Hard ceramic particles were frequently added to polymers to improve their mechanical properties, e.g. scratch resistance. In recent years, however, some members of carbon nano-family such as carbon nanotubes and nanodiamonds were also widely used as reinforcements in polymeric matrices. In the present research, three different fillers including nano-alumina -NA-, detonation -DND- and non-detonation -NDND- nanodiamonds were added to polyacrylic base automotive clear coats to improve the performance of the coating. Both nanodiamond types were surface functionalized to improve their dispersion and hence strengthening capacity. Several laboratory and industrial tests were performed on the coatings to study the mechanical behavior and resistance of the coatings to chemical reagents. The results showed that addition of these particles can strongly increase the scratch resistance of the coating while the other aspects of the coating was not deteriorated. In addition, the results proved the great potential of surface functionalization of DNDs over NDNDs on the performance of the coatings. The coating containing as-received DNDs and NDNDs showed scratch resistance lower than those containing NA however. However, the heat treated DNDs, unlike the heat treated NDNDs introduced a better scratch resistance in the coatings, considerably higher than the NA containing coatings.

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