Effect of composition on the properties of SEBS modified asphalts

We characterised, from both a morphological and a rheological point of view, polymer modified asphalts prepared by the addition of styrene–(ethylene-co-butylene)–styrene block copolymer to a soft base asphalt. It was found that, even if the two components showed poor compatibility and interfacial adhesion, storage-stable mixtures could be obtained if the polymer content was maintained below about 4 wt%, with respect to the total mass. In this case, the more polar part of asphalt stabilises the dispersed polymer-rich domains, which act similarly to a filler and do not change significantly the viscoelastic behaviour of the base asphalt. On the contrary, at higher polymer concentrations, a swelled polymer-rich phase creates a network that strongly influences the viscoelastic properties. In this case the material becomes unstable and tends to give macroscopic phase separation if stored at high temperature without stirring.