Abstract: | Molecular weight distributions for polypropylene samples have been determined by a permeation fractionation method (GPC). Porous silica beads were used as a packing material for the columns. The set of columns allows a good separation of the polypropylene macromolecular chains in a range of molecular weights from 5000 to 1.5 × 106, and the thermal and mechanical stabilities of these beads are very good. The calibration has been carried out with fractions of polypropylene of narrow molecular weight distribution prepared by a large-scale column fractionation. The molecular weights M?w and M?n and the ratios M?w/M?n calculated from the GPC curves show, in general, good agreement with the ones calculated from the column fractionation curves. However, the M?w/M?n ratios are always highter in the case of GPC fractionation. This could be due to diffusion phenomena. |