Epoxy-Aromatic Diamine Kinetics. Part 1. Modeling and Influence of the Diamine Structure

Abstract

The reactivities of different aromatic diamines, i.e. 4,4'-diaminodiphenyl sulfone (DDS), 4,4'-methylenedianiline (MDA),4,6-diethylaniline] (MDEA), and 4,4'-methylenebis [3chloro-2,6-diethylaniline] (MCDEA), cured with an epoxy prepolymer, the diglycidyl ether of Bisphenol A (DGEBA), were compared and correlated to their chemical structures. The reactivities of the diamines are in the following order: MDA > MDEA > DDS > MCDEA. Although MDA, MDEA, and MCDEA exhibit very different reactivities, the ratio of the reactivity of secondary to primary amine hydrogens (ki/ki) is found to be the same r = 0.65. On the other hand, the reactivity ratio of DDS is found to be r = 0.45. This lower value may be the result of the lower number of stable conformations afforded by the -SO2group in comparison to the -CH2group. No temperature dependence was observed. The DGEBA-DDS and DGEBA-MCDEA kinetics were fully characterized as regards conversions and Tg measurements with time at different temperatures. Relationships between the Tg and x were validated for both systems. Kinetics were modeled throughout the whole range of cure. For the DGEBA-MCDEA system, etherification reactions were found to occur and were then integrated into the kinetic model. The effect of diffusion control was incorporated by modifying the overall rate constant according to the Rabinovitch model. The Adam-Gibbs theory was preferred to express the temperature dependence of the diffusion rate constant. The kinetic models have been satisfactorily extended to the isothermal cure of an epoxy with a binary mixture of diamines.

Design of morphology in PMMA-modified epoxy resins by control of curing conditions. I. Phase behavior

“…These curves were fitted assuming that the principal reactions are the addition of epoxy groups to primary and secondary amine hydrogens, respectively, and that both of them take place by two mechanisms, one uncatalyzed and the other catalyzed by the existing OH groups. The model proposed by Girard-Reydet et al 22 was used in this study:…”

Kinetics modeling of the reaction for an Epoxy/PMMA/MMT ternary system

“…The mechanistic models [9][10][11][12] describing the mechanism of each elementary reaction (taking into account substitution effect for primary and secondary amines, chemical equilibrium) are much more complicated and need more sophisticated calculation methods in order to identify (often with a bad accuracy and more or less justified hypothesis) an important number of unknown parameters.…”

Tuning morphologies of thermoset / thermoplastic blends Part 1: Kinetic modelling of epoxy-amine reactions using amine mixtures

“…Fang et al [14] elaborated ''sandwich'' structures due to the different heating rates between core and layers. In order to control the morphology of the separated phase, the potentiality of using a mixture of two hardeners has been seldom mentioned or used in previous studies [15,16]. Although industrial thermosetting epoxy/amine formulations are often composed of mixtures of epoxy and amine molecules, literature reveals very little experimental work and modelling of the reaction of complex epoxi(es)/amine(s) formulations, e.g.…”

“…The mechanistic models [15,28], describing the mechanism of each elementary reaction (taking into account substitution effect for primary and secondary amines) are complicated and need sophisticated calculation methods in order to identify an important number of unknown parameters (often with a bad accuracy and more or less justified hypothesis). On the contrary, the phenomenologic models, even based on non justified approximations (as equireactivity of primary and secondary amines), often allows a correct modeling of experimental data.…”