Comparative studies of ethylene–α-olefin copolymers by thermal fractionations and temperature-dependent crystallinity measurements

In this work the crystallization behavior and thermal fractionation results of various ethylene–α-olefin copolymers (1-butene, 1-hexene, 1-octene, 1-tetradecene, 1-hexadecene, 1-octadecene, vinylcyclohexane as comonomer) were evaluated using differential scanning calorimetry (DSC). The step crystallization (SC) method was compared with the successive self-nucleation/annealing (SSA) method. SSA exhibited better separation than SC, especially in the low temperature regions, and provided results in a shorter time. The temperature-dependent crystallinities confirmed that for all more branched polymers a lot of material is present at ambient and can crystallize below that temperature. Significant differences in the temperature-dependent crystallinity curves existed between ZN- and metallocene-catalyzed copolymers at the same comonomer level (and comonomer type).