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Dyna-scratch

2015-10-17 21:54:45


Scratch resistance is an important characteristic for polymeric materials and coatings in a wide variety of applications. Damage on a surface due to scratch is one of the main reasons for the disturbance of a product’s quality.

Scratch easily appears on many types of materials and coating surfaces, e.g. metal, polymer, glass, optics, ceramics, with the size in macro, micro and nano scales due to different mechanisms. In many industrial applications, a deep and long scratch occurs during a fast and high dynamic motion, e.g. scratching on the exterior paint of a car with a key. This high dynamic scratch, namely Dyna-scratch, is done at the speed up to 100 cm/s with a scratch length h in centimeter range.
 
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Examples of Dyna-scratch on floor, car exterior, leather
 
So far, the conventional scratch testers normally run at quite slow speed (max. 6 cm/s) with short distance, and what it generates is not a scratch, but instead a mar, which characterizes the ability to resist light damage. The difference between mar and scratch is that mar is relatively fine scratch. Materials, especially polymers, have certain viscoelasticity and thermal recovery capability. Therefore, those temporarily removed surface materials will be then spread out over the surface, and this viscoelasctic recovery only shows as slight and fine scratches.
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Examples of scratches under different loads on leather