**1. Introduction**

346 Thermoplastic Elastomers

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Vol.26, No.5, pp. 384-392, ISSN: 0266-1144.

Vol.83, No.3, pp. 383-388, ISSN: 0141-3910.

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Thermoplastic elastomers (TPE) and, in particular thermoplastic vulcanizates (TPV), are a new class of materials, combining the properties of conventional elastomers (rubber) and the processibility of thermoplastics. Compared with conventional rubber elastomers, these materials can be more easily processed and more easily recycled. TPE are often used to replace conventional thermoset rubber, but those are also used for a great variety of new applications and products, particularly in hard/soft combinations with other thermoplastics. Due to the advantages over conventional thermoset rubber, the commercial uses for thermoplastic elastomers are growing rapidly (Schäfer, 2001; Bittmann, 2004).

Beside many advantages, some disadvantages do exist, also. In comparison to chemically crosslinked elastomers (e.g., EPDM or natural rubber), TPE materials have stronger limitations with respect to upper service temperature, which is caused by softening or melting of the hard phase. Furthermore, TPE exhibit higher creep and stress relaxation, than thermoset rubber, even at ambient temperatures (Holden et al., 2004). Thus, new demands on polymer testing arise from the assessment of thermoplastic elastomers (TPE) with respect to their rubber elastic use properties and stress relaxation behaviour, particularly at elevated temperatures.

Due to the complex molecular structure and phase morphology of TPE, traditional test methods normally used for characterization of elastomers give only limited information about the unique properties of TPE. For this reason, temperature scanning stress relaxation (TSSR) test method has been developed, recently (Vennemann et al., 2001, 2003). In this work, the basic principle of the TSSR test method as well as the theoretical background will be described. Furthermore, an overview of numerous results obtained from selected TPE materials, will be presented to demonstrate the versatility of the TSSR method. In addition, further development of the method will be presented, in particular for rapid determination of crosslink density of TPV.
