Undercutting of defects in thin film protective coatings on polymer surfaces exposed to atomic oxygen

Protection for polymeric surfaces is needed to make them durable in the low earth orbital environment. Thin film coatings of oxides such as SiO2 are viable candidates to provide this protection, but concern has been voiced over the ability of these coatings to protect when defects are present in the coating due to surface anomalies. When a defected coating protecting a polymer substrate is exposed to atomic oxygen, the defect provides a pathway to the underlying polymer allowing oxidation and subsequent undercutting to occur. Defect undercutting was studied for sputter deposited coatings of SiO2 on polyimide Kapton. Preliminary results indicate that undercutting may be limited as long as the coating remains intact with the substrate. Therefore, coatings may not need to be defect free to give protection to the underlying surface.