Study on the Effects of Hindered Phenol <scp>AO</scp> ‐80 on the Static and Dynamic Mechanical Properties of <scp>HNBR</scp> : Molecular Dynamics Simulations and Experiments

ABSTRACT Combining molecular dynamics (MD) simulations with experimental methods, the mechanistic effects of hindered phenol 3,9‐Bis[1,1‐dimethyl‐2‐[(3‐tert‐butyl‐4‐hydroxy‐5‐methylphenyl)propionyloxy]ethyl]‐2,4,8,10‐tetraoxaspiro [5,5] undecane (AO‐80) on the static and dynamic mechanical properties of hydrogenated nitrile rubber (HNBR) were investigated systematically. In the MD simulation respect, the composite systems with different AO‐80/HNBR ratios were constructed to analyze the changes in the solubility parameter ( δ T ), hydrogen bonding (H‐bond), fractional free volume, and binding energy ( E binding ), and then the influence mechanism of AO‐80 on the damping performance of HNBR is investigated from the microscopic perspective. The loss factor (tan δ ), tensile strength, elongation at break, hardness, tear strength, and swelling‐related mechanics were measured experimentally by dynamic mechanical analysis (DMA) and static mechanical test. The results indicate that with the increase of AO‐80 content (0–40 wt%), the damping performance of AO‐80/HNBR composites is enhanced. The molecular dynamics simulations showed that the tan δ of AO‐80/HNBR composites increased from 0.676 to 0.887 and the hysteresis loop area increased from 2.01231 × 10 to 2.17571 × 10 5 Pa in the temperature range of 5°C–15°C. In the DMA test results, loss‐peak area is increased from 31.95 to 40.63, and the maximum of tan δ is increased from 1.17 to 1.315 at room temperature. The effective damping temperature span (tan δ &gt; 0.3) is expanded from 31.31°C to 39.28°C, and the hysteresis loop area increased from 1.91303 × 10 4 to 2.07725 × 10 4 Pa. With the increasing of AO‐80, the vulcanization rate of AO‐80/HNBR composites is increased, and the cure rate index is increased from 32.63 to 50.51 min −1 . The tensile strength is decreased from 26.65 to 22.24 MPa; the elongation at break is increased from 375.19% to 382.753%; the hardness is decreased from 67.9HA to 61HA; the tear strength decreased from 50.25 to 39.02 MPa; the crosslinking density decreased from 13.55 to 10.25 mol/m 3 . After swelling, the mechanical properties of the composite material are decreased, but the change rate was stable and maintained good stability. Such as the average tensile strength is decreased by 36.46%, the fracture elongation rate is decreased by 32.1%, the hardness is decreased by 16.63%, and the tear strength is decreased by 33.62%. This study provides the microscopic influence mechanism and experimental basis for the damping performance of hindered phenol modified rubber. The AO‐80/HNBR composites are suitable for high damping and swelling resistance scenarios.