Tribological studies on polyetherimide composites based on carbon fabric with optimized oxidation treatment

Chemical inertness and hence limited wettability of carbon fibers (CF) with a selected matrix is the major problem for exploiting its full potential as reinforcement. Oxidation of CF with nitric acid is a classical method for treatment of CF which increases oxidative groups on fiber surface leading to enhanced adhesion with the matrix, but at the cost of damage to the fibers leading to reduction in strength. Thus the treatment has to be for optimum time to strike a balance between these opposite effects so that the composite will have best combination of performance properties. In depth studies on this aspect, however, are not reported especially in tribological studies. Hence nitric acid treatment was employed to carbon fabric for various time intervals (15–180 min). Eight composites with untreated and acid treated fabrics were developed based on polyetherimide (PEI) matrix and evaluated for mechanical and abrasive wear properties. It was observed that 90 min treatment time was ideal one to achieve maximum possible enhancement in strength and tribological properties. Fiber–matrix adhesion was improved due to inclusion of oxygenated functional groups as supported by Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy and increased surface roughening of fibers as supported by scanning electron microscopic (SEM) studies.