Toughness of two pure block copolymer blends in high molecular weight polystyrene

Abstract Blends of two commercial pure block copolymers, Phillips KRO-1 and KRO-3 Resins, in high molecular weight PS were prepared by solvent casting techniques to produce composite spherical particles with two different morphologies in a majority phase of the high molecular weight PS. One type of particle had the typical KRO-1 Resin morphology of randomly wavy and often interconnected PB rods in a topologically continuous block copolymer phase of PS, while the other type of particle made of KRO-3 Resin was in the form of concentric shells of alternating layers of PB and PS block copolymer phases. Both blends were found to result in only a marginal improvement of the toughness of homo PS even for particle volume fractions as high as 0.22. This inadequate performance in the case of the KRO-1 Resin blends results from the relatively large stiffness of the KRO-1 particles, while in the case of the KRO-3 Resin blend, it results from too small an average particle size, even though the particle stiffness in the latter case is low.