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RAILWAY PADS TAKE A HELLUVA BEATING
Railroad pads are energy-absorbing cushions used to protect the integrity of railway track systems by attenuating strain before it reaches the tie. They also electrically isolate the rail, needed for signalling purposes. Placed between the steel rail and concrete railroad tie, the pads must absorb impacts and compressive loads as each wheel of passing trains moves over the top of the pad and tie. With a predicted life of 20 years when used as railway pads, Arnitel thermoplastic copolyester elastomers (TPEs) from DSM Engineering Plastics offer better load-bearing capacity than rubber, better abrasion resistance, and the fabrication advantages of injection-moulded or extruded thermoplastics over thermoset rubber moulding. Pads made from competitive materials can fail early due to a loss of creep resistance from load, resulting in expensive replacement or maintenance. With consistent performance from -55 to 150C and the longest lifetime to failure vs. other TPEs - important owing to the expense and time required for replacing pads - Arnitel-TPE pads are especially effective at extending the length of continuous use performance and reducing system costs. All Arnitel-TPE grades being used for railroad pads include EM400, PM581 (excellent for heavy freight applications), and PL380 and PL460 (intended for high-speed, low-load passenger train applications). All are ultraviolet energy (UV)-resistant, resistant to hydrolysis, and chemical and fungus-resistant. “Arnitel is especially conducive to fine-tuning through a wide choice of grades and formulations,” said Andre Oosterlaken, Application Development Manager. “Higher loads generally demand harder grades, while areas where noise attenuation is important require different compounding. Arnitel TPE lends itself to a wide range of train speeds and masses, railway design norms and specifications, and localised performance needs. Plus, Arnitel TPE uniformly offers reduced system costs.” When used in railroad pads, Arnitel TPE exhibits outstanding creep resistance, cyclic compression fatigue behaviour, and hydrocarbon and environmental resistance. Arnitel TPE can be extruded or moulded, adding processing flexibility to its benefits. Arnitel TPE from DSM Engineering Plastics is a family of thermoplastic copolyester elastomers (TEEE or COPE) that combine the strength and processing characteristics of engineering plastics with the performance of thermoset elastomers. As thermoplastics, they do not require vulcanisation to obtain optimal qualities, which often leads to substantial part cost reduction. Relative to other elastomers, Arnitel TPE copolyester-based materials offer the most consistent performance over their entire operating temperature range, since their properties vary little from low to high-temperature extremes. In addition to railroad pads, Arnitel TPE has a broad range of applications, including automotive air ducts, constant-velocity (CV) joint boots, airbag covers, radio antennas, and fuel and vacuum hosing; building roofing membranes; surgical disposables; wire and cable insulation; hydraulic hoses; and household goods.
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