Optimization of Gelation to Prepare Hollow Foam Shell of Resorcinol-Formalin Using a Phase-Transfer Catalyst

We studied the gelation of an RF foam shell using a phase-transfer catalyst and density-match non-volatile silicon oil. A phase-transfe catalyst circumvent the problem of density-mismatch and achieve gelation at room temperature, by which the catalyst is contained in the outer oil (Oo) phase, and is then gradually transferred into the RF droplets. For the Oo phase, we used a nonvolatile silicon oil as a non-hazardous material instead of a toxic (mineral oil)/carbontetrachloride.

Vigorous agitation conditions were optimized based on three experiments. An emulsion was produced using a droplet generator, and was injected into a drum containg a mixture of 0.39% acetic acid and silicon oil. The drum was rotated and its speed were increased to 95 rpm within 15 minutes. Five minutes later, the rotation speed was increased to 120 rpm (maximum rotation speed), which was maintained for 1 minute, there after reduced to 95 rpm for 39 minutes.