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Keywords:

  • elasticity;
  • flow;
  • melt;
  • polyethylene (PE);
  • viscosity

Abstract

A method is proposed to characterize the elastic behavior of polyolefin melts, by calculating the first normal stress difference, N1 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 N1 from viscosity data, and iii) N1 values calculated with the Johnson & Segalman constitutive equation.6 These comparisons yield acceptable agreement.