Effect of branch content on the transition of crystalline structure and morphology of metallocene-catalyzed branched polyethylene

Transition of crystalline structure and morphology of metallocene-catalyzed butyl branched polyethylene with branch content has been studied. It was f ound that the long periods of the branched polyethylene were controlled by crystallization conditions for the lower branch content samples and by bran ch contents for the higher branch content samples. When the branch content increased to a critical value the branched polyethylene had no long period because the crystalline morphology was changed from folded chain crystal to a bundled crystal. The TEM observations supported the results. The transit ion of the crystalline morphology resulted from the reduction of lamellar t hickness with increasing of branch content since the branches were rejected from the lattice. The reduction of lamellar thickness with increasing of b ranch content also resulted in lattice expansion and decrease of melt tempe rature of the branched polyethylene. (C) 2001 Kluwer Academic Publishers.