>>>Why Pearl pigment yellowing in plastic?

Reasons:

The surface of the pearl powder is coated with titanium dioxide and titanium is a thixotropic agent. Under sufficient ultraviolet irradiation, it will react with polyolefin products and cause yellowing.
Solutions:
1.Choose anti-yellowing pearl pigments, which coated protection layer on the surface to avoid the contact between titanium and polyolefin.
2.Use pearl pigments in the compatible system.

>>>Why is there flow line for plastic when using pearl pigment?

Reasons:
The accumulation of metallic pigments or pearlescent pigments at the intersection location, resulting the density difference between different parts, then flow line is here.
solutions:
1.Proper design the shape of mold. Reduce or avoid corners, ribs and hole in the design.
2.Choose pearl pigments with bigger particle size.
3.Use professional spray-free mold.
4.Increase melting temperature, back pressure and pressure holding time.
5.Use fast hot and fast cool mold.