Fractionated crystallization in immiscible POM/(PS/PPE) blends Part 1: effect of blend phase morphology and physical state of the amorphous matrix phase

The fractionated crystallization behavior of POM in immiscible POM/(PS/PPE) blends has been investigated by Differential Scanning Calorimetry (DSC) and correlated to the blend phase morphology. By varying the PS/PPE composition, homogeneous amorphous phases with different glass transition temperatures, varying between 100 (T-g,T-PS) and 215 degrees C (T-g,T-PPE), and melt-viscosities were obtained, without altering the interfacial tension of the blend system. As such, a model blend system has been created which allows to investigate both the influence of the blend phase morphology and of the physical state of the amorphous PS/PPE matrix, on the crystallization behavior of the minor POM phase. The difference between low viscosity/low viscosity and low viscosity/high viscosity blend systems with respect to the development of the phase morphology during melt-mixing is reflected in various aspects of the fractionated crystallization behavior. The onset composition of fractionated crystallization can be related to the center of the phase inversion region for all blend systems. Within the same blend type, the extent of homogeneous crystallization can be related to the blend phase morphology (i.e. the number of droplets per volume unit of the dispersed phase). However, comparing different blend types reveals that other factors, such as the physical state of the amorphous matrix phase, also play a role. Further, multiple crystallization peaks were observed and have been related to the width of the particle size distribution of the dispersed POM phase. (C) 1999 Elsevier Science Ltd. All rights reserved.