Gelation kinetics of gelatin: A master curve and network modeling

The gelation kinetics of gelatin has been exhaustively studied using oscillatory rheometry for six molecular weight distributions, three concentrations, and four temperatures. Measurements lasted up to 3(1)/(2) months, much longer than previous studies. Remarkably, all of the data can be superimposed on a single master curve using suitable shift factors. The existence of a master curve shows that, over the broad range of variables studied, the gelation processes are identical; altering the variables just changes the scaling factors for elasticity and time. Empirically, it is found that neither high nor low molecular weight chains contribute to the elasticity. A statistical network model has been developed, based on Flory's phantom network formalism. It gives reasonable fits to the experimental gel times and is compatible with the observed dependence of elasticity on molecular weight distribution. A second order reaction kinetics model has also been developed which satisfactorily models the early stages of gelation.