Crystallizability of ethylene homopolymers by crystallization analysis fractionation

Abstract

The effect of molecular weight and long‐chain branching on the crystallization analysis fractionation (CRYSTAF) of ethylene homopolymers was investigated. Several ethylene homopolymers were prepared with different molecular weights and levels of long‐chain branching to isolate these effects from the dominant effect of comonomer content on crystallizability measured by CRYSTAF. Molecular weight effects might be significant for samples with number‐average molecular weights below 5000, but this effect can be corrected if terminal methyl groups are taken into account. Long‐chain branching has only a very small effect on the CRYSTAF profile of the samples investigated in this study. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1616–1628, 2001

Development of an Automated Cross‐Fractionation Apparatus (TREF‐GPC) for a Full Characterization of the Bivariate Distribution of Polyolefins

“…Figure 15 clearly shows the heterogeneity of this product. The pronounced tailing towards lower elution temperatures in the low molecular weight range is explained by the effect of the chain ends which act as a source of crystal defects as described by Nieto et al [14] and produce a depression in TREF elution temperatures. The fact that for molecular weights lower than 10,000 there is a rather sharp decrease in TREF temperatures is also in good agreement with Nieto's observations based on CRYS-TAF analysis of narrow-MWD polyethylene fractions and paraffins.…”

Easy one-pot method to control the morphology of polyethylene/carbon nanotube nanocomposites using metallocene catalysts

“…CRYSTAF and TREF analysis of the PE supported the above results. CRYSTAF and TREF can be used to measure chemical composition distribution (CCD) based on the continuous crystallization of polymer chains from a dilute solution [31][32][33][34]. The knowledge of a polymer's CCD is essential in investigations of structure-property relationships, polymerization kinetics and mechanisms, and polymer reaction engineering [33].…”

Study on LLDPE molecular structure characterization by preparative and analytical cross-fractionation

“…Our starting point is result from a study on CRYSTAF by Nieto et. al [8]. Fractionation using CRYSTAF depends as for TREF, that we used for CC fractionation, on the crystallization temperature.…”