A logistic kinetic model for isothermal and nonisothermal cure reactions of thermosetting polymers

Abstract

A model describing the low-temperature crystallization kinetics observed for thermoplastic polymers from the melt by differential scanning calorimetry (DSC) was shown to accurately predict the cooling curves as a function of time and temperature. The model was successful for treating data for several cooling rates as well as for isothermal DSC data. In this article, we extended the model to cure reactions of thermosetting polymers. The parameters representing lower and upper exotherm reference temperatures in crystallization events have a different meaning for curing events. Thus, the model was modified to account for this change of context. The new model was tested for exothermic reactions of a HysolV R FP4527 epoxy adhesive system using data from DSC ramp heating experiments at several heating rates and also from isothermal experiments. Good fits were obtained for all the varied experimental conditions. The model made use of three fitting parameters with physical significance: a lower critical temperature (T c ) an activation energy (E b ), and a reaction order (s 1 1). Additionally, to complete the kinetic fitting, the dependence of the time to reach the reaction peak maximum for isothermal cure was considered. That dependence was found to follow a more simple model which is formally equivalent to that observed in isothermal crystallization, and which makes use of two parameters related to the limits of the temperature range in which the polymerization may occur.

Thermogravimetric study of thermal degradation of polyetherimide

“…A value of 22 kJ mol −1 was obtained for the P1 process. This value is very different from others obtained in solid–solid and melting transformations …”

“…The and parameters represent the peak area and are related to the mass loss produced in each degradation step. The other parameter, τ, accounts for the asymmetry and is related to a reaction order ( n = 1 + τ) …”

“…While the generalized logistic function was proposed in 1959 as a flexible growth function for empirical use, it was not until our recent work that a true kinetic approach was used to interpret the processes that can be described by that function . A complete kinetic description should consider both isothermal and nonisothermal situations.…”

“…Provided the T c value obtained from ramp, E iso can be then calculated from a single isothermal experiment. This experiment should be performed at a relatively high temperature (higher b iso ) to minimize the effect of any possible experimental error on the slope . A value of 22 kJ mol −1 was obtained for the P1 process.…”

Kinetics of Thermal Degradation of Cellulose: Analysis Based on Isothermal and Linear Heating Data

“…The Eramp/Eiso rate is related to the accelerating effect of the temperature on the reaction rate (López-Beceiro et al 2014). Table 4 shows that the value obtained here, 4.3, was on the same order as that observed in the thermal degradation of other polymers.…”