Acidity and accelerated aging

The influence of ambient aging at 70°F and accelerated aging at 160°F on the stress-strain behavior of carboxy-terminated polybutadiene, polybutadiene-acrylic acid, polybutadiene-acrylic acid-acrylonitrile, and hydroxy-terminated polybutadiene composite propints is shown in Figures 10 and 11. The elastomers and curative agents for these formulations are listed below... 

M.R. Schilling, H.P. Khanjian, Gas Chromatographic Analysis of Amino Acids as Ethyl Chloroformate Derivatives. II. Effects of Pigments and Accelerated Aging on the Identification of Proteinaceous Binding Media, Journal of the American Institute of Conservation, 35, 123 144 (1996). 

Nalidixic acid is stable up to five years under reasonable conditions of temperature and humidity. Pawelczyk and Plotkowiakowa(17) subjected sodium nalidixate solutions to accelerated aging, but were unable to identify decomposition products. Detzer and Huber(lS) studied the photolysis and thermolysis of nalidixic acid in the presence of oxygen. Photolysis produced de-carboxylated nalidixic acid, structure A, and a diketone product, structure B, as well as carbon dioxide and ethylamine. 

There is a striking difference, however, in the action of various alkaline materials. Neutralizing acid paper with sodium carbonate, as is shown later, prolongs its life. Alkalizing paper to pH 10 with sodium carbonate causes paper to darken, to oxidize, and to degrade. The effects are most pronounced in humid-oven accelerated aging, less so in the dry-oven aging. 

In principle, if values of at could be determined n times throughout an accelerated aging experiment in which the empirical rate constant, k, is determined, then n simultaneous equations could be solved to yield the chemical rate constants, kt. However, in practice this is not feasible, and Equation 13 is of little analytical value. Nevertheless, our assumption that the property kinetic constant, k, is related linearly to chemical rate constants is verified. Thus, the apparent linearity of the empirical rate constant, kT in Equation 9, with respect to oxygen and acidity suggests the occurrence of chemical processes that are first order in oxygen and acidity. 

---