Concentration Effect on Temperature Dependence of Gelation Rate in Aqueous Solutions of Methylcellulose

The gelation kinetics in methylcellulose solutions of different concentrations is studied by DSC under rising temperature conditions. Isoconversional analysis reveals that the rate is a complex function of temperature represented by a concave downward dependence of the effective activation energy on temperature (E vs. T). Although the initial decreasing portion of the dependence is consistent with the Fisher-Turnbull nucleation model, a description of the final increasing part requires introducing activation energy of diffusion that varies with conversion according to a power law. Parameters of the modified model evaluated from the E versus T dependencies suggest that the diffusion contribution increases with increase in the concentration, whereas the free energy barrier to nucleation remains almost unaffected.

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