Gelation kinetics of non-aqueous Carbopol dispersions

The time evolution of the gelation process of non-aqueous Carbopol dispersions in PEG and glycerol was studied experimentally by tracking the evolving viscoelastic properties of the material by means of Fourier Transform Mechanical Spectroscopy (FTMS). A structural conversion degree related to the storage modulus was defined and a kinetic expression to describe its evolution was developed. UV-vis spectroscopy was employed to confirm the mechanism of gelation. It was found that an increase in both the concentration of glycerol and the gelation temperature increased the gelation rate. These trends seem to indicate a diffusion-controlled mechanism of the process, in which the solvent molecules penetrate the cross-linked structure of Carbopol particles, causing their uncoiling and subsequent swelling. Lastly, the kinetic relation found for the structural conversion degree was used to obtain conversion maps, which can be employed as a first guidance to design new continuous gelation formulation processes.