Investigation Into Effects of Nano‐ Al ₂ O ₃ Particle Shapes and Contents on the Curing, Mechanical, and Tribological Properties of Nitrile Butadiene Rubber Polymer

Composites were prepared by dispersing spherical, irregular, and platelet‐like nano‐Al 2 O 3 particles in NBR matrix by mechanical blending, with filler contents set at 0, 5, 10, and 15 phr. In this study, curing, mechanical, and tribological properties were tested to explore the impacts of particle shape. Irregular nano‐Al 2 O 3 most effectively enhanced the tensile strength and hardness of NBR composites, with the maximum tensile strength of 19.69 MPa at 10 phr. The sample containing platelet‐like nano‐Al 2 O 3 at 10 phr exhibited the lowest compression stress relaxation ratio of 25.6%, and the 15 phr platelet‐like one showed the minimum compression set rate of 23.15%. Tribological test results show that the addition of irregular nano‐Al 2 O 3 significantly reduced the worn volume. NBR material with 10 phr nano‐Al 2 O 3 exhibited the minimum worn volume, with a worn loss reduction of 36.81% compared with NBR base compound. In contrast, spherical nano‐Al 2 O 3 greatly reduced the friction coefficient (COF). The average COF of the NBR sample containing 15 phr spherical nano‐Al 2 O 3 particles achieved the lowest steady average COF, which was 25.17% lower than that of the NBR base compound. Scanning electron microscopy (SEM) images of the worn morphology reveal that irregular nano‐Al 2 O 3 rendered the worn surface smoother and significantly diminished abrasive wear. This study highlights the vital role of nanoparticle shape in regulating the mechanical and tribological properties of rubber composites.