Gunner Asch wrote:

If its not dynamically loaded..should work fine. If its loaded...it wont
last as long as other better Stuff will.

Thanks for the thoughts. It's a piston in a miniature air pump. Here's a
picture. The plastic layer is over the knurling you can see:
http://www.mythic-beasts.com/~cdt22/pump_piston.jpg

I had wondered about oil-filled nylon. It's definitely not epoxy as I've
been told it was thermally moulded.

Chris