The quality of automotive coatings is predominantly determined by its initial appearance, as well as its constancy in use. Evaluation and controlling of damages made to the appearance such as mar and scratch are therefore very important. Mar and scratch resistances of coatings are complex phenomena because they comprise of many different variables such as viscoelastic properties of coatings, and the size and type of damages incurred. Many attempts have been carried out to increase the scratch resistance of coatings by using appropriate additives. These additives may increase surface hardness and/or mechanical strength of the coatings. In the present study, the influence of type and concentration of conventional and nano additives on mar and scratch resistances of an acrylic-melamine clear coat were compared. A laboratory car wash simulator and a nano scratch tester were used to measure mar and scratch resistances respectively. In addition, micro-Vickers hardness, DMTA, AFM, ATR-FTIR, tensile testing and gonio - spectrophotometric techniques were used to elucidate the action of such additives. Results showed that there is an individual optimum concentration for each additive. Nano additives tend to improve scratch resistance by decreasing Tg to create plastic type scratches with healing capability. Conventional additives on the other hand increase scratch resistance by increasing surface hardness hence producing fracture type scratches. We attempted to describe scratch/mar morphology by the use of a gonio spectrophotometer as a new technique.
The effect of different additives on scratches and mar resistance of automotive clear coats
2007
22 Seiten, 22 Bilder, 7 Tabellen, 17 Quellen
Conference paper
English
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