Development of the laboratory-based accelerated service life testing - “tire aging test”- encountered difficulties due to complexity of multi-disciplinary processes in the tire materials while trying to induce thermo-oxidative degradation, similar to that taking place in the ‘worst case’ in-service. Preliminary experience with the oven aging at elevated temperatures showed that in some light truck tires damaging conditions occur in the form of sidewall blisters/detachments and casing separations due to inflation gas built up in interior tire layers during aging, even prior the roadwheel endurance testing [1].

Analysis and comprehensive modeling techniques are developed for gas diffusion and oxidation in the tire structure, with focus on the Intra-Carcass Pressure (ICP) build-up predictions.  In Finite Element models temperature dependent diffusion properties are used with account for their high heterogeneity in different tire components. Results of transient simulations predict higher oxidation/ degradation rate in the sidewall and detrimental effect of ICP build-up for Load Range E tires. Influence of the butyl liner barrier permeability and gauge is evaluated, as well as impact of other construction variations. Predicted trends agree with the available observations and measurements. ICP levels in simulations of the long-term gas diffusion under regular service conditions are significantly lower than in the aging test modeling.  Modified aging test conditions are proposed that will greatly reduce deleterious side-effect of the ICP buildup, as assessed in simulations.

1.  DOT HS 810799 “Research Report to Congress on Aging” (2007)