Additives degradation mechanism

In general, extrapolations are not permitted over a physical transition range, such as the glass transition or the melting range. Similarly, extrapolations must not be performed if additional degradation mechanisms, e.g., due to excessive temperature increase, occur that the model does not account for. 

When residual water produced during fuel cell operation remains in the electrodes after the stack is shut down, problems can arise, particularly when the environmental temperature is <0 °C. When the stack is exposed to subzero conditions, the residual water will freeze, so the volume of the electrodes (in particular, the catalysts layers) will expand due to ice formation, which will lead to structural damage and decreased electrochemical active surface area. This has been reported as an additional degradation mechanism in PEM fuel cells [21]. However, if the PEM fuel cell is operated at high temperatures, less liquid water will remain in the electrode and thus decrease the impact of fuel cell structure failure caused by frozen water. 

Additionally, organotin mercaptides can act as antioxidants, as they can sequester free-radical degradation mechanisms (48). The one drawback of mercaptide-based tin stabilizers is the discoloration of the sulfur after exposure to uv-radiation. Special precautions or formulations need to be developed for outdoor apphcations. 

Bhuiyan, A. L. Some Problems Encountered with Degradation Mechanisms of Addition Polymers. Vol. 47, pp. 1 —65. 

Applications Desorption chemical ionisation has proven potential in the analysis of thermally labile, nonvolatile and polar compounds [40,67,68], for the identification of unknown polymers and the study of the thermal degradation mechanisms of polymers. Considering the overall ease of DCI operation, the capability of analysing nonvolatile compounds, and the selectivity provided by choosing different reagent gases, DCI has found surprisingly few practitioners in the analysis of polymer additives. 

Carried out testing confirmed the supposition about the degradation mechanism of electrode in NiOx-carbon ultra capacitors (Figure 1). Obviously, the smaller are the dimensions of particles of conductive additive (colloidal graphite) and the more active its surface is (nickel powder), the faster oxidation processes are taking place on the surface of these particles. 

In order to evaluate the extent of attrition and its impact on the particle size distribution, there is a need of a qualitative and quantitative characterization. This, however, is not as simple as it may seem at first. There are many different properties, parameters and effects that manifest themselves and could be measured. In addition, as will be shown, the choice of the assessment procedure is strongly connected with the definition of attrition which, on its part, depends on the degradation mechanism that is considered to be relevant to the process. Hence there are a lot of procedures and indices to characterize the process of particle attrition. Section 3 deals with those which are relevant to fluidized beds and pneumatic conveying lines. 

Four Lewis acids and a radical trapper were used as additives in PMI in order to alternate the degradation mechanisms to... 

The thermal stability of PMI with additives is not changed by the introduction of clay, charcoal, AI2O3. These additives were quite stable over the temperature range under study (up 900°C). The lower thermal stability observed for the cases of ZnCl2 and NiC12 as additives may have resulted from a change in the degradation mechanism. 

It is explained in the report that the degradation mechanism remains the same, even after addition of nanoclays. 

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