The new pigment preparation from Merck will broaden styling possibilities in rotomolding to an unprecedented diversity. With the Iriodin® RMP series, which was specifically developed for the rotomolding application, it is possible to produce plastic products in which clear functions, flowing forms, and fascinating color effects unite into a unique whole.

For the first time, designers and architects can refine rotomolded objects with impressive effects, as Iriodin® RMP offers the opportunity to distribute platelet effect pigments uniformly to be visible at the outside of rotomolded parts. In this way, distinct products emerge that range from decorative components for toys to sporting goods, furniture, planters, and sculptural elements. These products can be furnished with any type of surface structure and custom colored to order.


Iriodin® RMP is an enhanced pigment preparation that consists of effect pigments and a supporting carrier that keeps the pigment from floating upon the fluidizing polymer within the mold – which is a typical problem when flaky pigments are applied in rotomolding. Four different products are available within the Iriodin®. RMP line - all of which have been specially developed for rotomolding. Iriodin® 119 WAY RMP offers a silver-white hue with excellent weatherability and yellowing resistance. Iriodin® 6163 RMP, has a much more sparkling effect and additionally offers the advantages of a synthetic substrate. Iriodin® 305 RMP gives plastics a genuine gold-touch of luxury while Iriodin® 504 RMP makes a bold-as-brass statement. Finally, these enchanting color effects can now adorn plastics formed through rotomolding.

General loading levels should be in the range of 2% Iriodin® RMP. Of course, this has to be adjusted individually for each product and formulation. To further increase styling potential different Iriodin® RMPs can be combined without any restrictions to create individual effects. Of course, it is also possible to combine Iriodin® RMP with standard absorption pigment or other colorants to achieve additional stylings.

To keep the best functionality, it is necessary to dry blend the RMP products into the polymer. The dry blend can be processed as usual – without additional equipment or extending the process time. The application of the pigment preparations guarantees an even and smooth appearance of the effect without clouding, even in case of large surfaces.


It is not recommended to use Iriodin® RMP in a compounding step by extrusion followed by grinding, as this will damage the preparation. Also high mixing intensity and high speed mixing are not recommended to avoid damages to Iriodin® RMP and to keep functionality.

Generally, Iriodin® RMP can be used in combination with all kind of surface structures, but certainly a high gloss mold surface will emphasize the visibility of the Iriodin® RMP effects. Matte finished molds may require larger particles to achieve the desired look. Thus, the influence of the mold surface should always be considered for the visible effect.

All in all, the new rotomolding preparations offer brand owners new inspirations for differentiating and enhancing their products to be more beautiful and desirable.

For any individual requests or more details on the Iriodin® rotomolding preparation, please get in contact with Cristiano Casiraghi from Merck Italy: He will be happy to support.

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