Environmentally benign metallization of material extrusion technology 3D printed acrylonitrile butadiene styrene parts using physical vapor deposition

Metallization has been widely used to enhance the aesthetics and performance of injection molded plastic parts, but the techniques have not been widely extended to 3D printed parts due to intrinsic differences in surface chemistry and morphology. Here, we investigate direct metallization of acrylonitrile butadiene styrene (ABS) 3D printed thermoplastic parts using low cost environmentally benign surface preparations and physical vapor deposition (PVD) to avoid the use of preparation with toxic chromic acid. Fourier transform infrared (FTIR) spectra are gathered for each surface preparation method prior to metallization. The metallized parts are then characterized for thin film adhesion, electrical resistivity, and optical reflectivity. Additionally, each part is imaged using a scanning electron microscope (SEM) post-metallization. The results show that surface preparation with solvent results in a smooth and aesthetically pleasing surface, but metallic film adhesion is poor. Conversely, when 2000 grit sandpaper is used to mechanically prepare the surfaces, the resulting films have poor electrical conductivity and optical reflectance, but excellent adhesion. Atmospheric plasma treatment of the parts results in the highest overall performance, with superior adhesion strength and optical reflectivity and low electrical resistivity. Electron microscopy and FTIR reveal that the high adhesion resulting from atmospheric plasma is caused by modification surface morphology, but not surface chemical termination. The results indicate that direct metallization of 3D printed ABS is a viable method for creating metallized parts with high performance and an aesthetically pleasing appearance and that the use of chromic acid in surface preparation is not necessary.