<正>Evolution and fractal character of the phase morphology of high impact polystyrene/poly（cis-butadiene） rubber （HIPS/PcBR） blends during melting and mixing were investigated using scanning electron microscopy （SEM）. The characteristic length L was defined as the size of particles of the dispersed phase in blends. Different fractal dimensions

Df and Dm

were introduced to study the distribution width of phase dimensions in the dimensionless region and the uniformity of the spatial distribution of particles

respectively. The results showed that the average characteristic length Lm and Df increase as the volume fraction of the dispersed phase increases

when the volume fraction of the dispersed phase is lower than 50%. In other words

the size of particles increases and their distribution in the dimensionless region becomes more uniform. Meanwhile

the uniformity of the spatial distribution becomes more perfect as the volume fraction increases. At a certain composition

Lm decreases in the initial stage of the mixing and levels off in the late stage. In the initial stage

Df becomes large rapidly with the process of blending

which means that the distribution of L in the dimensionless region becomes more uniform. Meanwhile

the spatial distribution tends to be ideal rapidly in the early stage and fluctuates in a definite range in the late stage of the mixing.