Miscibility and phase structure of at-polypropylene/ethylene-block-(ethylene-co-butylene)-block-ethylene-copolymer blend

Miscibility and phase structure in blends of atactic-polypropylene (aPP) with poly[ethylene-b-(ethylene-co-butylene)-b-ethylene] (E-b-EB-b-E) containing different butylene content in the mid-block were investigated by differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and field emission type scanning electron microscopy (FE-SEM). In DSC measurement, blends showed single glass transition temperature in no relation to the blend composition and the butylene contents of mid-block in the block copolymers. On the other hand, the melting point of PE block in the block copolymers was not varied systematically with variation of the blend composition with no relation to the butylene content. From these results, it is assumed that aPP dissolves in the EB block in the copolymers. In morphological observation, it was revealed that all blends have the islands–sea structures containing PE domain. In the blends using the high butylene content copolymer, it was observed that PE domain became smaller than that of neat block copolymer. On the other hand, in the lower butylene content copolymer, the microphase structure was not observed but fine dispersed phase separated structures were observed in the blends of aPP and the copolymer.