| 研究概要 |
The following has been achieved : (1) The surface tension at the liquid-liquid and liquid-gas interface for a system consisting of a microbubble nucleated inside a droplet of dichloromethane containing different concentrations of polymer which is immersed in a continuous phase of a 2% weight aqueous solution of polyvinyl alcohol was measured. (2) The size distribution of the microbubbles nucleated in the droplets and the produced microcapsules was measured. Inverted microscopy was employed to confirm that the capsules were formed of a single void and determine the thickness of the shell. SEM showed that the capsule surface is smooth and that the optimum conditions for fabricating uniformly sized hollow microcapsules are a low polymer concentration, a polymer of low molecular weight and the use of surfactant. (3) It was found that the solubility of air in dichloromethane increases as the concentration of the polymer increases. Therefore the effect of the polymer concentration and molecular weight on the solubility of gases in dichloromethane was measured. In order to mass produce the microcapsules, a higher concentration of the polymer is required because more air can be dissolved in the solution which translates to more microbubbles nucleating from the solution. (4) Mass production was achieved by employing ultrasound to enhance bubble nucleation in the droplet. The optimum conditions for achieving mass production without compromising the size uniformity of the microcapsule were determined.
|
