Functionalization of spherical alumina nano-particles for enhancing the performance of PAEK-based composites

Abstract Nano-particles (NPs) and their role in controlling the performance of composites is the most intensively researched field with still limited understanding. The domain of investigating nano-mechanisms operative during tribological contacts, especially when particles of contrasting properties are simultaneously added in the polymer composite for exploration of synergism, is almost an untouched area. In this work, graphite particles (soft and layer-lattice structure) (15 %) were co-added with 2 % NPs of alumina (hard and spherical) in a composite containing PAEK (poly aryl ether ketone) and short glass fibers (35 %). In another composite, these NPs were siloxane functionalized to investigate the effect of functionalization. In-depth investigations on physical, mechanical, and tribological properties along with detailed analysis of mechanisms by FESEM-EDAX (Field-Emission Scanning electron microscopy-Energy Dispersive Spectroscopy) , Micro-Raman spectroscopy (MRS), atomic force microscopy (AFM), goniometry, nano-indentation, etc. led to a conclusion that the inclusion of hard and spherical NPs changes the fundamental process of area contact to a point contact to a great extent resulting in further reduction in friction and wear. Particles of graphite, on the other hand, were finally found to be converted into nano-graphene sheets during severe shearing based on AFM investigations. Increase in hardness due to NPs was found to be a reason for enhanced wear resistance (WR). Functionalized NPs led to the best properties in every case because of enhanced adhesion with the resin, which minimized the chances of being thrown out in wear debris.