Life-time prediction of a chloroprene rubber (CR) O-ring using intermittent compression stress relaxation (CSR) and time-temperature superposition (TTS) Principle

Abstract

Intermittent compression stress relaxation (CSR) testing was used to examine the degradation of a large scale chloroprene rubber (CR) O-ring, rather than a reduced scale copy, as well as predict its life-time. An intermittent CSR jig was designed by considering the O-ring's environment during use. The testing allowed the observation of the effects of friction, heat loss and stress relaxation by the Mullins effect. Degradation of O-rings by thermal aging was observed between 40 and 120 o C. In the high temperature range of 80-120 o C, the O-rings exhibited linear degradation behavior and satisfied the Arrhenius relationship. The activation energy was approximately 72.7 kJ/mol. From the Arrhenius plots, the predicted life-times were 22.8 years and 34.5 years for the 50% and 40% failure conditions, respectively. Using the time-temperature superposition (TTS) principle, full predictions of failure at 40 o C could be made, saving considerable testing time. Between 40 and 80 o C, the activation energy decreased to 58.9 kJ/ mol. William-Landel-Ferry (WLF) plotting confirmed that the O-rings show non-linear degradation behavior under 80 o C. The life-time of the O-rings predicted by the TTS principle was 11.1 years and 18.1 years for each failure condition. The life-time predicted by the TTS principle was more conservative than that from the Arrhenius relationship.

Bayesian inference for a novel hierarchical accelerated degradation model considering the mechanism variation

“…Xiang et al 11 analyzed the degradation processes of butyl rubber materials through monitoring the compression set in the temperature range from 60°C to 100°C. Similar to the phenomenon in Lee et al, 10 the activation energy drops from 126.7 to 58.8 kJ/mol at around 75°C as displayed in Figure 2. This illustration is reproduced from Xiang et al 11 For more similar findings, one may refer to Patel and Skinner, 12 Achimsky et al, 13 Dole and Chauchard, 14 Gillen and colleagues 15,16 Nichols and Pett, 17 and Celina et al 18 Gu et al 19 conducted a further investigation and concluded that this phenomenon may be associated with the antioxidant effectiveness.…”

“…However, in some practical ATDTs, the activation energy changes when the test temperature rises to a certain high level. Lee et al 10 conducted ATDTs on chloroprene rubber O-rings from 40 °C to 120 °C. The natural logarithm of the acceleration factor referring to 40 °C versus the inverse of the absolute temperature is shown in Figure 1.…”

“…The natural logarithm of the acceleration factor referring to 40 °C versus the inverse of the absolute temperature is shown in Figure 1. This illustration is reproduced from Lee et al 10 For the Arrhenius model with a constant activation energy, the natural logarithm of the acceleration factor has a linear relation with the inverse of the absolute temperature. However, Figure 1 shows that the linear relationship is violated due to a variation in the activation energy.…”

“…A variation in the activation energy at around 80 °C for chloroprene rubber O-rings. This illustration is reproduced from Lee et al 10 …”

The effect of thermo-oxidation on the continuous stress relaxation behavior of nitrile rubber

“…Based on the rubber elasticity theory, the residual equilibrium stress can be calculated. The service life of rubber can also be predicted from the relaxation curves at evaluated temperatures by using the timeetemperature superposition principle to extrapolate the data to the service condition [14,15]. However, when rubbers are subject to harsh conditions (e.g., high temperature, presence of lubricant or solvent, radiation), changes in the network due to progressive chemical reaction would lead to a complex stress relaxation behavior [16e23].…”