Normalized Weibull distribution function for modelling the kinetics of non-isothermal dehydration of equilibrium swollen poly(acrylic acid) hydrogel

Abstract

The possibility of applying the normalized Weibull distribution function of reaction times (WDt), for kinetic description of the non-isothermal dehydration of equilibrium swollen poly(acrylic acid) hydrogel, was investigated. It was found, that the dehydration conversion curves at different heating rates, may be successfully described by the Weibull distribution function of reaction times, in wide range of the degree of conversion (α = 0.12-0.93). Also, it was found, that the increasing of heating rate leads to the exponentially increasing of Weibull distribution parameters (scalar (η) and shape (β) parameters). The procedure for kinetics parameters determination of hydrogel dehydration process and determination of the density distribution function of activation energies, based on the known normalized Weibull distribution of reaction times was exhibited. The obtained values of kinetics parameters calculated by the procedure mentioned above are in agreement with values of kinetics parameters, obtained using the stationary point (SP) and isoconversional methods. © 2006 Elsevier B.V. All rights reserved.