Kinetic analysis of non-isothermal dehydration of poly(acrylic acid)-g-gelatin hydrogel using distributed activation energy model

Abstract

The applicability of distributed activation energy model (DAEM) for describing non-isothermal dehydration kinetics of poly(acrylic acid)-g-gelatin (PAG) hydrogel has been examined. Thermogravimetric curves were recorded at different heating rates from 5 to 20 K min−1. The activation energy dependence on dehydration degree was determined by Kissinger–Akahira–Sunose and Vyazovkin’s methods. The possibility of applying thermodynamically inhibited nucleation and growth reaction model on investigating process has been examined. Miura–Maki method was used to establish the shape of activation energy distribution function and the dependence of pre-exponential factor on dehydration degree. Non-isothermal dehydration kinetics of PAG hydrogel can be successfully described by the DAEM. Here we defined the procedure by which DAEM can be successfully connected with kinetic models commonly used for reactions in solid state. The dependences of specific rate (i.e., rate constant) and reaction model function on dehydration degree were established for all of the investigated heating rates. It has been concluded that the specific rate changes with dehydration degree and that this is the one of the reasons why non-isothermal dehydration kinetics of PAG hydrogel is complex.