Blends of Styrene- Butadiene-Styrene Triblock Copolymer with Random Styrene-Maleic Anhydride Copolymers

Blends of styrene-butadiene-styrene triblock copolymer (SBS) with random styrene-maleic anhydride copolymers (PS-co-MA), having different MA content, were prepared in a Brabender Plastigraph mixer. The presence of polystyrene (PS) blocks in the SBS copolymer and the high styrene content (93 and 86 wt.-%, respectively) in the two kinds of used PS-co-MA samples afforded a good compatibility between the PS phases of the two polymers. On the other hand, the presence of polar anhydride groups allows a net improvement of the thermal properties of the polystyrene phase of the blends as shown by differential scanning calorimetry (DSC) analysis. In addition, the dynamic behavior of the blends, as highlighted by dynamic thermo-mechanical analysis (DMTA), shows in all cases a "stiffening" of the material in comparison to original SBS. Preliminary experiments aimed to convert, directly in the mixer, the anhydride groups into the corresponding zinc salt allowed only a partial neutralization. Both DSC and scanning electron microscopy (SEM) indicate that the reaction is not complete under the used experimental conditions.