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

✍ Scribed by Kai Chen; Ashley N. Baker; Sergey Vyazovkin

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 194 KB
• Volume: 210
• Category: Article
• ISSN: 1022-1352
• DOI: 10.1002/macp.200800518

✦ Synopsis

Abstract

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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