Isoconversional models toward the curing kinetics of self‐healable epoxy resin TGDDM and acid anhydride

Abstract

The reaction process and curing mechanism of self-healable epoxy resin TGDDM and curing agent TA are complicated. In this paper, the curing reaction kinetic mechanism of the system is studied from the perspective of isoconversional models. The nth-order model and autocatalysis model are established for observations of heat flow versus temperature and time during real-time curing obtained by non-isothermal differential scanning calorimetry (DSC), and evaluated under the standards of MSE, RMSE, and R-square. Under the guidance of least squares fitting, the pre-exponential factor (A), the activation energy (E α ), the order of models (n, m) and other parameters in f α ð Þ of the model are mainly estimated by Kissinger method, Ozawa method, Malek method, and other methods. The correlation between the activation energy (E α ) of the reaction and the degree of conversion α also analyzed by the Flynn-Wall-Ozawa method. The chemical reaction of the system is studied by Fourier transform infrared (FTIR) and the self-healing property of the system is characterized by scanning electron microscope (SEM). It was found that the esterification reaction occurred in the system, and the realization of the selfhealing property was also due to the transesterification reaction. In addition, the effect of the accelerator on the system is analyzed by the established autocatalysis model and dynamic mechanical analysis (DMA). The result shows that the addition of the accelerator does not change the curing reaction mechanism of the system, but accelerated the reaction process and increased the glass transition temperature.

Reliability evaluation of a new method developed for DSC curing kinetic model of epoxy resin

“…It is widely used in the case of a first order reaction. 47 Assuming that the maximum reaction rate is at the peak temperature, Kissinger method can be expressed as follows 30,31,47 :…”

“…[27][28][29] There are indeed quite a few works related to the simulation of curing kinetics including calculations of kinetic parameters and establishments of fitting models. It is well known that the evaluation of cuing kinetic parameters depends on the curing degree, the initial value of which is generally 0.1 3,[13][14][15]18,19,[29][30][31][32] or 0.2 33,34 or minimum value increment. 12,16 Due to the incapacity of Kamal-Sourour kinetic model for predicting cure behavior at the beginning stages of reaction, although the influence of different initial curing degrees on the accuracy of predicted values of the curing degree and time has been discussed, the initial curing degree is assumed as a very small nonzero initial value to be considered as the curing degree at the end of induction time, the maximum of which is 0.01.…”

“…To investigate the curing kinetics of resin, several experimental techniques have been used such as thermogravimetry analysis (TGA), [22][23][24]32,34 rheology, 2,19,29,35 differential scanning calorimetry (DSC). 3,[11][12][13][14][15][16][17][18][19][20][21]24,25,30,31 Among the techniques for determining the degree of conversion, TGA is performed by analyzing biomass decomposition. The data obtained from registering weight loss can be used to estimate the degree of conversion of biomass from solid to volatile state.…”

Modeling the curing kinetics of two thermoset adhesives under varying temperature conditions

“…Monitoring the curing process using differential scanning calorimetry (DSC) is one of the widespread techniques in understanding curing kinetics and determining key process parameters. 6,7 The curing process begins with the formation of short polymer chains, which were then branched and subsequently cross-linked to form three-dimensional networks. The curing process is typically accompanied by heat consumed or generated.…”