Application of K-BKZ Integral Constitutive Model in Uniaxial Extensional Flows for Two Type Polymeric Nanocomposites

چکیده مقاله

The focus of this research is on linear and nonlinear melt rheological investigations of polylactide (PLA) and nanographite platelet (NGP) based on bionanocomposites and polypropylene/layered silicate nanocomposites in uniaxial extensional flows. They were analyzed by using the K-BKZ constitutive equation with two damping functions, namely, the WD-FӦ and PSM-LT models in transient and steady extensional viscosities. Although pure PP matrix and uncompatibilized nanocomposite did not show the strain hardening, compatibilized nanocomposite exhibited outstanding strain hardening behavior due to three-dimensional network structure. Predictions of WD-FӦ and PSM-LT models gave a good agreement with the experimental results at low extensional rate region. However, the extensional viscosity calculated with the WD-FO¨ model did not predict the steady-state value and diverged to infinity when . The PSM-LT model offered a good description on transient and steady extensional viscosities even at higher extensional rates as well as on strong strain-hardening behavior of compatibilized nanocomposites. Through the numerical analysis, using the K-BKZ model with two types of damping functions, it was found that the PSM-LT model was superior to that of the WD-FӦ model in rheological modeling of PP/layered silicate nanocomposites. Also, genetic algorithm (GA) method was used to determine of linear viscoelastic relaxation spectrum from experimental data.