Safe MIL-M-24041 Polyurethane

[safetyman]

Are there any relatively safe polyurethanes available without MbOCA, TDI, or isocyanates? Are there any other compounds that pass the requirements of MIL-M-24041 that aren't polyurethanes? Perhaps a two part silicone.

 

[Deahl]

This is my question also. Did you ever get a response that helped?

Gene

 

[btrueblood]

Safe for what? Do you want a food-contact grade? Suggest you contact NSF, and pay the $$$ for use of their resources (they have a long list of polymers which pass their stringent requirements for food contact). You can also search using a combination of terms, like: "polyurethane + food grade + NSF"

 

[safetyman]

We injection mold using thermoplastic polyurethanes that are fully reacted. They are supplied in bags of dry pellets. The chemical reaction that creates diisocyanates has occurred, so the handling hazards are greatly reduced. The product may not meet MIL-M-24041, but works exceptionally well in our commercial applications.
I haven't gotten a response that that addresses the MbOCA and TDI concerns.

 

[btrueblood]

Can you pot using an epoxy compound?

There are 1-part moisture-cure urethanes available, not sure if they don't still contain TDI?

Finally, be careful if you end up using silicone. Some grades give off acetic acid (vinegar) during cure, which can attack/corrode some electronics and circuit boards. There are types/grades made specifically for electronics potting, which evolve (typically) ammonia, which is less corrosive to metals and evaporates/dissipates more quickly.

 

[Deahl]

No it has to be urethane and then epoxy used on the ends. Military requirements. Silicone has out gassing problems, even though I have GE looking at it.

Thanks

 

[patprimmer]

Bayer invented Polyurethanes around WW11 I think.

Several years ago they were still the market leader technically, but I don't know if they have restructured and divested their interests, but they must be worth a call.

Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Deahl]

The material that I use has to be a two part pour. The parts are several inches thick. We do the casins and cure them in ovens.

 

[safetyman]

If you use it in any quantity, I suggest you buy in gallon tubs and buy an auto mixer that keeps the components in pressure pots. Eliminates mixing and deairing. Ask your polyurethane supplier for equipment suggestions.

 

[Deahl]

i use 50 grams at a time.

 

[btrueblood]

So, what is OSHA's concern? Inhalation of TDI fumes? Can you not ventilate the assembly area and/or cure oven to an outdoor vent?