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A comment on Italian hospital saves Covid-19 patients by 3D printing valves. Parent comment

Re:Italian hospital saves Covid-19 patients by 3D printing v... by kragen on Monday March 16, 2020 @10:53AM (#22593224)
This is a really comprehensive table! It lists PLA as "Poly(L-lactide)", giving it a surprisingly good "Fair" grade for autoclaving, and polydimethylsiloxane as "Silicones", rating them "Good". It also lists polycaprolactone, which melts around 70° and can be easily molded by hand while molten, as "Fair". Surprisingly, though (to me), it lists nylon (6 and 6-6) and teflon (polytetrafluoroethylene) as only "Fair", like PLA and PCL, even though at least teflon is totally insensitive to water and commonly used with service temperatures up to 260° (among other things, in FDM printer hotends).

So I wonder if this table might have some significant errors in it? Maybe someone interchanged some plastics without intending to. It can't possibly be correct to put PTFE and PCL in the same category, can it?

Anyway, common plastics it rates as "Good" for autoclaving include acetal (Delrin), polypropylene, silicones, and (for some definitions of "common") PEEK.

Surprisingly polyimide (Kapton), the favorite high-temperature chemically-inert plastic of aerospace and electronics, isn't in the table at all.

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Re:Italian hospital saves Covid-19 patients by 3D printing v... by neltnerb on Monday March 16, 2020 @11:32AM (#22593543)
It is totally possible that different companies will have slightly different charts but usually they're about the same. The canonical way to know if to ask the manufacturer of the actual plastic you're using, these comprehensive tables are usually put out by distributors as general guidance.

I'm not surprised that some plastics may not be based on temperature only. For instance, nylon might crack if it's a thin piece due to thermal expansion. Or some may chemically react with steam.

I agree that it's weird that PCL would be okay while Teflon isn't, but it could be a molecular weight or thermal cycling thing. Teflon is very soft already so it might simply get deformed.

I'd trust such a table to point me in the right direction but find a second independent source if the answer seems weird.

Of course in practice you just try it and see if it survives and is functional. lots of plastics can survive a cycle or three but not five.

[ Parent | on HN ]