Evolution of phase dimensions and interfacial morphology of polypropylene/polystyrene compatibilized blends during mixing

The morphology development of polypropylene/polystyrene (PP/PS) blends was studied by means of effective mathematics methods. Time resolved fracture morphology measurements on PP/PS (20/80) blends compatibilized with styrene–butadiene–styrene block copolymer (SBS) suggested that PP/SBS domains acted as a warehouse supplying compatibilizer (SBS) to the phase boundary in the initial stage of mixing and promoted the formation and development of the transition layer. The development of the transition layer leaded to a more complicated morphology of fracture surface and strengthened the adhesion between phases, which was quantitatively investigated using Brown fractal dimension DBrown. In the early stage of the mixing (<2.0 min), the mean chord length Λm used to describe the domain size decreased; simultaneously, the distribution of Λ trended to uniform as the mixing proceeded. After 2.0 min, Λm fluctuated in a definite range. Further, a normalized distribution of dimensionless domain sizes Λ/Λm was independent of mixing time, indicating that the late stage of phase dispersion can be scaled with a time-depended single length parameter Λm. In other words, the morphology development shows a possible dynamic scaling behavior.