Comparative kinetic analysis of thermal destruction of hydrogel on the base of polymethylvinyl maleic acid ester linked with polypropylene glycol

Abstract

Kinetic analysis was made applying TG/DTG/HF data in nitrogen and air atmosphere
for thermal decomposition of hydrogel of polymethylvinyl maleic acid ester, linked with polypropylene glycol, at different heating rates. TG/DTG/HF data were processed according to the following
kinetic models: Friedman, Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose, Coates-Redfern and nonparametric kinetic method (NPK) was used, to obtain the following kinetic parameters: activation
energy and pre-exponential factor.
According to the attained values of activation energy, the mechanism of degradation of the hydrogel was suggested. Values of kinetic parameters attained by different methods, are compliant to each
other. Isoconversion method is one of the methods for definition of activation energy; this method
does not require knowledge on analytical form of conversion function, and gives the possibility to
define the activation energy against conversion degree as well.
To obtain full kinetic analysis it is necessary to process the data using non-parametric kinetic
method. Non-parametric kinetics method (NPK) of Serra, Nomen and Sempere is based upon the
suggestion that reaction velocity may be expressed as multiplication of two independent functions,
f (α) and k (T). Reaction model f (α) considers the dependence of conversion degree, and k (T)
considers the temperature dependence.