Characterization of high-molecular-mass polyethylenes by gel permeation chromatography—low-angle laser-light scattering

Abstract

Gel permeation chromatography—low-angle laser-light scattering (GPC-LALLS) has been applied to the analysis of high-molecular-mass polyolefins. It was found that changing the particle size of the column packing from 10 to approximately 50 μm resulted in an increase in the molecular mass of NBS 1476 of from 100 000 to 195 000. It was also found that changing the flow-rate from 1.0 to 0.1 ml/min resulted in an increase in the molecular mass of the same sample of from 195 000 to 280 000 for the large particle size gel columns. Increases were also seen with commercial low-density samples when changing these same conditions, but the increases were not as large in magnitude. A change in the frit size on the columns did not seem to have an effect on the measured molecular masses of the NBS 1476 samples. Another finding in this study was that slurry high-density polyethylene samples which previously had been very difficult to characterize using GPC-LALLS gave much higher molecular masses which were much more reproducible when characterized using the large particle size columns with low flow-rates.