Slippery and wear-resistant shape memory polymers enabled by the reinforcement of double transition metal-based MAX phase (Mo2TiAlC2)

Abstract

While polymeric components have emerged as potential replacements for metal counterparts in various moving mechanical systems, their unstable coefficient of friction and inferior wear resistance remain significant obstacles to their commercialization. MAX phase materials have demonstrated extraordinary potential for numerous applications, with M_n+1AX_n-type MAX phases being studied mainly for tribological applications. Here, we, for the first time, utilize double transition metal carbide M_xM'_yAX_(x+y-1)-based MAX phase materials, more specifically, Mo₂TiAlC₂ MAX phase, as the reinforcing agent within the shape memory polyurethane (PU) matrix. PU composites were fabricated via melt blending and injection molding, incorporating varying loadings of Mo₂TiAlC₂. Tribological performance was evaluated using a ball-on-disk tribometer under controlled conditions. The resulting composites demonstrated significant reductions in the coefficient of friction and substantial enhancements in wear resistance compared to pristine PU. Microstructural and spectroscopic analyses were employed to elucidate the underlying friction and wear control mechanisms. Thermomechanical testing further confirmed that the shape memory functionality of PU remained largely unaffected by the addition of filler. This discovery opens a new area of research for controlling the lubricating and wear properties of SMPs using a double transition metal carbide-based MAX phase, which can be extended to other polymeric and metallic systems.