Accelerated Weathering Conditions Research Articles

Influence of Accelerated Weathering on the Corrosion of Low‐Alloy Steels

In low‐alloy steels under accelerated atmospheric corrosion conditions the type of weathering, particularly the ratio of the time of wetness to the drying time, has a greater influence on the corrosion behavior than does the composition of the alloys. Electrochemical measurements show that the rust protection is not only due to the formation of compact macroscopic protective layers, but also to passivation effects. Passivation occurs for a prolonged period only at favorable accelerated weathering conditions. We propose a model for the interpretation of the corrosion behavior of low‐alloy steels.

The fracture of nylon 66 yarns which have been exposed to light

It has been shown from earlier work in this laboratory that the fracture morphology of light-degraded, delustred nylon is different from that of unexposed, delustred nylon. This paper illustrates the effects on breaking strength, extension, and morphology of delustred and bright nylon yarns when exposed to daylight for different lengths of time and discusses what factors have influenced the breaking behavior of the samples. The scanning electron microscope (SEM) has been used to examine the broken filaments and has revealed a wealth of detail which would have been impossible to detect in a light microscope. Nylon 66, 17 dtex, semidull monofil was used throughout the initial experimental work and was exposed to daylight, from behind glass, for up to a maximum of 24 weeks during both the summer and winter months. Samples were removed after set exposure periods and tested to break on an Instron testing machine. The same monofil yarn was exposed before a xenon lamp to enable comparisons to be made between samples degraded by normal daylight and accelerated weathering conditions. Further samples of bright and dull nylon 66 yarns, exposed to daylight in Florida, have also been examined.

Ethylene‐propylene terpolymers as paint films

The results of research conducted into air‐dried terpolymer films shows the effect of various factors on degradation under accelerated weathering conditions

Some applications of ultraviolet spectrophotometry in drying oil research

ConclusionsAn alkaline‐solution technique has been developed permitting the study of the drying and aging process of an oil film using the ultraviolet spectrophotometer. This technique has been found to be a valuable tool for investigating some of the chemical changes which occur as a vegetable oil film dries and ages.The drying or autoxidation of an oil film has been shown to proceed along the general lines of a three‐stage reaction with the short initial stage being characterized by an accumulation of conjugated diene and triene structures which reaches a maximum at the time the film has set up or becomes continuous. The second or curing stage was characterized by a slow decrease in the measurable conjugated diene and triene structures. The third or deterioration stage was not investigated; however, this method should be readily adaptable to studies involving film breakdown as represented by phenomena such as after‐yellowing since the development of absorption peaks characteristic of linolenic ketones, for example, would permit an early prediction of yellowing long before the concentration of the chromophore groups became great enough for visual observation.During the initial stage of drying there was also evidence for an increase in the alpha‐keto structures capable of enolizing in alkali to give absorption maxima characteristic of triene and tetraene conjugated systems. These enolizable structures also decreased in amount during the film curing period and are not characterizable on the basis of observed absorption maxima and published information.The method of obtaining a spectral solution of a dry, infusible oil film through the medium of alcoholic KOH was applied to investigations on the relationship existing between the light absorption of the film solution and the durability or weather resistance of the straight oil film. The results obtained verified the principle previously reported that the quantity of light absorbed by an oil film in the region of 320–400 mμ was indicative of the durability of the film upon exposure to accelerated weathering conditions.

Chemistry in archæology

This review presents an overview of the state of the art in understanding of the chemistries behind polyethylene terephthalate (PET) degradation under hydrolytic and photolytic conditions, which are the main degradation processes that operate in the natural environment. Laboratory studies, carried out under so-called accelerated weathering conditions, have been reviewed and are compared to findings obtained from field studies through hydrolysis and photolysis from natural exposure. The review concludes by correlating the techniques used to date and our current understanding of the mechanisms and key intermediates involved in PET degradation.