Gelation kinetics of gelatin: A master curve and network modeling

The gelation kinetics of gelatin has been exhaustively studied using oscill atory rheometry for six molecular weight distributions, three concentration s, and four temperatures. Measurements lasted up to 3(1)/(2) months, much l onger than previous studies. Remarkably, all of the data can be superimpose d 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 ge lation processes are identical; altering the variables just changes the sca ling factors for elasticity and time. Empirically, it is found that neither high nor low molecular weight chains contribute to the elasticity. A stati stical network model has been developed, based on Flory's phantom network f ormalism. It gives reasonable fits to the experimental gel times and is com patible with the observed dependence of elasticity on molecular weight dist ribution. A second order reaction kinetics model has also been developed wh ich satisfactorily models the early stages of gelation.