What is the plasticiser used in nylon tubing?

[charcinders]

I have some "extraflex" nylon pneumatic tubing which is quite nice for connecting components inside equipment because of its flexibility. I have noticed that after a few months it gets a coating of what I assume is plasticiser on it. You can't see it but you can feel it - it's greasy / sticky, a bit like glycerine. I feel the need to wash my hands whenever I've been handling the tubing.
Whatever it is is soluble in water.

Can anyone suggest what it is likely to be, and is it normal for it to be migrating out of the nylon?

- Chris

 

[patprimmer]

If the tubing is nylon 6, the plasticiser is almost certainly caprolactum.

Regards
Pat
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[charcinders]

Thanks Pat.

It has a very bitter taste (yes, I couldn't resist licking it) which ties in with it being caprolactu[a]m.
Interestingly the makers, Copely, recommend it for the transfer of food substances and liquids. Maybe they treat the inner surface in some way to stop the plasticiser leaking out, one would hope so. I've sent them an email asking them.

http://www.copely.com/products/eurolon/superflex_nylon.asp

 

[MatthewL]

Chris,

For Nylon 6,6 11 and 12, we use BBSA (butylbenzenesulfonamide), also oily, but I don't know what it tastes like.

Regards,

Matt

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[btrueblood]

mmm...caprolactum.

 

[charcinders]

Thanks Matt. BBSA is "almost insoluble in water" so it's not that. I'm pleased about that as BBSA is a neurotoxin!
This stuff wipes off with a damp cloth.

When I looked at the dates on it it's about 2 years old (doesn't time fly...) and it's been stored in a warm place, so that could be a contributing factor. I also noticed it on some normal (non-flexible) pneumatic tubing from the same manufacturer.