Volume 3, Issue 6 (June 2006)
Use of Optical Imaging/Image Analysis System for the Quantitative Analysis of Surface Changes Induced by Outdoor Weathering on Sealants
Six sealant samples that had been weathered outdoors for 6.8 years in Japan were evaluated using an Optical Imaging/Image Analysis System, Atlas VIEEW™. The specimens were first visually evaluated with aesthetic ratings assigned. These ratings were then used as the reference for the optical image analysis. Image analysis was carried out on sealant images taken under optimized diffuse illumination at a constant illuminance. Two sets of images were captured per specimen, first the weathered surface for deterioration evaluation, and second the unweathered surface as a control (reference) image. Four distinct surface defects are quantifiable in the samples. These are cracking (crazing), visual color change, spatial uniformity of deterioration (due to dirt pick-up and uneven color change, or both), and overall surface texture. Chalking and dirt pick up, as rated visually prior to this evaluation, could not be accurately assessed with the digital imaging technique. The analysis shows that surface cracking and crazing generally can be well characterized using the automated VIEEW™ system. Judging color changes visually is problematic, since cracking and crazing interferes with color judgment. Further investigations are needed to develop an automated surface characterization method for sealants.