Tribological performance of fluorinated polyimide-based nanocomposite coatings reinforced with PMMA-grafted-MWCNT

Abstract

The tribological behavior of PMMA-grafted-MWCNT nanocomposite coatings that were prepared by applying the direct casting method to aluminum surfaces was investigated. Amino-functionalized MWCNTs were first covalently functionalized with PMMA to introduce the interaction force. The PMMA-g-MWCNT exhibited a higher dispersive capacity in the 6FDA-based polyimide matrix than pure MWCNT composite due to strong interfacial interactions in the nanocomposite. The maximum possible amount of PMMA-g-MWCNT was 5 wt.% because excessive MWCNT in the nanocomposites makes them fragile and brittle. Sliding tests were performed in ball-on-disk configurations under dry conditions. The normal contact force was 9.7N against a 12.7-mm-diameter steel ball resulting in a Hertzian circular contact stress of 0.65 GPa. The sliding speed was 0.02 m/s and sliding tests were continued until the coefficient of friction stabilized. The nanocomposite coating reinforced with 3 wt.% MWCNT was the most stable and had the lowest coefficient of friction in this study. This was due to the formation of a thin, uniform friction film on the wear track during sliding, and we concluded that the friction film plays an important role in facilitating the stable frictional behavior of the nanocomposite coatings. (C) 2011 Elsevier B.V. All rights reserved.