How to improve scratch & abrasion resistance in coatings?

Abrasion resistance refers to a coating's ability to withstand physical wear and tear caused by friction or scraping against another object. It essentially determines how well a coating can hold up to scratches, gouges, or erosion.

Scratch resistance refers to a coating's ability to withstand localized damage caused by sharp or pointed objects. It essentially determines how well a coating can hold up to minor abrasions without permanent marks or deeper cuts.

Figure 1: Difference between mar resistance and scratch resistance (Source: Spektrochem¹)

If the applied force is small, elastic deformation of the coating occurs, and this is fully recoverable when the force is removed². As the force increases, the coating undergoes viscoplastic deformation, creating a mar. As the force increases further and exceeds a critical value, it causes fracture in the coating typically referred to as a scratch rather than a mar³. A coating fractured by a scratch is more severely damaged and easier to recognize as having a surface defect than a coating suffering from a shallower mar.

Figure 2: The formation of a mar or scratch on a coating

Figure 3: The surface morphology of a coating damaged with increasing force, showing the first indications of mar and scratch damage (Source: American Coatings Association)³
 

There are two strategies:

1. Make the coating surface hard – seems to be the strategy for abrasion resistance
2. Increase the slip of the surface – seems to be the strategy for mar and scratch

Let’s see what materials help and how:

• Abrasion resistance agents
• Scratch/scrub/mar resistance agents