Enhancing gamma irradiation resistance by a‐C film treatment on polytetrafluoroethylene (PTFE) surface

Abstract

Polytetrafluoroethylene (PTFE) solid self‐lubricating materials exhibit inferior tribological properties in the gamma‐irradiated environment. In this paper, amorphous hydrogen‐free carbon (a‐C) film was deposited on the PTFE polymer surface by magnetron sputtering, and the a‐C/PTFE samples were irradiated with gamma ray at a maximum dose of up to 5 MGy. The evolution of the structure and nanomechanical and tribological properties of a‐C/PTFE with different irradiation doses were investigated. The structural analyses reveal that the microstructure of a‐C films irradiated at 5 MGy doses is stable. Due to the covering of the a‐C film, significant cracks appear at the surface of the a‐C/PTFE sample only when the irradiation dose reaches 5 MGy. Before and after irradiation, the nanohardness and Young's modulus of the a‐C/PTFE are significantly higher than those of PTFE. The mechanical properties of PTFE are improved by a‐C film surface treatment. The friction experiments show that the average friction coefficients of both a‐C/PTFE and PTFE remain stable around 0.175 with increasing irradiation dose. When the irradiation dose is within 1 MGy, frictional behaviors occur only on the surface of a‐C films, and the wear rate of a‐C/PTFE is as low as 9.3 × 10−5 mm3/N.m, which is significantly lower than that of PTFE. The method of a‐C film treatment on the PTFE surface can dramatically improve the irradiation resistance of PTFE.