A method determining molecular weight distribution index D (MWD) from viscosity versus shear stress flow curves for polypropylene has been presented.Based on the experimental data,the correlation between the viscosity η of molten polypropylene and its MWD can be expressed as η/η-0=｛1+a(τD)+m｝+{-1},where η-0 is the zero shear viscosity, τ is the shear stress, a and m are empirical parameters.Furthermore,a simpler method to estimate the MWD from only two experimental data,i.e.the melt index (MI) and the zero shear viscosity has also been presented,the calculated results are in good agreement with the data from GPC measurements.
