Using special effects in rotomolding applications

Rotomolding is a popular low-pressure process for producing medium-to-very large parts with moderate complexity and detail, in a variety of thermoplastic polymer systems. However, rotomolding has lagged behind other plastic processing options in the availability of in-mold special effects. This is partly because it is difficult to disperse colorants evenly in the material, since there is no melt mixing step prior to introducing material into the mold. Further, since part thickness is built up as successive layers of "skin" frozen on the inside of the part, it can be challenging to create an effect solely on the surface of a part without impacting the base material. This paper looks at 3 key parameters of the technical challenge in creating special effects for rotomolded parts.