Aging of Natural Rubber in Air and Seawater

Abstract

Accelerated aging experiments were carried out on a natural rubber vulcanizate exposed to air and to seawater. Failure strain, shown to correlate well with the fatigue lifetime, was used to monitor the extent of degradation. The effect of temperature on the rate of aging followed an Arrhenius law, with activation energies equal to 90 ± 4 and 63 ± 3 kJ/mol for air and seawater aging, respectively. The difference can be accounted for by the difference in oxygen concentration for the two environments.

Strains in an Inflated Rubber Sheet

“…5,6 The present study was motivated by the development of an inflated rubber disk as an ejection system for torpedoes on US Navy Virginia-class submarines. [7][8][9] During fatigue testing, the failure properties were found to be dependent on the size of the disk. Such a scaling effect indicates that biaxial deformation at the pole, which is the largest strain, does not necessarily govern the failure.…”

Aqueous chloramine diffusion into elastomers

“…In the absence of a better technique to develop a composite curve, it is the conclusion of this research that the long-term performance curve developed using diffusion theory at 1 ppm, 23 C, is better representative than TTS curves. This conclusion was verified with 70-day mass intake experiment data of 32-inch elastomeric coupons.…”

“…For this study, unless otherwise noted, samples were cut into 2 Â 1 Â 0.08-inch coupons and were submerged in aqueous chloramine solutions with varying concentrations (1,30, and 60 mg/L) and temperatures (23,45, and 70 C) for 30 days. 9 The elevated temperatures and concentrations were necessary to generate measurable degradation within a reasonable testing period.…”

“…5 In previous work, 6 the research team characterized elastomer chloramine-induced degradation by measuring mass change, volume change, breaking stress, breaking strain, and hardness using accelerated degradation tests. For these tests, elastomers commonly found in the water distribution system were exposed to a combination of temperatures (23,45, and 70 C) and chloramine concentrations (1,30, and 60 mg/L) for 30 days. Using the TTS principle, extended-life prediction curves were developed for an equivalent 1 mg/L and 23 C service condition for tensile stress, tensile strain, and hardness.…”

“…Based on the appropriate solutions of the Fick's second law of diffusion, specific diffusion coefficients were computed for 1 mg/L chloramine concentration at three temperatures (23,45, and 70 C) and also for 23 C at three chloramine concentrations (1, 30, and 60 mg/L) and used to predict elastomer swell over extended time periods. The diffusion coefficient variation with respect to increasing temperature and chloramine concentration was analyzed.…”