Kinetic Analysis of Isothermal and Nonisothermal Epoxy‐Amine Cures by Model‐Free Isoconversional Methods

Abstract

Model‐free and model‐fitting kinetic approaches were applied to isothermal and nonisothermal DSC data on epoxy cure. The dependence of the effective activation energy on the extent of cure was determined using integral and differential isoconversional methods. A different shape of the dependence in the kinetically controlled regime (α < 0.4) was found when compared to the dependence typically reported for epoxy‐amine systems. This result was shown to arise from the presence of low amounts of bisphenol A in the present epoxy that are efficient catalysts for epoxy amine reaction. A model‐free method prediction of isothermal cure from isothermal data has also been considered.magnified image

Curing kinetics of epoxy-deep eutectic solvent mixtures

“…By applying Eq. (5), to the studied systems, an apparent activation energy E a of 56.59 kJ/mol has been found for the epoxy-amine system (E_TETA), which is consistent with typical results (50-70 kJ/mol) for a number of epoxy-amine polymerizations [51][52][53][54][55]. For the epoxy-DES systems the values of apparent activation energy are much higher, between 86.26 and 99.77 kJ/mol, as expected since in the systems the curing agent is not present, confirming the calorimetric results reported in Table 4.…”

Studies on Curing Kinetics and Tensile Properties of Silica-Filled Phenolic Amine/Epoxy Resin Nanocomposite

“…However, it is noteworthy that the E α varies in a narrower range (about 10 kJ/mol) with respect to α compared to the range reported for other epoxy-amine systems [34]. Values around 50 kJ/mol were obtained, which are in good agreement with Kissinger and Ozawa model-fitting kinetics values and literature data for the autocatalytic reaction of an epoxy–amine system [35]. The rate-determining steps for autocatalytic reactions correspond to the formation of a trimolecular transition state amine–epoxy–hydroxyl, maybe as shown in Figure 8, where HX represents a hydrogen-bond donor.…”

Recent Research Progress on Lignin-Derived Resins for Natural Fiber Composite Applications

“…It decreased gradually up to 30 kJ/mol due to the autocatalytic mechanism [ 60 , 61 , 62 ], as shown in Figure 3 a. Several studies have reported the same trends for the activation energy [ 62 , 63 , 64 ]. On the other hand, for cured DKL and DOL with DDM, the activation energy in the initial stage (α value from 0 to 0.8) slightly climbed, and after that it quickly increased in the later stage due to the self-curing reaction pathway ( Figure 3 a).…”