Morphological development with time for immiscible polymer blends with an in situ compatibilizer under controlled shear conditions

Abstract

We have studied morphological development with time under controlled shear condition for 75/25 wt/wt poly(butylene terephthalate) (PBT) and polystyrene (PS) blend having various amounts of poly(styrene- ran-glycidyl methacrylate) (PS-GMA) as an in situ compatibilizer prepared by solution blending method. The morphology of the blend without PS-GMA develops via a coarsening process during an annealing at higher temperatures. However, the dispersed domain size of the blend with PS-GMA increases slowly at an early stage of annealing, and then levels off. This is due to the in situ formation of graft copolymers at the interface. As the initial amount of PS-GMA in the blend increases, enough of the copolymers for the dispersed domain size in the blend to be levelled off are formed at shorter times. An oscillatory shearing with the frequency range 0.5–10 rad s −1 can induce the coalescence of the dispersed domain in the blend without PS-GMA. However, for the blend with PS-GMA the shear-induced coalescence of the dispersed domain is successfully suppressed by the graft copolymers formed in situ at the interface. The time evolutions of shear storage modulus ( G′) and complex viscosity ( η*) for blends with PS-GMA are strongly affected by the blend morphology which in turn depends on the initial amount of PS-GMA in the blend.