Morphology maps of binary blends of copolymers produced using the metallocene catalyst process

Abstract

Three lightly branched commercial polyethylene copolymers, produced using the metallocene catalyst process, were blended together in binary pairs. Two of the materials were ethylene–butene copolymers of differing butene content, the third was an ethylene–hexene copolymer with the same branch content as the more lightly branched ethylene–butene material. Note that the components of one system differ in both branch type and branch content; those of another, in branch content but not branch type; and those of the third in branch type only. Morphology maps were produced for all three systems. Where the two components had the same branch content, only one crystal type was seen on quenching melts of all compositions from all temperatures. Where the branch contents varied, two crystal types were seen when blends of some compositions were quenched from some temperatures, and the morphology maps resembled those found when copolymers produced by traditional methods are blended—or when a linear polyethylene is blended with a lightly branched copolymer. These findings confirm the view that it is the branch content of the copolymers that effects the morphology most strongly, the branch type is of secondary importance.