Vacuum Outgassing Characteristics of Unpigmented 3-D Printed Polymers Coated with ALD Alumina

Abstract

3-D printing offers enormous potential for fabricating custom equipment for space and vacuum systems, but in order to do this at low-costs, polymers are necessary. Historically polymers have not been suited for these applications because of outgassing, but if coated with a conformal, inorganic film introduced with atomic layer deposition (ALD), then outgassing can be reduced. Previous work on coating ALD layers showed promise with heavily outgassing carbon black containing 3-D printed polymers. In this study, ALD aluminum oxide and a commercially available vacuum sealant resin were used to coat clear, acrylonitrile butadiene styrene (ABS), polycarbonate (PC) and polypropylene (PP). Characterization of the films included spectroscopic ellipsometry for thickness, microstructure analysis with scanning electron microscopy, chemical analysis with energy-dispersive X-ray spectroscopy, and residual gas analysis to study relative change in outgassing. ALD-coated samples registered lower pressures than the resin-coated ones. The results showed that the ALD coatings could effectively inoculate unpigmented 3-D printed plastics, which could be used in contamination-sensitive environments such as semiconductor processing systems and space environments.