# Design of a Superlubricity System Using Polyimide Film Surface-Modified Poly-Ether-Ether-Ketone

## TL;DR

Researchers improved the friction performance of PEEK by coating it with a polyimide film, achieving superlubricity under certain conditions.

## Contribution

A polyimide film surface modification on PEEK is shown to significantly reduce friction and enable superlubricity when paired with steel.

## Key findings

- The friction coefficient of PI-modified PEEK decreased by 83.3% compared to pure PEEK.
- Induced alignment superlubricity was achieved under specific load and rotational speed conditions.
- Excessively high rotational speeds (above 300 rpm) reduced system stability.

## Abstract

Poly-ether-ether-ketone (PEEK) is widely used in dynamic sealing applications due to its excellent properties. However, its tribological performance as a sealing material still has limitations, as its relatively high friction coefficient may lead to increased wear of sealing components, affecting sealing effectiveness and service life. To optimize its lubrication performance, this study employs surface modification techniques to synthesize a thin polyimide (PI) film on the surface of PEEK. When paired with bearing steel, this modification reduces the friction coefficient and enhances the anti-wear performance of sealing components. The tribological properties of a friction pair composed of GCr15 steel and PI-modified PEEK were systematically investigated using a nematic liquid crystal as the lubricant. The friction system was analyzed through various tests. The experimental results show that, under identical conditions, the friction coefficient of the PI-modified PEEK system decreased by 83.3% compared to pure PEEK. Under loads of 5 N and 25 N and rotational speeds ranging from 50 rpm to 400 rpm, the system exhibited induced alignment superlubricity. At 50 rpm, superlubricity was maintained when the load was below 105 N, while at 200 rpm, this occurred when the load was below 125 N. Excessively high rotational speeds (above 300 rpm) might affect system stability. The friction coefficient initially decreased and then increased with increasing load. The friction system demonstrated induced alignment superlubricity under the tested conditions, suggesting the potential application of PI-modified PEEK in friction components.