Analysis of Creep Relaxation Behavior of NBR Seals Under Static Compression

ABSTRACT This study investigates the creep relaxation behavior of nitrile rubber (NBR) seals under static compression through a combination of molecular dynamics (MD) simulations and experiments, aiming to elucidate the microscopic mechanism behind the degradation of sealing reliability under long‐term loading. MD simulations reveal a three‐stage creep evolution: Stage I exhibits rapid strain and atomic mean square displacement (MSD) increase, reflecting instantaneous chain conformational adjustment; Stage II shows slowed strain/MSD growth due to entanglement resistance inhibiting chain slippage; Stage III demonstrates linear strain increase and stabilized MSD growth, indicating dynamic equilibrium after chain rearrangement. Stress relaxation simulations exhibit a rapid initial reduction in the radius of gyration ( R g ), indicating conformational contraction and orientational rearrangement, followed by long‐term stabilization of R g , which establishes a new equilibrium conformation with slow stress decay. Elevated initial stress enhances polar interactions between chains, increasing segmental mobility (MSD/diffusion coefficient increases) and creep strain accumulation while promoting chain contraction ( R g decreases) and orientational rearrangement. The latter accelerates stress relaxation by reducing interchain resistance. The experimental results are consistent with the simulation, providing a scientific basis and theoretical support for understanding the nature of the creep relaxation behavior of NBR seals.