Fire-Retardant and Tribological Performance of Painted Ultem 9085 Polymer–Coating Composites Produced via Fused Deposition Modeling

Materials applied in interior and non-structural aircraft components are required to satisfy rigorous safety and performance criteria, especially with respect to flame retardancy and wear resistance. Ultem 9085, a high-performance polyetherimide thermoplastic, is extensively used in aerospace applications owing to its advantageous strength-to-weight ratio and compliance with flame, smoke, and toxicity (FST) requirements. Nevertheless, the application of surface coatings, including paints, may modify their fire-retardant and tribological performance, with potential implications for service behavior and regulatory compliance. This work provides new insight into the behavior of painted Ultem 9085 components under fire exposure and frictional loading, addressing the critical need to determine whether surface finishing affects the material’s inherent performance advantages. Thus, the effects of different paint coatings on the fire-retardant and tribological properties of Ultem 9085 are investigated. Test specimens were manufactured using a Stratasys F900 system with 100% infill density and geometries adapted for standard vertical burn and heat release tests. Fire performance testing, including vertical burn, smoke and toxicity, and heat release rate, was performed in accordance with CS/FAR 25 Appendix F and AITM 3-0005 requirements. Tribological behavior was assessed using a ball-on-flat tribometer under dry-sliding conditions, while surface texture was analyzed using 3D profilometry. Seven polymer–coating composites were examined. It was experimentally confirmed that all coatings reduced vertical burn length but increased peak heat release rate and smoke density relative to unmodified Ultem 9085. Tribological results varied significantly, highlighting the critical role of paint selection in achieving optimal fire safety and wear resistance.