The effect of processing parameters on the morphology of an immiscible binary blend

In this study an immiscible blend of polypropylene(PP) and polycarbonate (PC) was examined. Experiments were carried out in an internal mixer and the objective was to examine the influence of the time of mixing, the speed of rotation of the rotors as well as the effect of time under quiescent conditions on the size and size distribution of the minor phase. The morphology was studied by light and electron microscopy and the photographs were quantitatively analyzed by semiautomatic image analysis. The effect of the time of mixing was studied for up to 20 min at three viscosity ratios for PC dispersed in PP. The most significant particle size deformation and disintegration processes take place within the first 2 min of mixing. After 2 min very little reduction in the size of the minor phase is observed up to 20 min mixing time, although some phase size/time dependence was observed at an intermediate viscosity ratio. The influence of rotor speed was also studied and the results indicate that this blend is insensitive to changes in the speed of rotation of the rotor over a three‐ to fourfold range. The effect of time at 250°C under quiescent conditions was studied at 7% and 23% composition (volume fraction) for PP dispersed in PC and also for PC in PP. Coalescence coarsening was observed only for 23% PC in PP where the particle size was found to increase by 75% after approximately 90 min at temperature.