Influence of the Mixture Viscosity on Mechanical Anisotropy and Processability of an NBR-Based Rubber Mixture for Additive Manufacturing

ABSTRACT Rubber-based polymers with high carbon black content can be three-dimensionally (3D) printed using the additive manufacturing of elastomers process. However, high-viscosity materials limit printing resolution, making it difficult to produce fine structures and high-precision parts, especially two-component (2K) parts. The viscosity of a rubber compound used for rod seal applications was reduced and adjusted using Nipol® 1312 liquid rubber and the alkyl sulfonic phenyl ester Mesamoll® II as plasticizers to lower the torque level during extrusion when a reduced nozzle diameter of 0.4 mm is used in 3D printing. In addition, the flowability of the compound was enhanced prior to vulcanization of the part, which could increase the layer–layer bond and thus reduce the mechanical anisotropy typically induced by fused filament fabrication. Using a viscosity-optimized rubber compound, a 2K rod seal consisting of a thermoplastic polyurethane with elastomeric properties and an acrylonitrile rubber-based O-ring was produced and dynamically tested for leakage.