Direct Coating Technology for Metallic Paint Replacement

Direct Coating is a new processing technique which applies a single-layer polyurethane coating directly to a plastic part within a 2-shot molding cycle. The advantages of Direct Coating over traditional paint are improved surface quality, scratch resistance, and cost-effective processing. This concept has been previously showcased in high-gloss piano black with the simple geometry of the exterior door garnish. In this paper, the capabilities of Direct Coating are expanded to include metallic pigments and complex geometries for interior trim. For this development project, the Hyundai Sonata center fascia was selected as the target application due to the complex flow geometry around the bezel, and the high occurrence of customer contact, necessitating scratch and chemical resistance. Results of plaque-level testing showed that the coating material passed all requirements, including interior chemical resistance and scratch resistance. The work outlined in this paper sought to evaluate the appearance of surface quality, as well as knit and flow lines of the coating material. A 2-shot molding prototype tool was made, and part molding trials were conducted using metallic pigmented polyurethane coating. Initial molding trials showed promising results of the coating quality and pigment dispersion. As expected, this process overcame the geometric challenges due to the low viscosity of the coating material, which allowed the material to seamlessly merge together where the flow fronts met around the cutout geometry. Furthermore, the low viscosity material closely replicated the surface of the tooling, enabling the potential variation of surface finishes such as high gloss, matte, soft-feel, grains, and even textured patterns that could otherwise only be achieved by masking.