Size dependence of the gelation kinetics of RF gels: experiments and modeling

Abstract

The gelation time of resorcinol-formaldehyde-aerogels was measured as a function of sample size. Drops of different sizes were brought inside of a rotating roundflask, filled with hot liquid paraffin. The gelation process changed he appearance of the drops from initially transparent to smokey and white. The sudden change in optical transmission or opacity was identified as onset of gelation. The time of gelation was measured. The measurement results were compared to a theoretical model, based on M. Smoluchowski's coagulation theory, which describes the dependency of gelation time on drop volume. The experimental results agree with the theoretical prediction.