Selective Functionalization of MWCNTs: Enhancing Wear Mechanisms and Friction-Induced Graphitization in Epoxy Composites

This investigation elucidates a novel methodology for augmenting the tribological and mechanical attributes of epoxy composites via selective functionalization of multi-walled carbon nanotubes (MWCNTs). The study optimizes wear mechanisms and friction-induced graphitization by incorporating pristine (P-MWCNTs), carboxyl-functionalized (COOH-MWCNTs), amine-functionalized (NH₂-MWCNTs), and silane-modified MWCNTs. Composites were characterized for tensile strength, compressive strength, surface hardness, coefficient of friction (COF), and specific wear rate (SWR). Incorporation of 0.3 wt.% COOH-MWCNTs yielded optimal performance, reducing SWR by 82% (0.07 × 10⁻⁶ mm³ N⁻¹·m⁻¹ at 8 Hz) and COF by 32% (0.37 at 10 N) relative to neat epoxy (SWR: 0.50 × 10⁻⁶ mm³ N⁻¹·m⁻¹, COF: 0.66 at 15 N). Enhanced dispersion, interfacial adhesion, and tribofilm formation account for superior tensile strength (≈90 MPa) and hardness (≈88 Shore D). X-ray diffraction and transmission electron microscopy validated friction-induced graphitization and partial structural degradation above 10 N. Applications encompass self-lubricating bushings, protective coatings, and wear-resistant surfaces for automotive and industrial components. Future investigations should target enhanced compressive strength and load-bearing capacity.