Development of dispersed phase size and its dependence on processing parameters

Through measurement of phase dimension via laser scattering, phase morphology development in immiscible blends of polyamide 12/poly(ethylene glycol) (PEG) with an extremely high viscosity ratio was investigated. The blends were prepared by melt blending in a batch mixer. The objective was to examine the influence of mixing time, rotor speed, as well as blending temperature on the size distribution of the minor phase. It is of interest that the breakup process of the dispersed PA 12 phase was observed for the blend systems even for extremely high viscosity ratios of <= 10(2)-10(3). Mixing time had a significant effect on the development of dispersed phase size distribution. It was found that the bulk of particle size reduction took place very early in the mixing process, and very small droplets with a diameter of 0.1-10 mu m were produced. The number of small particles then decreased, resulting in a larger average particle size. With further prolonged mixing, the particle size levels off. The particle size and its distribution were also found to be sensitive to the rotor speed. The average particle size decreased with increased rotor speed. The effect of blending temperature on size and size distribution, which has seldom been studied, was also examined in this work. When the blending temperature altered from 190 degrees C to 220 degrees C, the size and its distribution of the dispersed phase varied considerably, and the change of viscosity ratio was found to be the key factor affecting the dispersed phase size. (c) 2006 Wiley Periodicals, Inc.