Cyanide in polyurethane finishes

mardi 22 avril 2014

Over the last few days, thanks to 'rustynail' and 'apricotripper', I've become aware that some if not all polyurethane finishes contain cyanide, in the form of iso-cyanates, and that burning it produces Hydrogen Cyanide, which according to rustynail produces a blue flame when the product is burnt.

Especially relevant to anyone wanting to remove poly with a blowtorch, but also a potential problem for firies, as mentioned by 'MobyTurns' in the other thread.

The subject was first raised in the 'Liability for small shops' thread in the 'Woodwork - General' section, here: http://ift.tt/1f03IEz .

Rather than further hijack that thread, I decided to start a new one.

I was a bit shocked to hear this, and so undertook a little research. I downloaded copies of the MSDS from MinWax, Cabots, Feast Watson and Wattyl Estapol.

There was no mention of cyanide in the MinWax, Cabots and Estapol safety data sheets, but I struck gold when I checked out the Feast Watson MSDS, (Part 2), (excerpts below).

Feast Watson MSDS excerpt 1:

Hazards from combustion products:

Combustible liquid. On burning will emit toxic fumes, including those of hydrogen cyanide , oxides of carbon and oxides of nitrogen.

Feast Watson MSDS excerpt 2:

Isocyanate prepolymer - >60%

-Dipropylene glycol dimethyl ether 111109-77-4 10-<30%

-Ethylene glycol monobutyl ether acetate 112-07-2 1-<10% R20/21

Hexamethylene diisocyanate 822-06-0 <0.12% R23 R36/37/38 R42/43

:oo::o Over 60%! Wow!

Now I'm wondering if this is really the only poly that contains cyanide out of the ones that I checked.

The FW MSDS says that their poly is supplied by Cabots, yet the Cabots MSDS makes no mention of iso-cyanates at all. (Do they pass off the cheap, dangerous stuff to FW and keep the good stuff for themselves?)

I've emailed MinWax, (the brand that I usually use), to ask them if their product(s) contain iso-cyanates and am awaiting their reply.

From my reading/research, I learnt that not all polyurethanes use iso-cyanates in their production, but poly foam and poly paint are also high on the list.

I originally planned to do heaps of copying/pasting to move all relevant info from the other thread to this one, but some of it didn't sound right out-of-context.

Here's one quote, though, that I thought was worth reposting in it's entirety:

Quote:

Originally Posted by GraemeCook

Good Morning Hermit

Thank you for doing the above safety research and publishing it. Useful. Very useful.

I have just finished sanding down a lot of polyurethane - Estapol one pot oil based. I sanded because it would not burn off very easy - I tried and failed - lucky me! [high skirtings, 3 doors, architraves]

Way back in the 1960's when two-pack polyurethane first became available dad painted a cupboard, mantle piece and fire surround with a white two-pack paint which my [increasingly faulty] memory says was the first release of Estapol. It was white coloured, it was two pack and it was applied in the early sixties - I am not certain that it was a poly or that it was Estapol. It was an extremely hard very glossy finish that lasted for 30+ years. Therefore it might be possible that some coloured finishes also contain iso-cyanites.

I've attached the relevant material safety data sheets below.

Any or all comments/additions welcome.

N.B. I'll post the reply from MinWax if or when I get one.

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