Flexural and impact properties of sheet type α-MnO2 epoxy nanocomposites

Abstract The flexural strength and impact energy absorption capacity of a material are critical factors for ensuring the durability and safety of components. Epoxy nanocomposites containing α-MnO 2 show promise for structural applications. This study investigates the flexural and impact energy absorption properties of α-MnO 2 -epoxy nanocomposites, which have not been extensively explored in previous research. Nanocomposites with varying weight percentages of α-MnO 2 in epoxy were prepared using ultrasonication dispersion, combined with mechanical mixing technique. X-ray diffraction, scanning electron microscopy, and differential scanning calorimetry were employed to analyze the phase composition, surface morphology, and glass transition temperature of the materials. The successful synthesis of α-MnO 2 epoxy nanocomposites was confirmed by X-ray diffraction analysis and microscopic imaging. The three-point bend tests demonstrated that incorporating α-MnO 2 into the epoxy matrix reduces its flexural stress and strain. Specifically, the flexural stress of specimens with 0.1 wt%, 0.3 wt%, and 0.5 wt% loading decreased by 2.85%, 9.49%, and 26.7%, respectively, while the corresponding flexural strain values decreased by 6.35%, 19.36%, and 28.57%, respectively, compared to pure epoxy. Conversely, the flexural modulus increased by 1.2% and 27.99% for 0.1 wt% and 0.3 wt% loadings, respectively, but decreased by 6.17% at 0.5 wt% loading. Thus, the flexural modulus improved with α-MnO 2 addition up to 0.3 wt%. Drop weight impact tests revealed that the energy absorption capacity of nanocomposites containing 0.1 wt%, 0.3 wt%, and 0.5 wt% α-MnO 2 decreased by 11.26%, 15.73%, and 21.57%, respectively, relative to pure epoxy. Therefore, the impact test results also indicate a reduction in energy absorption capacity with increasing α-MnO 2 content. This decline in flexural stress, flexural strain, and energy absorption capacity is attributed to the filler material’s shape, pore formation during the sample fabrication, and the presence of agglomerated α-MnO 2 within the epoxy matrix, which elevates stress concentrations. Fractography analysis further revealed that the material exhibited brittle fracture rather than ductile deformation during testing.