On Testing Rubber
Abstract Measurements are basic to all natural sciences, in fact some say that science is measurement. Whether it is the measurement of the temperature on the moon or the hysteresis properties of a rubber compound, the measurements are intended to give us accurate data with which to proceed further in our understanding of nature. Measurements and analyses are essential in every stage of rubber science and technology from the synthesis of a new rubber chemical to measurements of performance of some complex product such as a tire in service. The all-pervading role of measurements is frequently not appreciated, but a simple observation which each of us can make will demonstrate this fact. A cursory examination of the slides presented at this and other Division of Rubber Chemistry meetings will show that at least 95% of them contain the results of physical or chemical tests required to demonstrate, illustrate or prove a point the speaker is attempting to make. Furthermore, many of the papers will be concerned solely with a new test method or method of analysis. Although as a compounder my work was only incidentally involved with testing, the subject of testing has been a most absorbing interest of mine and it seemed that a discussion of some aspects of it would be acceptable for this lecture. A rough distinction can be made between those tests involved with the fundamental science of rubber as a primary aim and those involved with the engineering practice of rubber technology, although there is an inevitable overlapping. My concern here will be with the latter group and, in general, with those methods which have been standardized by Committee D-11 of ASTM. My central theme will be that too much testing is done, that many of the methods are inadequate, that many are inadequately understood by the users and inadequate analysis and interpretation are made of the data obtained. In an attempt to brighten the picture a little, I will conclude by discussing some new methods which appear to be decided improvements, both from performance and in being adequate in respect to being easily understood by most users. What I have to say will be somewhat critical of the methods used and sympathetically critical of the people who use them. At the start I should point out that criticism of the methods is not a criticism of Committee D-11 of ASTM. It should be realized that D-11 almost invariably standardizes methods which are fairly widely used in the industry and for which a need for standarization is expressed by the industry. The Committee rarely develops new methods, although it can be said that in the process of standardization, methods are usually improved. One of the more important purposes of standardization is to formulate methods so that different laboratories will obtain reasonably reproducible values without which chaos would result.