JOURNAL OF POLYMER ENGINEERING

 Vol. 23, No. 3, 2003, page 177

MICROMECHANICAL STUDIES OF STYRENE/BUTADIENE BLOCK COPOLYMER BLENDS

¹R. Adhikari, ¹G. H. Michler, ²M. E. Cagiao and  ²F. J. Baltá-Calleja

¹Department of Engineering, Institute of Materials Science

Martin-Luther-Universität Halle-Wittenberg,   D-06099 Halle/Saale, Germany

²Department of Macromolecular Physics,Instituto de Estructura de la Materia, CSIC, Serrano 119, 28006 Madrid, Spain

 ABSTRACT

      The microhardness behavior of binary blends comprising a star block and a triblock copolymer, both consisting of polystyrene (PB) and polybutadiene (PB), was investigated over a wide composition range. In particular, a correlation between the microhardness H, the yield stress s_y and the Young’s modulus E was examined. The hardness was found to correlate with the mechanical parameters obtained by uniaxial tensile testing as follows: H/s_y ~ 2 and E/H ~ 30. In agreement with the studies performed in case of the pure microphase separated block copolymers, the microhardness behavior was found to be strongly dependent on the morphology of the blends. The glass transition temperature of the hard phase (T_g-PS) is shown to remain nearly constant in the blends with lower LN4 content. The glass transition temperature of the soft phase (T_g-PB), which varies with blend composition, is not related to the microhardness variation in the blends.

Keywords: Styrene/butadiene block copolymer blends, amorphous polymers, morphology, micromechanical properties, microhardness, electron microscopy

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