Temperature dependence of sol-gel conversion kinetics in gelatin-water system.
The conversion kinetics of an aqueous gelatin solution to gel was studied by temperature modulated and regular DSC under isothermal and continuous cooling conditions. Isothermal runs revealed a decrease in the quasi-static heat capacity primarily associated with syneresis (phase separation) of the gel. Above 19 degrees C the isothermal process demonstrated negative effective activation energy that turned positive below 14 degrees C. Continuous cooling runs detected a reversing heat flow apparently related to the continuing formation and melting of new gel structures. Isoconversional kinetic analysis of continuous cooling measurements yielded negative activation energy for the whole range of conversions and temperatures suggesting that nucleation remained a rate controlling step throughout the whole gelation process.
Chen
Kai
K
Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
Vyazovkin
Sergey
S
D002152:Calorimetry, Differential Scanning; D005780:Gelatin / Q000737:chemistry*; D007700:Kinetics; D044367:Phase Transition; D013696:Temperature; D014867:Water / Q000737:chemistry*
D014867:Water; D005780:Gelatin