Morphological development of latex particles in a solvent-free extrusion process

This paper reports on the influence of factors involved in the preparation of polyester latex in an aqueous medium using a twin screw extruder. In this work, screw speed was found to have no influence on the residence time (or axial mixing) in the process while the resin-to-water ratio in the early dispersion zone appeared to significantly affect both residence time and particle size. In an attempt to visualize the melt in the dispersion zone, conditions inside the extruder were used to hamper phase inversion. A morphological study of samples under such conditions by scanning electron microscopy showed a bi-continuous matrix formed stratified fibrils and nodular-extended clusters as mechanical action worked to increase the interfacial area between the water and resin leading up to the phase inversion point. Increasing the water content in the dispersion zone had the qualitative effect of increasing the presence of the bicontinuous morphology. s.