Enhanced Interfacial and Tribological Properties of Polyether Ether Ketone Composites by the Addition of Modified Carbon Fibers

Carbon fiber (CF)-reinforced polyether ether ketone (PEEK) composites exhibit excellent comprehensive properties. However, the inert surface and poor wettability of CF reduce the interfacial performance in CF/PEEK composites, thereby limiting their applicability in harsh environments. To address this limitation, CF was chemically grafted using two modifiers: a polyethyleneimine (PEI) sizing agent containing carboxylated multi-walled carbon nanotubes (MWCNTs), and a polyamidoamine (PAMAM) coupling agent also containing carboxylated MWCNTs. The amino groups in PEI and PAMAM can form amide bonds with carboxylated CF. Additionally, the long-chain structure of PEI physically entangles the CF, and its π–π conjugation with the PEEK matrix enhances interfacial bonding. As a result, CF-PEI-MWCNTs/PEEK composites (0.3 wt.% MWCNTs) demonstrated superior interfacial properties compared to CF-PAMAM-MWCNTs/PEEK composites (0.5 wt.% MWCNTs). The wear resistance of the composite is improved, and the wear mechanism changes from plastic deformation to mild adhesive wear.