E. Girardreydet et al., EPOXY-AROMATIC DIAMINE KINETICS .1. MODELING AND INFLUENCE OF THE DIAMINE STRUCTURE, Macromolecules, 28(23), 1995, pp. 7599-7607
The reactivities of different aromatic diamines, i.e. 4,4'-diaminodiph
enyl sulfone (DDS), 4,4'-methylenedianiline (MDA), 4,4'-methylenebis[2
,6-diethylaniline] (MDEA), and 4,4'-methylenebis[3-chloro-2,6-diethyla
niline] (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 ord
er: MDA > MDEA > DDS > MCDEA. Although MDA, MDEA, and MCDEA exhibit ve
ry different reactivities, the ratio of the reactivity of secondary to
primary amine hydrogens (k(2)/k(1)) is found to be the same r = 0.65.
On the other hand, the reactivity ratio of DDS is found to be r = 0.4
5. This lower value may be the result of the lower number of stable co
nformations afforded by the -SO2- group in comparison to the -CH2- gro
up. No temperature dependence was observed. The DGEBA-DDS and DGEBA-MC
DEA kinetics were fully characterized as regards conversions and T-g m
easurements with time at different temperatures. Relationships between
the T-g and x were validated for both systems. Kinetics were modeled
throughout the whole range of cure. For the DGEBA-MCDEA system, etheri
fication reactions were found to occur and were then integrated into t
he 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 depen
dence of the diffusion rate constant. The kinetic models have been sat
isfactorily extended to the isothermal cure of an epoxy with a binary
mixture of diamines.