Study of polymer/metal coating under stress using positron annihilation spectroscopy

Positron annihilation spectroscopy (PAS) has proven to be a very useful tec hnique for, e.g., the study or defects in materials and the characterizatio n of polymer free-volume. Positron lifetime, Doppler broadening of the anni hilation radiation (characterized by the so-called S parameter) and angular correlation of annihilation radiation (ACAR) are the techniques used mostl y. In the last few years these techniques have been extended to the study o f physical defects at the atomic level of coating systems. These studies sh ow that positron lifetime and the S parameter can monitor the degradation o f the coating due to environmental changes (water or UV exposure). The pres ent work is focused on the behavior of coatings under external stresses as studied by PAS. Results of positron annihilation measurements (before and a fter stretching) on interstitial free (IF) steel coated with epoxy using th e Delft variable energy positron (VEP) beam facility are discussed. (C) 200 0 Acta Metallurgica Inc. Published by Elsevier Science Ltd. AII rights rese rved.