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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Electrochemical Degradation of a Cooling System Component
Cracking and subsequent leakage occurred within a high power rectifier cooling system component. The leakage was observed after four years of rectifier service. The cracking was found at the bend of an elbow connector that joined two hoses. The investigation focused on the determination of the nature and cause of the failure. The results obtained during the evaluation indicated that the cracking was due to electrochemical polymer attack, which occurred as a consequence of an electrical potential present in the cooling system. This paper will focus on the testing used to characterize the failure mode and identify the cause of the cracking, thereby illustrating the failure analysis process.
Fractographic Characterization of Polycarbonate Failure Modes
Polycarbonate is an important plastic molding resin used to fabricate many engineered components. Because of its widespread usage, many different types of failures can result from various service conditions. Evaluating these failures through a systematic analysis program allows an assessment of how and why the parts failed. An essential portion of the failure analysis process is the fractographic examination, which provides information about the crack origin location, and the crack initiation and extension modes. The focus of this investigation was to characterize the surfaces of intentionally cracked laboratory samples in order to gain a more thorough understanding of polycarbonate fracture mechanisms. This paper will document some of the key fracture features associated with various polycarbonate failure modes.
Gas Moulding Problems
Injection of high pressure gas to assist moulding has developed quickly in the last decade, but there are problems in the technique. Foam moulded office chair arms are expensive and timeconsuming to make, while gas moulding appears to offer substantial saving in material costs and lowered cycle time. The case study shows how the project failed to address serious objections of structural integrity and process control, and so resulted in litigation. The case turned on demonstration samples, which on X-ray inspection, proved to be flawed internally. The case was resolved by negotiation before trial, with both parties compromising on costs and so saving goodwill.
Extension Ladder Failures
Accidents involving falls from a height are a common cause of death and serious injury in developed countries, coming second only to automobile accidents. One of our case studies shows how failure of one of the plastic tips fitted to an extension ladder misled the user into believing that the failure had caused the accident. However, examination of the trace evidence left showed that the tip fractured during the fall and did not cause the accident at all. The ladder had been leant at well below the recommended angle of 75°, practical reconstruction showing that the accident was probably caused by sideways movement by the user while at the top. It made the ladder unstable, and the tips slid down the wall by a stick-slip mechanism. The second case shows however, that accidents can be caused by poor maintenance of the elastomeric feet. Wear allowed them to swivel back into the aluminium stiles when erected, lowering the coefficient of friction with the floor. The severely injured workman was awarded substantial compensation.
Failure Analysis of Hinges: Application of Root Cause Analysis
Plastic hinges experience different types of stresses and end-use conditions that could lead to their failure. Root cause analysis (RCA) was used to investigate three different cases of the failure of hinges. An illustrative description of each case is stated followed by the suggestion of the potential causes and the investigation of the most probable cause(s). Some of the used investigation tools were macroscopy and finite element analysis (FEA). In these cases, the effects of the four common causes of failure (part design, material choice, processing factors, and end use) are discussed. Finally, some corrective actions are recommended to avoid future failures.
Materials and Processes Used in the Wright Brothers' Gliders and Flyer, 1900-1903
The first successful powered, controlled flights by Orville and Wilbur Wright in December 1903 were preceded by many designs and pre-flight experiments. Construction of their three gliders and the successful airplane followed a careful sequence of lessons learned from each trial. This paper discusses how they used many natural polymers and composites very effectively, to make aircraft built for impact resilience as much as for strength. Their testing of airfoils and the design of their propeller were major advances in aerodynamics. Their wise use of materials and assembly processes as well as their persevering innovations are a stimulation to present generations.
Novel Thermoplastic Elastomer Resulting from Physical Gelation of Telechelically Labeled Polydimethylsiloxane
Polydimethylsiloxane (PDMS) that has been labeled on both chain ends with a pyrene-based dye yields a novel thermoplastic elastomer. This behavior is due to thermoreversible physical gelation in the bulk state associated with nanocrystal formation of the pyrene dyes that are strongly insoluble in the PDMS. The gelation temperature, which is equal to the nanocrystal melting temperature, can be tuned by varying the PDMS molecular weight. At the nanocrystal melting temperature, a greater than three order of magnitude change in the value of tan ? is observed from oscillatory shear flow measurements. Significant hysteresis is observed upon heating and cooling due to the time needed to achieve equilibrium nanocrystal formation.
150°C Heat- and Oil-Resistant TPVs- Long-Term Fluid and Spike Temperature Comparison
New families of thermoplastic vulcanizates (TPVs) were commercially introduced in early 2003 offering 150°C heat and oil resistance in excess of 3000hrs. These TPVs are based on a continuous phase polyamide thermoplastic matrix and dynamically vulcanized polyacrylate (ACM) elastomer. Applications have a broad interest from underhood automotive to industrial applications.The heat and oil resistance of a commercialized TPV from this family will be compared at 150°C to conventional and silicone-based TPVs in addition to an ethylene-acrylate (AEM) thermoset elastomer, all of similar initial physical properties. Degradation after 175°C spike temperature exposure to air and an assortment of automotive fluids will also be compared. Finally, an overall comparison will be made to qualitatively measure the equivalency of these materials in manufacturing and end use application.
High Performance Thermoplastic Vulcanizates (TPVs) for Long Term High Temperature Application
New thermoplastic vulcanizates (TPVs) based on Hydrogenated Styrene Block Copolymer (HSBC) have been developed for long term high temperature applications. A comparative study using these new TPVs and conventional TPVs (Polypropylene(PP)/EPDM rubber) was performed. Standard factorial designs were used to evaluate material performance. The material characteristics under investigation were rheological properties, dynamic mechanical properties, tensile properties and morphology. These new TPV compounds showed increased solvent resistance and elastic recovery of approximately 20%, respectively relative to conventional TPVs.
A New TPV Technology Bringing Unique Features to the Market
A new TPV (EPDM/PP) product line has been commercialized by DSM Thermoplastic Elastomers. The new product line is based on a patented combination of a vulcanization system and compounding technology (WO 03068859) and is available in the Shore A 30 to 80 hardness ranges. It combines easy processing with excellent aesthetic appearance and a dry rubbery feel of the final products. The product line eliminates the gap between TPVs and SEBS compounds with respect to colorability and viscosity .Already, applications have been commercialized in the consumer market and in the automotive interior market in the EurAsia region.
Dynamically Vulcanized PP/EPDM Blends: Effects of Multifunctional Peroxides as Crosslinking Agents
Thermoplastic vulcanizates (TPVs) or dynamic vulcanizates are a special class of thermoplastic elastomers, produced by mixing and crosslinking of a rubber and a thermoplastic polymer simultaneously. In a previous study it was demonstrated that the use of dicumyl peroxide in combination with triallyl cyanurate as crosslinking agents provide a good overall balance of physical properties of PP/EPDM TPVs. Commonly used peroxides like dicumyl peroxide generally produce volatile decomposition products, which sometimes provide a typical smell or show a blooming effect. In this paper multifunctional peroxides are described, which reduce the above-mentioned problems. They consist of a peroxide and co-agent-functionality combined in a single molecule. The multifunctional peroxides provide properties of TPVs, which are comparable with commonly employed co-agent assisted peroxides. The solubility and kinetic aspects of the various peroxides are highlighted, as well as the decomposition products of the multifunctional peroxides with respect to the avoidance of smelly by-products. Particularly 2,4-diallyoxy-6-tertbutylperoxy- 1,3,5-triazine turns out for be a very good alternative to the dicumyl peroxide/triallyl cyanurate combination.
Novel Propylene-Based Specialty Elastomers - Structure and Properties
ExxonMobil Chemical has introduced a family of Specialty Polyolefin Elastomers, a novel type of polyolefin with isotactic propylene crystallinity, under the trade name Vistamaxx™. These polymers contain a predominant amount of propylene (>80%) with isotactic crystallinity, the balance being ethylene and other ?- olefins. These elastomers are highly elastic, with excellent recovery from deformation even without vulcanization. These elastomers, unlike the related EPR polymers, share the processability of conventional plastics such as polyethylene and isotactic polypropylene and can, thus, be easily formed into articles such as films, fibers and nonwoven fabrics, which are highly elastic, using conventional plastic processing processes. In this paper, we discuss the details of the structure-property relationships in these polymers and emphasize the factors leading to the elastic character of these elastomers.
Novel Specialty Polyolefin Elastomers - Structure, Defects and Miscibility
ExxonMobil Chemical has introduced a family of Specialty Polyolefin Elastomers, a novel type of polyolefin with isotactic propylene crystallinity. These polymers contain a predominant amount of propylene (>80%) with isotactic crystallinity, the balance being ethylene and other ?-olefins. Unlike the closely related EPR polymers, these polymers share the processibility of isotactic polypropylene and can thus be formed into fabricated articles using conventional processing equipment. In this paper we show SP elastomers combine an unusual and unexpected degree of elongation and elastic recovery without the need for crosslinking. These properties mimic those of crosslinked elastomers. We also show that the properties arise from the uniform introduction of small levels of crystallinity meso propylene residues.
TPV Laser Print Materials
Laser marking technology provides an alternative and effective route for printing on TPVs (Thermoplastic Vulcanizates). Natural color TPV materials containing laser sensitive additives can be easily laser marked using common Nd:YAG laser systems through a process and effect known as Color Change. Current black TPVs, however, have proven to be very difficult to laser mark, even with laser marking additives. Manufacturers have no choice other than to use pad printing techniques or some form of adhesive stickers to label their products. Recently introduced laser printable black grade offers all the benefits of current TPVs. This new grade can provide a high print definition and good contrast (yellow/tan on black) mark that is highly durable under a variety of environments.
Elastomeric Property Characterization of Thermoplastic Elastomers
The elastomeric properties of polyolefin thermoplastic vulcanizates (TPV) have been characterized by compression set, recoverable strain after hysteresis, and thermal scanning stress relaxation (TSSR) analysis. Unlike a thermoset rubber, a TPV is a two-phase system with highly crosslinked fine rubber particles dispersed in a thermoplastic matrix. Compression set, which was originally designed to characterize the elastomeric properties of a thermoset rubber, does not truly characterize the unique elastomeric properties for a TPV. Compression set for a TPV is not only highly dependent on the crosslinking density and structure, but also very sensitive to the orientation of the two phases in the TPV. For the same TPV with a fully crosslinked rubber phase, the compression set value can vary substantially depending on sample preparation and thermal history. Elastomeric properties can be better characterized by the recoverable strain after hysteresis and TSSR stress-temperature curve. The thermal-mechanical properties or stress relaxation behaviors provides more useful information for designing and producing all-thermoplastic parts, such as automotive seals, from TPV.
Characterization of a Poly(Ether-Block-Amide) Copolymer and its Significance for Polymer Processing Operations
Thermal and rheological properties of a poly(etherblock- amide) copolymer were characterized by means of differential scanning calorimetry (DSC) and dynamic rheological approaches. Based on the calorimetric and rheometric data, the microphase separation transition (MST) was studied, showing that upon heating the copolymer solid could be transformed into three different states: restructured solid, structured melt, and homogeneous melt. The driving force for the conversion among the three states is primarily due to crystal re-organization, crystallization, and melting. It is also found that different crystal structures in the solid state could be introduced by changing the conditions of cooling from a homogeneous molten state. The existence of a wide MST range and the conversion of the states imply a variety of proper process windows for various polymer processing operations. This knowledge is essential for understanding the processes and further assisting in rational process development.
"Hidden" Innovations in the Development and Commercialization of LLDPE
Technology revolutions sometimes span such a long timeline of business realization that critical innovations along the way can become lost or hidden in commonplace commercial acceptance. An essential understanding or supporting technical advance developed at just the right time and which contributed important value to business success can go under-appreciated or even unrecognized.The development and commercialization of LLDPE created new catalyst, process, and product technologies and seeded the emergence of new, world scale competitors in the polyolefins industry. It was a revolutionary development.This paper describes market facing technology innovations that were instrumental to LLDPE business success. These developments have helped set the stage for another burst of innovation in the ongoing development and commercialization of metallocene and other single-site catalyzed polyolefins.The polymer molecular design capabilities of the new single-site catalysis have created whole new families of polyolefins and has launched a new technology revolution for our industry. This product revolution builds upon and extends some of the innovations from Z/N LLDPE commercialization.
Relationship between Mould Temperature and Properties of Injection-Moulded Pure and Beta Nucleated Polypropylenes
An influence of the mould temperature (MT) on structure and properties of the samples injection-moulded from pure and ? nucleated isotactic polypropylene (?-iPP) was investigated. Pure and 0,03 wt. % of nucleating agent NJ Star NU-100 doped iPP was isothermally solidified in the range of mould temperature 40-120 °C. Polymorphic composition studied by means of wide-angle X-ray scattering did not show significant sensitivity to MT. On the contrary, moulding temperature notably influenced mechanical behaviour of both pure and ?-iPP samples.
Graphite Platelet/Nylon Nanocomposites
Natural crystalline graphite based graphite intercalated compounds [GICs] were exfoliated into sub-micron graphite flakes. Graphite nanocomposites were fabricated by combining the exfoliated graphite flakes with nylon66 resin. The mechanical properties of these composites showed considerably higher modulus than those of composites made with commercially available carbon reinforcing materials (i.e. CF VGCF and Carbon Black). Also the electrical property was improved by adopting appropriate fabrication conditions.
Carbon Fiber Tie Rods for Heavy-Duty Truck Applications
A joint effort between Delphi Corporation Hendrickson International and Oak Ridge National Laboratory has led to the development of carbon fiber reinforced polymeric tie rod for use in heavy-duty truck suspension systems. The composite tie rod tube assembly is 65% lighter than current metal tubes with equivalent or improved performance. This paper will summarize the design and test methodology which have led to successful implementation of this product for heavy truck applications.
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