Phase inversion and dual-phase continuity in polymer blends: Theoretical predictions and experimental results

In this work, the point of phase inversion for several polymer blends is investigated experimentally. Four different blends were studied: polystyrene/polyethylene, poly(methyl methacrylate)/polyethylene, polystyrene/poly(methyl methacrylate) and polycarbonate/polystyrene. Blends were prepared at the compositions where phase inversion is expected to occur according to the predictions of the model of Avgeropoulos, equating the torque ratio with the volume-fraction ratio. The morphology of the prepared blends was examined using scanning electron microscopy. The results obtained were then compared to the values of the point of phase inversion calculated with various semi-empirical models. The results show that the model of Avgeropoulos predicts satisfactorily the point of phase inversion for torque ratios close to unity, whereas using the viscosity ratio the prediction is far away from the experimental values. The model of Metelkin and Blekht and that of Miles and Zurek were found to overestimate the composition at which phase inversion occurs, while the model of Utracki was found to agree with the experimental results for blends having a viscosity ratio far from unity. Moreover, no correlation was found between the torque ratio and the shear or complex viscosity ratio for the different blends, suggesting that the model of Avgeropoulos cannot be used by substituting the torque ratio by the viscosity ratio. Copyright (C) 1996 Elsevier Science Ltd.