Improvement of the Mechanical Properties and Creep Resistance of SBS Block Copolymers by Nanoclay Fillers Siljana Lietz, Jing-Lei Yang, Eva Bosch, Jan K. W. Sandler, Zhong Zhang, Volker Altsta ¨dt * Introduction Thermoplastic elastomers (TPEs) are characterized by remarkable mechanical (stiffness, strength, toughness, etc.) and haptic properties as well as by generally good processing characteristics similar to those of conventional thermoplastics. Among the TPEs, the polystyrene-block- polybutadiene-block-polystyrene triblock copolymer (SBS) has the greatest commercial relevance, reflected by about 50% of the worldwide consumption of all TPEs, due to its good performance level and low price compared to other common TPE grades. [1] Owing to the widely sepa- rated glass transition temperatures (T g ) of the constituent phases, SBS triblock copolymers provide a broad range of service temperatures. [2] Their significance concern- ing technical applications lies in the fact that, at room temperature, the flexible rubbery blocks (T g 80 8C) are anchored on both sides by glassy chain ends (T g  100 8C). Moreover, through variation of the molecular weight, composition, chain architecture and processing conditions, the phase separation behavior as well as the dimensions Full Paper SBS nanocomposites based on a SBS triblock copolymer containing different weight fractions of a commercial Cloisite 20A organoclay were prepared by melt-processing. Extensive electron microscopy as well as WAXS and static tensile and tensile creep tests were used to evaluate the resulting morphological and mechanical properties of the nanocomposites. The nano- composite morphology is characterized by a combination of intercalated and partly exfoliated clay platelets with occasional clay aggregates present at higher clay contents; nanocomposite features that are reflected by the results of both the static tensile as well as the tensile creep tests at room temperature. For this particular thermoplastic elastomer nano- composite system, well dispersed nanoclays lead to an enhanced stiffness and ductility; effects that induce promising improvements in nanocomposite creep performance. S. Lietz, E. Bosch, J. K. W. Sandler, V. Altsta ¨dt Polymer Engineering, University of Bayreuth, 95447 Bayreuth, Germany Fax: þ49 921 55 7473; E-mail: altstaedt@uni-bayreuth.de J.-L. Yang, Z. Zhang Institute for Composite Materials, University of Kaiserslautern, 67663 Kaiserslautern, Germany Z. Zhang National Center for Nanoscience and Technology of China, 100080 Beijing, China Macromol. Mater. Eng. 2007, 292, 23–32 ß 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/mame.200600280 23