Effect of Shape and Size of Aluminum Flakes on the Sparkle Property ofMetallic Coatings

Sparkle is an essential aspect of visual texture in special-effects coatings (such as car finishes), andappears as small, bright points distributed over a dark background. The sparkle effect becomesevident under unidirectional illumination and highly depends on viewing geometry. This studyinvestigated the impact of metallic particle’s shape and size on the sparkle of metallic coatings. Forthis reason, ۲۴ samples in shades of silver, green, and black, with ۸ different flake sizes ranging from۸ to ۵۴ microns, including ۴ silver dollars and ۴ cornflake types, were prepared. A BYK-mac-i goniospectrophotometerwas employed to assess sparkle. In addition, spectral reflectance was obtained toinvestigate the color effect on sparkle. The results demonstrated that sparkle is significantly affectedby measuring geometry, and it is most prominent at angles close to the specular angle and graduallydiminishes as the angle deviates. Furthermore, larger particle sizes exhibit more sparkle than smallerparticles. Interestingly, silver dollar-shaped flakes show more significant sparkle than cornflakeshapedwith similar size. Additionally, near the specular angle, the impact of absorbing pigments onmeasured sparkle is minimal; this effect becomes more pronounced as the viewing angle increases.

کلیدواژه ها:

Metallic coatings ، sparkle ، flake size ، silver dollar ، cornflake