Wednesday, March 23, 2011

EVA vs. VAE

It's always bugged me that the two polymer abbreviations in the title exist. The E stands for ethylene, the VA for vinyl acetate. The abbreviations above are for the (random) copolymers of the two. I'm not 100% sure, but I believe that the two monomers can be copolymerized in almost any ratio (100% polyethylene exists, 100% polyvinyl acetate exists, and lots of grades in the middle exist so I would be surprised if there really was an intermediate value that couldn't be made).

Any way, getting back to the abbreviations, the only difference in the two is whether the copolymer has more than 50% vinyl acetate. If it does, go with the VAE, otherwise stick with the EVA. Strange and rather arbitrary.

I'd love to see someone proposing the similar name change for say, ABS (a terpolymer of acrylonitrile, butadiene and styrene), constantly renaming it depending on the relative amounts of A, B and S. Whoever would suggest such a system would already be starting in a hole since there typically is more styrene in the material than acrylonitrile or butadiene. But think of the possibilities: we could have 6 options:
  • ABS
  • ASB
  • BAS
  • BSA
  • SAB
  • SBA
Or consider ASA plastic, a terpolymer similar to the ABS with one of the A's standing for acrylate. How could you possibly tell the difference when there are two A's?

EPDM (ethylene, propopylene, diene - don't ask about the M) could also face a name change to PEDM (at least the D is consistently in last place).

Anyone proposing such a crazy scheme would probably be tarred-and-feathered (wood tar of course, since we want to biosource it!) so why do we tolerate it for EVA/VAE? Personally, I prefer EVA - it just rolls off the tongue so much better than VAE.

1 comment:

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