Short chain branching distributions of metallocene-based ethylene copolymers

The short chain branching distribution (SCBD) of six metallocene-based ethylene copolymers was evaluated by preparative temperature rising eluting fractionation and by differential scanning calorimetry (DSC) after stepwise isothermal treatment of the samples at different temperatures. It is found that the SCBD of ethylene copolymers varies with the density of the copolymers and the type of the comonomer. Both samples with narrow SCBD and samples with broad SCBD can be prepared by the same metallocene catalyst. The lamellar thickness distributions of the samples were also obtained by fitting the DSC melting traces. The reasons that lead to broad SCBD of metallocene-based LLDPE were also discussed.