Modeling of shear and uniaxial extensional viscosities in very wide deformation rates for linear isotactic polypropylene meltblown grades

Abstract

In this work, shear and uniaxial extensional viscosity data, experimentally determined at very wide deformation rates for two linear isotactic polypropylene meltblown grades, were used to assess the fitting capability of three different constitutive equations, which utilizes infinite shear viscosity as the material parameter. It was shown that Giesekus model has no capability to describe measured extensional viscosities at high deformation rates. Yao model was found to handle basic trends in both viscosities except of very high deformation rates. It was suggested that modification of slip viscosity function and addition of a termination viscosity could improve the Yao model behavior at very high deformation rates. The recently proposed Generalized Newtonian model was found to have high capability to fit shear and extensional viscosities including the very high deformation rate range. It is believed that obtained results can be used in process modeling for nano-sized polymeric products, where deformation rates can reach extremely high values. © 2020 Society of Plastics Engineers. All rights reserved.