The GMW 14698 standard, developed by the General Motors company, which includes brands such as Buick, Cadillac and Chevrolet, describes a test method for determining the scratch resistance of organic coatings that can be applied to single or multi-layer systems applied to metallic or polymeric substrates and self-adhesive films.
In the automotive industry, coatings are generally applied over a substrate to protect the surface. Coatings also affect the appearance of the substrate in terms of gloss and color. Scratches not only greatly reduce the surface aesthetics of a coated product, but also cause premature failure of the substrate. Visual detection of wear and tear with reduced surface aesthetics is simple. In contrast, the relationship between scratch testing, scratch resistance, chemical composition and coating properties is more complex.
There is no exact definition of scratch resistance and it is difficult to measure. Different terminologies are used, ranging from distortion for optical defects to friction, wear, erosion and cracking for mechanical defects. For example, scratch resistance, gloss reduction, turbidity, magnitude of deformation, resistance to deformation, weight loss or color change of the substrate.
The relationship between the deformation and properties of both the scratch surface and the coated substrate is complex. The contribution of different deformation mechanisms determines the overall shape, magnitude and characteristics of the resulting residual deformation. A scratch can be the result of three deformation components: an elastic, a ductile, and a brittle component.
The deformation response depends on both the contact conditions and the physical state of the material. For a coating to remain intact on the surface, cohesion in the bulk and good adhesion to the substrate are necessary. The scratch deformation mechanism is determined by the time-dependent properties of the polymer. Therefore, temperature and scratch rate are very important when it comes to polymeric materials. Current scratch testing methods differ in many respects, and comparing the results is not easy.
Among the numerous test, measurement, analysis and evaluation studies it provides for businesses in various sectors, our organization also provides test services to determine the scratch resistance of organic coatings and self-adhesive films, within the scope of the GMW 14698 standard, with its trained and expert staff and advanced technological equipment.
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