Chemical ageing stabilization techniques

One can envisage two possible ways of stabilization of the polymer matrix against chemical ageing  

During the past three decades, many research works have shown a significant improvement in the gas barrier properties of nanofiller reinforced polymer membranes (Espuche, 2011). It was demonstrated that the adding of nanofillers (layered clays, carbon blacks or nanotubes, etc.) into a polymer matrix increases significantly the tortuosity of diffusion paths. Unfortunately, this physical way of external stabilization is still often ignored by practitioners. 

In contrast, chemical ways of external stabilization, in particular for inhibiting the chain reaction such as by thermal or photo-oxidation, have long been well known by practitioners. They have been the subject of an abundant literature and reviews (Reich and Stivala, 1969 Hawkins, 1971 Kamiya and Niki, 1978 Zweifel, 2001). There are two main families of antioxidants which can be combined in a polymer matrix in order to constitute efficient synergistic blends of antioxidants  

Except for carbon black, antioxidants are synthetic products. They are relatively expensive and moderately soluble into polymers. Therefore, their 

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Many chemical and physical analysis techniques have been applied to the study of solid propellant aging. Valuable contributions have been made in improving formulations and in establishing confidence in the stability of propellants for a variety of applications. Fortunately, many... 

The chemical filing technique is very effective in modifying the redox property in the low temperature regions. The reduction temperatures of the chemically filed samples become lower than those of the non-filed ones without decreasing in the amount of the released oxygen. The redox activities of the chemically filed samples arc maintained even after several reduction and reoxidation aging at 1273 K. The reasons for these better redox activities have been attributed to the formation of trace amounts of Ce02 ultrafine particles with the evolution of zirconium and subsequent stabilization of the metastable k and phases. ... 

There are three primary methods to age catalysts and each addresses different failure modes. The first method is an ex situ thermal aging technique that measures support stability (Stevens et al. 2005). In this method, catalyst powder is weighed and placed in an oven. The weight loss of the powder is monitored over time (Fig. 3a). This technique studies the stability of the support to platinum-catalyzed chemical combustion and is very useful for determining the relative stability of different carbon supports. The second method is an in situ technique to measure the electrochemical... 

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