Abstract: In this paper, the induction effect of the interface between the third phase(such as the substrates, the foreign substances) and polymer blend system on the formation of the gradient morphology in polymer blend was studied. It was found that all the third phases(such as the substrates, the inserted films, the set foreign particles in this case) could lead to the formation of the gradient morphology in PP/EVAc blends by annealing. In other words, the particle size and the content of the EVAc dispersed phase gradually increased from the bulk to the interface between the third phase and the polymer blend system. When the two PIfilms were inserted into the blend system, the effect of the distance between the two inserted PIfilms on the morphology of LDPE/EVAc blend was also investigated. It was found that the interfaceinduced gradient structures began to overlap when the distance of the two inserted films was less than two times of the expectant formed thickness of the gradient morphology for the case of the individual PIfilm inserted. If the distance of the two films was smaller, all the droplets of the dispersed phase fastly grew simultaneously instead of forming the gradient morphology. It should be caused by the mutual interference of the induction effect of the interface between the two PIfilms and the blend system. This corresponds to the case of the dispersed droplet coarsening process under 2-dimentional conditions in polymer blend systems. All the results above supported the conclusion we presented in our previous paper, i.e., the existence of interface between the third phase and the polymer blend greatly accelerated the coarsening process of the droplets in the polymer blend.

Key words: Polypropylene, Polyethylene, Ethyl vinyl acetate copolymer, Coarsening, Interface induction, Gradient morphology