# Spatial Tribological Properties of PI/PTFE Based Self-Stratifying Composite Coatings Grafted by Amino-POSS

## TL;DR

This paper studies composite coatings that improve performance in space environments by reducing wear and increasing durability.

## Contribution

A new self-stratifying composite coating is developed using amino-POSS to enhance AO resistance and tribological performance in LEO conditions.

## Key findings

- Gradient coating reduced mass loss by 78% under atomic oxygen exposure.
- Friction coefficient was more stable and lower at low temperatures compared to high temperatures.
- POSS modification decreased wear rates by 77.5% and 50% at high and low temperatures, respectively.

## Abstract

In low Earth orbit (LEO), special environments such as atomic oxygen (AO), alternating high and low temperatures, and high vacuum can seriously affect the reliability and service lifetime of moving parts of space equipment. Therefore, there is an increasingly urgent demand for long-life, high-performance lubricating protective coatings with the rapid evolution of astronautical technology. In this study, polyimide (PI) was modified by polyhedral oligomeric silsesquioxane (POSS) with different numbers of functional groups to fabricate PI-based self-stratifying gradient composite lubricating coatings. The coating exhibited significantly enhanced AO resistance, and its vacuum tribological properties under alternating high and low temperature conditions were investigated. Results show that the mass loss of the gradient coating under AO exposure was significantly reduced by 78%, and the tribological properties of the coating under high and low temperature alternating conditions were significantly different. The friction coefficient was more stable and was smaller than that at high temperatures, and the wear rates of the POSS-modified coating also decreased by 77.5% and 50% for both high and low temperatures compared with that of the PI/PTFE coating.