Influence of melt processing induced orientation on the morphology and mechanical properties of poly(styrene-b-ethylene/butylene-b-styrene) block copolymers and their composites with graphite

• Orientation was induced during processing of SEBS, SEBS-MA and their composites.
• Static and dynamic mechanical tests in perpendicular directions were performed.
• 400–1600% difference in Young’s or storage modulus in function of orientation.
• Micro/nanoscale morphology and orientation investigated by POM, SEM and AFM.
• A method to improve the mechanical behavior by morphology control was proposed.

The effect of orientation induced during the manufacturing process on the self-assembled morphology and mechanical properties of poly(styrene-b-ethylene/butylene-b-styrene) block copolymer (SEBS), maleated SEBS (SEBS-MA) and their composites with graphite was examined in this paper. The roll milling process induced higher stiffness along the rolling direction, emphasized by the increase of Young’s modulus with 645% in this direction relative to the perpendicular one and the increase of storage modulus at room temperature with one order of magnitude. The addition of graphite particles diminished the anisotropy of static and dynamic mechanical properties but contributed to the increase of the total energy absorbed till break. The different self-assembled morphologies and degree of order observed by polarized optical microscopy (POM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) in SEBS and SEBS-MA explained some of the differences in their static and dynamic mechanical behavior. For the first time the anisotropy was emphasized by the different glass transition values obtained on the two stretching directions.