Respirators for Polyurethanes

[Mr Fixit eh]

It was pointed out in another thread that organic vapor cartridges do not provide any protection against Isocyanate, the key ingredient in polyurethanes. Are there filter cartridges for this fume?

Doing a little research on the web reveals that exposure to Isocyanates can be dangerous. I'm assuming that the risk is most severe when the poly is used in spray painting situations. I'm wondering how serious the risk is for those of use who use brush-on or wipe-on polyurethanes on an occasional basis.

If there is no filter cartridge, is there any way to prevent exposure to Isocyanate other than to work outdoors with it? I would assume there would be similar risk in working with polyurethane glues and foams.

Wow. Who knew woodworking was so hazardous to your health?

Steve

[Rumpty]

The normal carbon cartridge respirator does NOT protect you against Iso's. You need what is known as an air supplied respirator.

[Rumpty]

Steve,

If you are a home owner etc and buy a can of Poly down at the hardware store to finish your coffee table and used with proper ventilation it's probably safe for you. However if you are just starting out or have a woodworking shop and finish with poly you need to take precautions.

Everything in a wood shop can be dangerous, it's up to you to understand what you are using.

[Kyle Boatright]

As pointed out elsewhere, filters offer no protection against Isocyanates. However, isocyanates are generally found in the form of an additive that can be added to finishes. I doubt that the can of polyurethane someone would buy at Home Depot would have any isocyanate in it. It will, however, have nasty fumes which can have other nasty effects on you.

The way to look at isocyanates is to imagine that each of us has a cup attached to our belt. Every exposure to iso adds something to the cup, and you can never empty the cup. If you use iso based products without sufficient protection, that little cup will eventually fill up and you'll have a bad, potentially fatal, reaction. How big is this imaginary cup? It varies from person to person.

If you are using Isocyanate, you will need a fresh air source for breathing air. If you are spraying something with Iso in it, you don't want to leave any exposed skin.

My experience with paints containing isocyanate was painting an airplane using automotive paint with an isocyanate hardener. I spent $25 on a bathroom fart fan, $10 on a face shield, $3 on a poncho, and $5 on flex hose and built my own fresh air respirator. I figured it beat the heck out of spending $400 for a store bought respirator, especially since this was a one time job.

KB

[J. Clarke]

All polyurethane coatings contain isocyanates. Isocyanate is not an "additive", it is the key component of all polyurethanes.

Check what you were spraying more carefully. It didn't have an "isocyanate hardener".

[Andy Dingley]

Haven't there been some non-isocyanate polyurethanes recently (5 years ?)

AFAIR, these were being touted as upholstery foams with a reduced fire / toxic smoke hazard. I don't know if they were suitable as paint resins.

[Mr Fixit eh]

Rumpty posted a link to a government factsheet on Icocyanates. In the section on "Paint Mixing and Cleaning", you'll see this statement, .

This statement would seem to indicate that the health risk is for sprayed finishes, but not for brushed-on finishes.

Steve

[Andy Dingley]

That depends on your assessment of the risk from isocyanates. There's a big grey area about risks from sensitisation to them - if that's really the case, then even very low exposure levels could still be something to be avoided.

[Rumpty]

I have numerous associates who have problems with Iso's, me included. IMHO it ain't worth gambling with! Occasional use maybe Ok, but for the small shop, new guy, NO!

[J. Clarke]

The polyurethane polymer is formed by the reaction between isocyanate and polyol. While it's possible to produce coatings that do not contain isocyanate, they are not polyurethanes. Once it is _cured_, if the reaction goes to completion and the two reactants are properly balanced, there is no isocyanate present. But one cannot apply cured polyurethane to a surface unless one uses one of the thermoplastic formulations and applies it in hot molten form.

Upholstery foams are _cured_ polyurethane and will only have isocyanate present if there was a defect in the manufacturing process that results in an excess of isocyanate over polyol. The flame retardant polyurethane foams have a flame retardant additive, not any fundamental change in the chemistry.

[J. Clarke]

The trouble is that it's a sensitizer and the allowable exposures are based on statistical averages. With sensitizers, different people respond differently to a _drastic_ extent. Like one guy can spend his whole life working with them with no ill effects and another doesn't make it to the hospital the first time he's exposed.

For most people the risks from mixing polyurethanes or brushing them is very small. But if you're unlucky then you can get in big trouble real fast.

[Andy Dingley]

The inventor (or at least the most vociferous in the field) appears to be a Russian Dr. Shapovalov who moved to Israel and licensed the technology. However web searching then breaks down somewhat as you can't tell the real tech from the day-trader hyping.

There are certainly many sources pushing non-isocyanate polyurethanes as a specifically isocyanate-free polyurethane resin (either vapourware or maybe product), but I don't know enough chemistry to know any more their credibility.

[J. Clarke]

The paper in which Shapovalov describes them was apparently delivered in a nanotechnology conference. If it's nanotech then assume it's vaporware until you see it on the shelf.

I see what they're doing. They're adding something to the isocyanate to produce a molecule that according to the rules of chemical nomenclature (the rules are arcane and two almost identical substances can have very different names) has a name that does not contain "isocyanate" and calling the resulting product "isocyanate-free". During the reaction whatever group they have added gets knocked off and the isocyanate reacts with whatever is providing the polyol reaction. The generic term for such substances appears to be "blocked isocyanates" and you'll find a huge lot of literature if you search on that term. I even found one paper that has in its title "isocyanate-free blocked isocyanates", which title pretty much sums up the game.

I'd not trust these as there is unbound isocyanate present during the reaction and I doubt that any extensive testing has been performed on the "isocyanate-free blocked isocyanate" to determine its safety.

I would trust such "blocking" about as far as I could throw Hoover Dam.

If someone comes up with a _real_ isocyanate free urethane (i.e. one in which the isocyanate radical is not present at any time during the cure) and brings it to market you can bet that there will be much hype and fanfare and at least a "Popular Science" level description of the process.

[Rumpty]

John,

It sounds like your trust Iso's as much as I do!

So what do your finish your work with?

[Andy Dingley]

I have no concern whatsoever over toxicity issues with polyurethanes.

Polyurethanes _look_ lke crap, and that's why I don't use them.

(Oil, shellac, wax, 17thC spirit varnishes, bitumen)

[J. Clarke]

Well, having spent a good deal of the government's money trying to find something sprayable that would take more abuse, I don't see any real alternatives. Just be careful.

[Mr Fixit eh]

I received the following email from Flecto in response to my inquiry about the risk from isocyanate exposure...

[Max]

Thank You, Eh.

Max D.