A Note on the Elasticity of Polymer Melts Described by Primary Normal Stress Difference (N 1 )

A method is proposed to characterize the elastic behavior of polyolefin melts, by calculating the first normal stress difference, N 1 as a function of shear rate. The method is predicated on Cogswell's abrupt contraction flow analysis.1 These results are compared with experimental measurements and calculated values with a variety of methods, such as: i) Laun's rule2 for obtaining viscometric functions from linear viscoelastic data, ii) methods proposed by A. Khalik, et. al.3,4 and Wagner,5 for calculating N 1 from viscosity data, and iii) N 1 values calculated with the Johnson & Segalman constitutive equation.6 These comparisons yield acceptable agreement.