Estimation of Polymer Coating Scratch Tensile Strength by Nano-Indentation, Micro-Scratch Testing, and Finite Element Modeling

In a previous paper, polymer coating viscoelastic/plastic properties were determined using nanoindentation and the finite element method. In this work, the individual layers, once characterized, were assembled into a multi-layered structure and subject to micro-scratch tests. These tests determined a critical scratch indentation load for the layered structure, as designated by the first appearance during scratching of visible surface layer tensile cracks. Scratch tests were carried out for three different conical scratch tip radii. The top-layer tensile strength of the layered structures was then estimated, utilizing the individual layer properties, the top layer friction coefficients, the micro-scratch test critical loads, and a finite element scratch model, for each scratch tip radius. The values of the top layer scratch tensile strengths were in good agreement for each of the three tip radii, as anticipated. The top-layer scratch tensile strengths may be utilized for further analysis and comparison of differences in gloss retention after gloss reduction experiments. The method may be used as a basis for coating selection, comparison, and performance testing in scratch-resistant polymer coating applications.