Research on the Tribological Behavior of Polyurethane Acrylate Coatings with Different Matrix Constituents as Well as Graphite and PTFE

With the aim of developing a wear-resistant ultraviolet (UV)-cured self-lubricating coating, this study investigated the impact of matrix components and lubricants on UV-cured interpenetrating polymer network-polyurethane acrylate (IPN-PUA) self-lubricating coatings. Four coatings with different monomer combinations were prepared, using isophorone diisocyanate (IPDI) or tolylene-2,4-diisocyanate (TDI) in combination with hydroxypropyl acrylate (HPA) or 2-hydroxyethyl acrylate (HEA). These coatings were denoted as IPDI-HPA, IPDI-HEA, TDI-HPA, and TDI-HEA, respectively. The surface morphologies, compositions, friction and wear properties, as well as the comprehensive performances were investigated. The results indicated that IPDI-HPA had the lowest surface roughness and that TDI-HEA had the smallest wear rate, while TDI-HPA showed the best overall performance (roughness of 1.485 μm, coefficient of friction (COF) of 0.746, and wear rate of 10.64 × 10^-14 m³/N·m). With TDI-HPA as the matrix, graphite and polytetrafluoroethylene (PTFE) particles of different sizes were added as lubricants. The T-P-25F (TDI-HPA coating with 25 μm sized PTFE) coating had self-lubricating capabilities, as was manifested by a friction coefficient of 0.395, which was 47% lower than that of the pure TDI-HPA coating, and it simultaneously showed outstanding wear-resistance performance. The wear rate of the T-P-25F coating was 3.97 × 10^-14 m³/N·m, 62.7% lower than that of the pure TDI-HPA coating. This research provides valuable guidance for optimizing the performance of such coatings and yields a self-lubricating coating with excellent wear resistance.