SUBJECTS caoutchouc

It was known that caoutchouc and gutta-percha (another purified tree sap) had the same empirical formula. When gutta-percha was subjected to the same force applied to the caoutchouc, it did not deform as much, and it cooled, as expected What was so different about these two otherwise chemically identical substances Crystallinity The crystal deformed as an elastic body and the sample returned to the same temperature upon release of the force. Joule subjected caoutchouc to a cooling-bath at 0° Fahrenheit for a few days. The sample then became rigid and showed the same elasticity as the gutta-percha. Joule worked like Faraday he tried everything ... 

The study of the physical and chemical properties of rubber has received a decided impetus as a result of recent developments in colloidal chemistry, for it cannot be denied that in caoutchouc, the fundamental substance from which commercial rubber is ma de, we have a typical colloidal body. Many of the processes in the manufacture of both the crude rubber, caoutchouc, and the finished product, rubber, such as the coagulation of the latex, find no explanation from the purely crystalloidal chemical standpoint. Unfortunately in the discussions on the subject it has not always been recognized that in most instances both the colloidal and crystalloidal processes take place simultaneously. Consequently important facts are often ignored by the extreme advocates of the colloidal and the purely chemical schools. Only by a proper perspective involving both views, can we arrive at the true explanation of many of the phenomena connected with the chemistry of rubber. 

A great deal of work has been done of recent years on the process of vulcanization. Unfortunately the results of one experimenter often seem to contradict those of another consequently we have few undisputed facts upon which to base our theories. This want of accord among the experimental results is probably not due so much to inaccurate work as it is to the fact that raw caoutchouc is a complex product, varying in properties to a condderable degree with its source, method of preparation, a e, etc. A short summary and not an extended dis-cusdon of the two prindpal theories will be ven here. For a more comprehensive review of the subject the reader is referred to the original literature, or to Der Kautschuk by Ditmar. 

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