A study of the adhesion of thiokol-epoxy hermetics to a brass and an aluminum alloy substrate

ESEEM of copper complexes formed in the interlayer between thiokol-epoxy adhesive and brass substrate

“…Here we give some basic relations that are necessary for experimentalists to follow the treatment of our expe¡ results. The expression for the two-pulse ESEEM time-domain signal for one electron spin and one 1/2 nuclear spin with averaging in all orientation for a disordered system is given by [6] 3 Ti 2 (V(r)) = 1 -----2-7-[2 -4F(T• vir ) + cos(4n v~r) + F(2Ts)], 10 v~ (1) where T a is the perpendicular component of the anisotropic hyperfine tensor, is the nuclear Zeeman frequency, and r is the time delay between the two microwave pulses. Equation (1) is valid in the extremely weak hyperfine interaction limit, when v 87 T a and the isotropic hyperfine interaction parameter is supposed to be zero [6].…”

“…The study of the mechanism of adhesion of a thiokol-epoxy adhesive to a brass substrate was the subject of several investigations [1][2][3]. Electron paramagnetic resonance (EPR) studies of the interlayer between the adhesive and the brass substrate revealed the formation of square-planar copper complexes with sulphur-containing ligands.…”

“…This conclusion was made by simulating the experimental EPR spectra and by comparison with the data on similar systems. It was found that the number of complexes depends on the free-sulphur concentration [1]. The diffusion of the copper ions from the substrate into the thiokol-epoxy polymer was studied with EPR imaging [2].…”

EPR imaging study of paramagnetic centre distribution in thiokol-epoxy hermetics

“…In [2][3][4], the bond formation mechanism between thiokol-epoxy macromolecules and atoms of brass and duralumine substrates were studied. The role of nonstoichiometric sulfides Cu.S (Zn.S) in formation of strong contact between hermetic and substrate was established.…”

“…It was shown that the cohesion strength of the hermetics border layer is extremely dependent on the free sulfur 8 8 content in the composition and reaches a maximum value at 2-10 m.p. S8' It was previously found that the adhesion and cohesion strength of thiokolepoxy hermetic correlates with the number of free radicals in the carbon black filler: the lower the concentration of free radicals the higher the hermetic strength [2][3][4]. One can expect that the distribution of radicals is nonuniform near the substrate and that the distribution of radicals in the hermetic volume and in the interphase layer depends on the composition contents.…”