Thermally accelerated aging

Various problems related to the construction and performances of these batteries, such as changes in materials of membranes and additives both to the electrode materials and to the electrolyte, were studied in recent years. Some instability of the silver electrode during such storage period and the ways of avoiding these difficulties were studied and discussed [347]. Reserve activated silver oxide-zinc cells were constructed [348] with synthetic Ag20 and Pb-treated zinc electrodes were produced by a nonelec-trolytic process. The cells were tested before and after thermally accelerated aging. 

The examination of fold endurance and tensile strength of a series of polymer-paper systems under thermal accelerated aging indicates that only in the most favorable of circumstances is it possible to apply the Arrhenius equation to the system. It also seems unlikely that a sample addition relationship exists between the behavior of the individual components and their behavior as a system. A straight line plot of log folding endurance vs. aging time may reflect a fortuitous composite of several experimental variables leading to pseudo-first-order deterioration. 

The lack of an unambiguous method for demonstrating predictive validity of thermal accelerated-aging methods warrants extreme caution in extrapolating to long-term behavior for polymer-adhesive systems. The usefulness of such studies is often best applied to a ranking of preferred behavior under evaluative criteria. 

Reynolds, F. H., Thermally accelerated aging of semiconductor components, Proc. IEEE, 62 (1974) 149. 

R.L. Feller, Accelerated Aging, Photochemical and Thermal Aspects, The Getty Conservation Institute, Los Angeles, 1994. 

The use of quasi-solid-state electrolytes usually reaches the goal of a superior thermal stability with respect to liquid electrolytes cells can survive prolonged periods (accelerated aging of 1000 h) at relatively high temperatures (55-80°C) under... 

Photo-DSC on the other hand, is a much more recent technique which has been developed thanks to technological developments in thermal analysis and coupled techniques. Until very recently, it has been used mainly to study photopolymerization or photocuring reactions by measuring the heat of reaction. We proposed the use of this powerful technique to study polymer photo-aging, using the photo-DSC as an accelerated aging device and coupled in situ analysis of the modification of the morphology of the materials. In this case, the crystallizability of the polymer is used as an indicator of the structural modifications. 

A systematic investigation of intrinsic chemical stability was carried out on devices specially designed for high power applications [7]. For this purpose, accelerated ageing test procedures were developed for nc-DSCs and it turned out that, to first order, a separation can be made between the effects of visible light soaking, UV illumination and thermal treatment on long term stability. 

There is no evidence of delamination, corrosion, or other visual changes for TFML structures subjected to MIL-STD-883C tests for temperature cycling (-65°C to 150 C, 100 cycles), thermal shock (-55°C to 125°C, 15 cycles), moisture resistance (Method 1004.5), and accelerated aging at 85 C/85 percent r.h. for 1000 hours (unpublished results) ... 

Parks, E.J. and Hebert, R.L., "Accelerated Aging of Laboratory Handsheets Reflectance, Moisture Retain, Sonic Modulus and Differential Thermal Analysis, NBS Report 10-687, Feb. 22, 1972, NTIS COM 75 10602. 

When the peroxyl population was quickly destroyed by 2-methyl -2-nitrosopropane treatment, post-y oxidation still occurred (Figure 7). In addition, film which had been pre-oxidized by xenon-arc photo-initiated oxidation showed an identical, slow, thermal oxidation during storage, as well as a rapid embrittlement in the accelerated aging at 60°C (Figure 6). The photo-oxidation of PP is well... 

Polyethylene and polypropylene blended with iron carboxylate complexes, for example, acetylacetonate (FeAcAc) and stearates (FeSt), and irradiated by UV light under accelerated aging conditions were shown to act as effective phtoactivators giving rise to rapid photoxidation as shown from the rapid rate of carbonyl formation without any induction period (see Fig. 16.4a for FeAcAc in HDPE) and with a reduction in molar mass (see Fig. 16.2a for FeSt in LDPE). However, these complexes have been shown to cause considerable oxidation to both PE and PP during processing reflected in a sharp increase in the polymer s melt flow index (reflecting chain scission and drop in molar mass) (Fig 16.4b) and act, therefore, as thermal prooxidants and cannot be used without the use of additional antioxidants in the system [2,3,17-19,48,49]. 

One of the better heliostat sealants was found to be a butyl rubber, Adcoseal B-100. This module incorporated a design modification a 1/16" butyl rubber pad bonded between the mirror and the polystyrene foam substrate. The module looked extremely good after 12 months accelerated aging. A sealant of this type must be used with some degree of caution because butyl rubbers are not normally considered as thermally stable or UV resistant as silicones. 

---