VARIATION OF DROPLET SIZES DURING THE FORMATION OF MICROCAPSULES FROMEMULSIONS

The size distributions of microcapsules are important in determining t he surface area over which the contents of the microcapsules are relea sed. The size distribution is generally not normal arournd the mean, b ut biased toward smaller capsule sizes, forming a mode around some cha racteristic diameter. In order to assess the factors effective in dete rmining this characteristic drop size, size distribution analyses were carried out photographically at each stage of the complex coacervatio n process. In addition, the emulsion drop size distributions were inve stigated as a function of stirring rate, stirring time and phase ratio . The results agreed qualitatively with the theory of isotropy but wer e an order of magnitude smaller. This theory is valid for Newtonian li quids. Elongational stresses could be operative with large-sized macro molecules and a mechanism was proposed based on variation of elongatio nal stresses with velocity and rates of extension. Elongational viscos ities measured for the gelatin solutions supported the proposed mechan ism.