Effects of 2-D transition metal carbide Ti2CTx on properties of epoxy composites

Abstract

Here, 2-D nanostructured Ti₂CT_x was successfully synthesized by selectively exfoliating the Ti₂AlC MAX phase via a liquid etching technique. Investigated as a promising and functional reinforcement additive, 2-D Ti₂CT_x nanosheets were dispersed into an epoxy matrix evenly at different mass percentages to obtain self-lubricating and anti-friction Ti₂CT_x/epoxy resin (EP) nanocomposites with high toughness and low creep strain by in situ intercalative polymerization. The phase structure and morphology of Ti₂CT_x and Ti₂CT_x/EP nanocomposites were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Subsequently, this work studied the effect of Ti₂CT_x on the EP matrix in terms of fracture surface morphology, glass transition temperature (T_g), storage modulus (E_s), thermal stability, mechanical properties and dry sliding anti-friction properties. The results show that Ti₂CT_x interlayers were intercalated and exfoliated with EP molecular chains and intertwined with each other, which produced a greater interfacial area between the inorganic additive and the polymer matrix, resulting in the formation of Ti₂CT_x/EP nanocomposites without adverse structural defects. With the addition of an appropriate mass fraction of Ti₂CT_x, the fracture toughness and flexural strength of EP composites reached 17.8 kJ m⁻² and 98 MPa, which represented increases of 76% and 66%, respectively, compared with those of pure EP. In addition, increases in T_g and E_s of 15% and 38% were achieved, respectively, relative to those of pure EP when the concentration of Ti₂CT_x was 2.0 wt%. Moreover, tribological analysis indicated that there was a great improvement in anti-friction properties and the morphology of worn surfaces of the nanocomposites appeared to be smoother than that of pure EP, which implied the transformation of fatigue and abrasion wear into adhesion wear. This work is of great significance in that novel 2-D transition metal carbide crystals were employed to fill and modify a thermoset polymer resin and enhance its toughness and strength and, as a self-lubricating additive, enabled a great breakthrough in the anti-friction properties of polymer-matrix composites.