On the non-newtonian viscous behavior of polymer melts in terms of temperature and pressure-dependent hole fraction

A new theoretical non-Newtonian viscosity model is developed by taking the fractional series expansion of Eyring's shearing strain rate. A broad range of experimental rheological data of various polymer melts including polyethylenes, polypropylene, polystyrene, poly (methyl methacrylate), and polycarbonate are fitted well using the proposed model. From the model; zero shear, constant shear-stress and constant shear-rate viscosities are derived as a linear function of viscosity related quantity, Yh, called "thermo-occupancy function" and their coefficients are discussed in detail. The thermo-occupancy function is expressed in terms of temperature and structural vacancies such as hole fraction computed from the Simha-Somcynsky Hole Theory (SS). In addition, the derivative of the logarithm of viscosities with respect to the hole fraction, named as viscoholibility, is observed decreases with the increasing hole fraction. © 2014 Wiley Periodicals, Inc