Elements designed to minimize particle damage for compounding special-effect pigments.

The Omega series of twin-screw extruders from SteerAmerica Inc., Uniontown, Ohio, is now available with specially designed screw configurations for compounding special-effect pigments with minimal damage to the sensitive platelet structure, reportedly retaining up to 80% of the particle size in the compound from the pigment.

Specialized patented special elements are said to eliminate shear peaks, which Steer says are the biggest cause for attrition and damage to the structure. What’s more, the special mixing elements with a fully intermeshing and self-wiping profile prevent stagnation and degradation and the resultant char formation. The Omega line’s barrel-to-screw gap and screw-to-screw gap is maintained at less than 0.25 mm to have fully wiping effect rather than shearing effect addressing the issue of leakage, and the deeper root depth (1.71) draws more of the resin into the screw root and away from the shear forces that occur when the melt contacts the barrel wall.

Explains Rob Roden, Steer’s assistant v.p., “The root of all evil is shear. The standard elements used by the industry today are brutal, (and) virtually reduce pigment-particle size by half due to various inefficiencies. Therefore the quality of the compound is compromised.”

The Omega platform for processing special-effect pigments is available in various sizes for defined output.