Also for high temperatures

The growth rates for thermoplastic elastomers (TPE) are, on average, about 6.2% worldwide. This indicates that TPEs are replacing other elastomeric materials in new fields or are being discovered as an innovative material to optimize the function and design of products and components. Above-average growth opportunities are being observed especially for TPE-V, that is, compounds with a chemically cross-linked elastomer phase. These are found traditionally in the automotive sector, with its demanding requirements regarding resistance of compounds to heat and oil. Here, there is a trend to encounter TPE-V in the well-established markets for rubber formulations based on EPDM, CR or HNBR and even ACM rubber. These so-called Super TPE-Vs are intended for use at service temperatures of up to 175℃ while retaining excellent oil resistance and can be viewed as predestined for applications in the engine compartment. For some time, Kraiburg TPE, Waldkraiburg/Germany, has been working on innovative compound formulations and production processes that, with improved long-term temperature resistance, would open up new opportunities to expand into new fields of application. With the aid of novel concepts to raise the service temperatures of styrene block copolymers, it was possible to create a new product class of thermoplastic elastomers specifically for use at elevated temperatures. This was the first step on the path to successful development of the Super-TPV. Selective chemical cross-linking The softening temperature of the styrene domains represents the Achilles heel of the temperature resistance of TPEs based on hydrated styrene block copolymers (HSBC). This cannot be raised further even by increasing the molecular weight of the HSBC employed. Numerous attempts to improve the temperature resistance of HSBC via subsequent cross-linking have failed, since all known cross-linking agents react only with the elastic middle block. This, however, only has an adverse effect on its elastic qualities. The softening temperature of the styrene domains that limits the temperature resistance is not affected. A way out of this dilemma is to incorporate during production of the HSBC via anionic polymerization a comonomer into the styrene end blocks that permits selective chemical cross-linking of the end blocks. As a consequence of this new approach, cross-linking of HSBC is accompanied for the first time by a noticeable increase in the stiffness of the end blocks. The results are the following benefits versus the usual HSBC: ● Because of the selective chemical cross-linking of the end blocks, the restoring force of the elastic phase is retained even beyond the glass-transition of the end blocks and ● the service temperature range shifts to considerably higher temperatures and is limited solely by the onset of melting of the polypropylene. Production of such novel, chemically crosslinked HSBC (TPES-V) is accomplished through dynamic vulcanization in a twin-screw extruder. The new TPES-V compounds from Kraiburg TPE are based on cross-linked SEPS in a PP matrix. By chemically cross-linking the modified poly-styrene (PS) end blocks, it is possible to improve the strength of the PS domains significantly. The result is outstanding thermal stability and excellent hysteresis behavior combined with unusually little loss of sealing force when testing the compressive stress relaxation as well as unusually low long-term compression set at high temperatures. The new family of materials is especially well-suited for demanding applications that require a high level of weatherability and design flexibility. This makes the material extremely suitable for a multitude of applications in the automotive sector and industry in general, e. g. grommets for hose and cable feed-through openings, air ducts, cable clamps, seals, window encapsulation, housing gaskets, vibration-absorbing eladidas superstar damen glitzer silber