A new type of visco-plastic flow curve observed in certain concentrated diblock copolymer solutions

Abstract

A diblock copolymer of styrene and isoprene (hydrogenated) is dissolved in CH/CI2 n-paraffins and o-xylene (or cyclohexane) mixtures./Ma unusual type of flow curve is obtained in certain ranges of composition and under certain conditions of preparation. With increasing shear rates, the flow curve is first of the Bingham type, followed by a sudden shear thickening at almost discrete rate of shear and then by a second branch of almost linear increase. Time independent.and reproducible behaviour can be achieved. A linear model is proposed and the possible molecular arrangement that corresponds to this model is discussed.