抄録
The elongational behavior at a constant strain rate was studied for polypropylene melt samples with various molecular weights by means of an elongational rheometer with a pair of rotating clamps. The linear parts of the elongational viscosities depended strongly on the molecular weight: the dependence obeyed the 3.4 power law known for shear viscosity. The non-linearity parameters of the elongational viscosity were found to be almost independent of the molecular weight. The parameters predicted from the constitutive equation depended slightly on the molecular weight. Then, the molecular weight dependence found for polypropylene can be interpreted in terms of the Lodge model or the Wagner model.
