Effect of cryogenic aging and test-environment on the tribological and mechanical properties of PEEK composites

This study investigated mechanical and tribological properties of polyetheretherketone (PEEK) and PEEK composites, before and after aging in liquid nitrogen for 5 months. Tribological tests conducted at 25oC and at -100oC in air and in high vacuum (10-5Pa) environment revealed the effect of matrix modification, fillers, environment, temperature, and cryogenic aging on their performances. Cryogenic aging of the polymers resulted in cryogenic embrittlement and decrease of the fracture toughness by around 10% and increase of wear rate by at least 20%. Very low coefficient of friction (0.02) was achieved in cryogenic vacuum environment for carbon fiber, graphite, and PTFE reinforced PEEK. The results indicate the significant impact of aging, temperature and environment on PEEK and its composites.