RELAXATION BEHAVIOR OF 3D PRINTED NBR-BASED RUBBER O-RINGS AS INNER PART OF ROD SEALS

The viscoelastic properties of rubber polymer-based compounds are crucial for further applications but challenging in the manufacturing process using additive manufacturing techniques. The fact that the first layer is attached to the printing bed restricts free relaxation after extrusion, that the part shows a strong contraction along the printing direction after release and especially after vulcanization. In this study, the molar mass distribution and acrylonitrile (ACN) content of an NBR-based compound for the fabrication of O-rings for rod seal applications was varied to demonstrate the different degree of contraction resulting from 3D printing. An ACN content of 34% and an average molar mass Mw of 2.47·105 g·mol−1 with a dispersity index D of 2.6 was found to be a suitable compromise between the degree of contraction and compression set as a criterion for the application as O-ring as inner part of rod seals.