Charles Dufraisse

Applications of Ultraviolet Spectrography a Study of the Transformations of Tetramethylthiuram Disulfide When It Functions as a Direct Vulcanizing Agent

Abstract In addition to sulfur, which is the most common vulcanizing agent, rubber mixtures usually contain various kinds of accessory ingredients, both inorganic and organic. Among the organic ing...

A Manometer for Measuring the Oxidizability of Rubber

Abstract In view of the practical interest in a method for measuring directly the rate of oxidation, i. e., the oxidizability of rubber, it has seemed worth while to devise an apparatus with which the technic of making such measurements is so simple that it is within the compass of operators with no particular training. With this in mind the author has been led to construct a new manometer for measuring oxidizability. Before describing the apparatus and its method of operation, however, it is necessary to explain its principles. Later on, it is intended to deal in a more thorough way with the significance of the measurements, with the various causes of errors arising from the nature of the substance studied and the technic employed, and finally with different ways of expressing the results obtained.

The Influence of Vulcanization on Oxidizability in Relation to Aging. A Preliminary Study

Abstract Because of its preliminary character, the present investigation does not admit any definite conclusions. Rather, by bringing out clearly the various complications which arise in studying the oxidizability of rubber, especially when the aim is to establish a parallelism between oxidizability and the ill-defined phenomenon of aging, the investigation has shown the many difficulties in general involved in the problem. These complications are to a certain extent attributable to the nature of the phenomenon itself which has been measured, i. e., the oxidizability; but for the most part they owe their origin to the nature of the substance studied, and especially to its heterogeneous character. For these reasons the uncertainty in the results is increased by vulcanization, and the more vigorous the treatment, the greater is this uncertainty. As a result, considerable fluctuation in the measurements occurred. This is the reason why, in the past as well as now, so much emphasis has has been laid on the ad...

Applications of Ultraviolet Spectrography. A Study of Some Accelerators

Abstract Not only is the problem of determining the compounding ingredients originally present in a rubber mixture by an analysis of the vulcanized product of interest from a technical point of view, but it also is of importance from the theoretical point of view to know what becomes of these ingredients as a result of the thermal effects of vulcanization. This is particularly true of that class of ingredients which function as accelerators of vulcanization. Chemical methods which are applicable to this problem are in all cases very complicated and are inconvenient in various ways. For some ingredients there are no methods at all avaifable. Accordingly it was thought that a study of ultraviolet spectra, the general principles of which have already been described and which have already been utilized by Jarrijon for the determination of anti-oxygenic substances, might offer a more rapid and more reliable means of attaining the desired end. The aim of the experiments to be described was simply to show what i...

Principles of a Method of Vulcanization Based on Condensation Reactions. Prosthesis and Synesis

Abstract The term vulcanization was restricted originally to the treatment of rubber by sulfur at elevated temperatures, the purpose of which was to overcome the faults of the raw material and in general to make it of more practical value. For more than a half century, sulfur and a few sulfur compounds were the only agents known to have this remarkable property, but later selenium, tellurium, and finally various oxidizing agents and sulfurizing agents as well were found to be capable of vulcanizing rubber. In all these transformations, the vulcanizing effect is the result of the direct or indirect action of one of the elements of the second group of metalloids. On the assumption that vulcanization involves the formation of bridges between linear molecules, it was decided to attempt to bring about this bridge formation by classic condensation reactions under such conditions that it would be certain that elements of the second group of metalloids would play no part in the reaction. The difficulty in uniting...

The Influence of Vulcanization on the Oxidizability of Rubber. Vulcanizing Agents Other Than Sulfur

Abstract If it is attempted to sum up the important results obtained in the present study, the following points seem to be well established. First of all, with respect to selenium. Whether the oxidizabilities of products vulcanized by selenium alone or of products vulcanized by a mixture of selenium and sulfur are measured, they show the same general behavior as do mixtures vulcanized by sulfur alone. It is the percentage of vulcanizing agent in combined form that governs the oxidizability, for the addition of selenium to sulfur increases this oxidizability. If part of the sulfur is replaced by selenium, there is a decrease in the oxidizability, but this can be explained by the lesser reactivity of the selenium, as a result of which the product is vulcanized to a less extent. It is not true, then, that, for a given state of cure, selenium improves aging. The case of diazoaminobenzene is a more complicated one. This compound decomposes during vulcanization, with liberation of nitrogen and probable formatio...