Product lifecycle analysis shows that high-performance coatings with improved durability prevent inefficient use of material resources and energy from start to finish. Abrasion is one of the most important defects that deteriorates the durability of coatings. Abrasion is defined as the process of marring, scratching, or wearing away any part of a material by rubbing it against another surface.1 Although the terms abrasion, mar, scratch, and wear are sometimes used interchangeably in industry, they are different. Mar abrasion is the permanent deformation that has not ruptured the surface of a coating. However, wear abrasion is usually caused by mechanical actions that remove material from the surface. In most cases, such removal is gradual and progressive due to repetitive actions. In addition to abrasive wear, several other types of wear include adhesive, corrosive, cutting, deformation, fatigue, impact, and rolling. Scratch abrasion, typically seen as a line, is a surface deformation caused by indentation due to the displacement or removal of material by a harder object.2, 3Abrasion resistance is the resistance of a solid material to mar, wear, and scratch.
In the coatings industry, different approaches can be used to achieve the required abrasion resistance. Among them, surface treatment and matrix strengthening are the widely utilized approaches. In some cases, a combination of these complex approaches performs the desired level of abrasion resistance. In organic coatings, using specific additives based on modified polydimethylsiloxane (PDMS), as well as natural or synthetic wax products, can sometimes improve abrasion resistance.4 Although their working mechanism is not very well understood yet, it seems these additives can migrate to the surface and act as slip agents or physical spacers. In addition to surface treatment, matrix strengthening is an effective approach for improving the abrasion resistance of organic coatings. This approach usually uses polymers with high glass transition temperature (Tg) values. In self-crosslinked one-component (1K) or crosslinked two-component (2K) coatings, it is possible to improve matrix strength by increasing the crosslinking density of the systems. Another efficient strategy is introducing hard particles into the matrix of organic coatings.5 Although matrix strengthening is a common approach, increasing the elasticity of a coating can sometimes improve its abrasion resistance by recovering after the applied stress is removed. In general, the introduction of reinforcements can affect mechanical properties such as hardness, stiffness, elasticity, and plasticity.6-14 A summary of different approaches for improving the abrasion resistance of organic coatings is schematically illustrated in Figure 1.