Characterization of linear polyethylene fractions obtained by preparative GPC

Abstract

SynopsisA new preparative liquid-phase chromatograph, operating at a high temperature (ISO"C), allowed us to fractionate a linear polyethylene sample in narrow fractions (polydispersity about 1.1). These fractions, characterized by viscosity, light scattering, osmometry, and GPC measurement.s, can be used to calibrate any analytical GPC, i.e., to determine the variation of molecular weight and axial dispersion versus the elution volume.

Comments on the Paper “Comparison of the Rheological Properties of Metallocene-Catalyzed and Conventional High-Density Polyethylenes”

“…(a) Reported zero shear rate viscosities for metallocene-catalyzed HDPEs are higher than values previously published by other authors for conventional HDPEs of the same molecular weights and molecular weight distributions. − …”

“…In that article: 1 (a) Reported zero shear rate viscosities for metallocene-catalyzed HDPEs are higher than values previously published by other authors for conventional HDPEs of the same molecular weights and molecular weight distributions. [2][3][4][5][6][7] (b) Viscosity is said to depend on molecular weight with an exponent of 4.2 for metallocene-catalyzed HDPE and 3.6 for conventional HDPE.…”

Isothermal growth of low molecular weight polyethylene single crystals from solution. 1. Variation of equilibrium dissolution temperature with molecular weight and lamellar thickness with crystallization temperature

“…The rest of the fractions were prepared and characterized at the Research Center of SNPA at Lacq, France. The technique of fractionation by preparative gel permeation chromatography (GPC) has been described by Peyrouset et al12,13 The weightaverage molecular weights (Afw) were determined by analytical GPC previously calibrated by light scattering. Number-average molecular weights (Afn) were determined by vapor pressure osmometry.…”

Properties of amorphous and crystallizable hydrocarbon polymers. I. Melt rheology of fractions of linear polyethylene

“…Previous d i s~r e p a n c i e s~,~ are therefore probably attributable to differences in the determination of molecular weight. Results in Figure 3 are described by (10) in which qo is measured a t 190°C and [q] is measured in TCB at 135°C.…”