Any polymer resin that is commercially available has a technical data sheet with it. It is a short summary of what some of the mechanical attributes of the polymer are, such as the Young's modulus, the breaking strength, maybe the yield strength if the polymer behaves that way (glassy polymers need not apply), maybe some flexural properties, and maybe the heat deflection temperature. These are usually measured according to some ASTM or ISO standard (with modifications being made as the supplier wishes, such changes seldom being communicated).
In most cases however, I ignore this data [*].
These values are not worthless per se, as they do represent fundamental properties of a material and the values are fairly reproducible (although we all know that processing conditions can have an pretty big impact on a products properties). And the values can certainly be useful for making relative comparisons between polymers. The reason I ignore them however, is that they seldom represent how a material is used in its application. Tensile modulus is an extremely important value for ropes and anything similar that is only under unidirectional tension, but for most other situations, tensile stresses are combined with shear stresses, and if a part is being torqued or flexed at all, there would be compressive stresses too.
So when I read a statement that the Automotive Industry Action Group, in response to the Nylon-12 shortage has established "...guidelines [that] lay out specific requirements for replacements in areas such as tensile strength and elongation, chemical resistance, fuel exposure and other key performance issues", I have to laugh. Automotive parts are not under pure tension and so even if a replacement resin has the EXACT SAME tensile strength and elongation (it won't), it will still behave differently under shear and/or compression and so the products made from that material (not the material itself, but the products) will need to be requalified, which means a lot of long nights in the labs for the engineers doing this under a tremendous time crunch.
Ford Motor company however, seems to be ahead of the game. Their CFO said, "We’re pretty clean. That’s largely due to the fact that we have alternative materials that we can use. There had been some materials the team had previously tested, but didn’t use them at that time, so we had material already on the shelf that we could use." Pretty smart, huh?
[*] Much like an MSDS sheet. There very seldom is anything meaningful to me in them.
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