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I need to make PTFE caps on my test tubes. Why PTFE? The test tubes contain industrial solvent mixtures & the rubber caps that came with the test tubes are very, very slowly being dissolved.

I need about a dozen caps. If I were to make it out of solid PTFE, turned on a lathe creating the cap, then it would be expensive. So I'm thinking of having thick cups of PTFE. Then it would be filled by a soft elastomer, creating the cap. Seeing that most PTFE pieces are created by taking PTFE powder & thermoforming it in molds, the production method is expensive even if the cups are lightweight. So I'm thinking "what about vacuum forming?", so I'm here. Can Vacuum forming be used on PTFE?

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Normally no, after all the point of PTFE is that its has not the problems of thermoplastics.

But there exist products like moldflon that enables you to process them in this way. OTOH i would machine them as its cheaper on my time.

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Don't make them, just google "ptfe stoppers", and buy them. (You've asked an XY problem.)

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  • $\begingroup$ @peterh You are right, but sometimes people who pose questions here are not aware that a technical solution for their problem already exists. Hence I upvote Mr Duck, it is a great response. $\endgroup$
    – William Hird
    Mar 24 '19 at 20:58
  • $\begingroup$ @WilliamHird Agreed, okay, let is be so :-) $\endgroup$
    – peterh
    Mar 25 '19 at 7:07
  • $\begingroup$ +1 Well the question has many misconceptions. But there is a small chance that the OP's situation is special and this does not work. $\endgroup$
    – joojaa
    Mar 25 '19 at 7:40
  • $\begingroup$ @joojaa What would you call some of the OP's comments misconceptions, I'm curious? $\endgroup$
    – William Hird
    Mar 25 '19 at 16:45
  • $\begingroup$ @WilliamHird Machining is more expensive is not conclusively true, it really depends on what he has access to and who does it. Certainly if it were me and I needed to make less than 50 caps then machining is definitely cheaper, since I can just leave the cnc lathe running all night. Now vacuum forming is a n option but it needs a form, making this form costs money as you probably want more than one shape in one go. This may mean milling which is more expensive. I dont have access am automated vacuum former, it takes effort to do it manually. To have it done automated would have a setup cost. $\endgroup$
    – joojaa
    Mar 25 '19 at 17:27
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the cost to make the tooling required to sheet-mold the plastic will exceed the cost to machine the caps on a lathe, for quantities of caps in the hundreds.

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  • $\begingroup$ I agree, but it greatly depends on how and who makes the stuff. For my shop yes as the vacuum forming needs human intervention while the cnc lathe will happily churn these for hours at end without much input. $\endgroup$
    – joojaa
    Mar 23 '19 at 13:03

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