Local properties of organic coatings close to glass transition temperature

Acrylic coating applied on copper substrate has been investigated at different temperatures starting from the ambient one up to the level above the glass transition temperature. Its local topographic and electric properties have been examined with the atomic force microscopy (AFM) based approach including dc current mapping and local impedance spectroscopy. The local findings have been compared with the information from global impedance examination. It was possible to distinguish defected, lower-impedance regions of the coating from intact, high-impedance ones, thus overcoming the averaging shortage of global impedance measurements. Thanks to application of the AFM-based approach a phenomenon of gradual closing of coating defects has been discovered as polymer material began to enter the glass transition region. Such behavior has been attributed to increasing plasticity and flow of polymer upon heating. (C) 2014 Elsevier B.V. All rights reserved.