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
Wow. Who knew woodworking was so hazardous to your health?
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.
Radial Arm Saw Forum: http://forums.delphiforums.com/woodbutcher/start
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
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.
Rumpty posted a link to a government factsheet on Icocyanates. In the
section on "Paint Mixing and Cleaning", you'll see this statement,
<There is not enough unreacted isocyanate released during mixing to
require the wearing of air-supplied respirators>.
This statement would seem to indicate that the health risk is for
sprayed finishes, but not for brushed-on finishes.
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.
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.
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
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.
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.
I received the following email from Flecto in response to my inquiry
about the risk from isocyanate exposure...
<Good afternoon Steve
Sorry for the delay but I wanted to give your the right answer.
I sent out your message directly to our lab technicians and this is the
answer that I received.
Hope this help !
There is no free isocyanate with polyurethane dispersions used in our
products. They are confusing two component urethanes with single
component urethanes. Two components have an isocyanate resin reacted
with an acrylic or polyester polyol. The isocyanate resin carries about
0.1-0.3% free isocyanate. With oil modified urethanes or polyurethane
dispersions, the isocyanate is cooked at high temperatures and totally
reacted to make this type of single component urethane which has no
Thank-you for contacting Rust-Oleum Consumer Brands Canada
If you have any other questions please contact us at 1-800-387-9879.
Rust-Oleum Canada Technical Support>
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