Accelerating aging temperature effects

On the other hand, since most of these reactions are thermally activated, their kinetics are accelerated by the rise in temperature in an Arrhenius-like manner. Therefore, within a much shorter time scale, the adverse effect of these reactions could become rather significant during the storage or operation of the cells at elevated temperatures. In this sense, the long-term and the thermal stability of electrolytes can actually be considered as two independent issues that are closely intertwined. The study of temperature effects on electrolyte stability is made necessary by the concerns over the aging of electrolytes in lithium-based devices, which in practical applications are expected to tolerate certain high-temperature environments. The ability of an electrolyte to remain operative at elevated temperatures is especially important for applications that are military/space-related or traction-related (e.g., electric or hybrid electric vehicles). On the other hand, elevated tem-... 

Vacuum-Steam-Pressure Test. A special aging test which has been used successfully in the USA to accelerate aging to produce the effects of 6-month tropical exposure on certain types of sealed fuzes. It is primarily a development test which can be used during production The test consists of subjecting bare fuzes to 1000 fifteen-minute consecutive cycles in a vacuum-steam-pressure environment. The 1000 cycles takes about 10 days of continuous running time. The basic cycle consists of temperature-humidity cycling superimposed on pressure cycling in a test chamber with a salt laden atmosphere. Representative curves of temperature and pressure are shown in Fig 1... 

Environmental aging is usually less severe in service (laboratory tests tend to accelerate aging so that the testing can be completed in a reasonable time). However, the effects of the actual service environment are generally more complex. For example, there may be simultaneous exposure to cyclic stress, cyclic temperature, and humid environments. 

Recent approaches directed toward preventing oxidation of cotton cloth included using accelerated aging of alkaline-treated cotton cloth for neutralization of acidic, oxidized, cellulose decomposition components that in cellulosic textiles and in paper are responsible for age tendering and yellowing. Conclusions regarding the relative effectiveness of treatments at room temperature were based on results of treatments at one elevated temperature (8). Predictions of long-term effects of these treatments are unknown (9). 

Suib et at. (25, 254) reported the different effects of nickel and vanadium on the catalytic activity and selectivity for the fluid catalytic cracking by a photoluminescence technique and showed that the method is useful in predicting the catalyst deactivation caused by the deposition of metals on surfaces. The activity of the catalyst decreases monotonically with increasing vanadium content. With 1.5 wt% of V, the catalystad lost most of its activity, and with 2.0 wt% of V it became almost completely inactive. Such a deactivation of the catalyst was irreversible, with the extent being closely associated with the surface area covered with vanadium. Moreover, the extent of the deactivation was found to depend on the aging temperature, which was accelerated when aging was carried out under the same conditions normally sized in hydrothermal reactions. 

Temperature effects are important, not only in high temperature applications, but also during accelerated aging of a material for laboratory study and subsequent evaluation of in-service life-time. Solubility of water In Neoprene Increases greatly with temperature as does permeation rate. The relative permeation rates of 3.5% saltwater and deionized water were shown to depend on elastomer composition. 

The Effects of Temperature and Moisture on the Accelerated Aging of Paper... 

It became obvious that considerably more basic Information had to be developed on the degradation process for paper. Too little was known about the effect of water on the degradation of paper and since accelerated aging Involves exposing paper to higher than normal temperatures It would also be necessary to know whether the commonly used temperatures In laboratory aging were excessive. 

A study was conducted to determine the effect of moisture and temperature on the degradation of paper In an accelerated aging test (6). The results of that study clearly demonstrated that moisture had a profound effect on the degradation rate of paper and that possibly the optimum temperature for an accelerated test for paper should be In the vicinity of 70 C. Unfortunately, the humidity range Investigated In that study (0-30% R.H.) was too narrow to be able to specify the functionality of water In the degradation process or to be able to obtain adequate Information on the existence of an upper temperature limit. It was decided to expand the study to Include humidities up to 90% R.H. The results of both studies are reported below. 

The time accelerated aging method for electric wires and cables requires a high dose rate irradiation, but the exposure to polymer in air results only the oxidation of surface when the dose rate is higher. I previously reported the methodology study of time accelerated irradiation of elastomer (2). The study showed two appropriate methods, one was irradiation in pressurized oxygen at room temperature the other was irradiation at 70°C in air. The article studied the effect of higher dose (up to 10 MGy) irradiation on ethylene-propylene-diene elastomer (EPDM) by using the time accelerated method. Irradiation at 70°C in air was chosen as the time accelerated irradiation condition because of the experimental convenience. 

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