Mechanical Surface Characterization – A Promising Procedure to Screen Organic Coatings

By A. Krupicka, M. Johansson, A. Hult, G. Favaro

Combinatorial approaches have been used for over a decade now in pharmaceutical R&D to screen large numbers of compositions and formulations. In recent years, demands for coatings with lower envi­ronmental impact and retained or improved perform­ance have awakened greater interest in the issue of improved development procedures. To replace existing high-performance formulations, improved resin knowl­edge is required, which can only be accomplished by introducing more efficient ways to synthesize, blend, apply, and evaluate resin compositions. For obvious reasons, the concept of high-throughput screening has been given extensive attention in the field of coatings R&D, though it is still little practiced.

Applied to coating development, a desirable setup would include instrumental techniques that are adaptable to automa­tion and feasible for the production and screening of ranges of resin compositions on a milligram scale. For decorative coatings, the appearance is essential. Consequently, mechanical properties preserving the appearance are important. Nanocontact techniques that are also promising for the controlled screening of mechanical performance on a microscale have recently become available and found use in many applications.

Contact tests are particularly suitable in the coating industry, since surface properties are of primary con­cern. The relationship between bulk properties and sur­face properties is poorly understood. The occurrence of stratification, i.e., a gradient difference between bulk and surface properties, appears to be an issue in coating film layers. Commonly utilized tests measuring poly­mer bulk properties, such as tensile tests, are less appro­priate if coatings stratify.