Comparison of the Rheological Behavior of Iso- and Syndiotactic Polypropylenes
Öz
The rheological behavior of iso- and syndiotactic polypropylenes (iPP and sPP) for two different temperatures of 175 and 190˚C at atmospheric pressure is analyzed employing the Yahsi-Dinc-Tav (YDT) non-Newtonian viscosity model. The predicted viscosity with shear rates of 0.093 to 93.91 s-1 on PPs is compared with the corresponding estimations from the Cross-like model. The obtained results from the YDT model deviate from the reported experimental observations with 1.041 for iPP and 1.86 for sPP. From the zero shear viscosity correlation to temperature- and vacancy fraction- dependent thermo-occupancy function, Yh = Yh(h, T), viscosity parameters were ascertained and associated with polymer tacticity. From the zero shear viscosity relation, an increase in Yh = Yh(h, T) function and hole fraction loss results in increased viscosity. The dependence of the derivative of logarithm of viscosity (viscoholibility) on vacancy fraction, as a function of pressure and temperature, h=h(P,T), procured from Simha-Somcynsky hole theory displays an exponentially decreasing behavior.
Anahtar Kelimeler
Simha–Somcynsky, Isotactic and syndiotactic polypropylenes, vacancy fraction, steric hidrance, viscoholibility, tacticity
Kaynakça
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