Study on rheological behavior of polystyrene‐polyisoprene‐polystyrene around viscous flow transformation: Effect of polystyrene block content and molecular weight

Abstract

The flow behavior of triblock copolymer polystyrene‐polyisoprene‐polystyrene (SIS) was different below and above the viscous flow transition temperature (Tf). The study investigated the relationship between molecular structure (molecular weight and polystyrene block content) and the macroscopic rheological properties of SIS melt around Tf via capillary rheometer. The results indicated that below the Tf, shear viscosity of SIS melt was controlled by the polystyrene (PS) block content. On the other hand, above the Tf, shear viscosity was controlled by molecular weight. The rheological phenomena were explained based on the state change of the PS domains below and above Tf. The effect of PS block content on the viscous flow activation energy (Eη) and pressure drop of SIS melt was also investigated.