Metallocene polyolefins and their blends

Commercial copolymers of 1-octene and ethylene: metallocene catalyzed (mLLDPE) and Ziegler-Natta catalyzed (znLLDPE), a low density polyethylene (LDPE), and high density polyethylene (HDPE), were characterized with respect to branching, crystallization behaviour and dynamic-mechanical properties. It was found that the crystallinity of the polymers is more influenced by the homogeneity of the short-chain branching than by its content. The study of blends of mLLDPE and znLLDPE with LDPE and HDPE showed that the interaction between mLLDPE and LDPE is stronger than between znLLDPE and LDPE. Blends containing mLLDPE showed a composition depending improvement of the storage modulus G' which was not observed in znLLDPE/LDPE blends. The HPDE blends followed a linear mixing rule. Co-crystallization was found mLLDPE/LDPE and partially in znLLDPE/LDPE and znLLDPE/HDPE blends, respectively.