Degradation ageing phenomena

Obviously, use of such databases often fails in case of interaction between additives. As an example we mention additive/antistat interaction in PP, as observed by Dieckmann et al. [166], In this case analysis and performance data demonstrate chemical interaction between glycerol esters and acid neutralisers. This phenomenon is pronounced when the additive is a strong base, like synthetic hydrotalcite, or a metal carboxylate. Similar problems may arise after ageing of a polymer. A common request in a technical support analytical laboratory is to analyse the additives in a sample that has prematurely failed in an exposure test, when at best an unexposed control sample is available. Under some circumstances, heat or light exposure may have transformed the additive into other products. Reaction product identification then usually requires a general library of their spectroscopic or mass spectrometric profiles. For example, Bell et al. [167] have focused attention on the degradation of light stabilisers and antioxidants... 

This phenomenon has been investigated [27] by artificially ageing beeswax. It was hypothesized that the loss of alkanes was due either to the fact that the wax was heated during use or to its sublimation over the centuries under particular environmental conditions. Figure 7.2 summarizes the chemical mechanisms involved in beeswax degradation [27]. 

One particular phenomenon, often shown with oxidising reactions in polymers, is an induction period for ageing, whereby relatively little change is seen during this period but then the rate of degradation increases abruptly. It is easy to see how this can happen in materials protected by antioxidants in that with time the protective additives will be consumed. 

At higher temperatures and in the presence of an active environment the effect of aging and degradation can be preponderant leading to failure at unexpectedly low stresses. This phenomenon is treated in detail by Alt-stadt in this Volume [65]. 

Fuel cells experience ageing. Proton current, flux of water and thermal effects inevitably change the structure and composition of cell components, thus causing the degradation of cell performance. The phenomenon of cell ageing is well known, though the mechanisms of ageing are not fully understood [18]. 

Aging and the related failure phenomenon of electrolytes and electrolyte-based ESs are important issues that need to be addressed. Understanding component aging mechanisms will be beneficial for the development of ESs with wider voltage windows and will also be necessary for guidance in the safe and reliable use of ESs. Performance degradation of ESs is mainly due to the following ... 

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