I have a laser cutting machine and have always read that PVC (or types of vinyl in general) are very dangerous to cut because it releases chlorine gas. Chlorine gas = toxic (plus the $\ce{HCl}$ thing), makes perfect sense. This is well-known information, and it appears all over informational sites about laser cutting materials.

But I now have someone telling me that cutting polyurethane foam is way more dangerous since it produces $\ce{HCN}$ (hydrogen cyanide). Now this information is in a few limited places and mentioned kinda as a footnote, but it is not nearly as widespread as the Chlorine gas risk that is talked about elsewhere. (I know that the chlorine gas presence during cutting of PVC effectively makes $\ce{HCl}$ gas which clearly does damage to the laser system itself which might explain the prevalence of the information about it)

I know that polyurethane is made with isocyanates, which I'm wondering if that is leading to some people seeing that word and getting confused and assuming that there is cyanide in the foam.

What is confusing about this is that polyurethane is generally considered a very "laser friendly" material to cut (stated all over the place on laser hobbyist and professional websites under acceptable materials). Producing the same gasses that were used in gas chambers seems pretty darn dangerous and like there should be red flags up everywhere.

Can anyone here speak to the chemistry of this, firstly how much if any HCN would be produced by using a 10000nm laser (meaning intense heat based, but nonflaming cutting). And if properly ventilated with an industrial air handling system designed to move the full volume of air from the cutter outside many times per minute what are the risks involved? Does HCN bond to surfaces and stick around? Or is it fully ventilated as a gas?

Clearly, I'm not a chemistry expert, so looking for someone who knows more to help me understand what is real and what is just scary sounding jargon.


From SDS:

Special hazards arising from the substance or mixture: carbon oxides ($\ce{CO}$, $\ce{CO2}$) nitrogen oxides ($\ce{NO}$, $\ce{NO2}$ etc.) hydrocarbons, isocyanate vapours and hydrogen cyanide can be released in case of fire.

The polyurethane polymer formulation greatly changes so the fumes that can form at high temperatures (above the melting temperature). A suction and exhaust system is required. To measure the exact composition of the fumes very specific analysis are required.

  • $\begingroup$ Can you share the link to the SDS that this came from? Clearly a suction and exhaust system is present, but what is the likely hood of these elements being produced with no flame present? $\endgroup$ Jul 11 '17 at 14:42
  • $\begingroup$ I cannot share SDS from my suppliers, you can read this document. goo.gl/A452Cu $\endgroup$ Jul 11 '17 at 15:00
  • $\begingroup$ So based on what I'm reading here, I would say that cutting polyurethane foam may generate some hydrogen cyanide, but not really much more than even burning wood would. So it can be GRAS? (with the proper ventilation system in place). Is that the conclusion that you are driving at? $\endgroup$ Jul 11 '17 at 15:57
  • $\begingroup$ Yes, it can be safe. Think to TPU melting between 160-200°C. As long as the temperature is below 250° C you may assume that no combustion occurs (DSC test). $\endgroup$ Jul 12 '17 at 13:35

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