Quantitative scratch visibility assessment of polymers based on Erichsen and ASTM/ISO scratch testing methodologies

A lack of effective quantitative tools for evaluating scratch visibility resistance of polymers has hindered the fundamental understanding of visible scratch-induced defects and effective approaches to improve performance. Thanks to the recent establishment of the Erichsen and ASTM/ISO scratch testing protocols, researchers are now able to give quantitative assessments of scratch visibility resistance with ease. Unfortunately, the above two methods differ in testing and evaluation approaches. The main objective of this work is to disseminate the similarities and differences between the two industrial scratch visibility determination methodologies, i.e., delta L (ΔL) for Erichsen and contrast for ASTM/ISO. A good correlation between the two methods can be established if the ΔL value is normalized against the original L value for the undamaged surface, similar to the concept of contrast. The surface deformation that gives rise to light scattering, such as scratch groove formation and the surface roughness on the scratch path, was studied for both methods using a set of three model thermoplastic olefin systems. The implication of the current research for quantitative scratch visibility assessment is discussed.