Effect of metal ions on positron annihilation characteristics in metal ion containing epoxies

In the course of developing improved moisture-resistant epoxy resins, two different types of epoxy resins containing variable mole ratios of chromium ions per polymer repeat unit were developed. Positron annihilation characteristics have been investigated in these resins as a function of their metal ion content. In both cases, the presence of metal ions reduces the lifetime as well as the intensity of the long life component. The long life component intensity reduction is considerably more pronounced than the lifetime reduction. These results have been discussed in terms of increased unpaired electron density at Ps formation sites due to the presence of chromium ions in the matrix.