Manufacturing of tetrahedral metal effect pigment particles and analysis of their orientation in polymer melts

In this study, novel micro particles in the shape of irregular tetrahedrons in a two to three digit micrometer size range are presented. The particle manufacturing feasibility was investigated in three different ways shaping, casting and rolling. Rolling showed the potential for mass production. The suitability of tetrahedral particles for the use as metal effect pigment was assessed by comparison with conventional platelet shaped metal effect pigments. Optical inspection showed a strongly reduced luminance inhomogeneity in weld line regions in the case of the tetrahedral particles. It was found by synchrotron X ray tomography examination of particles in solidified polymethylmethacrylate PMMA that particle depletion is not the main reason for visible flow lines. The orientation of platelet shaped pigment particles was identified to cause such flow lines. PMMA filled with tetrahedral particles, in contrast, shows homogenous optical properties independent from the particle orientation. Thus, flow lines in weld line regions can be omitte