene the mechanisms are nearly clear. For amorphous thermoplastics this mechanisms were examined in many researches, but are still not really clear. Especially for polycarbonat (PC) in contact with aqueous solutions systematic examinations of the ESC behavior are rare. In this paper examinations of the ESC behavior of PC in different aqueous solutions are presented. The tests were done by a medium-tensile-creep test. Different pH-values of water and a surfactant were examined about their influence on the ESC behavior. Also distinctive types of PC and their influence on the ESC behavior were examined. It is determined that the ESC of PC in contact with aqueous solutions is not only, like classical approach, controlled by physical effects. A large effect of chemical mechanism is also part of the failure mechanism.

Post-consumer plastic waste in Australia contains over 50,000 tonnes p.a. of HDPE blow moulded bottles, with half still ending up in landfill. Recycled milk-bottle grade HDPE is known to be too high in molecular weight for processing by injection molding. In this study, the target was to make injection-molded compositions with a content of the recycled material of 75% or higher by blending with commodity plastics. The results of rheological, thermal and mechanical studies of the blends are presented.

There has been increased interest in developing alternatives to phthalate plasticizers used in the processing of polyvinyl chloride (PVC). This paper describes research on modifying the composition of vegetables oils such as soybean oil for use as primary plasticizers for PVC. Advanced computational chemistry and modeling studies have been conducted to correlate structures of modified soybean oil with their compatibilities in PVC resin. The new soy oil derived plasticizers have excellent plasticizing efficiency with significantly reduced migration and volatility. Properties and performance of the new modified soy oil compositions as primary plasticizers in typical PVC formulations are summarized and compared to those of a standard phthalate PVC plasticizer.

Thermoset process scrap costs companies millions of dollars annually. Specific thermoplastics could benefit from the addition of recycled thermoset material. The incorporation of thermoset regrind into thermoplastic material would provide a viable alternative for the thermoset scrap that is currently sent to the landfills.

It is becoming common for long fiber-reinforced thermo-plastics (LFT) to replace existing GMT-type applications as well as to capture new applications. This is especially true in the European automotive industry, where the market for parts made from LFT is experiencing tremendous growth. The following paper discusses the available materials, the mechanical and physical properties, machine techniques and processing details of the LFT process. It will also discuss potential applications for LFT. The paper will cover different process techniques such as direct processing and make comparisons with other processes. An explanation on the effects that LFT has on properties and economics will be made. It will show how the economics can be improved by adding recycled material to the process. This paper will provide a better understanding of the LFT-process and how you could get benefits from this process.

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.

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.

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."

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.

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.

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 [1]. 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 [2]. 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 [5], 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 [8]. Measurements with the atomic force microscope (AFM) reveal strongly anisotropic friction properties that are correlated with the orientation of the conjugated polymer backbone orientation [9]. 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 [7]. This represents the first time that mechanochromism has been observed at the nanometer scale. Dramatic structural changes are associated with this mechanochromic tr

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.

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.

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.

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

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.