View from Britain on testing in the U.S.

The first thought would be that testing rubber in the U.S. is exactly like testing rubber in Britain, France, Germany, etc. Doubtless, there are a great deal more similarities than differences, but it is interesting to examine where things diverge. This article is the perceived view of one Brit and not the result of a careful study, but nevertheless, perceptions can be as important as the truth. The source of knowledge from which the perceptions formed is to a very large extent based on the activities of ASTM D11 and its subcommittees, plus the stances taken by the U.S. in ISO TC45.

Apart from pure research activities, standards are the basis for testing and it is from the national standardization activities that many similarities or differences will stem. In the U.S., it is ASTM that we think of as the producer of rubber testing standards, even though it is not the national standards body. In the U.K. and elsewhere, the national standards body produces all the standards thought of as national. In Europe, government departments, industry and various institutions do produce standards, but, in Britain at least, there is nothing to compare to ASTM. Hence, in the practice of developing standard methods, ASTM equates to the British national body, BSI.

The modes of operation are basically similar; producing consensus standards through a committee structure. However, BSI has no formal voting system, if you don't comment it is assumed you agree. With no voting there is no formal procedure for dealing with objections - simply discussion until some sort of consensus is reached. BSI committees have members from manufacturers, users and general interest, but there is no formal head count. Members generally represent trade bodies, institutions, etc., and not their company, although people can be co-opted. Membership is not freely open like ASTM, although the BSI committee for rubber testing did once have a Dutch member who was extremely popular for the duty free goods he brought to meetings.

These differences do not really account for any differences in standard test methods, but it is noticeable that there is much better industry support in the U.S. for standardization than in Britain these days. Here, test method standards in particular are not a priority when cost saving is prevalent. The greater level of support may mean that a wider range of views has to be accommodated.

The big difference comes in policy. ASTM and British standards are not identical because no ASTM standard is a reproduction of an ISO method verbatim. In fact, very few ASTM standards are technically identical to ISO. Virtually all British standards are copies of ISO - if we vote yes we adopt it lock, stock and barrel. So, the strong Brit view is that the U.S. is insular, the test methods always have a slightly different speed or test piece geometry and, if you are not careful, they will use imperial units. The belief is that most of the U.S. industry knows little about ISO and cares even less but we do note that times appear to be changing quite rapidly.

One sideline of the national emphasis is that test pieces and procedures retained in ASTM, but not in ISO, are wanted because somebody uses them, regardless of whether they are internationally recognized or even still a good idea - how else could you have six dumbbell test pieces for tensile stress strain properties? We also get the impression that U.S. law and regulations are more of a problem than in Britain and can restrict even the editorial presentation of a standard.

We differ on the most basic of measurements - hardness. Dead load IHRD methods were developed to overcome the disadvantages of springs and flat ended indentors, but traditional Shore has reigned across the water, despite ASTM including the international dead load method. Really, we are both wrong, the better approach is constant indentation.

It took a long time for the U.K., and for ISO, to standardize the ODR curemeter, although the instrument came into almost universal use quite quickly. The problem here was that it was apparently not British to standardize a patented apparatus, even the sources of equipment are not normally put in the standard. This has never prevented named apparatus of course, such as the Wallace Rapid Plastimeter, which completely replaced the parallel plate, or Williams instruments. Curiously, ISO (but not U.K.) only standardized the parallel plate in fairly modern times, whereas ASTM only has the rapid type instrument for plasticity retention index.

ISO and ASTM have similar compression set methods, but there is no equivalent tension set procedure in ASTM, only a quick 10 minute extension at room temperature or the dubious practice of fitting the ends of a dumbbell back together after break. It would be interesting to know the reason for the inequality of status for compression and tension in America.

Abrasion testing has seen considerable international trade in test methods, but not unification. In the U.K., we adopted Akron and DuPont many moons ago and have hung on to them, although they are fading fast. More recently we imported the Taber and the DIN methods, in the meantime dropping our own Dunlop apparatus. In ASTM, DuPont and Akron are nowhere to be seen and Taber is only for coated fabrics, but there are the Pico and NBS machines which failed to ever make the sea crossing. ASTM now also has the DIN method, which is the sole procedure standardized by ISO and, hence, the only international bond originated in Germany.

One could cite many more cases of differences, fatigue, heat aging and resilience for example. Actually, the U.K. and the U.S. usually end up voting the same way in ISO, but it is the action afterwards which differs. Neither country votes negative at the last stage very often, but there is one unique case of both voting negative, which was concerning a Russian method for crystallization by a compression procedure.

The U.S. introduced the rest of us to precision statements. The official line is what a marvelous development it was which found out so much about the poor reproducibility of our methods. Unofficially, we wish you had kept them to yourselves. Precision leads you to calibration and to laboratory accreditation. Europe doesn't really understand the U.S. situation where there appears to be a number of commercial schemes. In Britain, there is a national official accreditation body, UKAS (formerly NATLAS and then NAMAS), and "approval" by them is virtually essential for independent laboratories. ISO 9000 has now caught on in the U.S. but, while any respectable company in Britain is so registered, it is not a qualification for test or calibration labs.

Does any of this matter? At best the differences in test methods are a nuisance in that results are not comparable and more than one apparatus may be needed. However, at worst it is an unfortunate barrier to trade and communication.