Evaluation of Small Amounts of Synthetic Rubber

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Abstract
In research on rubber synthesis, as in any broad program of chemical research, it is a distinct advantage to be able to do all work on a normal laboratory or test-tube scale. With rubber, however, the standard laboratory testing methods require from 200 to 500 grams of rubber for each batch. Hence it was obvious that, if the advantages of small-scale work in the preparational stages were to be realized, a new technique of rubber testing would have to be developed. The use of entirely new and unrelated procedures has two definite objections. In the first place the new procedures must be thoroughly tested and compared with the older methods of testing or with the processing and use requirements of the new rubbers. In the second place the significance of the results of such new tests can be conveyed, even to experienced rubber technologists, only after considerable interpretation of the methods. It seemed best, therefore, to modify standard rubber-testing methods so that they could be applied to very small amounts of synthetic rubber. More recently, the shortage of natural rubber has made necessary a reduction in the amount of rubber used for testing. For this purpose the same small-scale procedures are highly advantageous. While some idea of the quality of a sample of natural or synthetic rubber can be obtained from examination of the crude rubber itself, it is much better to know the physical properties of the vulcanized product. This means that one or more balanced compounds must be mixed and tested. The purpose of this paper is to describe a technique which has been developed in the Goodrich laboratories whereby, with as little as 5 grams of rubber, the stress-strain characteristics may be determined, and with 9 grams of rubber a fairly comprehensive evaluation can be made. This method has been used to evaluate polymers made on the 10-gram scale by Fryling.

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