Blends of homogeneous ethylene-octene copolymers

Blends of ethylene-octene copolymers prepared by Dow's INSITE(TM) constrained geometry catalyst and process technology were characterized. (INSITE(TM) is a trademark of The Dow Chemical Company.) A previously described classification scheme based on density, or comonomer content, was the basis for the choice of blend components. The blends combined a low density Type I copolymer (0.865 g cm(-2)) with a higher density copolymer. The second component was either another Type I copolymer (0.887 g cm(-3)), a Type II copolymer (0.901 g cm(-3)), or a Type III copolymer (0.913 g cm(-3)). The melting and crystallization behaviour suggested that the components crystallized separately in all the blends. However, dynamic mechanical analysis indicated that the noncrystalline portions of the Type I blends formed a single phase, whereas the noncrystalline regions of blends with the Type II or Type III copolymer appeared to be phase separated in the solid state. The stress-strain behaviour at ambient temperature correlated with density, or total crystallinity, regardless of whether the material was a copolymer or a blend. (C) 1997 Elsevier Science Ltd.