TPE manufacturers have been trying all along to find ways of catching up with the performance of classic elastomers in their products. Although there have been a few successes with thermoplastic copolyester elastomers (TPCs) and thermoplastic polyamide elastomers (TPAs), it has not previously been possible to find a “universal super-TPE” that could match the properties of elastomers or rubbers. This is mainly due to the wide variety of typical applications in the field.
“To close the performance gap between established TPEs and elastomers, particularly in relation to thermal resistance, we are therefore taking an approach that focuses rigorously on applications and customers,” explains Dirk Butschkau, Head of Business Development EMEA at Kraiburg TPE. “For example, we select the proportions of elastomers and thermoplastics in each compound on the basis of their specific compatibility and suitability for the required application temperature, chemical resistance and mechanical performance.”
The result is a “custom-engineered” TEH compound with a completely crosslinked elastomer component – which in contrast to conventional elastomer mixtures can be processed just as economically for injection molders of technical thermoplastics. The finishing that is usually necessary with most rubbers is not necessary and even sophisticated two-component applications with PP, PBT or PA can be implemented without bonding agents.
The new technology platform provides advanced TPE materials with a hardness range of 55 to 80 Shore A, with significantly improved performance based on different combinations of elastomers and thermoplastics. Along with excellent mechanical properties, the materials provide continuous operating temperatures up to 150°C and outstanding chemical resistance to oils, greases, lubricants and fuels. In addition, they remain completely recyclable, as the material is not crosslinked during the production of moldings from TEH.
The thermoplastic workability of TEH compounds can reduce the cycle time at comparable wall thicknesses by up to 80% in comparison with rubbers. This means they provide not only an extremely cost-effective alternative but also a wide range of possible new applications. The processing and characteristics profile are aimed particularly at parts of engine covers, oil sumps, fuel filler caps and oil caps, as well as cooling and/or temperature control units.
Additional examples are noise-absorbent and vibration-absorbent components in gearboxes, engines and pumps, and also includes connectors, screwed cable glands and fasteners. Initial successes include a component that is used in the lubrication circuit of a two-liter diesel engine, in permanent contact with the engine oil and exposed to considerable amounts of diesel and blow-by gases during driving with a cold engine.
Following an extensive development phase and various basic research investigations, Kraiburg TPE sees tremendous potential for further expansion of this new technology. “We are currently testing the use of butyl rubbers to improve barrier properties and we’re following various approaches to achieve softer TEH ratings below 50 Shore A,” says Butschkau.