Precision in Rubber Seal Lifetime Prediction: The Critical Role of Aspect Ratio

ABSTRACT Rubber seals are widely used in industry, with reliability assessed via aging studies adhering to international standards. However, sealing components often have high aspect ratios, with length exceeding height. This study shows how aspect ratio affects aging behavior, potentially leading to non‐representative lifetime predictions under standard conditions. NBR and EPDM rubber were submitted to thermo‐oxidative cycles with aspect ratios (AR) of 2.5, 7.5, 30, and 60 with temperatures ranging from 80°C to 170°C, and up to 180 days. Specimens were obtained from commercial gaskets and were evaluated employing compression set, indentation modulus, hardness, crosslink density, and calorimetric analyses. Under 140°C, NBR is more susceptible to aging with greater kinetics of CS evolution, hardness, crosslink density, and variation in Tg. The higher reaction rate of NBR also makes it more prone to diffusion‐limited oxidation (DLO) from a temperature of 110°C, while for EPDM, DLO only appears at 170°C. The findings indicate that higher aspect ratios present enhanced resistance to thermo‐oxidative aging due to their longer diffusive path. For the prediction of sealing component service life, sample geometry with an aspect ratio equal to or exceeding 30 is proposed. The appropriate selection of test specimens can more accurately reflect the in‐service performance of these components, reducing unnecessary maintenance and material consumption.