Biodegradation of PEEK Piston Rings

Abstract

Polyether ether ketone (PEEK) is considered a high performance thermoplastic with excellent mechanical, chemical, and thermal properties. It is generally believed that this material is chemically and biologically inert, and is used for various biomedical and industrial applications, especially in the form of fiber reinforced polymeric composites. Contrary to the general belief, the present work reports the biodegradation of PEEK piston rings that were used in a reciprocating CO2 compressor. A series of circumstantial and direct evidences were collected by following various tests and characterization methods to confirm the degradation of the piston rings by bacterial attack. The bacterial cells were extracted from the degraded piston rings, cultured in agar medium and then studied using scanning electron microscope. An experimental simulation was carried out by depositing and incubating a bacterial culture on the pristine surface of a PEEK specimen. The simulation experiment revealed an early stage of bacterial degradation in the form of cracking of the PEEK specimen surface. The results of various tests, characterization, and the experimental simulation presented in the paper suggest that PEEK based composites degrade due to enzymatic hydrolysis process by Myxococcus Xanthus, the rod–shaped soil bacteria.