A linear dependency of zero shear, constant shear-rate and constant shear-stress viscosities with temperature and hole fraction (“thermo-occupancy” function) was derived for polyacrylonitrile-butadiene-styrene (ABS), polypropylene (PP) and polystyrene (PS). The relation of viscosity parameters, such as transmission coefficient and a measure of activation energy coefficient, with shear-rate and shear-stress was also investigated and some conclusions on the differences for the studied polymers were discussed. In particular, it was found that, for all materials, the derivative of logarithm of viscosities at zero shear, constant shear-rate and constant shear-stress decreases with decreasing rate with the hole fraction.
The elongational flow behavior of polyethylene, polypropylene, polystyrene, poly(methyl methacrylate), and polycarbonate, temperatures from 70 to 290 °C and pressures up to 70 MPa, is examined with the Yahsi-Dinc-Tav (YDT) model and its particular case known as the Cross model. The viscosity data employed in the range of 3-405 s-1 elongational rates were acquired from the literature at ambient and elevated pressures. The predictions and the fitting results of the proposed YDT model with the same measurement data are compared with the Cross model. The average absolute deviations of the viscosities predicted by the YDT model range from 0.54% to 9.44% at ambient and 1.95% to 6.28% at high pressures. Additionally, the linear formulations derived from the YDT model are employed to relate the viscosity with temperature and hole fraction (“thermooccupancy” function) at zero level of elongational rate and constant elongational rate along with constant elongational stress. The effects of the four viscosity parameters (such as transmission and activation energy coefficients in these equations) on the elongational viscosity are analyzed in detail and some conclusions on the structural differences for the polymers are discussed.
The reported pressure−volume−temperature (PVT) data of five different diesel fuels at T=297. 95−373.06 K and P=0.1−457.2 MPa were described by the Simha-Somcynsky (SS) equation of state (eos). From the equilibrium condition imposed on the eos, the hole fraction, h=h(P,T), a form of free volume measure, was computed. Furthermore, our physically-based correlation implicating the thermo-occupancy function, Yh=Yh(h,T), in terms of a function of h=h(P,T) and T has been extended in this study to estimate the dynamic viscosity, , for the mixtures of commercially available fuels. The model bridges a direct relation from an equilibrium property, h, to the transport process, , of the system and predicts the viscosity with the range from 0.15% to 0.31%. Newly designates "viscoholibility" function defined as the derivative of logarithm of viscosity with respect to hole fraction has been discussed. It has an exponential decaying behaviour with respect to h.
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