Browse Publications Technical Papers 2019-01-0186

Direct Coating Technology for Metallic Paint Replacement 2019-01-0186

An introduction to Direct Coating was showcased last year with high-gloss piano black finish for Hyundai’s exterior door appliques. In this paper, the capabilities of Direct Coating are expanded to include more complex geometries, different surface texture, and addition of metallic flake for interior trim. In recent years, metal trim components have been replaced by painted plastic to reduce cost and weight. Although this gives the appearance of metallic trim, paint leaves imperfect surface smoothness, and is susceptible to scratching. Another competing technology is molded-in-color, where pigment is added directly to the plastic resin, and no paint is applied. Although this results in cost savings over paint, careful consideration must be given to avoid knit and flow lines, limiting the application to simple geometries or requiring expensive molding operations such as rapid heating and cooling. In contrast, Direct Coating applies a single-layer polyurethane coating directly to the plastic part within a 2-shot molding cycle. The advantages of Direct Coating are reduced orange peel, improved scratch resistance, and cost-effective processing. For this project, the Sonata center fascia was selected as the target application due to the complex flow geometry around the bezel, as well as the risk of exposure to air fresheners and the high occurrence of customer contact, necessitating scratch and chemical resistance. Results of material testing show that the coating passes all requirements. It is expected that this process will also overcome the limitations of molded-in-color due to the low viscosity of the coating, which allows it to flow together without the appearance of knit lines. A prototype tool was made, and initial trials were conducted with clear coating, which show promising results of the coating quality. A metallic coating trial is scheduled for September, to evaluate appearance and optimize equipment set-up and processing parameters for seamless metallic coating.


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