GELATION KINETICS: SIZE EFFECTS AND OTHER ISSUES

Kurzfassung

We experimentally and theoretically investigate the size effect of gelation using Resorcinol-Formaldehyde aerogels. We find a clear dependence of gel time on the sample size under mild shear conditions. We developed a theoretical model based on Smoluchowski’s aggregation model adding, however, a growth term which accounts for the continuous growth of the colloidal particles while clustering happens. The model is solved analytically and agrees very well, even quantitatively with our experimental observations for base catalyzed RF-gels. Applying the same model to describe gelation of acid catalyzed RF-aerogels yields also an excellent agreement for the gel-time dependence on catalyst concentration.