Tensile Strength: Yield or Break

Yield-Right-of-Way

Most of us in the plastic materials industry have some familiarity with the various ASTM and ISO test methods that are reported on data sheets and certificates of analysis. However, if you do a deep dive into any of the test methods, and by deep dive I mean read from stem to stern, you will find all kinds of things that you might not have thought of. Having set up and run an accredited testing laboratory in the past, I performed deep dives into many of the ASTM and ISO procedures.

Today, I want to explore one small part of the ASTM D 638 procedure for tensile properties. Before you say that you would rather drink battery acid, let me assure you that I will not dive too deep and I will leave you with some practical information and you will be able to point out a mistake on a lot of data sheets and certificates of analysis in the future.

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Izod Impact: ISO vs ASTM

math-class-1916
Sorry for all of the math in this post

If you are unaware, there are two sets of test methods that are currently in use for many of the common tests that we see reported on data sheets and certificates of analysis. This has caused a lot of confusion.

To add to the confusion, I have seen many data sheets and certificates of analysis in which data is reported incorrectly. None more than izod impact. There is currently an ASTM method and an ISO method for testing izod impact. Although some data sheets claim that they are, the two test methods used for izod impact are definitely not equivalent. They are two different test methods and there is no way of converting between the two.

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