The molecular weight distribution of polypropylene

The Gel Permeation Chromatograph has been used for obtaining values of weight‐average and number‐average molecular sizes Aw and An and the heterogeneity indices Aw/An for a series of polypropylenes. Absolute values of Mw and Mn, the weight‐average and number‐average molecular weights, have also been obtained from the same samples with light‐scattering and osmotic pressure methods. Comparisons of the data from the gel permeation chromatograph with the data from the absolute measurements have been used for calculating Q, the constant used for converting Aw and An to the corresponding Mw and Mn values. Other correlations of interest, such as intrinsic viscosity versus weight‐average molecular weight and melt flow, and Newtonian viscosity versus weight‐average molecular weight, are also given.