Low Loading of Tannic Acid-Functionalized WS2 Nanosheets for Robust Epoxy Nanocomposites

Two-dimensional tungsten disulfide (WS2) nanosheets hold great potential for improving the mechanical properties of polymer nanocomposites, yet their large-scale preparation, dispersion, and toughening efficiency remain challenging. Herein, a facile, scaled-up, and eco-benign method was developed to simultaneously exfoliate and fabricate surface-functionalized WS2 nanosheets with the assistance of biobased polyphenols, such as tannic acid (TA) from peel waste. Benefiting from the strong interfacial interaction between TA-modified WS2 nanosheets (WS2-TA) and the epoxy resin (EP) matrix, considerable improvement in the mechanical properties of the EP/WS2-TA nanocomposites was achieved. The introduction of barely 0.25 wt % WS2-TA nanosheets increased the tensile and flexural strengths by 63 and 35%, respectively. Meanwhile, with the same low loading of 0.25 wt %, the impact strength and fracture toughness (K-Ic) of the nanocomposites, respectively, increased by 131 and 96%, realizing highly efficient toughening of EP. Besides, the thermal properties of the EP/WS2-TA nanocomposites also achieved noticeable improvements, which were attributed to the good dispersion of the nanosheets, combining inherently rigid and flexible nature, and the strong interfacial interaction between the nanosheets and the EP matrix. This work not only highlighted the simultaneous exfoliation and surface functionalization of the two-dimensional (2D) nanosheets but also broadened their applications in high-performance nanocomposites.