Water-in-alkyd-resin emulsions: Droplet size and interfacial tension

Ultrasound and dynamic shear measurements were used to investigate nonintrusively a water-in-alkyd-resin emulsion in which the resin was a typical highly viscous component of an offset-ink vehicle. The aging of the emulsion was studied over 40 days and an increase in the size of the suspended water droplets was observed. The value of the mean radius R of these droplets was calculated from ultrasonic attenuation data at three stages of the emulsion aging, in the frequency range 600 kHz to 2.5 MHz. At each stage, the value of the ratio between the interfacial tension gamma and the mean droplet radius R was obtained from dynamic shear measurements data in the frequency range 10-230 Hz. The values of R and gamma were found to be in good agreement with the corresponding results obtained by conventional techniques. The merits of the concomitant application of the two nonintrusive techniques are emphasized in terms of the possibility of characterizing quantitatively the features of the highly viscous emulsions encountered in lithography.