Novel strategy to improve the tribological property of polymer: In-situ growing amorphous carbon coating on the surface

Abstract

Surface of ethylene-propylene copolymer (EPC) plastic was continuously treated by carbon plasma in a direct-current magnetron sputtering deposition (DC-MSD) system. Microstructure evolution of the polymer surface with different treating time was analyzed by Diffusive Reflectance infrared Fourier Transform (DRIFT) spectroscopy, Raman Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and Focus Ion Beam Scanning Electron Microscopy (FIB-SEM), respectively. The adhesion strength and tribological performance were measured by scratch tester and reciprocating ball-on-disc tribometer. Results showed that the bombardment of energetic plasma was capable of activating the surface polymer substrate, which could induce an in-situ transformation from organic carbon to inorganic carbon of the surface layer, following with an epitaxial growth of amorphous carbon upon the in-situ transition layer with the continuous treatment of carbon plasma. This kind of in-situ growing a-C coating on polymer including the in-situ transformation of top layer and the epitaxial growth on in-situ transition layer endow the weak substrate an excellent protective surface with strong adhesion, which exhibited much lower friction and wear. The possible wear mechanism of a-C coatings on polymer substrates was also presented.