Improved thermal fractionation technique for chain structure analysis of ethylene/alpha-olefin copolymers

In this report, we describe an improved thermal fractionation technique use d to characterize the polydispersity of crystalline ethylene sequence lengt h (CESL) of ethylene/alpha -olefin copolymers. After stepwise isothermal cr ystallization, the crystalline ethylene sequences are sorted into groups by their lengths. The CESLs are estimated using melting points of known hydro carbons. The content of each group is determined using the calibrated peak area. The statistical terms: the arithmetic mean (L) over bar (n), the weig hted mean (L) over bar (w) and the broadness index I = (L) over bar (w)/(L) over bar (n) are used to describe the distribution of CESL. Results show t hat improved thermal fractionation technique can quantitatively characteriz e the polydispersity of CESL with a high degree of accuracy. (C) 2001 Elsev ier Science Ltd. All fights reserved.